Cast-in-place reinforced soil retaining wall for gravel backfilling side slope

Abstract

The cast-in-place reinforced earth retaining wall comprises a slope surface and a slope body, the slope surface is a concrete layer, a reinforcing mesh is laid in the concrete layer, the slope body comprises gravel and multiple layers of horizontally-laid steel-plastic two-way geogrids, the gravel is filled between the steel-plastic two-way geogrids, and the gravel is filled between the gravel and the multiple layers of steel-plastic two-way geogrids. The vertical distance between the steel-plastic two-way geogrids is 1 m, the lap joint length is not smaller than 300 mm, and the steel-plastic two-way geogrids are fixed to the outer side of the reinforcing mesh in a bent mode and anchored into the concrete layer. The steel-plastic two-way geogrid can be effectively prevented from being rubbed and damaged by broken stones, the reinforcing mesh in the slope surface concrete layer provides tensile performance for the slope protection concrete layer, the concrete layer is prevented from cracking, the steel-plastic two-way geogrid is tensioned in the longitudinal direction and the transverse direction, bent and fixed to the outer side of the reinforcing mesh and anchored into the concrete layer, and the slope protection effect is achieved. The steel-plastic two-way geogrid can be effectively fixed in a slope body, the purpose of slope supporting is achieved, and the applicability to slope types is greatly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of geotechnical engineering, in particular to a cast-in-place reinforced soil retaining wall for gravel backfill slope, which is especially suitable for large backfill slope support engineering. BACKGROUND

[0002] Today, with the rapid development of China's economy, the state is investing more and more in infrastructure, whether it is transportation, water conservancy and hydropower engineering, or today's ecological restoration engineering, slope engineering has always been a problem that cannot be ignored in engineering construction. China has a large land area and complex topography and geomorphology, of which the mountainous area accounts for about 51.9% of the total area of the country. There are quite a number of natural slopes or artificial slopes in mountainous areas due to development and construction. With more and more slopes and higher and higher slopes, under the action of natural and human factors, the slope is very prone to instability.

[0003] Achieving the "double carbon" goal is a broad and profound economic and social systemic change. As an important part of achieving the "double carbon", energy transformation is leading China's industrial transformation in recent years. China's new energy development represented by wind power and photovoltaic power generation has achieved remarkable results, and most of the supporting power stations are located in mountainous areas and other areas with large changes in terrain, which need large-area backfill to provide enough space for power stations. The slope control problem of high slope backfill is crucial.

[0004] Most of the existing backfill slopes are soil slopes, which use backfill soil purchased from the site or outside to backfill, but in many mountainous areas in China, there are a large number of mountains. In order to balance the excavation and filling of earthwork and to purchase soil outside, gravel is used for filling, and due to the limitation of land use red line, there is not enough area to use as a retaining wall or a slope. However, due to different regions, the traditional geogrid design anchoring construction method is not suitable, and the cost is high and the construction speed is slow. There are two methods for the design of the current geogrid reinforced soil retaining wall for slope:

[0005] 1. The geotextile bag with pre-embedded grass seeds is used in cooperation with the geogrid, which is laid on the slope surface and the geogrid head is bent and pre-embedded into the bottom of the upper geogrid, and the slope surface is protected by greening. However, in the northern part of China, the annual rainfall is low, and the geotextile bag embedded in the slope surface cannot play the role of greening slope protection, so it is not suitable.

[0006] 2. The existing engineering method for slope protection is to use concrete precast blocks and place the geogrid in the gap between the precast blocks to fix it. However, for strongly weathered rock (soil) slope, most of the slope body is composed of gravel, and it is difficult to use concrete precast blocks in this case.

[0007] In summary, for the rock (soil) slope composed of gravel with low rainfall, a more reasonable and practical structure needs to be proposed to stabilize the overall stability of the slope body. SUMMARY

[0008] The present application provides a cast-in-place reinforced soil retaining wall for gravel backfill slope, which uses steel-plastic bidirectional geogrid to effectively prevent gravel friction damage, and the reinforcement mesh in the slope surface concrete layer provides tensile resistance for the slope protection concrete layer to prevent the concrete layer from cracking, and the steel-plastic bidirectional geogrid is tensioned in the longitudinal and transverse directions, bent and fixed outside the reinforcement mesh and anchored into the concrete layer, so that the steel-plastic bidirectional geogrid can be effectively fixed inside the slope body to achieve the purpose of slope support.

[0009] The present application is implemented by the following technical solutions.

