In-wall drainage retaining wall using comprehensive geosynthetics and its construction method

Abstract

The present invention discloses an in-wall drainage retaining wall and a construction method that comprehensively utilizes geosynthetics, including an in-wall drainage system, a retaining force structure, and a wall structure. The in-wall drainage system is composed of geodrain pipes, geotextiles, geomembranes, drainage bins, drainage troughs, and water collection wells; the retaining force structure is composed of precast concrete hollow square piles and geogrids; and the wall structure is composed of wall panels, wall cores, and wall eaves. The present invention utilizes the anti-seepage, anti-filtration, drainage, and reinforcement functions of geosynthetics, and adopts a variety of geosynthetics and precast concrete hollow square piles to form an in-wall drainage system and a retaining force structure. The wall panels and other wall structures are only used for aesthetic design, and the division of labor of each structural component is clear. The design parameter calculation and optimization are used to ensure the construction quality and engineering safety. It has the advantages of novel structure, environmentally friendly materials, and integrated design and construction. It is particularly suitable for various scenes such as park landscape and urban cultural construction.

Description

Technical Field

[0001] The invention relates to the technical field of geosynthetics and slope engineering, in particular to an in-wall drainage retaining wall and a construction method thereof which comprehensively utilizes geosynthetics. Background Art

[0002] Geosynthetics are a type of artificially synthesized polymer engineering material commonly used in civil engineering, water conservancy and other projects. According to different functional requirements, they can be made into various types of products, such as geotextiles, geogrids, geomembranes, geodrains, etc. They can be placed inside or on the surface of the soil or between various soil bodies to play the role of filtration, reinforcement, protection, anti-seepage and drainage. They have been widely used in geotechnical, municipal, water conservancy and environmental projects.

[0003] Retaining wall is a common geotechnical structure, often used in geotechnical, municipal, water conservancy and environmental engineering. Traditional retaining wall relies on the deadweight of the wall to resist the lateral earth pressure of the soil behind the wall to maintain the stability of the slope. When the slope behind the wall is high, the lateral earth pressure is large, especially when the soil pressure increases due to water accumulation in the slope after rain, which can easily cause dangers such as wall tilt and collapse. Generally, it is necessary to drain the water in the slope behind the wall by installing drainage pipes in the wall body and anti-filtration facilities behind the wall. However, in actual use, traditional retaining walls still have the following shortcomings, which need to be improved:

[0004] 1) Traditional retaining walls use the wall body as the soil pressure carrier, and the foundation needs to be excavated and compacted within a certain range. On this basis, concrete is poured on site or a masonry wall is built. This has high requirements on the bearing capacity of the foundation, large on-site engineering workload, long construction period, high project cost, and insufficient aesthetics.

[0005] 2) The construction of the anti-filtration facilities behind the retaining wall is inconvenient, and the pores of the anti-filtration material are easily blocked by fine soil particles, resulting in poor anti-filtration effect. The wall drainage pipe is easily blocked, resulting in poor drainage; the drainage pipe passes through the wall, and the outlet is located on the surface of the retaining wall. When draining, the water carries mud and sand through the wall surface, destroying the aesthetics of the wall, and eroding the wall surface over time.

[0006] 3) The general design of retaining walls only considers conventional overall calculation and analysis such as anti-slip, anti-tilting, and base stress, and lacks calculation and optimization analysis of specific structural design parameters such as the depth of retaining piles driven into the foundation and the spacing of drainage holes. This can easily lead to low utilization of construction materials. In addition, when encountering extreme weather such as heavy rainstorms, the drainage demand exceeds the conventional limit, and the accumulated water behind the wall is difficult to be discharged in time, threatening the safety of the retaining wall. Summary of the invention

[0007] The technical problem to be solved by the present invention is to provide an in-wall drainage retaining wall and a construction method that comprehensively utilize geosynthetics in view of the deficiencies of the above-mentioned prior art. The in-wall drainage retaining wall and the construction method that comprehensively utilize geosynthetics can comprehensively utilize the anti-seepage, anti-filtration, drainage, reinforcement and other functions of geosynthetics, and adopt a variety of geosynthetics and precast concrete hollow square piles to form an in-wall drainage system and a retaining force structure. Wall structures such as wall panels are only used for aesthetic design. The division of labor of each structural component is clear, and the construction quality and engineering safety are guaranteed through optimization of design parameter calculation. It has the advantages of novel structure, environmentally friendly materials, and integrated design and construction. It has the advantages of novel structure, convenient construction, and environmentally friendly materials. It is particularly suitable for various scenes such as park landscape and urban cultural construction.

