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TB 10025-2019

Chinese Standard: 'TB 10025-2019'
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BASIC DATA
Standard ID TB 10025-2019 (TB10025-2019)
Description (Translated English) Code for design of retaining structures of railway earthworks
Sector / Industry Railway & Train Industry Standard
Word Count Estimation 150,168
Date of Issue 2019-07-31
Date of Implementation 2019-12-01
Older Standard (superseded by this standard) TB 10025-2006
Regulation (derived from) Natural Resources Department Announcement No. 7 of 2019

TB 10025-2019
UDC
INDUSTRY STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
P TB 10025-2019
J 127-2019
Code for design of retaining structures of railway
earthworks
铁路路基支挡结构设计规范
ISSUED ON: JULY 31, 2019
IMPLEMENTED ON: DECEMBER 01, 2019
Issued by: State Railway Administration
Table of Contents
Foreword ... 7 
1 General ... 10 
2 Terms and symbols ... 10 
2.1 Terms ... 10 
2.2 Symbol ... 13 
3 Basic provisions ... 15 
3.1 General provisions ... 15 
3.2 Design requirements ... 17 
3.3 Selection of retaining structure form ... 19 
4 Design load ... 20 
4.1 General provisions ... 20 
4.2 Main force ... 21 
4.3 Additional force ... 24 
4.4 Special force... 25 
5 Materials and properties ... 25 
5.1 General provisions ... 25 
5.2 Concrete, mortar rubble and cement mortar ... 26 
5.3 Steel ... 27 
5.4 Geosynthetics ... 27 
5.5 Filler and geotechnical ... 28 
6 Gravity retaining wall ... 29 
6.1 General provisions ... 29 
6.2 Design and calculation ... 30 
6.3 Construction requirements ... 38 
7 Cantilever and counterfort retaining wall ... 40 
7.1 General provisions ... 40 
7.2 Design and calculation ... 41 
7.3 Construction requirements ... 47 
8 Groove retaining wall ... 48 
8.1 General provisions ... 48 
8.2 Design and calculation ... 49 
8.3 Construction requirements ... 55 
9 Reinforced soil wall ... 56 
9.1 General provisions ... 56 
9.2 Design and calculation ... 57 
9.3 Construction requirements ... 62 
10 Soil nailing retaining wall ... 64 
10.1 General provisions ... 64 
10.2 Design and calculation ... 64 
10.3 Construction requirements ... 69 
11 Anchored wall ... 70 
11.1 General provisions ... 70 
11.2 Design and calculation ... 72 
11.3 Construction requirements ... 77 
12 Prestressed anchored cable ... 79 
12.1 General provisions ... 79 
12.2 Design and calculation ... 80 
12.3 Construction requirements ... 84 
13 Slide-resistant pile ... 87 
13.1 General provisions ... 87 
13.2 Design and calculation ... 89 
13.3 Construction requirements ... 94 
14 Pile-wall structure ... 95 
14.1 General provisions ... 95 
14.2 Design and calculation ... 97 
14.3 Construction requirements ... 100 
15 Gravity retaining wall on pile foundation and beam ... 101 
15.1 General provisions ... 101 
15.2 Design and calculation ... 101 
15.3 Construction requirements ... 104 
16 Composite pile structure ... 105 
16.1 General provisions ... 105 
16.2 Design and calculation ... 106 
16.3 Construction requirements ... 109 
17 Other structures ... 110 
17.1 Gravity retaining wall with short relieving slab ... 110 
17.2 Anchor slab wall ... 112 
Appendix A Common types and applicable conditions of retaining structure 117 
Appendix B Track and train loads above the formation surface ... 118 
Appendix C Material performance parameters of structural members ... 121 
Appendix D Basic bearing capacity of foundation ... 124 
Appendix E Resistance design of reinforced concrete members ... 130 
Appendix F Calculation of maximum crack width of rectangular pile reinforced
concrete flexural members ... 136 
Appendix G Reference values of relevant parameters for design of groove
retaining wall ... 138 
Appendix H Reference values of anti-pullout design parameters for anchor rods
and cables ... 139 
Appendix J Anchor rod (cable) test ... 140 
Appendix K Selection of prestressed anchor cable and design parameters 146 
Appendix L Reference value of anchor pile’s foundation factor ... 149 
Explanation of wording in this code ... 152 
Code for design of retaining structures of railway
earthworks
1 General
1.0.1 This standard is formulated to unify the design technical criteria of the
retaining structures of railway earthworks, so that the design of the retaining
structure meets the requirements of safety, reliability, advanced technology,
reasonable economy and green environmental protection.
1.0.2 This code is applicable to the design of retaining structure of railway
earthworks and related projects.
1.0.3 The retaining structure of the railway earthwork shall be designed
according to track and train loads, engineering geology, hydrogeology,
environmental conditions.
1.0.4 The retaining structure design shall meet the requirements of safety,
applicability, durability.
1.0.5 The retaining structure for earthwork be well designed for connection with
bridge abutments, tunnel openings, catenary pillars, sound barrier foundations
and other projects.
1.0.6 Retaining structure’s design shall promote the use of safe and reliable
new technologies, new structures, new materials and new processes.
1.0.7 In addition to meeting this code, the design of the retaining structure shall
also comply with the relevant national standards.
2 Terms and symbols
2.1 Terms
2.1.1 Retaining structure
Structures which are used to support and strengthen the rock-soil body and
maintain its stability.
2.1.2 Gravity retaining wall
A retaining structure that resists the earth pressure and prevents the soil from
slumping by the weight of the wall. When there is a counterfort platform on
the back of the wall, it is called a counterfort retaining wall.
