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TB 10001-2016

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BASIC DATA
Standard ID TB 10001-2016 (TB10001-2016)
Description (Translated English) (Code for design of railway subgrade (with description))
Sector / Industry Railway & Train Industry Standard
Classification of Chinese Standard P65
Classification of International Standard 93.100
Word Count Estimation 245,257
Date of Issue 2016-12-20
Date of Implementation 2017-04-01
Older Standard (superseded by this standard) TB 10001-2005
Regulation (derived from) State-Railway-Technology-Regulation (2016) No.50

TB 10001-2016
INDUSTRY STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
UDC
P TB 10001-2016
J 447-2017
Code for design of railway earth structure
铁路路基设计规范
ISSUED ON: DECEMBER 20, 2016
IMPLEMENTED ON: APRIL 01, 2017
Issued by: State Railway Administration
Table of Contents
Foreword ... 8 
1 General ... 11 
2 Terms and symbols ... 12 
2.1 Terms ... 12 
2.2 Symbols ... 16 
3 Basic requirements ... 17 
3.1 Elevation of subgrade shoulder ... 17 
3.2 Shape and width of formation surface ... 19 
3.3 Subgrade stability and settlement control criteria ... 29 
3.4 Deformation observation and evaluation ... 36 
3.5 Design service life ... 37 
4 Design load ... 37 
4.1 General provisions ... 37 
4.2 Main force ... 39 
4.3 Additional force ... 47 
4.4 Special forces ... 48 
5 Engineering materials ... 48 
5.1 General provisions ... 48 
5.2 Filler ... 48 
5.3 Stone ... 54 
5.4 Concrete ... 55 
5.5 Cement mortar ... 56 
5.6 Steel ... 58 
5.7 Geosynthetics ... 59 
6 Subgrade bed ... 62 
6.1 General provisions ... 62 
6.2 Subgrade bed structure ... 62 
6.3 Embankment subgrade bed ... 64 
6.4 Subgrade bed for cutting ... 65 
6.5 Compaction criteria of subgrade bed ... 66 
6.6 Treatment measures of subgrade bed ... 68 
7 Embankment ... 68 
7.1 General provisions ... 68 
7.2 Filler and filling requirements ... 69 
7.3 Compaction criteria ... 70 
7.4 Slope form and slope rate ... 72 
8 Cutting ... 73 
8.1 General provisions ... 73 
8.2 Soil cuttings ... 73 
8.3 Rock cutting... 74 
9 Transition section ... 75 
9.1 General provision ... 75 
9.2 Transition section between subgrade and abutment ... 76 
9.3 Transition section between subgrade and lateral structure ... 78 
9.4 Transition section between embankment and cutting ... 80 
9.5 Transition section between cutting and tunnel ... 81 
10 Ground treatment ... 82 
10.1 General provisions ... 82 
10.2 Main technical requirements ... 83 
10.3 Common measures ... 85 
11 Retaining structure ... 86 
11.1 General provisions ... 86 
11.2 Main design principles ... 87 
11.3 Types of common retaining structure and scope of application ... 89 
12 Subgrade protection ... 90 
12.1 General provisions ... 90 
12.2 Plant protection ... 90 
12.3 Skeleton protection ... 91 
12.4 Physical slope protection (wall) ... 92 
12.5 Hole-window slope protection (wall) ... 93 
12.6 Anchor framed girder slope protection ... 93 
12.7 Shotcrete (mortar) slope protection ... 94 
12.8 Gabion protection ... 94 
12.9 Protection net ... 95 
12.10 Geosynthetics protection ... 95 
12.11 Subgrade plane protection in wind and sand and snow damage areas ... 96 
12.12 Thermal insulation of subgrade ... 98 
13 Water prevention and drainage of subgrade ... 99 
13.1 General provisions ... 99 
13.2 Surface water ... 100 
13.3 Groundwater ... 104 
14 Reconstruction of railway subgrade for existing line and addition of second
line ... 108 
14.1 General provisions ... 108 
14.2 Reconstruction of subgrade of existing line ... 110 
14.3 Addition of subgrade for a second line ... 113 
14.4 Reconstruction, reinforcement, utilization of existing structures ... 114 
15 Borrow (spoil) area and earthwork allocation ... 115 
15.1 General provisions ... 115 
15.2 Borrow area ... 116 
15.3 Spoil area (heap) ... 116 
15.4 Reclamation and protection of borrow (spoil) area ... 117 
15.5 Earthwork allocation ... 118 
16 Subgrade interface design ... 118 
16.1 General provisions ... 118 
16.2 Safety protection facilities ... 119 
16.3 Cable trough ... 120 
16.4 Others ... 120 
Appendix A Grouping classification of ordinary fillers ... 121 
Appendix B Design of improved soil and test requirements ... 131 
Appendix C Steel model, concrete grade and strength ... 137 
Appendix D Common ground treatment methods and measure application
conditions ... 140 
Appendix E Green protection for subgrade slopes ... 142 
Appendix F Diagrams for design of subgrade waterproof and drainage ... 144 
Explanation of wording in this code ... 150 
Code for design of railway earth structure
1 General
1.0.1 This code is formulated to unify the technical standards for railway
subgrade design, make the subgrade design meets the requirements of safety,
reliability, advanced technology, economic rationality.
1.0.2 This code is applicable to the design of standard gauge subgrades for
high-speed railways, intercity railways, passenger-freight level I and level II
railways, heavy-duty railways.
1.0.3 The subgrade project shall be designed according to the geotechnical
structure, to ensure that it meets the requirements of strength, stability and
durability; meets the relevant requirements of environmental protection, soil and
water conservation, cultural relic protection, etc.
1.0.4 The subgrade engineering shall, through geological mapping,
comprehensive exploration, testing and analysis, ascertain the geotechnical
structure and physical and mechanical properties of the subgrade base, cutting
slope, retaining structure foundation, etc., as well as the nature and distribution
of the filler. Perform design based on reliable geological data.
1.0.5 The subgrade engineering design should avoid high filling, deep
excavation, long cutting; avoid areas with adverse geological conditions. In the
comparison and selection of subgrade, bridge, tunnel engineering, it shall make
comprehensive analysis in terms of technical conditions, construction
conditions, land occupation, possible environmental and social impacts, urban
construction planning, construction investment, operation and maintenance
costs, to determine the type of project.
1.0.6 The railway train’s load shall be determined according to railway
transportation characteristics, mobile equipment, design speed, etc. High-
speed railway should adopt ZK load diagram. Intercity railway should adopt ZC
load diagram. Passenger-freight railways should adopt ZKH load diagram.
Heavy-load railway should use ZH load diagram. When the characteristics of
passenger-freight railway meet the standards of heavy-duty railways, it shall
use the ZH load diagram.
