TB 10035-2018 PDF in English
TB 10035-2018 (TB10035-2018) PDF English
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Code for Design on Special Railway Earth Structure
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TB 10035-2018: PDF in English TB 10035-2018
INDUSTRY STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
UDC
P TB 10035-2018
J 158-2018
Code for Design on Special Railway Earth Structure
ISSUED ON: OCTOBER 12, 2018
IMPLEMENTED ON: JANUARY 1, 2019
Issued by: National Railway Administration of the PRC
Table of Contents
1 General ... 11
2 Terms and symbols ... 13
2.1 Terms ... 13
2.2 Symbols ... 17
3 Subgrade of soft soil section ... 19
3.1 General provisions ... 19
3.2 Stability analysis and settlement calculation ... 22
3.3 Embankment ... 31
3.4 Cutting ... 33
3.5 Foundation treatment ... 35
4 Earth structure of expansive rock and soil ... 39
4.1 General provisions ... 39
4.2 Embankment ... 40
4.3 Cutting ... 41
4.4 Slope protection and reinforcement ... 43
4.5 Foundation treatment ... 45
4.6 Subgrade waterproof and drainage ... 46
5 Loess subgrade ... 48
5.1 General provisions ... 48
5.2 Embankment ... 49
5.3 Cutting ... 50
5.4 Slope protection and reinforcement ... 52
5.5 Foundation treatment ... 52
5.6 Subgrade waterproof and drainage ... 56
5.7 Sinkhole treatment ... 57
6 Saline soil and salt rock subgrade ... 58
6.1 General provisions ... 58
6.2 Embankment ... 58
6.3 Side slope protection ... 61
6.4 Foundation treatment ... 62
6.5 Subgrade waterproof and drainage ... 63
7 Earth structure of permafrost area ... 65
7.1 General provisions ... 65
7.2 Embankment ... 66
7.3 Cutting ... 69
7.4 Slope protection and retaining ... 70
7.5 Transition section ... 71
7.6 Subgrade waterproof and drainage ... 73
7.7 Borrow pits and spoil banks ... 75
8 Earth structure of seasonal frozen soil area ... 76
8.1 General provisions ... 76
8.2 Embankment ... 76
8.3 Cutting ... 79
8.4 Subgrade retaining and protection ... 80
8.5 Subgrade waterproof and drainage ... 82
9 Earth structure of granite weathered residual soil ... 83
9.1 General provisions ... 83
9.2 Embankment ... 84
9.3 Cutting ... 85
9.4 Slope protection and reinforcement ... 86
9.5 Subgrade waterproof and drainage ... 88
10 Subgrade of filling site ... 90
10.1 General provisions ... 90
10.2 Embankment ... 91
10.3 Cutting ... 91
10.4 Foundation treatment ... 94
10.5 Subgrade waterproof and drainage ... 96
11 Subgrade of landslide section ... 97
11.1 General provisions ... 97
11.2 Landslide stability analysis and sliding force calculation ... 97
11.3 Prevention and control engineering ... 99
11.4 Engineering landslide prevention... 102
11.5 Landslide monitoring ... 103
12 Subgrade of dangerous rock, rockfall, collapse and talus section ... 105
12.1 General provisions ... 105
12.2 Subgrade of dangerous rock, rockfall, and collapse section ... 105
12.3 Subgrade of talus section ... 106
13 Subgrade of karst and artificial pothole section ... 108
13.1 General provisions ... 108
13.2 Subgrade of karst section ... 109
13.3 Subgrade of artificial pothole section ... 112
14 Subgrade in area of sand blown by the wind ... 115
14.1 General provisions ... 115
14.2 Embankment ... 116
14.3 Cutting ... 117
14.4 Subgrade slope protection ... 117
14.5 Plane protection of sand blown by the wind ... 118
14.6 Windproof measures in windy areas ... 122
15 Subgrade of snow-damaged area ... 124
15.1 General provisions ... 124
15.2 Subgrade section form ... 125
15.3 Protective measures ... 125
16 Submerged subgrade ... 128
16.1 General provisions ... 128
16.2 Subgrade of pond and waterlogged sections ... 131
16.3 River beach and riverside subgrade ... 131
16.4 Coastal subgrade ... 132
16.5 Subgrade of reservoir section ... 135
Appendix A Classification and relevant characteristics of special rock and soil
... 138
Appendix B Calculation of foundation settlement and thickness of insulation
layer in permafrost ... 153
Appendix C Calculation of load of sand blown by the wind ... 165
Appendix D Calculation method of buried depth of sand barrier column
foundation ... 166
Descriptions for word use of this Code ... 169
2 Terms and symbols
2.1 Terms
2.1.1 Earth structure of special area
The general term for earth structure of special rock and soil area and earth
structure of special condition.