2.1.3 Cantilever retaining wall
A retaining structure which is composed of standing arm plate, a toe plate, a
heel plate, etc., which resists the earth pressure by the gravity of the wall body
and the soil body above the heel plate.
2.1.4 Counterfort retaining wall
A retaining structure which is composed of standing arm plate, a toe plate, a
heel plate, a buttress, etc., which resists the earth pressure by the gravity of the
wall body and the soil body above the heel plate.
2.1.5 Groove retaining wall
A retaining structure of U-shaped which is composed of side walls and a
baseplate, that withstands earth pressure, water pressure, buoyancy,
meanwhile prevents surface water or groundwater from infiltrating.
2.1.6 Reinforced soil wall
A retaining structure which is composed of wall system, reinforcement and filling
soil, which uses reinforcement and filling as a whole to resist the earth pressure.
2.1.7 Soil nailing retaining wall
A retaining structure which is composed of soil nails and wall panels, which
uses soil nails and the reinforced rock-soil together to form a composite
structure to resist the earth pressure.
2.1.8 Anchored wall
A retaining structure which is composed of a wall system and an anchor rod,
which maintains stability and resists earth pressure by the tension of the anchor
rod.
2.1.9 Prestressed anchored cables
Retaining structure by applying tension to the anchor cable to strengthen the
rock-soil body to reach a stable state or improve the internal stress of the
structure.
2.1.10 Slide-resistant pile
Laterally stressed piles resisting the lateral earth pressure above the anchoring
section or the sliding force of the landslide by the lateral foundation resistance
2.1.20 Total safety factor
The factor used in engineering structure design to reflect the overall safety of
the structure.
2.1.21 Total safety factor method
The method of engineering structure design by the use of the total safety factor.
2.1.22 Partial factor
In order to ensure that the design structure or component has the specified
reliability, the partial safety factor used in the design expression of the limit state
method, which is divided into the action partial factor and the resistance partial
factor.
2.1.23 Partial factor method of limit states
A method of structural design using partial factors.
2.1.24 Action
The force exerted on the retaining structure (direct action, also called load), or
the cause of the effect of external deformation or constrained deformation of
the structure (indirect action).
2.1.25 Resistance
The ability of a structure or component to withstand actions.
2.1.26 Bearing capacity of subgrade
Under the condition of ensuring the stability of the foundation, the bearing
capacity of foundation which does not make the structure produce beyond the
allowable settlement or deformation.
2.2 Symbol
P0 - Track load;
Q - Train load;
q - Unit load;
λ0 - Static earth pressure factor;
λa - Active earth pressure factor;
embankment’s stability is affected by water erosion.
6 In sections where it requires saving land, occupying less farm-land or
protecting important existing buildings.
7 In sections where it requires protecting the ecological environment.
8 In sections where it has needs such as stations and scenic spots.
3.1.2 The section where the retaining structure is set up shall be identified with
engineering geology, hydrogeological conditions, environmental conditions and
physical and mechanical properties of rock-soil.
3.1.3 In the curved section, the plane layout of the shoulder’s retaining wall shall
meet the requirement of widening the formation surface in the curved section.
3.1.4 When installing catenary pillars and sound barrier foundations on the
structure, it shall consider the influence of its load on the retaining structure and
ensure the integrity and stability of the formation surface as well as the smooth
drainage.
3.1.5 Subgrade’s retaining structures located in soft soil, slopes and other
sections shall be checked for overall stability.
3.1.6 At certain intervals in the longitudinal direction of the retaining structure
and at the junction with other buildings, it shall provide expansion joints. Where
the base stratum changes, it shall provide settlement joints; the expansion joints
can be combined with the settlement joints. The joint width should be 20 mm ~
30 mm. The stuffing material in the joint may be asphalt hemp, asphalt wood
board, glue or rubber strip, etc. The plug depth shall not be less than 0.2 m.
3.1.7 The retaining wall shall be provided with a drain hole from the back of the
wall; the drainage slope shall not be less than 4%.
3.1.8 Reverse filter layer shall be set at the back of the water inlet side wall of
the drainage hole. The reverse filter layer should be made of bagged sand with
gravel (pebble), geosynthetic material, sand-free concrete block or other new
materials. The thickness of the reverse filter layer made of sand-free concrete
block or sand-containing pebble shall not be less than 0.3 m. When the back of
the wall is swelling soil, the thickness of the reverse filter layer shall not be less
than 0.5 m. The top of the reverse filter layer and the lower part of the water
inlet of the lowest row of drain holes shall be provided with a water barrier.
3.1.9 When excavating the foundation pit, it shall take temporary support
measures for the slope with poor stability. The materials for temporary support
may be shaped steel or scrap steel rails. After the pouring of the retaining
structure is completed, the foundation pit shall be backfilled and tamped in time.
4.3.2 The design load of the retaining structure in the frozen soil area shall
consider the frost heaving force acting on the foundation and the back of the
wall. The earth pressure and frost heave force shall be calculated separately
based on the warm season and the cold season. The earth pressure and frost
heave force shall not be superimposed.
4.4 Special force
4.4.1 The calculation of earthquake action shall comply with the provisions of
the current "Code for seismic design of railway engineering" GB 50111. The
static method can be used to calculate the seismic force on the rigid structure
and the fractured prism of the soil.
4.4.2 The earth pressure on the wall back of the retaining structure shall include
the horizontal seismic force. Gravity retaining structure or the non-gravity
retaining structures with large self-weight shall consider the horizontal seismic
forces on the structure.