1.0.7 The design of subgrade engineering shall be based on railway grade,
subgrade structure, and other factors; according to local conditions, reasonably
select engineering materials. Meanwhile it shall meet the application conditions
and use requirements of subgrade engineering. Subgrade fillers shall be
A geotechnical structure directly supporting the track structure formed by
excavation or filling.
2.1.2 Embankment
Subgrade filled with soil and stone on the ground.
2.1.3 Cutting
Subgrade dug down from the ground surface.
2.1.4 Subgrade shoulder
The part at both sides of the formation surface which is not covered by the
ballast bed.
2.1.5 Elevation of subgrade shoulder
The elevation of the outer edge of the shoulder.
2.1.6 Width of formation surface
The horizontal distance between the outer edges of the subgrade shoulders on
both sides of the formation surface.
2.1.7 Subgrade bed
Subgrade superstructure below the elevation of subgrade that is significantly
affected by train loads. The subgrade bed consists of a surface layer and a
bottom layer.
2.1.8 Lateral structure
A collective term of such structures as culverts, frame bridges, rigid-frame
bridges (steel-structure bridges) which cross the railway subgrade.
2.1.9 Transition section
The section at the joint between the subgrade and bridge abutments, lateral
structures, tunnels, embankments and cutting, which needs special treatment.
2.1.10 Post-construction settlement of subgrade
Settlement of the subgrade after the completion of the track laying project.
2.1.11 Settlement evaluation
According to the settlement observation data, combined with the geological
conditions and ground treatment measures, the process of comprehensively
2.1.20 Permeable soil
Giant grain soil and coarse grain soil (except fine sand) which has fine grain
soil content of less than 10% and permeability coefficient greater than 1 x 10-5
m/s.
2.1.21 Geosynthetics
A general term for various types of materials based on synthetic polymers used
in civil engineering.
2.1.22 Optimum moisture content
The moisture content corresponding to the peak point on the relationship curve
between the dry density and the moisture content obtained by the compaction
test.
2.1.23 Ground treatment
Technical measures taken to improve the bearing capacity of the foundation
and improve its deformation or permeability.
2.1.24 Granular column composite foundation
Composite foundation which uses sand piles, sand gravel piles and gravel piles
for vertical reinforcement.
2.1.25 Flexible pile composite foundation
Composite foundation which uses flexible pile for vertical reinforcement.
2.1.26 Rigid pile composite foundation
Composite foundation which uses friction-type rigid pile for vertical
reinforcement.
2.1.27 Retaining structure
Structures which support the lateral earth pressure or resistance to soil sliding.
2.1.2 Stability factor of slope
In slope stability analysis, the ratio of the sliding force (moment) of the soil along
a sliding surface to the sliding force (moment).
2.1.29 Revetment, slope protection
Protective engineering for preventing weathering, peeling, slipping, scouring of
the roadbed slope (gentle than 1:1.0).
addition of the second line shall be determined at the feasibility study
stage based on years of operation and water disaster.
3.1.2 The elevation of the shoulders of riverbanks and bench land
embankments shall be greater than the sum of the designed flood level, the
height of the backwater (including backwater caused by the opening of the river
or the building, the super-high water level of the river bay), the high wave
invasion or the partial flush of the oblique flow, the height due to riverbed
deposition, the safe height. Among them, it shall take the larger of the wave
invasion height and the oblique current partial upsurge.
3.1.3 The height of the shoulder of the reservoir subgrade shall be greater than
the sum of the design water level, wave invasion height, backwater height
(including the backwater of the reservoir and the backwater on the shore), the
safe height. When the design water level calculated according to the prescribed
flood frequency is lower than the normal high-water level of the reservoir, use
the normal high-water level of the reservoir as the design water level.
3.1.4 For coastal embankments, when no wave barrier wall is provided on the
top, the elevation of shoulder shall be greater than the sum of the designed tidal
water level, wave invasion height (wave climbing height), safe height, etc.;
when a wave barrier wall is provided, the elevation of shoulder shall be greater
than sum of design high tidal level and safe height.
3.1.5 For the subgrade of the higher groundwater level or groundwater area,
the elevation of shoulder shall be greater than the sum of the highest
groundwater level or the highest ground area water level, the strong rise of
capillary water, the safe height.
3.1.6 The elevation of the shoulder of the subgrade in the seasonal frozen soil
area shall be greater than the sum of the groundwater level before freezing or
the surface water level before freezing, the strong rise of capillary water, the
depth of harmful frost heave, the safe height.
3.1.7 The elevation of the shoulder of the saline soil subgrade shall be greater
than the sum of the highest groundwater level or the highest surface area water
level, the strong rise of capillary water, the depth of strong influence of
evaporation, the safe height. When there is seasonal freezing damage to the
saline soil subgrade, the elevation of shoulder shall be calculated separately
according to the provisions of clause 3.1.6 of this code and this clause,
whichever is greater.
3.1.8 When the subgrade adopts measures such as lowering the water level
and setting capillary water partitions, the elevation of the shoulder may not be
subject to the restrictions specified in clause 3.1.5 to 3.1.7 of this code.
3.1.9 The safe height in clauses 3.1.2 ~ 3.1.7 of this code should be 0.5 m.
mXs - The empirical correction factor for the settlement of the underlying layer,
which is related to the foundation conditions, load strength, loading rate, etc.;
S2 - Calculated value of the settlement of the underlying layer (m).
3.3.9 The calculation of foundation settlement shall meet the following
requirements:
1 The calculated depth of the compression layer of the high-speed railway
and ballast-less track’s foundation is determined by the additional stress
which is 0.1 times the self-weight stress; the calculated depth of the
compression layer of the other railway’s foundations is determined by the
additional stress which is 0.2 times the self-weight.
2 If there is still a soft soil layer below the calculated depth, it shall
continuously increase the calculated depth.
3 In the calculation of the settlement of the double track foundation, the track
load can be designed as a double line; the train load should be designed
as a single line.
3.4 Deformation observation and evaluation
3.4.1 Subgrade of high-speed railway and ballast-less track railway shall be
subjected to settlement evaluation. The heavy-load railway, ballasted track
railway with design speed of 200 km/h and in such sections as in soft soil and
collapsible loess should be subject to foundation settlement evaluation.
3.4.2 Subgrade deformation observation shall focus on the observation of
formation surface settlement and foundation settlement. During the filling period
of the embankment of the soft soil section, it shall also observe the horizontal
displacement of the slope foot of the subgrade, control the filling rate, ensure
the subgrade stability.
3.4.3 The layout of deformation observation sections and observation facilities
shall be comprehensively determined based on topographic and geological
conditions, ground treatment methods, subgrade types, embankment heights
and other factors in combination with the construction period. The distance
between observation sections should be 50 m ~ 100 m.
3.4.4 Deformation observation methods and accuracy shall meet the
requirements of relevant railway standards of different grades. Subgrade shall
be continuously observed after the start of construction. After finishing the
subgrade filling or applying the preload, the settlement observation time should
be not less than 6 months. If the observation data is insufficient to evaluate or
the post-construction settlement assessment cannot meet the requirements, it
4 When the slope surface is protected by mortar spray, the strength grade of
cement mortar should not be lower than M10.