[0008] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0009] The invention discloses an internal drainage retaining wall which comprehensively utilizes geosynthetics, comprising a wall structure, an internal drainage system and a retaining force structure.

[0010] The outer surface of the soil slope is covered with geotextile;

[0011] The wall structure includes a wall panel and a wall core; the wall core is vertically arranged outside the earth slope; the wall panel is arranged outside the wall core;

[0012] The internal drainage system includes geotextile drain pipes, drainage bins, drainage gutters and collection wells.

[0013] A geomembrane is laid on the wall core facing the soil slope, and the drainage bin is formed between the geomembrane and the geotextile.

[0014] The drainage trough is arranged at the bottom of the drainage bin and is connected with a water collection well arranged at one side of the bottom of the earth slope.

[0015] There are a number of geotextile drainage pipes which are all arranged in the soil slope, and the outlet of each geotextile drainage pipe is directed to the drainage bin.

[0016] The retaining structure includes unidirectional geogrid, bidirectional geogrid and several precast concrete hollow square piles.

[0017] A number of precast concrete hollow square piles are evenly arranged in the drainage bin along the length direction of the drainage bin, the bottom of each precast concrete hollow square pile is driven into the foundation below, and adjacent precast concrete hollow square piles are connected by a unidirectional geogrid.

[0018] The bidirectional geogrid is laid on the top of the slope and connected to the top of all unidirectional geogrids.

[0019] Wall eaves are arranged on the top of the wall core and the drainage bin.

[0020] Maximum spacing of precast concrete hollow square piles l max The calculation formula is:

[0021]

[0022] in:

[0023]

[0024] Where f is the earth pressure acting on every 1m wide slope; S, τ, k and B are the equivalent cross-sectional area, shear strength, shear safety factor and width of the precast concrete hollow square pile respectively; γ is the weight of the slope soil; h is the outer height of the slope top; is the friction angle of the soil slope; c is the cohesion of the soil slope.

[0025] Each precast concrete hollow square pile is driven into the foundation to a depth of h r The calculation formula is:

[0026]

[0027] in:

[0028] f r =β2f a

[0029] Where β1 is the reduction factor of the vertical compressive strength of the foundation converted to the horizontal compressive strength; f r is the standard value of vertical compressive strength of foundation; f a is the characteristic value of foundation bearing capacity; β2 is the conversion coefficient between the characteristic value of foundation bearing capacity and the standard value of foundation vertical compressive strength; h is the outer height of the top of the slope; B is the width of the precast concrete hollow square pile.

[0030] The top of each precast concrete hollow square pile is flush with the outside of the top of the slope, so the calculation formula for the total height H of each precast concrete hollow square pile is:

[0031] H=h+h r .

[0032] The tensile strength σ of the unidirectional geogrid must satisfy the following formula:

[0033]

[0034] Among them, θ satisfies the following formula requirements:

[0035]

[0036] Wherein, θ is the angle change of the unidirectional geogrid from the initial state to the stressed tensile state at the connection between the unidirectional geogrid and the precast concrete hollow square pile; δ is the standard elongation of the unidirectional geogrid; l and B are the spacing and width of the precast concrete hollow square piles, respectively; b and d are the width and thickness of the unidirectional geogrid, respectively.

[0037] The geotextile drainage pipes are arranged at equal intervals in each layer, and the calculation formula for the number of layers m is:

[0038] m=Q / q

[0039] in:

[0040] Q=0.278αwA

[0041] q=nΔ×v

[0042]

[0043] In the formula, Q is the total drainage flow of the soil slope; q is the drainage volume of each layer of geotextile drainage pipe; n is the number of roots of each layer of geotextile drainage pipe; α is the infiltration coefficient; w is the maximum daily rainfall; A is the catchment area of ​​the slope; v is the water flow velocity in the geotextile drainage pipe; Δ is the flow area of ​​the geotextile drainage pipe; h0 / D is the design fullness.

[0044] A construction method for an in-wall drainage retaining wall using geosynthetics comprehensively comprises the following steps.