4.4.3 In the case of flood level, the earth pressure on the wall back of the
retaining structure shall consider of the flood action; but it shall not be
considered at the same time as the seismic force.
4.4.4 The verification of the retaining structure of the embankment section shall
consider the temporary loads such as the transportation & erection equipment
and its load weight. The unit load of the wheel-rail type transportation-erection
load track acting on the formation surface may be calculated according to
formula (4.2.5). The unit load of the erector may be calculated according to
formula (4.2.6), where Q is the axle load of the erector divided by the
longitudinal axis spacing of the erector. The load of the wheel-tire type erector
shall be calculated according to the vehicle model and the beam’s carrying
method.
5 Materials and properties
5.1 General provisions
5.1.1 The concrete, steel bar, geosynthetic material, filler, stone and cement
mortar used in the retaining structure shall be determined according to the
structure type, function, scope of application, application environment, etc.
5.1.2 The physical and mechanical properties of the retaining structure’s
materials shall be determined according to the standards of corresponding test
method. When using the test results of the standard test pieces to determine
the actual performance of the material, it shall also consider the difference
C.0.1 of Appendix C of this code; the elastic modulus in compression and
tension shall be adopted in accordance with clause C.0.2 of Appendix C of this
code.
5.2.4 The retaining structure of cement mortar masonry shall be designed
based on the environment type, structure type and railway grade, construction
and maintenance conditions, etc. according to the requirements of durability
and service life. The strength grade and application scope of masonry mortar
can be determined in accordance with clause C.0.3 of Appendix C of this code.
5.2.5 The strength of the stone material used for the retaining structure shall
not be lower than MU30. The performance of materials such as cement mortar
shall comply with the relevant provisions of the current "Code for design on
subgrade of railway" TB 10001.
5.3 Steel
5.3.1 The steel bars, prestressed steel wires and steel strands used in the
retaining structure shall meet the following requirements:
1 Ordinary steel bars and prestressed steel bars shall be selected in
accordance with the provisions of clause C.0.4 of Appendix C of this code.
2 The strength of ordinary steel bars, pre-stressed steel wires and steel
strands shall be determined based on the model in accordance with
clause C.0.5 of Appendix of this code.
3 The elastic modulus of ordinary steel bars and prestressed steel bars shall
be used in accordance with clause C.0.6 of the Appendix C of this code.
5.3.2 The steel material’s specifications and performances of steel plates,
section steels, bolts, anchors used in the retaining structure shall comply with
the provisions of the current "Technical specification for steel reinforced
concrete composite structures" JGJ 138 and related standards.
5.4 Geosynthetics
5.4.1 The geosynthetics in the retaining structure can be geogrid,
geomembrane, geo-composite and geotechnical special materials. When used
for anti-seepage, reinforcement, reverse filtration, drainage in the retaining
structure, the properties of the geosynthetics adopted shall meet the
corresponding functional design requirements.
5.4.2 The mechanical properties, hydraulic properties, durability and friction
factor of geosynthetics with soil should be determined through tests. When the
4 When the longitudinal slope of the base is greater than 5%, the base shall
be designed in the form of steps.
5 When the retaining wall is controlled by sliding stability, the inclined base
of not more than 0.2:1 can be used in the lateral direction. Retaining walls
in soaking areas should not be set with inclined bases.
6 When the retaining wall is controlled by the eccentricity of the base or the
bearing capacity of the base, the wall toe steps can be set; the angle
between the connecting line of the steps and the vertical line shall not
exceed 45°.
7 Lime soil and other cushions should be set at the bottom of the clay
foundation wall. For special soil foundations such as collapsible loess or
swelling soil, it shall take measures to eliminate collapse or prevent
downward seepage of water.
6.3.2 The structural design of the retaining wall shall meet the following
requirements:
1 The thickness of the cap stone on the top of the retaining wall of the mortar
rubble shoulder shall not be less than 0.4 m; the width shall not be less
than 0.6 m; the width of the cornice shall be 0.1 m.
2 Every 10 m ~15 m along the longitudinal length of the wall, it shall provide
expansion joints or settlement joints, which shall comply with the
provisions of clause 3.1.6 of this code.
3 For the portion of the retaining wall that is above the ground surface, it shall
be provided with drain holes every 2 m ~ 3 m alternatively. Behind the wall
of broken line shape where it is prone to water cumulation, it must provide
drain hole, at a longitudinal spacing preferably of 2 m. The design of drain
hole shall comply with the provisions of clause 3.1.7 of this code.
4 Between the upper part and lower part of counterbalanced retaining wall,
it should use short steel bars for connection.
5 The concrete pouring of the retaining wall shall be carried out continuously;
the wall shall not form horizontal through joints. When one-time pouring is
not possible, it shall take measures to ensure that the strength of the two
pouring locations meets the design requirements.
6 The wall surface of the embankment’s retaining wall in the soaking area
should be smooth and straight, which can be achieved by adjusting the
width of the platform on the top of the wall.
6.3.3 Behind the wall at the inlet side of the drain hole, it shall provide reverse
subjected to normal service limit state checking in accordance with clause 3.2.6
of this code. The calculation of the action effect shall comply with the provisions
of clause 7.2.6 of this code. The normal use limit value shall comply with the
provisions of clause 8.2.14 of this code.
8.2.13 The foundation soil layer of the groove retaining wall shall be checked
for bearing capacity and deformation. When the requirements are not met, it
shall take measures such as replacement or foundation reinforcement.
8.2.14 The limit value of the crack width of the groove retaining wall structure
shall comply with the provisions of the current "Code for durability design on
concrete structure of railway" TB 10005. The horizontal deformation of the top
of the wall shall not be greater than 1/150 of the height of the cantilever section.