5.6 Steel
5.6.1 The steel for subgrade work any use the reinforcing steel bars,
prestressed steel wire, steel strand, steel plate and section steel. The strength
of reinforcing steel bars, prestressed steel wires, strands shall be determined
according to their models in accordance with Appendix C.
5.6.2 Ordinary steel bars and prestressed steel bars shall be selected according
to the following requirements:
1 The longitudinally stressed steel bars for the retaining and bearing
reinforced concrete structure should use HRB400 and HRB500 steel bars;
it may also use HPB300 steel bars. The stirrups should use the HPB 300,
HRB400, HRB500 steel bars.
2 Tensioned anchors for anchor retaining wall and soil nailed wall structures
should use ribbed steel bars, prestressed threaded steel bars; it should
not use galvanized steel and the diameter should not be less than 16 mm.
The vertically prestressed anchor retaining walls and other structural
prestressed anchors should use cold-drawn steel bars.
3 Structurally tensioned anchors such as slope hanging net protection or
framed girder slope protection should use HRB400 and HRB500 steel
bars, the diameter of which should not be less than 16 mm.
5.6.3 Prestressed anchor rods should use prestressed threaded rebar;
prestressed anchor cables should use high-strength low-relaxation prestressed
steel strands; the diameter of steel strands may use Φ12.7 mm or Φ15.2 mm.
5.6.4 Steels such as steel plates, sections, bolts and anchors shall meet the
following requirements:
1 Steel plates are divided into U-shaped, Z-shaped, S-shaped, linear and
other types; section steel is divided into I-shaped steel, channel steel,
angle steel, round steel and other types.
2 The temporary supporting for small-scale foundation pits and slope
excavation may use steel plates, I-beams or channel steels, or waste steel
rails.
3 The dimensions of anchor plate’s tie rods, anchor retaining wall’s anchor
rods, pre-stressed anchor rod’s end fixed steel backing plates shall meet
the requirements for calculation of local bearing strength.
1 The water isolation anti-seepage layer of the Newly built railway subgrade
bed water-proof and anti-seepage layer, and embankment base capillary
water insulation cushion layer, it is advisable to use water-tight
geomembrane, composite geomembrane, capillary or composite water-
proof drainage board, etc. The frost-resistant area should meet the frost
resistance requirements; when used for capillary water partition, it shall
have long-term corrosion resistance and aging resistance to sulfate,
chloride, carbonate.
2 When the existing subgrade bed’s strength is insufficient, or such defects
as subsidence, sinking, water accumulation and so on are treated, it may
use the geotechnical cells for reinforcement and seepage pipes or
drainage boards to lead and drain water.
3 The subgrade bed in the freezing disaster area may adopt polystyrene or
polyurethane foam insulation layer; its performance indicators such as
apparent density, compressive strength, thermal conductivity, water
absorption shall meet the design requirements.
4 The lateral drainage cushion layer on the embankment base, slope
protection, protection wall, retaining wall or anti-filtration layer after
intercepting drainage ditch, seepage ditch, blind drain of intercepting ditch,
back anti-filtration layer of blind drain, anti-filtration layer between fillers of
different grain sizes may use non-woven geotextile or its wrap of gravel
and macadam as the anti-filtration material. The soil retention, water
permeability, anti-blocking index, puncture strength of the non-woven
geotextile shall meet the design requirements.
5 For drainage of groundwater, it may use seepage pipes or geotextiles and
wrap of gravel and macadam for filtration and drainage.
6 The water seepage pipe shall have good water permeability, filtration,
longitudinal drainage performance; it shall have the characteristics of high
ring stiffness, chemical resistance, long life and so on.
5.7.5 When geosynthetics are used for subgrade slope protection, it shall meet
the following requirements:
1 For soil slopes, it may use grass, bush and plant such as geonets, geonet
mats or three-dimensional vegetation slope protection nets for greening.
2 For subgrade slopes such as sandy soil, gravelly soil, or rocky soil, which
are not suitable for plant growth, it may use geonets to plant grass, plant
belts, plant bags or ecological bags to plant grass for greening.
3 The ultimate tensile strength of the geonet mat shall not be less than 0.8
kN/m.
5.7.6 When geosynthetics are used for subgrade scour protection, it may use
mold bag concrete slope protection. When the cement mortar is filled in the
geo-mold bag, the allowable flow rate is 2 m/s ~ 3 m/s. When the concrete is
filled, the allowable flow rate is 2 m/s ~ 5 m/s. When underwater construction is
required, the allowable flow rate is not more than 1.5 m/s. For slope protection
and bottom protection with a severe erosion rate of 4 m/s ~ 5 m/s, it may use
woven geotextile. The rupture strength of the geo-film bag cloth shall not be
less than 40 kN/m and the elongation shall not be greater than 30%. The zonal
rupture strength of the woven geotextile shall be not less than 20 kN/m. The
material’s aging resistance shall meet the engineering needs.
5.7.7 When geosynthetics are used in the reinforced soil structure of subgrade
slopes, they shall meet the following requirements:
1 When the embankment’s fill slope is high and the slope is susceptible to
storm erosion, it may lay a two-way geogrid in the shallow layer of the
slope for enhanced protection. The ultimate tensile strength of the geogrid
shall not be less than 25 kN/m.
2 Reinforced earth embankments or reinforced earth retaining walls on steep
slopes should use plastic uniaxially stretched geogrids with high strength,
low elongation, small creep, good weather resistance and chemical
resistance. The ultimate tensile strength of a geogrid shall not be less than
35 kN/m; the nominal elongation shall not be greater than 10%.
5.7.8 When geosynthetics are used for subgrade treatment, they shall meet the
following requirements:
1 Reinforcement of cushions should use geogrids, geotextiles or geocells
with higher strength and smaller elongation. The vertical drainage in the
deep drainage consolidation method for soft soil foundations may use
drainage belts or bagged sand wells. For large-area processing sections,
it may use large-diameter seepage pipes or flexible pervious pipes as
water collection wells, to accelerate the consolidation and drainage of the
foundation.
2 The ultimate tensile strength of the geogrid, geotextile or geocell shall not
be less than 50 kN/m; the nominal elongation is not greater than 10%. The
tensile strength, corrosion resistance, flexibility of the core material of the
drainage belt as well as such performance indicators as vertical drainage
capacity, filter jacket strength, anti-filtration capacity shall comply with the
requirements of relevant standards. The bag materials for bagged sand
wells shall be made of tough polypropylene or other suitable geotextiles;
the ultimate tensile strength shall not be less than 15 kN/m; the mass shall
not be less than 95 g/m2; the equivalent aperture O95 shall be not more
than 0.05 mm; the permeability coefficient shall be more than 5 x 10-5 m/s.