[0045] Step 1: Determine the parameters of the slope and foundation: Conduct field tests such as cross-plate shear test and standard penetration test on the slope soil and foundation to determine the parameters of the slope and foundation; the slope parameters include the friction angle of the slope soil The soil cohesion c, soil weight γ and the outer height of the slope bottom h, foundation parameters include the foundation bearing capacity characteristic value f a .

[0046] Step 2: Calculate the design parameters of precast concrete hollow square piles: Calculate the design parameters of precast concrete hollow square piles based on the soil slope and foundation parameters determined in step 1; the design parameters of precast concrete hollow square piles include the layout spacing l, the depth of the pile into the foundation h r and total height H.

[0047] Step 3: Lay out geotextile drainage pipes: Lay out m layers of geotextile drainage pipes in the soil slope, and the drainage outlets of each layer of geotextile drainage pipes point to the drainage bin.

[0048] Step 4: Laying geotextile: Lay geotextile on the outer side of the slope.

[0049] Step 5: Driving precast concrete hollow square piles: Driving precast concrete hollow square piles with a total height of H into the foundation at a spacing of l and a depth equal to h.r ; Each precast concrete hollow square pile is close to the geotextile on the outside of the slope.

[0050] Step 6: Lay out unidirectional geogrid: Use unidirectional geogrid to connect two adjacent precast concrete hollow square piles.

[0051] Step 7. Laying bidirectional geogrid: Lay bidirectional geogrid on the top surface of the slope. The top of the bidirectional geogrid is anchored to the slope, and the bottom of the bidirectional geogrid is connected to the precast concrete hollow square piles and the unidirectional geogrid.

[0052] Step 8, dig drainage ditches: dig drainage ditches on the foundation outside the precast concrete hollow square piles, and lay geomembrane in the drainage ditch; then, connect the drainage ditch to the water collection well on one side of the bottom of the slope.

[0053] Step 9. Install the wall core: Install the wall core vertically on the foundation outside the drainage ditch, and lay the geomembrane on the wall core facing the drainage ditch, and connect it to the geomembrane of the bottom drainage ditch.

[0054] Step 10. Install the wall panels: Install the wall panels on the outside of the wall core, and install the wall eaves above the wall core and the drainage bin.

[0055] In step 4, the effective pore size O of the geotextile e <0.08mm.

[0056] The geomembrane in step 8 and step 9 is a 1.5 mm thick HDPE geomembrane.

[0057] The present invention has the following beneficial effects:

[0058] 1. The present invention combines precast concrete hollow square piles and unidirectional geogrids as earth pressure bearing bodies, has low requirements on foundation bearing capacity, and only requires simple leveling of the foundation, with fast construction. In addition, bidirectional geogrids are arranged on the surface of the earth slope to reinforce the slope and enhance the safety of the wall and the earth slope. It is particularly suitable for areas with poor foundation conditions and lack of stone materials.

[0059] 2. The present invention designs a drainage system inside the wall, which is composed of geotextile drainage pipes, geotextiles, geomembranes, drainage grooves, water collection wells, etc. to form drainage channels inside the wall, which can filter and drain water, avoid the conventional retaining wall directly passing through the wall to discharge water, and ensure the integrity and aesthetics of the wall structure. The drainage capacity of the designed drainage system can meet the drainage needs under the maximum rainfall intensity, ensure that the water in the soil slope behind the wall is drained in time, and will not generate water pressure on the wall.

[0060] 3. The present invention adopts prefabricated structures and various functional geosynthetics for rapid on-site construction, optimizes and controls the construction quality through standardized prefabrication and design parameter calculation, and gives full play to the superior retaining and drainage functions of the new retaining wall. In addition, the design and construction are integrated, the utilization rate of construction materials is high, the construction period is short, and it is beneficial to save construction costs.

[0061] 4. The present invention has a novel structure, and each structural component has a clear division of labor. The drainage system and the retaining force structure inside the wall are responsible for drainage and retaining bearing respectively, and the wall structure is only used for aesthetic design. By designing the wall panels and wall eaves into different forms for retaining walls, the retaining walls are particularly suitable for various scenes such as park landscapes and urban cultural construction.