[0010] A cast-in-place reinforced soil retaining wall for gravel backfill slope, comprising a slope surface and a slope body, the slope surface being a concrete layer, the concrete layer being internally laid with a reinforcement mesh, the slope body comprising gravel and multiple layers of horizontally laid steel-plastic bidirectional geogrid, the gravel being filled between the steel-plastic bidirectional geogrid, the vertical spacing of the steel-plastic bidirectional geogrid being 1m, the overlapping length between the steel-plastic bidirectional geogrid being not less than 300mm, and the steel-plastic bidirectional geogrid being bent and fixed outside the reinforcement mesh and anchored into the concrete layer.

[0011] Further, the steel-plastic bidirectional geogrid is fully laid every 1m.

[0012] Further, the steel-plastic bidirectional geogrid is fixed by overlapping with steel bars or steel wires.

[0013] Further, the steel-plastic bidirectional geogrid is bent by not less than 1m, and the bent part is fixed by binding with the reinforcement mesh using iron wire.

[0014] Further, the arrangement of the reinforcement mesh is The intersection of the reinforcement mesh is fixed by binding with iron wire.

[0015] Further, the thickness of the concrete layer is 200mm, and the concrete strength is C25.

[0016] Further, the retaining wall comprises a slope top, the slope top is capped with MU25 flagstones using M5 mortar, and a 20mm wide deformation joint is provided every 15-20m.

[0017] Further, the retaining wall comprises a slope foot, the slope foot is capped with MU25 flagstones using M5 mortar, and a 20mm wide deformation joint is provided every 15-20m.

[0018] The present application has the following beneficial effects:

[0019] 1、The retaining wall adopts steel-plastic bidirectional geogrid, which is internally provided with steel wires, can effectively prevent the damage caused by gravel friction, is suitable for gravel backfill slope support; the steel mesh provides tensile property for the concrete layer and prevents the concrete layer from cracking; the steel-plastic bidirectional geogrid is pulled in two longitudinal and transverse directions, is bent and fixed on the steel mesh and is anchored into the concrete layer, so that the steel-plastic bidirectional geogrid can provide good shearing capacity in different directions inside the slope body, to achieve the purpose of stabilizing the slope.

[0020] 2、The retaining wall solves the problems of overall stability of large gravel filling slope and greening slope protection in areas lacking rainfall, and also solves the difficulty of rock slope composed of gravel that cannot be supported by soil nail wall (because gravel cannot provide the bonding strength of anchoring body), can be used for gravel backfill slope in areas lacking rainfall, has low cost, rapid construction, good protection effect, and has been put into use in actual engineering. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 It is a side sectional view of the reinforced earth retaining wall of the present application.

[0022] Figure 2 It is a detail view of the reinforced earth retaining wall of the present application.

[0023] Figure 3 It is a detail view of the reinforced earth retaining wall of the present application. Figure 2 It is a partial enlarged view of A in the middle.

[0024] Figure 4 It is a horizontal sectional view of the reinforced earth retaining wall of the present application.

[0025] Figure 5 It is a large sample view of the slope top pressing of the present application.

[0026] Figure 6 It is a large sample view of the slope foot sealing of the present application.

[0027] Figure 7 It is a force analysis diagram of the slope of the present application.

[0028] The drawing label: gravel 1, steel-plastic bidirectional geogrid 2, bending part 21, steel mesh 3, concrete layer 4, slope top 5, slope foot 6. DETAILED DESCRIPTION

[0029] The technical solutions of the present application will be clearly and completely described below in conjunction with the embodiments, obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor belong to the protection scope of the present application. The described embodiments only play an explanatory role, and should not limit the present application.

[0030] In the description of the present application, it should be understood that the terms "upper", "lower", "front", "back", "left" and "right" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the indicated position or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application. In addition, the terms "first", "second" and the like are only for the purpose of description, and cannot be understood as indicating or implying relative importance.

[0031] In the description of the present application, unless otherwise explicitly specified and limited, "connection", "fixing" and the like should be understood in a broad sense, for example, "fixing" can be fixed connection, or detachable connection, or integral; can be direct connection, or indirect connection through intermediate medium, can be the internal communication of two elements or the interaction relationship of two elements, unless otherwise explicitly limited. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0032] I. Finite Element Simulation

[0033] For the overall stability of the slope, the reinforced soil retaining wall is used, which is composed of slope gravel, and ordinary plastic geogrid is easily damaged by direct sliding of gravel. If the tensile direction is damaged, the tensile strength of the slope will be greatly reduced, and the soil sliding force will be concentrated in the damaged part, causing shear effect on the slope and landslide. Therefore, the steel-plastic bidirectional geogrid is used, and the steel-plastic bidirectional geogrid is provided with steel wire inside, which can effectively prevent the damage of geogrid caused by gravel friction, and can ensure that the slope can provide good shear capacity in different directions.

