Soft soil subgrade structure and construction method thereof

Abstract

This invention discloses a soft soil subgrade structure and its construction method. Belonging to the field of subgrade construction technology, the soft soil subgrade structure includes a first sheet pile wall, a second sheet pile wall, a reinforcement layer, a backfill layer, a pavement layer, and a drainage and maintenance system. The backfill layer includes, from top to bottom, a second sand and gravel backfill, a water-retaining element, and clay backfill. The use of clay backfill as part of the filling material reduces the amount of the first sand and gravel backfill used in the backfill layer, thus saving project costs. The water-retaining element prevents water from falling into the clay backfill, helping to keep the clay backfill dry, thereby ensuring the structural strength of the backfill layer and the stability of the soft soil subgrade structure.

Description

Technical Field

[0001] This invention relates to the field of roadbed construction technology, and more specifically, to a soft soil roadbed structure and its construction method. Background Technology

[0002] In recent years, my country has vigorously developed the construction of transportation infrastructure such as highways and railways. Geosynthetic reinforced soil structures, with their outstanding advantages such as low carbon and environmental friendliness, rapid construction, and strong deformation coordination capabilities, have attracted much attention from engineers in transportation infrastructure construction.

[0003] The Beijing-Tianjin-Hebei region, the Yangtze River Delta, and the Pearl River Delta, urban clusters in my country with huge demand for transportation infrastructure, all have large areas of soft soil. Soft soil is characterized by high water content, high porosity, and high compressibility. The construction of transportation infrastructure in soft soil areas usually faces prominent problems such as insufficient bearing capacity, excessive settlement, and high risk of instability.

[0004] In related technologies, to ensure the stability of the roadbed on soft soil, excavation and filling are required during construction. This involves excavating the soft soil and then filling it with sand and gravel. The sand and gravel are generally loose materials of rock and soil type, which need to be transported from outside to the construction site. The amount of sand and gravel used for filling is relatively large, resulting in higher project costs. Summary of the Invention

[0005] This invention aims to at least partially solve one of the aforementioned technical problems in the prior art. To this end, this invention proposes a soft soil subgrade structure, which is beneficial for reducing engineering costs.

[0006] The present invention also proposes a construction method for the above-mentioned soft soil subgrade structure.

[0007] According to an embodiment of the present invention, a soft soil subgrade structure is provided on a soft soil foundation. The soft soil subgrade structure includes: a first sheet pile wall, a second sheet pile wall, a reinforcement layer, a backfill layer, a pavement layer, and a drainage and maintenance system. The first sheet pile wall and the second sheet pile wall are arranged opposite to each other, and portions of both the first sheet pile wall and the second sheet pile wall are buried in the soft soil foundation. A backfill space is formed between the first sheet pile wall and the second sheet pile wall. The reinforcement layer is provided in the backfill space, and at least a portion of the reinforcement layer is located below the surface of the soft soil foundation. The reinforcement layer includes a first sand and gravel backfill. The backfill layer is provided in the backfill space and is located above the reinforcement layer. The backfill layer includes a series of materials arranged from top to bottom. The second backfill consists of gravel, a water-retaining element, and clay backfill; the road surface layer is located above the backfill layer; the drainage maintenance system includes a hollow steel pipe, a drainage ditch, and an electrode rod. The drainage ditch is located below the reinforcement layer and extends to the outside of the first sheet pile wall and the second sheet pile wall. The hollow steel pipe passes through the reinforcement layer and the backfill layer. The hollow steel pipe has an inlet hole and a drain hole. The inlet hole communicates with the water-retaining element, and the drain hole communicates with the drainage ditch. At least a portion of the electrode rod is buried in the soft soil foundation outside the backfill space. The electrode rod is adapted to be connected to the positive terminal of a power source, and the hollow steel pipe is adapted to be connected to the negative terminal of a power source, or the first sheet pile wall and the second sheet pile wall are adapted to be connected to the negative terminal of a power source.