When the horizontal deformation of the top of the wall is strictly limited, it shall
not be greater than 1/200 of the height of the cantilever section. When the
surrounding environment has special requirements for the deformation of the
groove retaining wall, it shall also meet the requirements of relevant industry
standards.
8.2.15 The groove retaining wall shall be designed for interception and drainage
according to the surface water catchment conditions.
8.2.16 When the groove retaining wall is constructed in seasonal frozen soil or
swelling soil area, it shall consider the adverse effects of frost heave force or
swelling force on the structure, take anti-frost heave or anti-swelling measures.
8.3 Construction requirements
8.3.1 The constructional requirements of the reinforcing rate, steel bar overlap,
anchoring length of the groove retaining wall and the uplift pile shall comply with
the relevant provisions of the current "Code for design of concrete structures"
GB 50010. The requirements for uplift pile’s construction shall also meet the
following requirements:
1 The main ribs shall be provided in through-length and uniformly arranged.
2 Stirrups should be spiral; the diameter shall not be less than 6 mm; the
spacing should be 200 mm ~ 300 mm.
3 The thickness of the concrete protective layer of the main reinforcement of
the uplift pile shall not be less than 50 mm. When the large-diameter
prestressed pipe pile or square pile is used for the uplift pile, the thickness
of the protective layer of high-strength precast concrete members may not
be restricted by this clause.
8.3.2 For groove retaining wall, it may set the settlement joints, expansion joints
stage wall should not be greater than 10 m.
9.1.2 Geotextiles and other geosynthetic materials should be used for
reinforced materials. The specific requirements shall comply with the relevant
provisions of clause 5.4 of this code.
9.1.3 The filler in the reinforcement shall be sandy soil (except silt), gravel soil,
macadam soil, or group C fine-grained soil filler. It shall not use stone block soil.
The filler shall be compacted in layers. The filler’s compaction shall comply with
the provisions of the current "Code for design on subgrade of railway" TB 10001.
9.1.4 The physical and mechanical indexes of the filler shall be determined
according to the test. When test data is lacking, it can be adopted in accordance
with the provisions of clause 5.5 of this code.
9.1.5 Panels can use integral rigid panels, composite rigid panels, block panels
or modular panels. Block panels may be divided into rectangular, cross,
hexagonal, etc. Between modular panels, it should use reinforcement and other
measures to strengthen the overall rigidity. When the requirements for
deformation are high, it shall use integral panels and composite panels.
9.1.6 When connecting between reinforcements or between reinforcement and
wall panels, the connection strength shall not be lower than the design strength.
Connection rods or other connection methods may be used between the wall
panel and the geogrid.
9.2 Design and calculation
9.2.1 Reinforced soil wall shall be checked for internal and external stability; if
necessary, it shall perform post-construction settlement check and horizontal
deformation check, etc. The internal stability check shall include the tie-bar
strength, uplift force check, wall panel structure design, etc. The external
stability check shall include the (horizontal) sliding stability, anti-overturning
stability, foundation bearing capacity check, etc. On the weak foundation, it shall
be subject to overall sliding stability analysis of the embankment and the
foundation.
9.2.2 During the internal stability check, the filling soil on the reinforcement of
the embankment wall shall be converted into an equivalent uniformly distributed
fill load (Figure 9.2.3 (b)). The height of the load soil column hz shall be
calculated in accordance with the formula (9.2.2). When conducting external
stability calculations, the load of the fill soil above the top of the reinforced soil
wall shall be calculated according to the geometry of the fill soil.
at the elevation of the bottom surface of the formation surface. A platform
shall be set on the top of the embankment wall; the width of the platform
should not be less than 1.0 m.
2 The length of the concrete hat stone section may be equivalent to 2 ~ 4
wall panel’s width, meanwhile it is not more than 4.0 m and the thickness
is not less than 0.5 m. When the railing is installed, it may take treatment
measures such as pre-buried U-shaped bolts or pre-buried welded steel
plates in the cap stone.
3 Every 15 m ~ 25 m along the wall, it shall provide expansion joints or
settlement joints; their design shall comply with the provisions of clause
3.1.6 of this code.
4 The wall surface of the reinforced soil wall shall be provided with a row of
drain holes near the ground. For the integral panel and the composite
panel, it shall be provided with drain holes on the integral wall; the aperture
of the drain hole is not less than 100 mm. The drain holes on the integral
wall are distributed from bottom up according to the plum blossom type of
2 m ~ 3 m, meanwhile meet the requirements of clause 3.1.7 and clause
3.1.8 of this code.
5 Under the wall panel, it shall provide a strip foundation of concrete or mortar
rubble with a thickness of not less than 0.4 m and a burial depth of not
less than 0.6 m. In front of wall, it shall set a 4% lateral drainage slope. It
shall provide a longitudinal drain ditch at locations where it is impossible
to provide lateral drainage. The bottom of the foundation shall be located
below the bottom of the external drain ditch.
6 The pre-embedded steel bars and connecting steel bars used for
reinforced earth structure should be subject to anti-rust treatment.
9.3.3 Sections with pole frames, trenches and pipelines on the formation
surface shall take measures to ensure the integrity and stability of the reinforced
soil wall.
9.3.4 The filler shall comply with the provisions of the current "Code for design
on subgrade of railway" TB 10001. The part where the filler directly contacts the
ribs shall not contain sharp-angled blocks. The maximum particle size in the
filler shall not be greater than 100 mm and should not be greater than 1/3 of the
compacted thickness of a single layer of filler.