[0034] The technical solutions provided by the present application are: Figures 1-6As shown, a cast-in-place reinforced soil retaining wall for gravel backfill slope includes a slope surface and a slope body, the slope surface is a concrete layer 4, the concrete layer 4 is internally laid with a steel mesh 3, the slope body includes gravel 1 and horizontally laid multiple layers of steel-plastic bidirectional geogrids 2, the gravel 1 is filled between the steel-plastic bidirectional geogrids 2, the vertical spacing of the steel-plastic bidirectional geogrids 2 is 1m, the overlapping length between the steel-plastic bidirectional geogrids 2 is not less than 300mm, and the steel-plastic bidirectional geogrids 2 are bent and fixed outside the steel mesh 3 and anchored into the concrete layer 4.

[0035] The steel-plastic bidirectional geogrids 2 are fully laid at the slope bottom, every 1m is fully laid, the steel-plastic bidirectional geogrids 2 are tensioned in the longitudinal and transverse directions, and short steel bars can be used for fixation, so that the steel-plastic bidirectional geogrids 2 can fully provide shear resistance in the soil body. The overlapping length should not be less than 300mm, and steel bars and steel wires are used for fixation at the overlapping position. The overlapping length refers to when the length of a piece of steel-plastic bidirectional geogrid is not enough, another piece is used to splice this piece, and a part of overlap is required when splicing, and the overlapping length is the overlap length.

[0036] Each layer of steel-plastic bidirectional geogrids 2 is laid according to the calculation results of the finite element software in the longitudinal position, and is laid with a vertical spacing of 1m, and is laid layer by layer to the slope top, and needs to pass through the potential sliding surface in the longitudinal direction, so as to provide shear resistance to the slope body, and to achieve the standard of overall stability of the slope. As shown in Figure 1 .

[0037] 1. Soil pressure calculation

[0038] 1.1 Active earth pressure calculation

[0039] The active earth pressure calculation method adopts Coulomb theory.

[0040] The Coulomb active earth pressure calculation formula is:

[0041] E a =Q max =1 / 2γH2K a , wherein,

[0042]

[0043] In the formula,

[0044] γ, ———the specific weight and internal friction angle of the backfill soil of the retaining wall;

[0045] H———the height of the retaining wall;

[0046] ε———the included angle between the wall back and the vertical line, which is positive when the wall back is inclined, and negative otherwise;

[0047] δ———the friction angle between the wall back and the fill, which is related to the roughness of the wall back, the nature of the fill, the inclination shape of the wall back, etc., and can be determined by test or reference to empirical data;

[0048] β———the inclination angle between the fill surface and the horizontal plane;

[0049] K a ———the Coulomb active earth pressure coefficient, which is a function of δ, ε, β.

[0050] 1.2 Passive earth pressure calculation

[0051] The passive earth pressure calculation method uses the Mazindrani (Rankine) theory.

[0052] The Rankine passive earth pressure calculation formula is:

[0053] For cohesive soil:

[0054] K p ———the Rankine passive earth pressure coefficient, and

[0055] II. Overall Slope Stability Check

[0056] Figure 7 is a force analysis diagram of the slope.

[0057] The stability coefficient Fs = 1.195

[0058] The radius R = 28.26 m

[0059] Strip block 1: L1 = 1.75 m; α1 = -13.36°; c1 = 0.00 kPa;

[0060] Thrust and bending moment:

[0061] W1 = 6.55 kN / m

[0062] FX 1,surch = 0.00 kN / m

[0063] FY G,1 = 0.00 kN / m

[0064] FX 1,Kh = -0.33 kN / m

[0065] M 1,W = -42.72 kNm / m

[0066] FY 1,surch = 0.00 kN / m

[0067] M 1,FY,G = 0.00 kNm / m

[0068] M 1,Kh = 8.97 kNm / m

[0069] M 1,surch = 0.00 kNm / m

[0070] FY 1,Kv = 0.00 kN / m

[0071] M 1,Kv = 0.00 kNm / m

[0072] Resistance and bending moment:

[0073] FX 1,reinf = 0.00 kN / m, FY 1,reinf = 0.00 kN / m, M 1,reinf = 0.00 kNm / m

[0074] N1 = 7.60 kN / m T1 = 3.67 kN / m M 1,T = 103.81 kNm / m.