[0062] 5. The present invention uses geosynthetics as the main structural component of the retaining wall, giving full play to the reinforcement, anti-seepage, drainage, filtration, protection and other functions of geosynthetics, and adopts customized PVC wall panels and lightweight, energy-saving and environmentally friendly materials to cast the wall core, which has the advantages of low cost, convenient construction, ecological and environmental protection, strong aesthetics, and a wide range of application occasions. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 The present invention is a schematic structural diagram of an in-wall drainage retaining wall that comprehensively utilizes geosynthetics.

[0064] Figure 2 for Figure 1 The enlarged view of the part in the dotted circle;

[0065] Figure 3 for Figure 1 Schematic diagram of the cross section along section BB.

[0066] Figure numerals: 1. wall panel; 2. wall core; 3. geomembrane; 4. precast concrete hollow square pile; 5. one-way geogrid; 6. geotextile; 7. drainage trough; 8. drainage bin; 9. geodrain pipe; 10. two-way geogrid; 11. wall eaves; 12. water collection well; 13. earth slope. DETAILED DESCRIPTION

[0067] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific preferred embodiments.

[0068] In the description of the present invention, it should be understood that the terms "left side", "right side", "upper part", "lower part" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. "First", "second" and the like do not indicate the importance of the components, and therefore cannot be understood as limiting the present invention. The specific dimensions used in this embodiment are only for illustrating the technical solution, and do not limit the scope of protection of the present invention.

[0069] like Figures 1 to 3 As shown, an internal drainage retaining wall which comprehensively utilizes geosynthetics includes a wall structure, an internal drainage system and a retaining force structure.

[0070] The bottom of the earth slope is covered with geotextile 6.

[0071] The wall structure includes a wall panel 1, a core 2 and a wall eave 11. The wall core is vertically arranged outside the bottom of the earth slope, and the wall panel is arranged outside the wall core. The wall eave 11 is arranged on the top of the wall core and the drainage bin described below.

[0072] The drainage system inside the wall includes geotextile drainage pipes 9, geomembrane 3, drainage bins 8, drainage grooves 7 and water collection wells 12.

[0073] The geomembrane is laid on the wall core facing the slope, and a drainage chamber is formed between the geomembrane and the geotextile.

[0074] The drainage trough is arranged at the bottom of the drainage bin and is connected with a water collection well arranged on one side of the soil slope.

[0075] There are a number of geotextile drainage pipes which are all arranged in the soil slope, and the outlet of each geotextile drainage pipe is directed to the drainage bin.

[0076] The geodrain pipe has a permeable wall and a corrugated shape. The pipe mouth is located in the trough, which is not easy to be blocked and can smoothly discharge the pore water in the soil slope. The geodrain pipe meets the drainage demand under the maximum rainfall intensity, so that the accumulated water in the soil slope behind the wall can still be discharged in time under extreme weather conditions such as heavy rain. The number of layers of geodrain pipes is determined according to the maximum rainfall intensity in the area.

[0077] The earth retaining structure includes a unidirectional geogrid 5 , a bidirectional geogrid 10 and a plurality of prefabricated concrete hollow square piles 4 .

[0078] A number of precast concrete hollow square piles are evenly arranged in the drainage bin along the length direction of the drainage bin, the bottom of each precast concrete hollow square pile is driven into the foundation below, and adjacent precast concrete hollow square piles are connected by a unidirectional geogrid.

[0079] The bidirectional geogrid is laid on the top of the slope and connected to the top of all unidirectional geogrids.

[0080] The above-mentioned precast concrete hollow square piles and one-way geogrids jointly bear the earth pressure of the soil slope behind the wall, thereby preventing the wall core and other wall structures from being stressed.

[0081] A construction method for an in-wall drainage retaining wall using geosynthetics comprehensively comprises the following steps.

[0082] Step 1: Determine the soil slope and foundation parameters

[0083] Soil slope parameters include the friction angle of soil slope The soil cohesion c, soil weight γ and the outer height of the slope bottom h, foundation parameters include the foundation bearing capacity characteristic value f a .

[0084] The optimal method for determining soil slope and foundation parameters is:

[0085] A. Carry out more than 5 groups of on-site cross-plate shear tests at different positions of the soil slope behind the wall, select the test results with the smallest standard deviation and not exceeding 10% of the average value, and determine the internal friction angle of the soil behind the wall by the average value of the small values ​​of the test results. Cohesion c, soil weight γ and outer height of slope bottom h.