9.3.5 The surface layer of the foundation bed of the reinforced soil wall should
be provided with a closed layer; the inside of the wall panel shall be provided
with a reverse filter layer.
requirements are not met, it shall lengthen the soil nails or properly set anchor
cables.
10.3 Construction requirements
10.3.1 The surface layer of soil nailing retaining wall is composed of two layers
of steel mesh, shotcrete and formwork concrete. The soil nails shall be
effectively connected to the surface layer. The outer end of the soil nail shall be
connected to the steel cushion or reinforced steel by the use of threaded-end
anchors or welding.
10.3.2 The design and construction of soil nailing retaining wall shall follow the
principle of "maintaining the middle and stabilizing the slope foot". For the
layered excavation height of the soil nailing retaining wall, it should be 0.5 m ~
2.0 m for soil layer, or 1.0 m ~ 4.0 m for rock layer. The soil nails in the middle
of the side slope should be properly densified and lengthened. The concrete
wall foot is used to strengthen the slope foot, meanwhile make it form a whole
with the soil nailing retaining wall.
10.3.3 The soil nailing material should adopt HRB400 steel bar; the steel bar’s
diameter should be 16 mm ~ 32 mm; the borehole diameter should be 70 mm
~ 130 mm. The soil nail reinforcement shall be provided with positioning bracket.
It may take measures such as epoxy coating on the surface of steel bars used
in corrosive environments. When it is difficult to form holes or the hole easily
collapses, the soil nail may use self-drilling anchors.
10.3.4 The grouting material for nail holes shall be cement mortar, the strength
should be M30 and it should not be lower than 20 MPa. Grouting shall use hole
bottom grouting method; the grouting pressure should be 0.2 MPa.
10.3.5 The thickness of the sprayed concrete surface shall not be less than 50
mm; the strength of the sprayed concrete shall not be lower than C20. The
thickness of the formwork concrete surface should not be less than 250 mm.
The concrete’s strength grade shall meet the relevant requirements of the
current "Code for durability design on concrete structure of railway" TB 10005.
10.3.6 In the surface layer of the sprayed concrete and the formwork concrete,
it shall be respectively configured with one layer of steel mesh. The diameter of
the steel bar is 6 mm ~ 10 mm; the spacing is 150 mm ~ 300 mm. The overlap
of the steel mesh should be welded.
10.3.7 The soil nailing retaining wall shall be provided with an inclined drain
hole. The drain hole should be inclined upwards at a 5° ~ 10°. The length of the
drain hole shall be slightly larger than the length of the soil nail. In the hole, it
shall be provided with permeable pipes or perforated polyethylene pipes filled
with coarse sand.
1 The anchored wall should be set to single-stage or two-stage. The height
of each stage of wall in the rock layer should not be greater than 10 m.
For the column plate type anchored wall in soil layer or assembled and
prefabricated, the height of each stage of wall should not be greater than
8 m and the total height should not be greater than 16 m. It shall provide
platform between the upper and lower stages of walls; the width of
platform should not be less than 2 m.
2 The vertical rib’s spacing of the ribbed plate type anchored wall should be
3 m ~ 6 m; the rib spacing of the column of the column plate anchored
wall should be 2 m ~ 3 m. The cross-section of the column may use
rectangular or T-shaped; the earth retaining plate may be rectangular or
trough-shaped.
3 The anchors on each stage of vertical ribs or columns can be designed as
double or multiple layers. The anchor rods may be arranged on the
principle of equal bending moments or equal fulcrum reaction forces. The
anchor rod is inclined downwards; the angle with the horizontal plane
should not be greater than 45°, preferably 10° ~ 35°. The spacing between
the upper and lower rows of anchors should not be less than 2.5 m; the
horizontal spacing should not be less than 2 m.
11.1.3 Anchored wall should adopt low-prestressed anchor rods. The
prestressed anchor rods may be tensile type or compressive type. Tensile type
anchors are suitable for strata where the anchoring section is a rock layer, whilst
the compressive pressure anchors can be used for anchoring section of rock
layer, soil layer, or highly corrosive rock-soil layer.
11.1.4 The selection of materials for anchored wall shall meet the following
requirements:
1 Pre-stressed anchors may choose pre-stressed threaded steel bars. It
should not use galvanized steel. The non-pre-stressed anchor materials
should use ordinary ribbed bars with strengths of HRB400 and above.
Cement should use ordinary Portland cement, or anti-erosion cement for
aggressive environment. The strength grade of cement mortar used for
anchor hole grouting shall not be lower than M35.
2 The concrete’s strength grade of the anchored wall shall comply with the
relevant provisions of the current "Code for durability design on concrete
structure of railway" TB 10005. The performance of steel bars in reinforced
concrete shall comply with the provisions of Appendix C of this code. The
arrangement of main bars, stirrups, longitudinally distributed bars,
structural bars shall meet the requirements of the current "Code for design
of concrete structures" GB 50010.
1 When the displacement control requirements of the anchored wall are high,
the initial preload value should be the design value of the anchor tension.
2 When the displacement control requirements of the anchored wall are low,
the initial preload value should be 0.70 to 0.85 times the design value of
the anchor tension.
3 When the anchoring section is located in a special stratum, its initial preload
value can be determined according to the design requirements.
11.2.12 The limit state design of the bearing capacity of reinforced concrete
members includes bending resistance and shearing resistance, which shall
comply with the provisions of clauses 3.2.5 and 7.2.6 of this code. The partial
factors of the action effect of columns, slabs and lattices shall use 1.35; the
design of normal service limit state includes crack width check and deflection
check, which shall comply with the provisions of clause 3.2.6 and clause 7.2.6
of this code. The design of reinforced concrete structural members shall also
comply with the provisions of the current "Code for design of concrete
structures" GB 50010.