[0075] Strip 2: L2 = 1.73 m, a2 = -9.83°, c2 = 0.00 kPa,

[0076] Thrust and bending moment:

[0077] W2 = 17.87 kN / m

[0078] FX 2,surch = 0.00 kN / m

[0079] FY G,2 = 0.00 kN / m

[0080] FX 2,Kh = -0.89 kN / m

[0081] M 2,W = -86.17 kNm / m

[0082] FY2, surch = 0.00 kN / m

[0083] M 2,FY,G = 0.00 kNm / m

[0084] M 2,Kh = 24.63 kNm / m

[0085] M2, surch = 0.00 kNm / m

[0086] FY 2,Kv = 0.00 kN / m

[0087] M 2,Kv = 0.00 kNm / m

[0088] Resistance and bending moment:

[0089] FX 2,reinf = 0.00 kN / m

[0090] FY 2,reinf = 0.00 kN / m

[0091] M 2,reinf = 0.00 kNm / m

[0092] N2 = 19.79 kN / m

[0093] T2 = 9.57 kN / m

[0094] M 2,T = 270.34 kNm / m.

[0095] III. Slope Overturning and Sliding Stability Check

[0096] Overturning stability check:

[0097] Resistance moment M res = 72949.33 kNm / m

[0098] Overturning moment M ovr = 4148.76 kNm / m

[0099] Safety factor = 17.58 > 1.30

[0100] Overturning stability check is satisfactory.

[0101] Sliding stability check:

[0102] Resistance to sliding (parallel to base) H res = 3082.32 kN / m

[0103] Sliding force (parallel to base) H act = 440.35 kN / m

[0104] Safety factor = 7.00 > 1.10

[0105] Sliding stability check is satisfactory.

[0106] IV. Design for Slope Surface Protection

[0107] Reinforcement details:

[0108] Miragrid GX 160 / 30

[0109] Controlled tensile strength Tult = 160.00 kN / m

[0110] Long-term strength design value Rt = 77.23 kN / m

[0111] Action model uncertainty integral system coefficient FSUNC = 1.20

[0112] Internal stability checking:

[0113] Checking the bearing capacity of the reinforcement, reinforcement number: 1.

[0114] Tensile bearing capacity checking:

[0115] Tensile strength R t = 77.23 kN / m

[0116] Reinforcement force F x = 10.56 kN / m

[0117] Safety factor = 7.31 > 1.00

[0118] The tensile bearing capacity of the reinforcement checking meets the requirements.

[0119] Uplift bearing capacity checking:

[0120] Uplift strength T p = 5154.74 kN / m

[0121] Reinforcement force F x = 10.56 kN / m

[0122] Safety factor = 487.97 > 1.00

[0123] The uplift bearing capacity of the reinforcement checking meets the requirements.

[0124] The total bearing capacity of the reinforcement checking meets the requirements.

[0125] The steel-plastic bidirectional geogrid 2 is internally provided with steel wires, which can effectively prevent it from being damaged by gravel friction. The steel mesh 3 provides tensile performance for the concrete layer 4 to prevent the concrete layer 4 from cracking. The steel-plastic bidirectional geogrid 2 is tensioned in two longitudinal and transverse directions, bent and fixed on the steel mesh 3 and anchored into the concrete layer 4, so that the steel-plastic bidirectional geogrid 2 can fully provide shear resistance inside the slope body 1 to achieve the purpose of stabilizing the slope body. The steel-plastic bidirectional geogrid 2 is available on the market, and its structure is not described here.

[0126] As an optional embodiment, the steel-plastic bidirectional geogrid 2 is bent by not less than 1m on the slope surface, is fixed to the outside of the steel mesh 3, and the slope surface adopts concrete spraying, that is, the transverse grid of the steel-plastic bidirectional geogrid 2 is opened and anchored into the steel mesh 3 in the concrete layer 4, and the bent part 21 is fixed by binding with the steel mesh 3 by using iron wire.

[0127] As an optional embodiment, the steel mesh 3 is arranged in the following manner The joint of the steel mesh 3 is fixed by binding with iron wire. Indicates that the steel bar diameter is 8mm, and one is arranged every 150mm.

[0128] As an optional embodiment, the thickness of the concrete layer 4 is 200mm, and the concrete strength is C25. Wherein, C25 means that the compressive strength of the concrete test block is not less than 25Mpa under the laboratory conditions (temperature 20 degrees) for 28 days.