[0008] According to an embodiment of the present invention, the backfill layer of the soft soil subgrade structure includes a second sand and gravel backfill, a water-retaining component, and a clay backfill arranged sequentially from top to bottom. The use of clay backfill as part of the filling material in the backfill layer can reduce the amount of the first sand and gravel backfill in the backfill layer, thereby saving engineering costs. The water-retaining component can prevent water from falling into the clay backfill, which helps to keep the clay backfill dry, thereby ensuring the structural strength of the backfill layer and the stability of the soft soil subgrade structure.

[0009] According to some embodiments of the present invention, both the first sheet pile wall and the second sheet pile wall are connected to the hollow steel pipe through the water-blocking member.

[0010] According to some embodiments of the present invention, the water-retaining component includes a first sub-water-retaining component and a second sub-water-retaining component with identical structures. Both the first sub-water-retaining component and the second sub-water-retaining component include a first geogrid, a water-retaining plate, and a second geogrid stacked together. The first geogrid and the second geogrid of the first sub-water-retaining component are both connected between the first sheet pile wall and the hollow steel pipe; the first geogrid and the second geogrid of the second sub-water-retaining component are both connected between the second sheet pile wall and the hollow steel pipe.

[0011] According to some embodiments of the present invention, there are multiple backfill layers, a third geogrid is provided between two adjacent backfill layers, and at least one of the first sheet pile wall and the second sheet pile wall is connected to the third geogrid.

[0012] According to some embodiments of the present invention, the distance between the water-blocking member and the third geogrid in the vertical direction is H1, which satisfies the relationship: 0.4m≤H1≤0.6m.

[0013] According to some embodiments of the present invention, the distance between the hollow steel pipe and the first sheet pile wall is the same as the distance between the hollow steel pipe and the second sheet pile wall.

[0014] According to some embodiments of the present invention, the hollow steel pipe includes a plurality of detachably connected hollow sub-steel pipes.

[0015] According to some embodiments of the present invention, the drainage maintenance system further includes a water collection well located in the soft soil foundation outside the backfill space, and the water collection well is connected to the drainage channel.

[0016] According to another embodiment of the present invention, a construction method for a soft soil subgrade structure, wherein the soft soil subgrade structure is the aforementioned soft soil subgrade structure, the construction method includes: constructing the drainage maintenance system; connecting the electrode rod to the positive terminal of a power supply and the hollow steel pipe to the negative terminal of a power supply to perform electro-osmotic consolidation on the soft soil foundation; constructing a first sheet pile wall and a second sheet pile wall; and sequentially arranging a reinforcement layer, a backfill layer, and a pavement layer.

[0017] According to the construction method of soft soil subgrade structure according to an embodiment of the present invention, the backfill layer includes a second sand and gravel backfill, a water-retaining component, and a clay backfill arranged sequentially from top to bottom. The use of clay backfill as part of the filling material in the backfill layer can reduce the amount of the first sand and gravel backfill in the backfill layer, thereby saving engineering costs. The water-retaining component can prevent water from falling into the clay backfill, which helps to keep the clay backfill dry, thereby ensuring the structural strength of the backfill layer and the stability of the soft soil subgrade structure.

[0018] According to some embodiments of the present invention, the construction method further includes: excavating soft soil on the soft soil foundation outside the soft soil subgrade structure, and drying the soft soil to obtain the clay backfill soil.

[0019] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a soft soil roadbed structure and a soft soil foundation according to an embodiment of the present invention;

[0021] Figure 2 This is a schematic diagram of the connection between the hollow steel pipe and the second sheet pile wall according to an embodiment of the present invention;

[0022] Figure 3 This is a schematic diagram of the connection between the first sub-water-retaining component and the third geogrid and the second sheet pile wall according to an embodiment of the present invention;

[0023] Figure 4 This is a schematic diagram of a hollow steel tube according to an embodiment of the present invention;

[0024] Figure 5 This is a flowchart of a construction method for a soft soil subgrade structure according to an embodiment of the present invention.