11.3 Construction requirements
11.3.1 The thickness of the overlying soil layer in the anchoring section of the
first row of bolts should not be less than 4 m; the thickness of the overlying rock
layer should not be less than 2 m.
11.3.2 The diameter of the anchor rod should be 18 mm ~ 32 mm. Non-
prestressed anchor steel bar should not be more than 3 per hole. The part of
the anchor rod which does not anchor into stratum shall be subject to anti-
corrosion treatment. In a corrosive environment, the surface of the steel bar can
be treated with epoxy coating.
11.3.3 The diameter of the anchor hole shall be determined according to the
diameter of the anchor rod, the number of rods, the size of the grouting pipe,
the position of the steel bar support, which can be 90 mm ~ 150 mm. The area
of steel bar in the single anchor hole shall not exceed 20% of the area of the
anchor hole. The thickness of the cement mortar’s protective layer of the anchor
rod shall not be less than 25 mm.
11.3.4 The cross-sectional width of the vertical ribs or columns or web width
shall not be less than 300 mm; the cross-sectional height should not be less
than 400 mm. On both sides of assembled vertical ribs or columns, it shall be
configured with through-length stressed steel bar. The thickness of the retaining
plate should not be less than 150 mm; it should not be less than 200 mm when
cast in situ. The overlapping length of the retaining plate on the vertical ribs or
columns shall not be less than 100 mm.
1 The diameter of the borehole shall be determined according to factors such
as the design anchoring force, the nature of the rock-soil layer, the type of
anchorage, the number of tensile materials, the construction equipment,
etc. In general, the diameter of the borehole should be 100 mm ~ 150 mm.
2 The area of the anchor cable in the borehole shall not exceed 15% of the
borehole area.
12.3.4 The production of the anchoring section of the tension type anchor cable
should adopt a series of tight hoop rings and expansion rings (isolation frame)
to make it corrugated, so as to form a jujube core shape after grouting. The
isolation frame shall be set every 1 m ~ 3 m along the axis of the anchor cable,
which shall take smaller value for soil layer and larger value for rock layer. The
pressure-type anchor cable shall be composed of the rod of the protective
sleeve that does not bond to the grouting as well as the bearing body at the
bottom of the grouting in the anchoring section.
12.3.5 The anchor cable in the anchoring section shall be cleaned and de-
rusted. The free section of anchor cable shall also be coated with antiseptic
agent, meanwhile covered with polyethylene plastic sleeves for isolation and
protection. The tensioned section of anchor cable shall also be coated with
antiseptic agent. When the ground is corrosive or the groundwater is corrosive,
the anchor cable shall be protected by full-length bellows. The anticorrosion of
the anchor cable shall comply with the provisions of the current "Technical code
for engineering of ground anchoring and shotcrete support" GB 50086. The
casing material and bellows shall meet the following requirements:
1 It shall have sufficient strength to ensure that it is not damaged during
processing and installation.
2 It shall have water resistance and chemical stability.
3 There shall be no adverse reactions in contact with cement slurry, cement
mortar or anti-corrosion grease.
12.3.6 For the anchoring section in non-corrosive rock-soil layer, the thickness
of the protective layer of cement slurry or cement mortar shall not be less than
25 mm. For the anchoring section in the corrosive rock-soil layer, it shall take
special anti-corrosion treatment measures.
12.3.7 The anti-corrosion material used for anchor cable should adopt special
anti-corrosion grease. The anti-corrosion material shall also meet the following
performance requirements within the design life of the anchor cable:
1 It shall maintain its anti-corrosion performance and physical stability.
2 Within the specified working temperature or during the tensioning process,
12.3.13 The anchor cable’s test should include basic test, creep test,
acceptance test. The test content and requirements shall meet the
requirements of Appendix J of this code. The test data shall meet the following
requirements:
1 At the initial stage of the construction of the anchoring project, it shall
perform a basic test of prestressed anchor cable. The number of basic
tests may be controlled according to 3% of the working anchor cable,
meanwhile it shall not be less than 3. However, it can be appropriately
increased when there are special requirements. The minimum pull-out
force of the basic test shall not be less than the over-tension of the
prestressed anchor cable, meanwhile the difference in the pull-out force
of each anchor cable shall be less than 30%. If the maximum difference is
greater than 30%, it shall increase the quantity of basic tests according to
the proportion of 3%.
2 When creep tests are required for special formations, the number shall not
be less than 3.
3 After the construction of the anchor cable is completed, in order to check
the construction quality of the anchor cable, it shall also perform an
acceptance test of the anchor cable. The 5% of the total number of anchor
cables and not less than 5 anchor cables shall be subjected to a multi-
cycle tensile acceptance test.
12.3.14 Pre-stressed anchor cables shall be subject to prestress monitoring.
The monitoring period shall be until the completion of the project handover and
not less than 2 years. The monitoring quantity should not be less than 5% of
the total number of anchor cables; meanwhile it shall be not less than 3 at each
location.
13 Slide-resistant pile
13.1 General provisions
13.1.1 Slide-resistant piles are suitable for general areas, soaking areas and
earthquake areas. It may be used to strengthen landslides, mountains and
special subgrades, as shown in Figure 13.1.1.
GB 50010 and the current "Code for design of building foundation" GB 50007.
13.3 Construction requirements
13.3.1 The strength grade of the concrete of the pile and the performance of
the steel bars shall comply with the provisions in Appendix C of this code.