2.1.2 Earth structure of special rock and soil area
The earth structure located in special rock and soil sections such as soft soil,
expansive rock and soil, loess, saline soil.
2.1.3 Earth structure of special condition
The earth structure located in bad geological sections, as well as the earth
structure strongly affected by natural factors such as water and climate.
2.1.4 Soft soil
The cohesive soil deposited in still water or slow flowing water environment and
characterized by large water content (w≥wL), large void ratio (e≥1.0), high
compressibility (a0.1~0.2≥0.5 MPa-1), and low strength (Ps< 0.8 MPa).
2.1.5 Loose-soft soil
The strata such as cohesive soil, silt, and sandy soil that cannot reach the soft
soil index in the earth structure engineering, which are characterized by larger
water content or void ratio, higher compressibility (a0.1~0.2≥0.25 MPa-1), and
lower strength or bearing capacity (σ0≤150 kPa).
2.1.6 Expansive soil
The cohesive soil in which clay minerals are mainly composed of hydrophilic
minerals and which has the characteristics of water swelling, softening,
disintegration, and rapid shrinkage and cracking from water loss, and can
produce reciprocating deformation.
2.1.7 Loess
The soil, formed under arid and semi-arid climatic conditions since the
Quaternary, whose particles are mainly composed of powder particles and
contain calcium carbonate and a small amount of soluble salts, and which has
the engineering geological characteristics such as macro-void and vertical
joints, poor water resistance, easy disintegration and subsurface erosion, and
3 Subgrade of soft soil section
3.1 General provisions
3.1.1 Soft soil can be classified according to its physical and mechanical
properties in accordance with Appendix A.0.1 of this Code. Subgrade shall
consider its following engineering characteristics and effects:
1 Soft soil has the characteristics of low natural strength and high
compressibility, resulting in poor subgrade stability and large foundation
settlement deformation.
2 Soft soil has the characteristics of low permeability and slow consolidation.
The consolidation of the foundation lasts a long time. The consolidation
time and its settlement amount vary greatly with the consolidation
conditions, which affects the post-construction settlement of subgrade and
construction period control of deep thick soft soil foundation.
3 When the high-sensitivity soft soil has thixotropy, construction vibration and
disturbance will cause the strength of the soft soil to be seriously reduced,
affecting the stability, deformation, or safe use of existing projects around
the construction period.
4 High-plasticity or over-consolidated soft soil has rheological properties.
Under undrained shear conditions, it will lead to more long-term strength
reduction and continuous increase of deformation of soft soil, affecting
long-term stability, deformation control, and surrounding environment
safety of the subgrade.
3.1.2 Loose-soft soil can be classified according to its physical and mechanical
properties in accordance with Appendix A.0.1 of this Code. Subgrade stability,
post-construction settlement control shall consider its engineering
characteristics such as low strength, high compressibility or easy liquefaction
and influences.
3.1.3 The subgrade of the soft soil section should be in the form of embankment.
Its height should not be less than the thickness of the foundation bed. The
choice of subgrade location shall meet the following requirements:
1 It is advisable to choose a section with narrow area and thin thickness of
soft soil.