[0086] B. Select test points and carry out foundation on-site standard penetration tests in sequence until three groups of test results with a range not exceeding 30% of the average are obtained. The average value of the three groups of test results is selected as the foundation bearing capacity characteristic value f a .

[0087] Step 2: Calculate the design parameters of precast concrete hollow square piles: Calculate the design parameters of precast concrete hollow square piles based on the soil slope parameters determined in step 1; the design parameters of precast concrete hollow square piles include the layout spacing l, the depth of the pile into the foundation h r and total height H.

[0088] The maximum layout spacing of the above precast concrete hollow square piles is l max The calculation formula is:

[0089]

[0090] in:

[0091]

[0092] Where f is the earth pressure acting on every 1m wide slope; S, τ, k and B are the equivalent cross-sectional area, shear strength, shear safety factor and width of the precast concrete hollow square pile respectively; γ is the weight of the slope soil; h is the outer height of the slope top; is the friction angle of the soil slope; c is the cohesion of the soil slope.

[0093] Each precast concrete hollow square pile is driven into the foundation to a depth of h r The calculation formula is preferably:

[0094]

[0095] in:

[0096] f r =β2f a

[0097] Where β1 is the reduction factor of the vertical compressive strength of the foundation converted to the horizontal compressive strength; f r is the standard value of vertical compressive strength of foundation; f a is the characteristic value of foundation bearing capacity; β2 is the conversion coefficient between the characteristic value of foundation bearing capacity and the standard value of foundation vertical compressive strength; h is the outer height of the top of the slope; B is the width of the precast concrete hollow square pile.

[0098] The top of each precast concrete hollow square pile is flush with the outside of the top of the slope, so the calculation formula for the total height H of each precast concrete hollow square pile is:

[0099] H=h+h r .

[0100] In this embodiment, the preparation specification of the precast concrete hollow square piles is preferably 400mm×400mm (or Φ200mm).

[0101] Step 3: Laying out geotextile drainage pipes: Laying out m layers of geotextile drainage pipes in the soil slope, with the drainage outlets of each layer of geotextile drainage pipes pointing to the bottom of the soil slope. In this embodiment, the geotextile drainage pipes are preferably corrugated geotextile drainage pipes with a diameter of 200 m.

[0102] The geotextile drainage pipes are arranged at equal intervals in each layer, and the calculation formula for the number of layers m is:

[0103] m=Q / q

[0104] in:

[0105] Q=0.278αwA

[0106] q=nΔ×v

[0107]

[0108] In the formula, Q is the total drainage flow of the earth slope; q is the drainage volume of each layer of geotextile drainage pipe; n is the number of roots of each layer of geotextile drainage pipe; α is the infiltration coefficient; w is the maximum daily rainfall; A is the catchment area of ​​the earth slope; v is the water flow velocity in the geotextile drainage pipe; Δ is the flow area of ​​the geotextile drainage pipe; h0 / D is the design fullness, that is, the ratio of the effective water depth h0 in the geotextile drainage pipe to the pipe diameter D, which is 0.5~0.9 and is set manually.

[0109] Step 4: Laying geotextile: Lay geotextile on the outer side of the bottom of the slope. The thickness of the geotextile is preferably 2 mm, and the effective pore size is 0. e <0.08mm. Geotextile is set up to prevent soil particles from being lost when water is discharged from the soil slope.

[0110] Step 5: Driving precast concrete hollow square piles: Driving precast concrete hollow square piles with a total height of H into the foundation at a spacing of l and a depth equal to h. r ; Each precast concrete hollow square pile is close to the geotextile on the outside of the slope.

[0111] Step 6: Lay out unidirectional geogrids: Use unidirectional geogrids to connect two adjacent precast concrete hollow square piles. The tensile strength σ of the unidirectional geogrid must satisfy the following formula:

[0112]

[0113] Among them, θ satisfies the following formula requirements:

[0114]

[0115] Wherein, θ is the angle change of the unidirectional geogrid from the initial state to the stressed tensile state at the connection between the unidirectional geogrid and the precast concrete hollow square pile; δ is the standard elongation of the unidirectional geogrid; l and B are the actual layout spacing and width of the precast concrete hollow square piles, respectively; b and d are the width and thickness of the unidirectional geogrid, respectively.