6.6 Treatment measures of subgrade bed
6.6.1 The natural foundation soil within the range of the bottom of the subgrade
bed complies with the provisions of clause 6.3.2 of this code. If the natural
compactness does not meet the requirements of clause 6.5.3 of this code, it
may take measures such as cutting & backfill or rolling compaction.
6.6.2 If the soil or filler within the range of the bottom of the subgrade bed does
not meet the requirements, it may be treated by taking the replacement or
reinforcement measures.
6.6.3 When the subgrade bed is affected by groundwater, it should take
measures such as lowering the groundwater level and setting up embankment-
type cutting, to reduce and empty the water in the area of the subgrade bed.
6.6.4 For the semi-filled and semi-cut subgrade bed on steep slope section, the
range not less than 1 m below the subgrade bed at the semi-cut side shall be
cut and filled; the filler shall meet the requirements of clauses 6.3.1 and 6.3.2
of this code.
7 Embankment
7.1 General provisions
7.1.1 The height of the embankment slope shall be reasonably determined in
combination with railway grade, track type, foundation conditions, source of filler,
land use nature, environmental factors, which should not exceed 20 m.
7.1.2 The surface treatment of the subgrade of the embankment on stable slope
section shall meet the following requirements:
1 When the surface slope is slower than 1:5, it shall remove the vegetation
on the surface.
2 When the slope of the ground surface is (1:5) to (1:2.5), it shall cut steps
on the original surface; the width of the steps shall not be less than 2 m.
When the overburden on the bedrock surface is thin, it should first remove
the overburden before digging the steps; when the overburden is thick and
stable, it may dig the steps directly on the original ground surface.
7.1.3 The safety factor of sliding stability of the subgrade and the soft layer
below subgrade for the steep slope embankment which has a lateral steep
slope on the ground surface steeper than 1:2.5 shall not be less than 1.25.
When the requirements are met, it shall design the steps on the original ground;
2 The maximum particle size of the filler for ballasted track railway with a
design speed of 200 km/h shall not be greater than 150 mm.
3 The maximum particle size of the filler for ballast-less track railway and the
ballasted track railway with a design speed of 200 km/h or more shall be
not more than 75 mm.
7.2.5 When the embankment is filled with different fillers, it shall meet the
following requirements:
1 When the seepage soil is filled above the non-seepage soil, the top surface
of the non-seepage soil layer shall be provided with a 4% herringbone
drainage slope to both sides.
2 When the particles of the upper and lower layers of fillers do not meet the
requirements of the formula (6.1.4) of this code, it shall set isolation
cushion or take other measures on the parting plane. When the filler for
the lower layer is chemically improved soil, it is not subject to the
restrictions of this clause.
7.2.6 When the embankment below the subgrade bed uses sandy soil in group
C2 and group C3, it shall take reinforced protection measures.
7.3 Compaction criteria
7.3.1 The compaction control index of the embankment’s filler below the
subgrade bed shall meet the following requirements:
1 For fine-grained soil, sandy soil, gravelly soil, macadam soil, block stone
soil, etc., it shall use the compaction coefficient and foundation
deformation coefficient as control indicators.
2 The improved soil shall use the compaction coefficient and 7d saturated
unconfined compressive strength as control indicators.
7.3.2 The compaction criteria of the embankment filler below the subgrade bed
shall meet the requirements in Table 7.3.2.
or slope foot walls with a width of not less than 1 m.
8 Cutting
8.1 General provisions
8.1.1 The height of the cutting slope shall be comprehensively determined
according to the lithology of the stratum, the degree of fragmentation of the rock
mass, the hydrological conditions. It should not exceed 30 m.
8.1.2 Soil, soft rock and strongly weathered hard rock cuttings shall be provided
with side drain platforms, the width of which shall not be less than 0.5 m; cutting
slopes shall be provided with slope platforms at the interface between soil and
rock boundaries, permeable and impermeable layers; the width should not be
less than 2 m.
8.1.3 In the sections where groundwater develops, drainage is difficult, swelling
soil (rock) presents, it may be designed in the form of embankment-type cutting
structure.
8.1.4 The design of cuttings shall reduce the damage to natural vegetation and
mountains and prevent inducing geological disasters.
8.1.5 High soil slopes and weak loose rock cuttings should, according to the
engineering geological conditions, rock stratum weathering and joint
development, combined with construction technology, use the layered
excavation, layered stabilization, slope foot pre-reinforcing technology.
8.2 Soil cuttings
8.2.1 The form and slope rate of soil cutting slopes shall be comprehensively
determined in accordance with engineering geology, hydrogeology and
meteorological conditions, slope height, water drainage measures, construction
methods, etc., combined with the investigation and mechanical analysis of
natural stable hillsides and artificial slopes.
8.2.2 When the height of the soil cutting slope is less than 20 m, the slope rate
can be determined according to Table 8.2.2; when there are special conditions
such as unfavorable stratum interfaces, sliding surfaces, groundwater cropping,
etc., it needs to be determined through stable analysis and calculation.
mixed with not less than 3% cement in layers; the compaction criteria shall
meet the compaction coefficient K ≥ 0.95, foundation deformation
coefficient K30 ≥ 150 MPa/m, dynamic deformation modulus Evd ≥ 50 MPa.
2 Passenger-freight shared railway with a design speed of 200 km/h may be
filled with graded macadams in a layered manner. The range 2.0 m away
from the structure shall be mixed with not less than 3% cement; the
compaction criteria shall meet the compaction coefficient K ≥ 0.95,
foundation deformation coefficient K30 ≥ 150 MPa/m.
3 Heavy-duty railways shall be filled with group A fillers in layers. The
compaction criteria shall meet the compaction coefficient K ≥ 0.95,
foundation deformation coefficient K30 ≥ 150 MPa/m, dynamic deformation
modulus Evd ≥ 40 MPa.
4 Ballasted track intercity railways with design speeds below 200 km/h and
passenger-freight shared railway shall be filled with group A fillers. The
compaction criteria shall comply with the relevant provisions of the bottom
layer of the subgrade bed in clause 6.5.3 of this code.
5 The grading range of graded macadam shall comply with the provisions of
clause 5.2.11 of this code.
9.2.5 The fillers in the immersed part of the transition section shall meet the
technical requirements for pervious soil fillers except for graded macadams.
9.2.6 The abutment pit of the transition section of the high-speed railway,
ballast-less track and ballasted track intercity railway with a design speed of
200 km/h shall be backfilled with concrete or layered with gravel or improved
soil. The foundation pit of the bridge abutment in the transitional section shall
be filled in layers with gravel and improved soil. Concrete shall meet the design
strength requirements. The gravel and improved soil filling shall meet Evd ≥ 30
MPa.
9.2.7 The foundation reinforcement measures for the transition section shall
meet the post-construction settlement control requirements, meanwhile
consideration shall be given to coordination with the deformation of the bridge
abutment and adjacent subgrade sections. If necessary, it may set reinforced
concrete slabs behind the platform.