2 In low hilly areas, closed or semi-closed depressions should be avoided.
3 In the valley between mountains, it is advisable to avoid being located in
φi - The internal friction angle of the bottom of the ith soil strip (°);
Ei-1 - Sliding force of the i-1-th soil strip transferring the ith soil strip (kN);
φi-1 - Transfer coefficient of remaining sliding force.
5 When the embankment base is reinforced with geosynthetics, the tensile
force it bears shall be calculated as the slide-resisting force.
3.2.3 When using composite foundation treatment, the overall sliding stability
analysis of the embankment and the foundation shall be based on geological
conditions, composite foundation type, and possible failure modes; adopt
appropriate methods; and, shall meet the following requirements:
1 The composite foundation of discrete material piles and of reinforced soil
piles in general sections can, in accordance with subclause 3.2.2 of this
Code, be checked and computed by the arc method or the unbalanced
thrust transfer coefficient method. According to the stratum and range of
the slip circle cutting, the composite foundation shall respectively adopt the
shear strength index of the composite or natural foundation soil. When
using discrete material piles, the drainage consolidation effect on the
foundation can be considered; the shear resistance of the soil between the
piles, increased by consolidation under the load of the embankment, can
be considered.
2 Rigid pile composite foundation, and reinforced soil pile composite
foundation in sections with complex conditions such as high embankment,
soft soil characteristics, or environmental sensitivity shall be analyzed
according to the possible failure modes of the composite foundation, using
appropriate methods or combining numerical methods. When the arc
method is used for analysis, the influencing factors such as soft soil
characteristics and pile-soil modulus ratio shall be fully considered; the
form and effect of pile-soil load sharing shall be reasonably determined;
and, the sliding surface force shall be calculated. If necessary, the
horizontal bearing capacity of the pile should be calculated, to check the
lateral stability of the pile.
3.2.4 When using rigid pile foundation treatment, the stability of the
embankment shall be analyzed according to the rigid pile foundation of the pile-
supported embankment; and, shall meet the following requirements:
1 The vertical bearing capacity of the rigid pile foundation of the pile-
supported embankment shall meet the vertical load requirements of the
embankment above the pile top. The vertical allowable bearing capacity of
a single pile shall be determined according to the following formula:
3.3.4 The boundary between embankment and other structures, the section
with large strata change, and the junction of different foundation treatment
measures shall adopt gradual transition foundation treatment measures, to
reduce uneven settlement.
3.3.5 Embankment design using drainage consolidation method for foundation
treatment shall comply with the following provisions:
1 Through the stability check analysis during the construction period, the
construction instructional design shall be conducted on the filling
parameters, such as the critical height of rapid filling, embankment filling
loading form, stepped height and loading time (including precompression).
The critical height of filling can also be determined by empirical formula
calculation.
2 When constructing a new embankment and reserving the second line, it is
advisable to design a double-line embankment at a time.
3 In accordance with the construction organization arrangement and the
construction period requirements, the construction shall be arranged in
advance. After the embankment filling construction is completed, it shall
be placed for a period of time. If necessary, the load can be increased for
precompression.
3.3.6 The subgrade of ballasted track railway with design speed of 200 km/h
and below shall be reserved for post-construction settlement widening of the
subgrade. The widening value on each side shall be calculated and determined
according to the post-construction settlement and the slope ratio of the track
bed slope.
3.3.7 Embankment shoulders should be made of dry masonry stones or precast
concrete blocks. When using mortar masonry stones or precast concrete blocks
or cast-in-place concrete, it shall strengthen measures to prevent longitudinal
uneven settlement and ensure smooth transverse drainage of foundation bed.
When the post-construction settlement is large, the road camber or its
transverse drainage slope should be enlarged. If necessary, on the top or
bottom surface of the foundation bed surface layer, an impermeable layer may
be set.