HRB400 should be used for the stressed steel bars. Structural durability shall
comply with the relevant provisions of the current "Code for durability design on
concrete structure of railway" TB 10005.
13.3.2 The slide-resistant piles shall be excavated by skipping piles. A lock shall
be provided at the wellhead of the digging pile. When the pile hole is located in
the soil layer and the weathered and broken rock layer, it shall provide a
protective wall. Before grouting the piles and protective wall, it shall remove the
loose stones and floating soil in the hole wall; the concrete for protective wall
shall be placed close to the surrounding rock. When there is groundwater, it
shall take dewatering measures. The permeable layer shall adopt the protective
wall and be closed in time.
13.3.3 The diameter of the longitudinal reinforcement of the pile shall not be
less than 16 mm. The net distance should not be less than 120 mm, which can
be reduced appropriately under difficult circumstances, but it shall not be less
than 80 mm. When tendons are used, the number per bundle should not be
more than 3. When it is difficult to configure a single row of steel bars, it may
provide 2 or 3 rows. The reinforced concrete’s protective layer shall not be less
than 70 mm.
13.3.4 It should not install diagonal reinforcement in the pile. It shall take
measures such as adjusting the diameter and spacing of the stirrups and the
cross-sectional size of the pile, to meet the shear requirements of the inclined
cross-section.
13.3.5 Stirrups shall be closed. The number of limbs should not be more than
4; the diameter should not be less than 14 mm. The spacing shall not be greater
than 400 mm.
13.3.6 On both sides of the rectangular section pile and the compressive side,
it shall be configured with appropriate longitudinal structural steel bars; the
spacing shall not be greater than 300 mm; the diameter should not be less than
12 mm. At both sides of the pile's compressive side, it shall be equipped with
erection steel bars, which has a diameter of not less than 16 mm. When the pile
is longer, the diameter of the longitudinal structural reinforcement and the
vertical erection reinforcement shall be increased.
13.3.7 When using concrete circular bored piles, the concrete strength grade of
the pile, the configuration of steel bar, the thickness of the concrete protective
b - The horizontal distance from the inner edge of the load to the back of the
wall (m);
hi - The vertical distance from the back of the wall to the shoulder (m);
l0 - Action width of strip unit load of track and train (m).
14.2.2 The slope with potential sliding surface shall be designed according to
the most unfavorable load in thrust and earth pressure. The landslide thrust can
be determined according to the provisions of clause 13.2.2 and clause 13.2.5
of this code through calculation.
14.2.3 The load acting on the pile may be calculated according to half of the
distance between the two adjacent piles on the left and right; the width of the
load acting on the retaining plate may be calculated according to the calculated
span of the plate. The load width of the retaining wall between the piles may be
calculated according to the net distance between the piles. The earth pressure
on the retaining wall and retaining plate between piles may be calculated based
on the stability of the rock (soil) between the piles and the setting method of the
retaining wall and retaining plate, considering the horizontal soil arch effect
between the piles, according to the total rock (soil) pressure or partial rock (soil)
pressure.
14.2.4 The calculation of the internal force and deformation of the pile of the
cantilever section shall comply with the provisions of clause 13.2.7 of this code.
The final deformation of the pile of the cantilever section shall consider the
influence of the displacement of the top of the anchoring section. When an
anchor cable is provided on the pile, the calculation of the internal force and
deformation of the pile and the anchor cable shall comply with the provisions of
clause 12.2 of this code.
14.2.5 The internal force and deformation of the pile in the anchorage section
shall be calculated according to the clause 13.2.8 of this code using the
foundation factor method according to the bending moment, shear force at the
anchorage point as well as the elastic resistance of the soil in the anchorage
section. The lateral compressive stress of the pile onto the foundation shall
meet the requirements of clause 13.2.9 of this code.
14.2.6 Pile’s bottom support may, combined with rock-soil conditions and pile
bottom embedding depth, use free end or hinged end.
14.2.7 Anchor rope pile-plate retaining walls in embankment sections shall
avoid the secondary stress of the anchor cable as caused by the sinking of the
filler.
14.2.8 The limit state design of the bearing capacity of the pile-wall structure
shall comply with the provisions of clause 3.2.5 of this code. The design shall
this code. The maximum crack width’s limit value may be adopted in
accordance with the provisions of the current "Code for durability design
on concrete structure of railway" TB 10005. If it has experience, the
maximum crack width’s limit value may be appropriately relaxed and it
shall take appropriate additional anti-corrosion measures.
3 The limit value of the horizontal total displacement of the pile top can be
controlled by 1/100 of the length of the cantilever section; it should not be
greater than 100 mm. It should not be more than 60 mm for the shoulder’s
pile-plate wall of high-speed railway. The limit value of the maximum
deflection in the mid span of the retaining plate may take 1/200 of the
calculated span of the retaining plate.
14.2.10 The design and calculation of the retaining wall between piles and the
soil nailing retaining wall between piles shall comply with the provisions of
clauses 6 and 10 of this code.
14.2.11 The design of reinforced concrete members shall comply with the
provisions of the current "Code for design of concrete structures" GB 50010.
14.3 Construction requirements
14.3.1 The materials used in the pile-wall structure shall comply with the
relevant provisions of clause 5 of this code. The structural durability design shall
meet the relevant requirements of the current "Code for durability design on
concrete structure of railway" TB 10005.
14.3.2 The reinforcement ratio, steel bar overlap and anchor length of pile-plate
retaining wall shall comply with the relevant provisions of the current "Code for
design of concrete structures" GB 50010. The structure of the anchored pile
shall comply with the provisions of clause 13.3 of this code.