[0116] Step 7. Laying bidirectional geogrid: Lay bidirectional geogrid on the top of the slope. The top of the bidirectional geogrid is anchored to the top of the slope, and the bottom of the bidirectional geogrid is connected to the precast concrete hollow square piles and the unidirectional geogrid.

[0117] In this embodiment, the bidirectional geogrid preferably has a width of 6m and a grid bar width of 50mm.

[0118] Green plants are planted in the gaps of the bidirectional geogrid to reduce the scouring of the slope by rainwater and enhance the aesthetics.

[0119] Step 8: Dig drainage trenches: dig drainage trenches on the foundation outside the precast concrete hollow square piles, and lay geomembranes in the drainage trenches; the geomembranes are preferably 1.5 mm thick HDPE geomembranes. Then, connect the drainage trenches to the water collection well on one side of the bottom of the earth slope.

[0120] After being discharged from the geotextile drainage pipe, the water flows through the geotextile, falls from the drainage bin into the drainage trough, and finally flows into a 50cm deep collection well. The entire drainage process will not have an adverse effect on wall structures such as wall cores.

[0121] Step 9, install the wall core: vertically install the wall core on the foundation outside the drainage ditch, and preferably lay a 1.5mm HDPE geomembrane on the wall core facing the drainage ditch to prevent the soil slope drainage from seeping into the wall core and generating water pressure on the wall core.

[0122] Step 10. Install the wall panels: Install the wall panels on the outside of the wall core, and install the wall eaves above the wall core and the drainage bin.

[0123] The wall panels are preferably prefabricated from PVC boards and assembled on site, and are provided with patterns customized according to the scene requirements of the retaining wall; the wall core behind the wall panels is preferably cast from lightweight, energy-saving, and environmentally friendly materials; the wall eaves are preferably installed above the wall core through a connecting frame.

[0124] The wall structure of the above-mentioned wall panels, wall cores and wall eaves only bears its own weight and aesthetic design functions, does not need to bear the soil retaining and drainage functions, and does not bear the pressure of soil slope drainage.

[0125] The present invention utilizes the anti-seepage, filtration, drainage, reinforcement and other functions of geosynthetics, and adopts a variety of geosynthetics and precast concrete hollow square piles to form an in-wall drainage system and retaining force structure. Wall structures such as wall panels are only used for aesthetic design. The various structural components have a clear division of labor, and the construction quality and engineering safety are guaranteed through optimization of design parameter calculations. It has the advantages of novel structure, environmentally friendly materials, and integrated design and construction. It is particularly suitable for various scenarios such as park landscape and urban cultural construction.

[0126] The preferred embodiments of the present invention are described in detail above; however, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various equivalent transformations can be made to the technical solutions of the present invention, and these equivalent transformations all belong to the protection scope of the present invention.

Claims

1. An in-wall drainage retaining wall using geosynthetics, characterized in that: Including wall structure, drainage system inside the wall and retaining structure; The outer surface of the soil slope is covered with geotextile; The wall structure includes a wall panel and a wall core; the wall core is vertically arranged outside the earth slope; the wall panel is arranged outside the wall core; The wall drainage system includes geotextile drain pipes, drainage bins, drainage gutters and water collection wells; A geomembrane is laid on the wall core facing the side of the soil slope, and the drainage bin is formed between the geomembrane and the geotextile; The drainage trough is arranged at the bottom of the drainage bin and is connected to the water collection well arranged at one side of the bottom of the earth slope; There are several geotextile drainage pipes, all of which are laid out in the soil slope, and the outlet of each geotextile drainage pipe points to the drainage bin; The retaining structure includes one-way geogrid, two-way geogrid and several precast concrete hollow square piles; A number of precast concrete hollow square piles are evenly arranged in the drainage bin along the length direction of the drainage bin, the bottom of each precast concrete hollow square pile is driven into the foundation below, and adjacent precast concrete hollow square piles are connected by a one-way geogrid; The bidirectional geogrid is laid on the top of the slope and connected to the top of all unidirectional geogrids.

2. The internal drainage retaining wall using geosynthetics as claimed in claim 1 is characterized by: Wall eaves are arranged on the top of the wall core and the drainage bin.