3.3.8 When the subgrade base on the subgrade on the soft soil foundation in
the earthquake area adopts sand and gravel cushion, the cushion material shall
be gravel (pebble) or coarse gravel (pebble). Fine sand must not be used. It is
not suitable to use medium and coarse sand for the embankment base cushion
in earthquake areas of 9 degrees and above.
3.3.9 Based on conditions such as embankment filler properties, slope height,
3.4.3 According to the nature of the weak soil, thickness, bottom lateral slope,
hydrogeological conditions, and types of reinforcement measures, etc., using
the circular sliding method or the unbalanced thrust method, the cutting slope
shall be subjected to stability analysis according to the relevant provisions of
section 3.2 of this Code. Combined with factors such as slope height,
environmental conditions, construction methods, it shall comprehensively
determine the slope form, slope ratio, and the load size and distribution
characteristics of rock-soil pressure or sliding force acting on the retaining
structure.
3.4.4 Slope reinforcement protection and retaining measures shall be
determined according to the engineering geological and hydrogeological
conditions of the slope, the height of the slope, the external environmental
conditions and other factors, combined with the stability analysis of the slope,
and according to the following provisions:
1 When the weak layer of the slope is thick, composite foundation treatment
measures such as cement-soil mixing piles and rotary jet piles can be used,
to reinforce the slope. The slope surface can be protected by ecological
bag flexible protection, mortar masonry stone or skeleton slope protection.
2 When the slope is not high, the slope toe should be reinforced by a low
retaining wall or a rubble stack. When the slope is high or the weak layer
is thick, the slope toe should be retained using reinforced concrete row
piles, L-shaped retaining wall, U-shaped groove structure, or
comprehensive measures, etc.
3 According to the safety and stability needs of the construction excavation
process, combined with the construction conditions, necessary water stop,
precipitation, and temporary reinforcement protection measures may be
taken.
3.4.5 The cutting shall be set with side ditch platform. The width should not be
less than 2.0 m. When the height of the cutting slope is large, or for the interface
between the soft and hard layers, the slope platform should be set. The width
should not be less than 3.0 m.
3.4.6 The cutting slope shall, in accordance with factors such as topography,
hydrological characteristics, and surrounding environment, take reasonable
waterproof and drainage measures. If necessary, support seepage ditches or
upward inclined drainage holes may be provided, to strengthen the removal of
groundwater in the slope.
3.4.7 When the back of the retaining structure wall adopts sand-pebble inverted
layer, its thickness must not be less than 0.5 m.
3.5.9 When adopting rigid pile foundation treatment measures, the following
requirements shall be met:
1 It shall comprehensively consider factors such as the embankment height,
the nature of foundation soil, the topography, and the environmental
conditions; and, combine the suitability of the pile board, pile raft, and pile-
net structure, to reasonably determine the appropriate structural form.
2 For low embankment, slope or non-crusted silt, muddy soil foundation, and
when settlement deformation is strictly controlled, pile board or pile raft
structure should be adopted. When using a pile-net structure, appropriate
treatment measures shall be taken to ensure lateral stability.
3 Driven and pressed prefabricated reinforced concrete piles should be used.
When the foundation soil is sandwiched with stones, boulders or is uneven
in hardness, reinforced concrete cast-in-situ bored piles may be used.
4 When the top of rigid pile is above the ground and buried in the filling
embankment, the filling embankment under the pile top shall be stable.
After its settlement is basically completed, a rigid pile foundation shall be
set.
3.5.10 Grouting, micro piles, etc. can be used for soft soil and loose-soft soil
foundation treatment under special conditions or reinforcement of existing
subgrade foundation. The design shall comply with the relevant provisions of
the current "Technical code for improvement of soil and foundation of existing
buildings" JGJ 123.
3.5.11 When there is a soft layer beneath the composite foundation and the
bearing layer at the bottom of the rigid pile, the bearing capacity of the
foundation shall be verified; and, shall meet the corresponding requirements.
3.5.12 For composite foundations and rigid pile pile-net (pile raft) structures, a
reinforced cushion of sand gravel or rubble with a thickness of not less than 0.4
m shall be placed on the top of the pile (cap). The reinforcement should be a
geogrid. The ultimate tensile strength shall not be less than 50 kN/m.