[0129] As an optional embodiment, as shown in Figure 1 and 5 , the retaining wall comprises a slope top 5, the slope top 5 adopts M5 mortar to build MU25 stone pressure top, one 20mm wide deformation joint is arranged every 15-20m, and reference is made to Figure 5 . Wherein, M5 refers to the strength of cement mortar, and the specific parameter is 5.0MPa. MU25 refers to the strength grade of the built stone, and the standard value of the compressive strength is 25mpa. The stone pressure top is a construction requirement, which provides a higher safety factor for the concrete layer, and the deformation joint is to prevent thermal expansion and cold contraction and uneven settlement from damaging the slope surface.

[0130] As an optional embodiment, as shown in Figure 1 and 6 , the retaining wall comprises a slope foot 6, the slope foot 6 adopts M5 mortar to build MU25 stone pressure foot, one 20mm wide deformation joint is arranged every 15-20m, and reference is made to Figure 6 . Wherein, the stone pressure foot is a construction requirement, which provides a higher safety factor for the concrete layer, and the deformation joint is to prevent thermal expansion and cold contraction and uneven settlement from damaging the slope surface.

[0131] The construction steps of the application are as follows:

[0132] The steel-plastic bidirectional geogrid 2 is laid at the slope bottom, and the length required for the steel-plastic bidirectional geogrid 2 to be exposed on the slope surface is reserved, the steel-plastic bidirectional geogrid 2 is overlapped by the steel bars, the laid steel-plastic bidirectional geogrid 3 is first pulled tight along the longitudinal and transverse directions, and is fixed on the ground by the steel bars; then the gravel 1 is filled and laid on the steel-plastic bidirectional geogrid 2, and is compacted, the steel-plastic bidirectional geogrid 2 is laid on the gravel layer, and the process is sequentially performed, the steel-plastic bidirectional geogrid 3 of each layer is kept to be laid horizontally and in parallel, and the layers are sequentially laid to the top of the slope body 1; finally, the steel-plastic bidirectional geogrid 2 exposed on the slope surface is wrapped into the outside of the steel bar mesh 3, and is anchored into the concrete layer 4.

[0133] The above only describes the preferred embodiments of the present application and is not used to limit the present application. Although the present application is described in detail with reference to the foregoing embodiments, those skilled in the art can modify the technical solutions recorded in the foregoing embodiments or equivalently replace some technical features, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A cast-in-place reinforced soil retaining wall for gravel backfill slopes, comprising a slope surface and a slope body, characterized in that: The slope is a concrete layer with a steel mesh inside. The slope body includes crushed stone and horizontally laid multi-layer steel-plastic bidirectional geogrid. The crushed stone is filled between the steel-plastic bidirectional geogrids. The vertical spacing of the steel-plastic bidirectional geogrids is 1m. The overlap length between the steel-plastic bidirectional geogrids is not less than 300mm. The steel-plastic bidirectional geogrids are bent and fixed to the outside of the steel mesh and anchored into the concrete layer.

2. A cast-in-place reinforced soil retaining wall for gravel backfill slopes according to claim 1, characterized in that: The steel-plastic bidirectional geogrid is fully laid every 1m.

3. A cast-in-place reinforced soil retaining wall for gravel backfill slopes according to claim 1, characterized in that: The steel-plastic bidirectional geogrids are fixed together by steel bars or steel wires.

4. A cast-in-place reinforced soil retaining wall for gravel backfill slopes according to claim 1, characterized in that: The steel-plastic bidirectional geogrid is bent at least 1m, and the bent part is fixed by binding the wire and steel mesh.

5. A cast-in-place reinforced soil retaining wall for gravel backfill slopes according to claim 1, characterized in that: The arrangement of the steel mesh is as follows: The joints of the steel mesh are secured with wire.

6. A cast-in-place reinforced soil retaining wall for gravel backfill slopes according to claim 1, characterized in that: The thickness of the concrete layer is 200mm, and the concrete strength is C25.

7. A cast-in-place reinforced soil retaining wall for gravel backfill slopes according to claim 1, characterized in that: The retaining wall includes a sloping top, which is topped with MU25 rubble masonry using M5 mortar, and a 20mm wide expansion joint is provided every 15-20 meters.

8. A cast-in-place reinforced soil retaining wall for gravel backfill slopes according to claim 1, characterized in that: The retaining wall includes a slope foot, which is constructed with M5 mortar and MU25 rubble stone footing, with a 20mm wide expansion joint every 15-20 meters.

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