[0025] Figure label:

[0026] First sheet pile wall 1; Second sheet pile wall 2;

[0027] Reinforcement layer 3; First sand and gravel backfill 31; Third geotextile 32;

[0028] Backfill layer 4; Second sand and gravel backfill soil 41; Water-retaining component 42; First sub-water-retaining component 42a; Second sub-water-retaining component 42b; Clay backfill soil 43;

[0029] Road surface layer 5;

[0030] 6. Drainage maintenance system; 61. Hollow steel pipe; 611. Water inlet; 612. Drainage hole; 613. Hollow sub-steel pipe; 6131. ​​Joint; 62. Drainage trough; 63. Electrode rod; 64. Water collection well;

[0031] First reinforcement hook 71; Second reinforcement hook 72; Second reinforcement clamp 73; Third geogrid 74; First sub-geogrid 74a; Second sub-geogrid 74b; Third sand and gravel backfill soil 75; Fourth reinforcement clamp 76; Square plastic blind pipe 77;

[0032] Sheet pile wall pile cap 8;

[0033] Soft soil subgrade structure 10;

[0034] Soft soil foundation 20. Detailed Implementation

[0035] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0036] In the description of this invention, it should be understood that the terms "thickness", "upper", "lower", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0037] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0038] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0039] The following is combined with Figures 1-5 The soft soil subgrade structure 10 and its construction method according to embodiments of the present invention are described in detail.

[0040] Reference Figure 1As shown, according to an embodiment of the present invention, the soft soil subgrade structure 10 is provided on a soft soil foundation 20. The soft soil subgrade structure 10 includes a first sheet pile wall 1, a second sheet pile wall 2, a reinforcement layer 3, a backfill layer 4, a pavement layer 5, and a drainage maintenance system 6. The first sheet pile wall 1 and the second sheet pile wall 2 are arranged opposite to each other, and a portion of the first sheet pile wall 1 and a portion of the second sheet pile wall 2 are buried in the soft soil foundation 20. A backfill space is formed between the first sheet pile wall 1 and the second sheet pile wall 2. The reinforcement layer 3 is provided in the backfill space, and at least a portion of the reinforcement layer 3 is located below the surface of the soft soil foundation 20. The reinforcement layer 3 includes a first sand and gravel backfill 31. The backfill layer 4 is provided in the backfill space and is located above the reinforcement layer 3. The backfill layer 4 includes a second sand and gravel backfill arranged sequentially from top to bottom. The system includes a fill layer 41, a water-retaining component 42, and a clay backfill layer 43. The road surface layer 5 is located above the backfill layer 4. The drainage maintenance system 6 includes a hollow steel pipe 61, a drainage ditch 62, and an electrode rod 63. The drainage ditch 62 is located below the reinforcement layer 3 and extends to the outside of the first sheet pile wall 1 and the second sheet pile wall 2. The hollow steel pipe 61 passes through the reinforcement layer 3 and the backfill layer 4. The hollow steel pipe 61 has a water inlet hole 611 and a drainage hole 612. The water inlet hole 611 is connected to the water-retaining component 42, and the drainage hole 612 is connected to the drainage ditch 62. At least part of the electrode rod 63 is buried in the soft soil foundation 20 outside the backfill space. The electrode rod 63 is suitable for connecting to the positive terminal of a power source, and the hollow steel pipe 61 is suitable for connecting to the negative terminal of a power source. Alternatively, the first sheet pile wall 1 and the second sheet pile wall 2 are suitable for connecting to the negative terminal of a power source.