3. The internal drainage retaining wall using geosynthetics as claimed in claim 1 is characterized by: Maximum spacing of precast concrete hollow square piles l max The calculation formula is: in: Where f is the earth pressure acting on every 1m wide slope; S, τ, k and B are the equivalent cross-sectional area, shear strength, shear safety factor and width of the precast concrete hollow square pile respectively; γ is the weight of the slope soil; h is the outer height of the slope top; is the friction angle of the soil slope; c is the cohesion of the soil slope.

4. The internal drainage retaining wall using geosynthetics as claimed in claim 3 is characterized by: The tensile strength σ of the unidirectional geogrid must satisfy the following formula: Among them, θ satisfies the following formula requirements: Wherein, θ is the angle change of the unidirectional geogrid from the initial state to the stressed tensile state at the connection between the unidirectional geogrid and the precast concrete hollow square pile; δ is the standard elongation of the unidirectional geogrid; l and B are the spacing and width of the precast concrete hollow square piles, respectively; b and d are the width and thickness of the unidirectional geogrid, respectively.

5. The internal drainage retaining wall using geosynthetics as claimed in claim 3 is characterized by: The geotextile drainage pipes are arranged at equal intervals in each layer, and the calculation formula for the number of layers m is: m=Q / q in: Q=0.278αwA q=nΔ×v In the formula, Q is the total drainage flow of the soil slope; q is the drainage volume of each layer of geotextile drainage pipe; n is the number of roots of each layer of geotextile drainage pipe; α is the infiltration coefficient; w is the maximum daily rainfall; A is the catchment area of ​​the slope; v is the water flow velocity in the geotextile drainage pipe; Δ is the flow area of ​​the geotextile drainage pipe; h0 / D is the design filling degree; h0 is the effective water depth in the geotextile drainage pipe; D is the pipe diameter.

6. A method for constructing an in-wall drainage retaining wall using geosynthetics according to any one of claims 1 to 5, characterized in that: The steps include: Step 1: Determine the parameters of the slope and foundation: Carry out cross-plate shear test and standard penetration test on the slope soil and foundation respectively to determine the parameters of the slope and foundation; the slope parameters include the friction angle of the slope soil The soil cohesion c, soil weight γ and the outer height of the slope top h, foundation parameters include the foundation bearing capacity characteristic value f a ; Step 2: Calculate the design parameters of precast concrete hollow square piles: Calculate the design parameters of precast concrete hollow square piles based on the soil slope and foundation parameters determined in step 1; the design parameters of precast concrete hollow square piles include the layout spacing l, the depth of the pile into the foundation h r and total height H; Step 3: Lay out geotextile drainage pipes: lay out m layers of geotextile drainage pipes in the soil slope, and the drainage outlets of each layer of geotextile drainage pipes point to the drainage bin; Step 4: Laying geotextile: Lay geotextile on the outer side of the slope; Step 5: Driving precast concrete hollow square piles: Driving precast concrete hollow square piles with a total height of H into the foundation at a spacing of l and a depth equal to h. r ; Each precast concrete hollow square pile is close to the geotextile on the outside of the slope; Step 6: Laying out one-way geogrid: Use one-way geogrid to connect two adjacent precast concrete hollow square piles; Step 7, laying bidirectional geogrid: laying bidirectional geogrid on the top surface of the soil slope, the top of the bidirectional geogrid is anchored to the soil slope, and the bottom of the bidirectional geogrid is connected to the precast concrete hollow square pile and the unidirectional geogrid; Step 8, digging drainage ditch: dig drainage ditch on the foundation outside the precast concrete hollow square pile, and lay geomembrane in the drainage ditch; then, connect the drainage ditch to the water collection well on one side of the bottom of the slope; Step 9, install the wall core: vertically install the wall core on the foundation outside the drainage trough, and lay the geomembrane on the wall core facing the drainage trough side, and connect it with the geomembrane of the bottom drainage trough; Step 10. Install the wall panels: Install the wall panels on the outside of the wall core, and install the wall eaves above the wall core and the drainage bin.

7. The construction method of the internal drainage retaining wall using comprehensive geosynthetics according to claim 6, characterized in that: In step 4, the effective pore size O of the geotextile e <0.08mm.

8. The construction method of the internal drainage retaining wall using comprehensive geosynthetics according to claim 6, characterized in that: The geomembrane in step 8 and step 9 is a 1.5 mm thick HDPE geomembrane.

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