9.3 Transition section between subgrade and lateral structure
9.3.1 At the junction of the subgrade and lateral structures (overpass frame
structure, box culvert, etc.), the transition section is set according to the terrain
and geological conditions. It should use the longitudinally inverted trapezoidal
transition form along the line, as shown in Figure 9.3.1-1. When the construction
1 For the ground treatment by shallow layer treatment method and drainage
consolidation method, it should follow the method as specified in clause
3.3.7 of this code to carry out calculation.
2 The settlement of the reinforced area of the granular column composite
foundation and flexible pile composite foundation should be calculated
according to the composite modulus method; the underlying layer should
be calculated according to the Boussinesq method and the stress
dispersion method.
3 The settlement of the reinforced area of the rigid pile composite foundation
should be calculated according to the bearing capacity ratio method; the
underlying layer should be calculated according to the Boussinesq
method, the stress dispersion method, L/3 method, etc.
4 The settlement of the underlying layer of the reinforced concrete pile net
(raft) and pile-slab structure foundation should be calculated according to
the equivalent solid method and the L/3 method.
10.2.4 The calculation and the ground treatment measures of the swelling
deformation of the swelling soil and frozen soil foundation shall be determined
in accordance with the current national relevant codes in combination with the
foundation soil’s swelling grade and frost heaving grade.
10.2.5 Subgrades in collapsible loess areas shall be analyzed and calculated
for compression settlement and ground subsidence. According to the post-
construction settlement requirements of the railways of different grades, take
measures to prevent, reduce or eliminate ground collapsibility.
10.2.6 The karst and cave foundations shall be subject to stability evaluation.
Between the subgrade and the unstable area of subsidence, it shall reserve a
certain safety distance. The safety distance shall be determined
comprehensively according to the railway grade, track type, buried depth of the
cave roof. Take ground treatment measures to eliminate subsidence.
10.2.7 At the boundary between the subgrade and other structures, the sections
where the stratum changes greatly, the connection between different ground
treatment measures, it shall carry out calculation of differential settlement. Take
the gradual transitional foundation treatment measures, to reduce uneven
settlement.
10.2.8 Where the ground treatment neighbors existing railways, highways,
underground pipelines or other building sections, it shall carry out necessary
calculation and evaluation of the impact of existing facilities; enhance
monitoring and take necessary treatment measures, to ensure the normal use
and safety of existing facilities.
complicated or the embankment is high, it may take comprehensive
consolidation measures such as drainage consolidation, composite
foundation and reinforced concrete pile net (raft).
5 For relatively steeper lateral slope at the bottom of weak layer or the slope
weak foundation, it shall enhance the anti-sliding stability. It should take
the treatment measures such as composite foundation, reinforced
concrete pile net (raft) or the combination of the both for comprehensive
reinforcement.
10.3.4 For karst and man-made pothole foundation treatment, it may take such
treatment measures as dynamic compaction, backfilling, replacement filling,
spanning, grouting, or reinforced concrete pile net (raft).
10.3.5 When the geological and environmental conditions are complex, the
treatment of loose coarse-grained soil, unsaturated silt and cohesive soil,
collapsible loess foundation or the reinforcement of the existing engineering
foundation may take special measures such as grouting or micro piles.
11 Retaining structure
11.1 General provisions
11.1.1 The design of the subgrade’s retaining structure shall meet the
requirements of strength, stability and durability. The selection of the structure
type and the determination of the installation location shall be safe and reliable,
economical and reasonable, convenient for construction and maintenance.
11.1.2 The subgrade should be provided with retaining structures in the
following cases:
1 Reduce the excavation of the thin layer of the cutting slope and the filling
section of the thin layer of the embankment slope; or strengthen the steep
slope subgrade of the embankment’s stable section.
2 Cutting sections which shall avoid large volume cutting, reducing slope
height, reinforcing slope stability.
3 Foundations, slopes, mountains, dangerous rocks, or falling rocks under
adverse geological conditions.
4 The riverside and coastal embankment sections affected by the erosion of
water current.
5 Sections which save land, occupy less farmland, or protect important
2 Reinforced concrete members should be checked for resistance to bending,
shear, tensile, compression, torsion, deflection, crack width in accordance
with the Code for design of concrete structure GB 50010. The item factor
of load shall be valued in accordance with the requirements of Code for
design of retaining structure of railway subgrade TB 10025.
11.2.5 The subgrade’s retaining structures located in soft soil, slopes and other
sections shall be subject to overall stability calculation and the stability safety
factor shall meet the requirements of clause 3.3.5 of this code.
11.2.6 The seismic design of the retaining structure shall comply with the
provisions of the Code for seismic design of railway engineering GB 50111.
11.2.7 The durability of the retaining structure shall comply with the provisions
of Code for durability design of railway concrete structures TB 10005.
11.3 Types of common retaining structure and scope of
application
11.3.1 The type of retaining structure shall consider factors such as load type,
topographical conditions, geological conditions, surrounding environment, land
acquisition, demolition, engineering investment; make selection reasonably
based on the characteristics of the retaining structure. If necessary, it may
select the form of combining two or more types of retaining structures.
11.3.2 The retaining structure provided in general areas shall meet the following
requirements:
1 The retaining structures of railway cuttings should be selected from gravity
retaining walls, soil nailed walls, pile-sheet retaining walls, anti-sliding
piles, prestressed anchor cables, anchor retaining walls.
2 Retaining structures for railway embankments should choose gravity
retaining walls, cantilever and buttress retaining walls, pile foundation joist
retaining walls, pile-sheet retaining walls, reinforced earth retaining walls,
anti-sliding piles, etc.
11.3.3 Retaining structures for railway embankments in flooded areas should
be selected from gravity retaining walls, cantilever retaining walls, pile
foundation joist retaining walls, pile-sheet retaining walls.
11.3.4 When the railway cutting in seismic areas is provided with retaining
structures, it should select the structural types such as pile-sheet retaining walls,
prestressed anchor cables, gravity retaining walls. When the railway
embankment is provided with retaining structures, it should select cantilever
plants, or spraying vegetation.
12.2.3 Embankment slopes immersed in seasonal water currents and where
the velocity is less than 1.8 m/s shall be protected by shrubs with developed
rhizomes, strong entanglement, resistant to moisture and flooding. At the lower
slope or slope toe for embankment along the river, it may take such anti-
scouring measures as planting trees and shrubs.
12.2.4 The common plant species for plant protection shall be selected in
accordance with Appendix E in accordance with the natural conditions of plant
growth, precipitation and air temperature. It shall not use oily plants.
12.2.5 Plant protection shall not affect the safety of driving and railway
equipment. The minimum horizontal distance between plants and underground
pipelines shall meet the requirements of Appendix E.
12.2.6 The configuration of mixed sowing grass, shrub or vine plant seeds shall
follow the principles of combining fast-growing and slow-growing, combining
leguminous and non-legume, combining shallow and deep roots, combining
different varieties at the greening stage.