3.5.13 For sections reinforced using composite foundation or rigid piles, before
construction, according to the design, technical test piles shall be carried out,
to confirm that the design and construction related parameters are technically
feasible.
3.5.14 The upper subgrade project can be constructed only after the foundation
reinforcement quality test is passed.
top of the cutting should not be less than 5 m.
4.6.2 For medium and strong expansive rock and soil cutting slopes, slope
seepage ditches or upward inclined drainage holes should be set, to strengthen
the drainage of groundwater.
4.6.3 The sealing and water isolation treatment OF the top surface of the bottom
layer of foundation bed or the bottom surface of the replacement SHALL be
strengthened. The embankment and the cutting foundation bed with developed
groundwater should adopt waterproof materials, which can be laid continuously
on site. When geosynthetics are used for sealing and water isolation, they
should not be overlapped along the cross-sectional direction; and, along the
line direction, the overlapping shall be reduced. For the cutting foundation bed
with developed groundwater, it shall take measures for prevention and drainage
of groundwater, such as lowering or deepening the side ditch, setting necessary
vertical and horizontal drainage seepage ditches and seepage pipes, etc.
4.6.4 For the cutting where groundwater is developed, underground drainage
measures such as upward inclined drainage holes, slope seepage ditches, and
longitudinal blind ditches should be adopted.
4.6.5 The slope toe of embankment shall be provided with measures such as
drainage ditches, elevated berms, or retaining walls, to prevent water
immersion.
4.6.6 The basement of the low embankment and low-lying section shall be filled
with permeable soil filler. The bottom is provided with an anti-seepage sealing
layer. If necessary, measures such as vertical and horizontal drainage seepage
ditches and seepage pipes can be added, to prevent and eliminate surface
water accumulation.
4.6.7 The gutters, intercepting ditches, side ditches, drainage ditches, and
platforms shall be reinforced by anti-scouring and anti-seepage measures. For
the side ditches of cuttings, it shall strengthen the treatment measures to
prevent accumulation and seepage. The structural design of the side ditch shall
consider the influence of horizontal expansion force.
Note: 1 The listed slope ratio refers to the comprehensive slope ratio of a single soil layer.
If there are multiple soil layers, it can be determined by comprehensive
consideration, according to the differences in the nature of the soil layers at
different times and genesis and their proportion in the slope.
2 For the graded slope ratio of stepped slopes, the same slope ratio value can be
taken for homogeneous soil layers; different slope ratio values can be selected for
heterogeneous soil layers.
3 When the ground lateral slope of the top of the cutting is less than 20°, its influence
on slope ratio is not considered. When it is 20°~35°, the height of Q4 loess slope
is greater than 12 m; the height of ଷୟ୪,୮୪ loess slope is greater than 15 m. The
slope ratio can be slowed down by one level (calculated as 0.25). When greater
than 35°, it shall be determined through stability checking.
4 For Q2 and Q1 loess, it shall consider the influence of structural fissures on slope
stability.
5.3.5 The stability checking of the cutting slope should adopt the arc method.
The stability safety factor shall not be less than 1.25.
5.4 Slope protection and reinforcement
5.4.1 For slope protection and reinforcement, based on conditions such as soil
quality, precipitation, slope height, slope ratio, it shall take reinforcement
measures to prevent spalling, erosion, and deformation.
5.4.2 When the embankment height is greater than 3 m, the geogrid should be
laid horizontally in layers on both sides of the slope. The vertical spacing shall
not be greater than 0.6 m. Embankment slopes can be protected by geonet
cushion, hollow bricks, and water intercepting skeleton slope protection, etc.
5.4.3 For the cutting slope, it is advisable to adopt hollow brick, water
intercepting skeleton slope protection, anchor frame beam slope protection,
hole-window retaining wall, slope toe wall or comprehensive measures for
protection and reinforcement and waterproof and drainage treatment.