14.3.3 When installing anchor cables on piles, the distance between the anchor
hole and the pile top should not be less than 1.5 m. The stirrups in the pile body
near the anchor point shall be properly densified. The anchor cable structure
shall comply with the relevant provisions of clause 12.3 of this code.
14.3.4 The retaining plate shall be provided with a drain hole. It shall install a
reverse filter layer behind the retaining plate. The reverse filter layer shall be
provided in accordance with the provisions of clause 3.1.8 of this code.
14.3.5 In addition to the requirements of this chapter, the construction
requirements shall also comply with the provisions of chapter 6 and chapter 10
of this code.
used for stressed steel bars; its performance shall meet the requirements of
Appendix C of this code.
15.3.4 Reinforcement of reinforced concrete members shall also comply with
the relevant provisions of the current "Code for design of concrete structures"
GB 50010.
16 Composite pile structure
16.1 General provisions
16.1.1 The composite pile structure is suitable for general areas, earthquake
areas, soaking areas. It may be installed on shoulders, embankments, cuttings.
16.1.2 The composite pile structure is composed of pile foundation and
superstructure or pile and connecting beam, which can be divided into pile
foundation cantilever retaining wall, pile foundation counterfort retaining wall,
chair pile, frame pile, as shown in the Figure 16.1.2.
16.1.3 Pile foundation cantilever retaining wall and pile foundation counterfort
retaining wall can be used for embankment sections with insufficient foundation
bearing capacity or uneven settlement; chair piles can be used for steep slope
subgrade sections; frame piles can be used for large rock piles, deep cutting
section inside the landslide.
16.1.4 The height of pile foundation cantilever retaining wall and pile foundation
counterfort retaining wall should not exceed 10 m. The pile foundation may be
double-row pile or multi-row pile. The baseplate of the retaining wall and the
lower pile foundation should be rigidly connected.
16.1.5 The maximum height of the chair pile and frame pile structure should not
exceed 15 m; the vertical pile spacing can be 3 ~ 5 times the vertical pile width,
which should be 5 m ~ 8 m; the lateral spacing should not be less than 2.5 times
the lateral pile width.
16.1.6 The pile foundation’s diameter of the pile foundation cantilever retaining
wall and pile foundation counterfort retaining wall should not be less than 800
mm. When the pile foundation is a friction pile, the center distance between
adjacent piles should not be less than 2.5 times the design pile diameter. When
the pile foundation is an end bearing pile, the center distance between adjacent
piles should not be less than 2 times the design pile diameter.
16.1.7 A soil nailing retaining wall, a retaining plate or a gravity retaining wall
may be provided between the piles of the chair-type pile and the frame pile
structure in the sections where it bears the landslide thrust or earth pressure.
16.2.8 The internal force’s calculation of the anchoring pile in the composite pile
structure shall meet the requirements of Chapter 13 of this code
16.2.9 The structural design of the components in the composite pile structure
shall be subjected to verification of bending and shear resistance, crack width,
deformation. The design verification shall comply with the provisions of
chapters 7, 13 and 14 of this code.
16.2.10 In addition to the design of reinforced concrete members of the
composite pile structure in accordance with this code, it shall also comply with
the provisions of the current "Code for design of concrete structures" GB 50010.
16.3 Construction requirements
16.3.1 Expansion joints shall be set between each section of the pile foundation
cantilever retaining wall and the pile foundation counterfort retaining wall; the
distance between the expansion joints shall not be greater than 20 m; the
expansion joints, settlement joints, drain holes shall be set in accordance with
the provisions of clause 3.1.6 and clause 3.1.8 of this code.
16.3.2 The pile foundation shall extend into the baseplate of the cantilever
retaining wall or counterfort retaining wall of not less than 100 mm. The length
of the stressed reinforcement of the pile foundation as extended into the
baseplate shall meet the minimum calculated anchorage length and not less
than 200 mm.
16.3.3 During the construction of the composite pile structure, the concrete
pouring of the pile shall be completed at one time. If the pouring of other parts
is interrupted, it shall be treated strictly according to the construction joint, to
ensure that the concrete strength meets the design requirements.
16.3.4 The reinforced concrete grade of the composite pile structure should not
be lower than C35. When the groundwater is corrosive, the structural durability
design shall meet the relevant requirements of the current "Code for durability
design on concrete structure of railway" TB 10005.
16.3.5 The thickness of the concrete protective layer at the part where the
composite pile structure directly contacts the soil should not be less than 70
mm. The thickness of the protective layer shall meet the requirements of current
"Code for durability design on concrete structure of railway" TB 10005.
middle of the two adjacent ribs.
2 The rib column is calculated according to the bending member and bears
the earth pressure from the wall panel. The connection between the rib
column and the tie-bar as well as between the rib column and the
foundation are the reaction force’s fulcrums.
3 The calculation of the bending moment, shear force and tension of the tie-
bar of the rib column shall be determined according to the number of tie-
bar layers, the connection form of the column bottom and the foundation.
4 The design of the ribs column also needs to consider the deformation of
the fulcrums of the rib columns, as well as the abnormal load conditions
such as uneven loading of the tie-bar during handling, lifting and
construction, to configure stressed steel bars at the inside and outside of
the rib column.
17.2.7 The design of the tie-bar shall meet the following requirements:
1 The distance between the uppermost row of tie-bars and the top surface of
the filling soil shall not be less than 1.0 m.
2 The length of the tie-bar shall meet the overall stability requirements of the
wall, meanwhile......
Related standard:   TB 10301-2020  TB 10302-2020
   
 
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