12.2.7 The sowing amount of grass, shrub or vine plant seeds shall be
determined in accordance with the rock and soil properties of the slope of the
site, slope rate, seed germination rate, grain weight, design coverage and
survival rate.
12.2.8 The water used for plant protection construction and curing shall not
contain components that endanger plant growth. If necessary, perform water
quality analysis.
12.3 Skeleton protection
12.3.1 The skeleton slope protection may be used for the protection of
embankment slopes and soil, fully weathered rock formations, cutting slopes of
strongly weathered soft rock.
12.3.2 Skeleton slope protection may be assembled using stone masonry,
concrete pouring or precast concrete components.
12.3.3 Skeleton slope protection should adopt arched, herringbone, checkered,
etc.; the skeleton spacing should use 2 m ~ 4 m. The interval between skeletons
should be determined comprehensively by using rock properties of slope, slope
nature, climatic conditions, which shall not be less than 0.4 m.
12.3.4 The skeleton slope protection can be set in multiple stages. The slope
rate shall not be steeper than 1:1. The height of each stage should not be
2 The buried depth of the retaining wall’s foundation used for the cutting
slope shall not be less than 1.0 m.
12.5 Hole-window slope protection (wall)
12.5.1 Hole-window slope protection (wall) can be used for the protection of
easily weathered or weathered broken rocky cutting slopes and soil cutting
slopes that are susceptible to erosion.
12.5.2 The hole-window slope protection (wall) may be made of rubble or laid
by concrete prefabricated blocks or poured by concrete.
12.5.3 The single-stage height of the slope protection (wall) should not exceed
12 m. When it exceeds, it should set a platform or use staged masonry or
pouring.
12.5.4 The slope rate of hole-window slope protection (wall) should not be
steeper than 1:0.75; the opening size should be 2 m ~ 4 m; in the window
opening it should spray mixed vegetation or growing plants.
12.5.5 The buried depth of the window-type retaining wall shall not be less than
1 m.
12.6 Anchor framed girder slope protection
12.6.1 Anchor framed girder slope protection can be used for protection of soil,
soft rock and weathered hard rock cutting slope. It can be used with plant
protection, geonet padding for soil vegetation, hollow brick inside soil vegetation,
spray mixed vegetation, ecological bags, vegetation bags, spray anchor nets,
flexible protective nets and other protective combinations.
12.6.2 Anchor framed girder slope protection can be set in multiple stages, the
slope rate should not be steeper than 1:0.75, the height of a single stage should
not exceed 15 m.
12.6.3 Anchor framed girders shall adopt cast-in-situ reinforced concrete, which
may be arranged in a square or diamond shape. The cross-section size shall
not be less than 0.3 m; the concrete strength grade shall not be lower than C30.
The distance between anchors should not be less than 2 m. The length of
anchors should not be less than 5 m.
12.6.4 The width of 0.5 m at the starting point and end point of slope protection
shall be edge-reinforced with cast-in-situ concrete or mortar rubble stone
masonry. The cutting top of the slope protection shall set concrete or mortar
rubble edge protection. The toe of slope protection shall set concrete or mortar
12.9 Protection net
12.9.1 Protective measures for dangerous rocks and falling rocks shall be
comprehensively determined based on factors such as their distribution range,
scale, slope height, and distance from the line. Protective net protection may
be set in combination with protective measures such as removing dangerous
rocks.
12.9.2 If dangerous rocks on the slope are distributed more and have larger
volume, it may use verification to take active protection net for protection or
passive protection net for protection. When dangerous rocks and solitary rocks
on the slope are scattered and difficult to clean, it should use passive protective
nets for protection or comprehensive treatment.
12.9.3 The falling rock’s kinetic energy and its bounce height should be
determined through field rockfall test observations; when field rockfall test
observations are difficult to implement, it may use theoretical calculations or
numerical simulation calculations to determine it.
12.9.4 The design height of the passive protective net shall not be less than the
maximum bounce height of the falling rocks plus 1.0 m; the minimum design
height shall not be less than 2.0 m.
12.9.5 The height of the steel columns of the passive protection net shall not be
lower than the design height of the protection net. The spacing between the
steel pillars shall not be greater than 12.0 m; the minimum spacing shall not be
less than 4.0 m.
12.10 Geosynthetics protection
12.10.1 Geosynthetics can be combined with other engineering materials and
engineering measures for subgrade protection.
12.10.2 When geonets, geonet mats, three-dimensional vegetation slope
protection nets are used for subgrade protection, they shall meet the following
requirements:
1 It can be used to protect the slope of soil, weathered rock and easily
weathered soft rock subgrade suitable for plant growth.
2 It can be used for wind erosion protection of embankment slopes filled with
fine sand and cutting slopes of fine sand formations.
3 It can be used for sand fixation and sand blocking projects on both sides
of aeolian subgrade.
protection belts, protective belts, vegetation protection belts in order from the
slope foot (or cutting top) of the embankment (or cutting). The engineering
protection and plant protection measures in the protective zone shall coordinate
with each other to give play to their overall effectiveness.
12.11.3 Sand prevention forests and protective belts using flammable materials
such as grass shall be laid with pebble soil, macadam soil, coarse gravel soil,
etc. at the foot of the subgrade slope or at the top of the cutting. The width of
the fire protection zone shall meet the requirements of Code for fire protection
design of railway engineering TB 10063.
12.11.4 On both sides of the subgrade, it shall, based on such factors as sand
source, wind conditions, dune activity conditions, natural vegetation conditions,
set the protective belts and vegetation protection belts according to severe,
medium and light aeolian sand sections.
12.11.5 The type of protection shall be determined comprehensively according
to the characteristics of the aeolian sand activity, the amount of sand
transported, the terrain and the nature of the protective materials. It may take
measures such as paving coarse-grained soil, setting up sand blocking barriers,
sand retaining walls or high vertical sand barriers.
12.11.6 In areas where there are water sources and the available or average
annual precipitation is more than 250 mm, it shall adopt sand fixation by plant.
In areas where the average annual precipitation is 100 mm ~ 250 mm and the
moisture of the wet sand layer is more than 3%, it should adopt sand fixation
by plant. The plant for sand fixation shall be local desert plants which have good
growth and strong sand-fixing ability.
12.11.7 In areas with snow disaster, it shall be based on the terrain, landform,
vegetation, climate, wind direction, snow thickness, as well as other factors
such as the location of the line and the height of the subgrade, to design the
protective forest belts on one or both sides of the subgrade. Shelterbelts should
be mixed with arbors and shrubs. According to the local soil and climatic
conditions, the tree species of the forest belt should be suit for local growth,
easy to survive, fast-growing.