5.5 Foundation treatment
5.5.1 For subgrades in loess areas, according to settlement calculations or
stability checks, appropriate foundation treatment measures shall be taken, to
ensure that the subgrade is stable and the post-construction settlement is
controlled.
5.5.2 For non-collapsible loess foundations, treatment measures shall be taken
in accordance with the current "Code for design of railway earth structure" TB
to the top surface of the non-collapsible loess layer, take 1.0 for I and II
regions of non-self-weight collapsible loess site; and, for the remaining
areas, take the β0 value of the area where the project is located;
αi - The coefficient of submergence probability of foundations at different
depths, which is based on regional experience. When there is no regional
experience, within the depth of 0~10 m below the basement, take 1.0.
Within a depth of 10 m~20 m below the basement, take 0.9. Within a depth
of 20 m~25 m below the basement, take 0.6. Below 25 m below the
basement, take 0.5. If the groundwater is likely to rise into the collapsible
soil layer, or the section where the influence of lateral flooding is inevitable,
take 1.0.
2 The calculated depth of collapse ΔS shall be calculated from the basement
(the excavation section shall be from the road shoulder), and at the non-
self-weight collapsible loess site, accumulate to 10 m below the basement
and the depth of the foundation compression layer; at the self-weight
collapsible loess site, accumulate to the top surface of the non-collapsible
loess layer. The soil layer with collapsibility coefficient (δs) less than 0.015
is not accumulated.
5.5.5 At non-self-weight collapsible loess sites, when the sum of the additional
stress and the saturated self-weight pressure of the overlying soil is greater
than the initial collapse pressure of each soil layer, the collapse is calculated.
5.5.6 The post-construction settlement of subgrade of collapsible loess
foundation shall be determined according to the following provisions:
1 When adopting treatment measures that penetrate the collapsible
foundation to prevent the influence of collapsible deformation or
completely eliminate the collapsibility of the foundation, the post-
construction settlement shall be determined according to the calculation of
compressive deformation settlement of the foundation after treatment.
2 When the treatment measures to partially eliminate the collapsibility of the
foundation are adopted, the post-construction settlement shall be
calculated and determined according to the remnant collapse of the treated
foundation and the settlement of the foundation compressive deformation.
3 The calculation of compressive deformation settlement of the foundation
shall comply with the relevant provisions of the current national standard
"Standard for building construction in collapsible loess regions" GB 50025.
5.5.7 Collapsible loess foundation shall be analyzed according to factors such
as post-construction settlement requirements, foundation characteristics,
treatment depth, construction equipment, material sources, and impact on the
6 Saline soil and salt rock subgrade
6.1 General provisions
6.1.1 Saline soil can be classified based on the chemical composition and
content of salt and the degree of collapse and salt expansion according to
Appendix A.0.4 of this Code. The subgrade in the saline soil area shall consider
the influence of the following characteristics:
1 After the soluble salt in the saline soil is soaked and dissolved in water, the
soil structure is loosened and collapse occurs.
2 Saline soil is swellable and hygroscopic. The soil is prone to salt expansion
or softening.
3 Saline soil is highly corrosive.
6.1.2 According to the main mineral composition, salt rock can be divided into
gypsum rock, potash rock, and mirabilite rock. The subgrade in salt rock area
shall consider the influence of the following characteristics:
1 The salt rock in the dry state has high strength and low compressibility;
and, after immersion in water, is prone to latent erosion and collapse.
2 When temperature and moisture change, salt rock will swell.
3 Salt rock is highly corrosive.
6.1.3 The location of the subgrade in the saline soil area shall be selected in
the section with high terrain, deep groundwater level, smooth drainage, low salt
content in the soil, low salinity of groundwater, and small distribution range of
saline soil; and, it shall pass as an embankment.
6.1.4 The subgrade in the salt rock area shall avoid the section with abundant
surface water and groundwater and concentrated development of salting-in. It
shall......
......
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