12.11.8 When the protective forests are not suitable and before the protective
forests function, it may set fixed or movable snow fences, snow dikes, snow
ditches or wind deflectors on the windward side, which shall be perpendicular
to the prevailing wind direction. When the terrain is wide and snow is heavy, it
may use the comprehensive protective system which combines a snow dike,
snow fence, shrub belts.
12.11.9 In sections prone to severe snow damage or avalanches which bury
lines, it may use protective measures such as open holes or sheds.
flowing water purposes; the discharged water flow shall not directly enter
drinking water sources, breeding ponds, farmland, etc.
13.2.5 The design of surface drainage facilities shall meet the following
requirements:
1 When the geological or soil conditions are poor and leakage or deformation
may occur, it shall take appropriate reinforcement and protection
measures.
2 The longitudinal slope at the bottom of the ditch should not be less than
2‰. When the length of a single-sided drainage slope is greater than 400
m, it shall add an outlet at an appropriate position.
3 The line of the ditch shall be smooth; the curve should be made into an arc.
4 The height of the top surface of the trench shall be at least 0.2 m higher
than the design water level.
13.2.6 Overhead ditches and drainage ditches that are drained into natural
ditches shall have energy dissipation and sedimentation facilities at their ends,
to avoid erosion of the surface by concentrated water.
13.2.7 In areas where natural and artificial ditch are well developed, it shall
provide water delivery bridges and culverts for dredging. It should not use
pipelines for dredging.
13.2.8 In areas with arid climate and extremely difficult drainage, it may use
concentrated earth borrowing pits or specially excavated pits to build
evaporation ponds.
13.2.9 The subgrade drainage of the filling section shall meet the following
requirements:
1 Drainage facilities shall be provided outside the foot of the subgrade slope
according to the terrain and weather, to collect and drain the water on the
slope and the formation surface.
2 Drainage ditch shall be set outside the natural protection channel; it can be
arranged on one or both sides according to the topography.
3 For areas where the ground surface lateral slope is not obvious,
embankments with a filling height of less than 2.5 m shall be provided with
drainage ditches on both sides of the embankment.
4 When setting the skeleton slope protection, it shall, combining the
precipitation, use the arch, herringbone or checkered skeleton structure
with interception trough.
reserved by the side ditch’s wall of the line.
7 Water from overhead ditch shall not be drained to the side ditch of the
cutting. When it is restricted by terrain and it needs to drain the water from
the overhead ditch to the side ditch through the rapid trough (hanging ditch)
or rapid flow pipe, it shall adjust the size of the side ditch according to the
flow rate, meanwhile perform such treatment as reinforcement and energy
dispersion for the water inlet and outlet, set the water retention wall.
8 The intercepting ditch of the cutting slope’s platform can be reinforced
according to the soil quality of the slope.
9 The distance from the inner edge of the cutting’s overhead ditch to the top
of the top of the cutting should not be less than 5 m. When reinforcement
measures are adopted in the ditch, the distance shall not be less than 2
m.
10 According to the railway grade and regional engineering practice
experience, the rapid-flow trough shall adopt a rectangular section made
of concrete or mortar rubble. The main part of the rapid-flow trough shall
be provided with anti-skid platforms every 2 m ~ 5 m, which are embedded
in the slope.
11 When the side ditch of the existing line’s reconstruction section is
controlled by drainage elevation, it may take measures to heighten the
side ditch’s wall, but it shall not weaken the existing subgrade drainage
conditions.
13.2.11 The water prevention and drainage of the formation surface shall meet
the following requirements:
1 Formation surface water shall be led into drainage ditch or side ditch by
appropriate measures, or a water collection well shall be set for
centralized drainage. The formation surface with special requirements
shall be treated with waterproof infiltration.
2 Drainage holes shall be reserved for facilities such as cable troughs and
shoulder guards.
3 In the widening section of the formation surface of the existing line shall be
provided with outward drainage lateral slope at the slope toe of the ballast
bed of the existing line.
4 When the formation surface of an existing line is raised or excavated, it
shall set a 4% lateral drainage from the center of the line to both sides.
5 The drainage of the formation surface of the additional second-line section
13.3.7 For complex strata composed alternatively of multiple aquifers and
confining beds, it should use vertical drainage facilities in conjunction with
horizontal drainage facilities below it.
13.3.8 The location of the manhole shall meet the following requirements:
1 At the interval of about 30 m for blind drain.
2 At the interval of about 120 m for water seepage tunnel.
3 At the plane turning point, cross section or vertical slope change point, etc.
13.3.9 Drainage facilities such as blind drains, seepage tunnels, seepage wells
shall be provided with appropriate anti-filtration layers according to the stratum
conditions of the aquifer. When the manhole doubles as a seepage well, the
well wall shall be provided with an anti-filtration layer. The anti-filtration layer
may be made of sand gravel, sand-less concrete slab, geotextile and other
materials. The number of layers, thickness and particle gradation of the anti-
filtration layer shall be determined according to the soil quality of the pit wall
and the material of the anti-filtration layer, meanwhile it shall meet the following
requirements:
1 Gravel sand shall be screened and washed, wherein the content of
particles less than 0.15 mm shall be not more than 5%; meanwhile it shall
not contain grass roots, leaves or other debris.
2 The thickness of the sand-less concrete slab shall be selected according
to the specific drainage facilities, which should be 10 cm ~ 20 cm. When
the soil of the pit wall is cohesive soil, silt or fine sand, it shall add a
medium coarse sand or geotextile anti-filtration layer which has a
thickness of 10 cm ~ 15 cm on the outside of the slab.
3 Non-woven geotextiles that are resistant to corrosion and aging shall be
used for the geotextiles; meanwhile it shall meet the relevant provisions
of clause 5.7 of this code.
13.3.10 Filling materials for blind drains and seepage wells should be screened
and washed pebbles, macadams, gravel, coarse sand, rubble. A seepage pipe
shall be set in the inclined drainage hole; the seepage pipe shall meet the
requirements of corrosion resistance and aging resistance.
13.3.11 When there is spring water exposed within the range of subgrade, it
shall set blind ditch or concealed pipe to lead the water outside the slope toe of
the embankment or into the side drain of the cutting. The bottom of the blind
ditch shall be no less than 20 cm above the maximum water level of the ditch
at the water outlet; it is prohibited for back irrigation.
of the seepage tunnel shall meet the following requirements:
1 The layout of the tunnel should be strip-shaped or branch-shaped, using
the layout of shortest drainage path.
2 The tunnel should be buried in a stable formation below the main water-
bearing formation to be intercepted. The top of the tunnel in the landslide
area shall be at least 0.5 m below the sliding surface (sliding zone).
3 The cross section type of the tunnel shall be determined according to the
nature of the stratum in which it is located. When the tunnel passes
through strata of different properties, it may use different lining sections
and set settlement joints at the boundaries.
4 Seepage holes are reserved in the top arch of the tunnel and in the water
inlet part of the side wall. An anti-filtration layer corresponding to the size
of the seepage holes and the properties of the location of the tunnel shall
be provided on the periphery.
5 The location of the tunnel entrance should be selected according to the
local terrain, geological conditions and conditions that facilitate rapid
drainage. The excavation of the tunnel entrance should not be too deep.
6 The tunnel entrance’s wall shall be designed as a retaining wall. It should
use an inclined gravity retaining wall. The bottom of the water outlet should
be at least 0.5 m above the design flood level of the local natural ditch.
7 The entrance of the tunnel shall take closure measures.
13.3.16 The use of flat borehole drainage, uphill slopes, water outlets shall meet
the following requirements:
1 It can be used in conjunction with vertical seepage well groups.
2 The uphill drainage slope shall be based on the principle of rapid drainage.
It may use an average uphill slope of 10% ~ 15%.
3 The gap between the borehole and the drainage pipe shall be blocked
within a distance of not less than 0.6 m near the water outlet.
13.3.17 The layout, depth and cross section of vertical seepage wells and
seepage pipes shall meet the following requirements:
1 The layout and spacing of the seepage wells or groups of seepage pipes
shall be determined according to the distribution of aquifers and the nature
of the seepage, the radius of influence of the wells or pipes, the use
requirements.
and tests, to find out the types, characteristics, causes and hazards of defects
of the existing subgrade, analyze the impact of the newly-built project onto the
existing project and its operation.
14.1.2 For the reconstruction of the existing single line or in the section where
double line detours, the subgrade shall be designed in accordance with the
criteria for newly built project. Meanwhile, it shall pay attention to the connection
and transition between the newly built detour section and the section with
exiting subgrade.
14.1.3 The subgrade design for reconstruction of existing line and the addition
of second line shall meet the following requirements:
1 The filler of various widened parts of the subgrade shall be not lower than
the filler of the existing subgrade.
2 It shall guarantee the smooth drainage of existing subgrade.
3 It shall make full use of the existing subgrade and its structures. Existing
subgrade and structures that support, protect, and drain water that limit
the increase in operating speed and do not meet the requirements of
design standards shall be reinforced or completely rebuilt in accordance
with the engineering conditions.
4 When the damage of the subgrade of existing line severely affects the
operation or endangers the subgrade stability of the newly built second
line, it shall be treated in accordance with the principle of thorough
remediation without leaving aftermath.
5 Weak soil ground, high fill and subgrade section which is prone to slope
deformation, it shall analyze the widened subgrade and its upper load onto
the stability or settlement deformation of the existing subgrade; take
necessary measures to reinforcing the subgrade and the existing
subgrade slope; meanwhile perform necessary deformation observation.
6 When excavating near the existing line, excavation shall be carried out in
segments by troughing; meanwhile it shall take necessary protective
measures for temporary excavation.
14.1.4 The subgrade design of the reconstruction of existing line and the newly-
built second line shall take measures to reduce the interference of construction
on the operation, to ensure driving safety and construction safety.
14.1.5 For the subgrade section wherein existing line is reconstructed or the
second line is added which may exceed boundary, impact the operation safety
of existing line, seriously limit the driving speed and the construction period
control, it should take such temporary measures as building temporary line
requirements:
1 The width of the formation surface of the rebuilt railway shall be determined
through calculation in combination with the width of the existing formation
surface, the requirements for the layout of various equipment on the
subgrade shoulder, the requirements for operation and maintenance. It
shall not be less than the width of the existing formation surface.
2 When the elevation of the existing formation surface is unchanged, the
width of the subgrade shoulder shall not be less than the width of the
existing shoulder and comply with the requirements of clause 3.3 of this
code. That for the embankment of the grade I railway in difficult section
shall be not less than 0.6 m. That for the cutting of the grade I railway and
the grade II railway shall be not less than 0.4 m.
14.2.6 The widening of the subgrade of the existing line shall meet the following
requirements:
1 When the elevation of the existing formation surface is unchanged but only
the subgrade is widened, it shall make a 4% lateral drainage slope from
the slope toe of the ballast bed of the existing line outwards;
2 The slope form and slope rate of the widened embankment comply with
the provisions of clause 7.4 of this code.
3 The width of the top of the widening part should not be less than 1.0 m; the
bottom should not be less than the value of the top widening part. When
the widening fill is difficult to implement, it may use the mortar rubber or
cast-in-situ concrete shoulder protection wall to widen the subgrade
shoulder. The height of the shoulder protection wall should not be more
than 1.5 m.
4 When widening the embankment, it shall cut a step with a width of not less
than 1 m along the slope surface of the existing embankment, then
reinforce and compact in layers.
5 The filler of the widened embankment shall meet the standards for newly-
built railways.
6 In areas where it is not appropriate to widen the cutting, it shall take such
measures as setting slope toe support, changing the form of side drain,
reducing side drain’s platforms, installing side drain’s covers to widen the
subgrade. The width of the side drain’s platform should not be less than 1
m.
14.2.7 The pavement raising and slope adjustment of the subgrade of existing
line shall meet the following requirements:
5 In sections where the slope damage of the existing cutting has stabilized
after years of remediation, comprehensive surveys, testing, safety and
stability assessments shall be conducted during reconstruction, to
determine treatment measures. It should minimize the demolition works;
it should not interfere with the original side slope.
6 Embankment slope damage shall be treated by corresponding side slope
grouting, anchoring, retaining, drainage reinforcement, slope surface
protection measures based on the existed problems of the subgrade filler
and compaction, drainage conditions of subgrade slope, deformation of
existing slope surface, reinforcing protection equipment.
14.2.9 In case of earthwork removal due to cutting expansion at the existing
rock cutting, it shall, according to the conditions of the existing lines, earthwork
removal width, height of cutting’s side slope, hardness of rock, development
and weathering degree of joints and cracks, bedding, etc., use the closing-line
key-point construction; take such measures as mechanical excavation, smooth
blasting, static blasting, pre-split blasting; take such temporary blasting
protection measures for slope as blasting cushion and pipe shed; protect such
equipment as the overhead contact net, communication signal line as well as
other cable and track facilities of the existing line, to guarantee the operational
safety of the existing line.
14.3 Addition of subgrade for a second line
14.3.1 For the addition of the subgrade of a second line, it shall consider the
mutual impact with the subgrade of the existing line; carry out overall planning;
take the transitional measures such as constructing temporary line and
maintaining temporary operation if necessary. Especially in the areas of loose
and soft soil, soft soil, collapsible loess, it shall fully consider the impact of the
additional second line on the settlement and deformation of the subgrade of the
existing line; take necessary reinforcing protection and deformation monitoring
measures.
14.3.2 The elevation of subgrade shoulder, the width of the formation surface,
the slope rate of the newly added second line shall with the relevant provisions
of this code.
14.3.3 When the subgrade shoulder of the newly added second line which is
parallel to the original line has different height from the exiting s......
Related standard: TB 10006-2016    TB 10012-2019
Related PDF sample: TB 10035-2018    TB 10106-2010