[0041] The first backfill soil 31 can be well-graded quartz sand with an internal friction angle greater than 40°. During construction, the first backfill soil 31 needs to be compacted to a relative density of over 90% to achieve foundation reinforcement. The second backfill soil 41 can be quartz sand with an internal friction angle greater than 38°. During construction, the second backfill soil 41 needs to be compacted to a relative density of over 95%, which is beneficial to improving the structural strength of the soft soil subgrade structure 10, thereby ensuring the service performance and stability of the soft soil subgrade structure 10. The clay backfill soil 43 can be the soft soil foundation 20 outside the soft soil subgrade structure 10. The soft soil is excavated and dried to reduce the amount of second sand and gravel backfill soil 41 in backfill layer 4, which helps save project costs. The road surface layer 5 can be stone asphalt concrete with strong deformation resistance, and its thickness can be 0.2m~0.3m. The drainage channel 62 can be a "U" shaped channel made of concrete with a strength grade of not less than C30. The drainage channel 62 can be filled with square plastic blind pipes 77. Two layers of first geotextile can be laid on the top of the drainage channel 62 to prevent the first sand and gravel backfill soil 31 in reinforcement layer 3 from entering the drainage channel 62 and to prevent the drainage channel 62 from being blocked.

[0042] It is understandable that the second sand and gravel backfill 41, the water-retaining component 42, and the clay backfill 43 of the backfill layer 4 are arranged sequentially from top to bottom. The water-retaining component 42 is located above the clay backfill 43. In the event of rainfall or river erosion, the water-retaining component 42 can prevent water from flowing into the clay backfill 43, thus keeping the clay backfill 43 dry and ensuring the structural strength of the backfill layer 4. In addition, the water blocked by the water-retaining component 42 can flow into the hollow steel pipe 61 through the water inlet 611 connected to the water-retaining component 42. Then, under the action of gravity, it can flow through the drainage hole 612 of the hollow steel pipe 61 to the drainage ditch 62 and be discharged from the drainage ditch 62. This can prevent water from accumulating in the soft soil subgrade structure 10, prevent water from affecting the soil strength, and thus help reduce the risk of structural instability and failure of the soft soil subgrade structure 10.

[0043] When constructing the drainage maintenance system 6, the electrode rod 63 can be connected to the positive terminal of the power supply and the hollow steel pipe 61 can be connected to the negative terminal of the power supply. The electrode rod 63 can be used as the anode and the hollow steel pipe 61 can be used as the cathode to guide the water in the soft soil foundation 20 to flow towards the cathode. The water can flow into the hollow steel pipe 61 through the water inlet hole 611 and flow to the drainage trough 62 through the drainage hole 612 of the hollow steel pipe 61 to drain the water in the soft soil foundation 20, thereby realizing the electroosmotic consolidation of the soft soil foundation 20, thereby improving the structural strength of the soft soil foundation 20. When the first sheet pile wall 1 and the second sheet pile wall 2 are buried in the soft soil foundation 20, the electroosmotically consolidated soft soil foundation 20 can stably and reliably support the first sheet pile wall 1 and the second sheet pile wall 2, which helps to reduce the risk of the first sheet pile wall 1 and the second sheet pile wall 2 overturning.

[0044] After the drainage maintenance system 6 is constructed, the electrode rod 63 can be connected to the positive terminal of the power supply, and the first sheet pile wall 1 and the second sheet pile wall 2 can be connected to the negative terminal of the power supply. The electrode rod 63 is used as the anode and the first sheet pile wall 1 and the second sheet pile wall 2 are used as the cathode to prevent the first sheet pile wall 1 and the second sheet pile wall 2 from corroding and rusting, thereby helping to extend the service life of the first sheet pile wall 1 and the second sheet pile wall 2.

[0045] According to an embodiment of the present invention, the soft soil subgrade structure 10 includes a backfill layer 4 comprising a second sand and gravel backfill 41, a water-retaining element 42, and a clay backfill 43 arranged sequentially from top to bottom. The backfill layer 4 utilizes the clay backfill 43 as part of the filling material, which can reduce the amount of the first sand and gravel backfill 31 used in the backfill layer 4, thereby saving engineering costs. The water-retaining element 42 can prevent water from falling into the clay backfill 43, which helps to keep the clay backfill 43 dry, thereby ensuring the structural strength of the backfill layer 4 and the stability of the soft soil subgrade structure 10.

[0046] In some embodiments of the present invention, reference is made to... Figure 1As shown, the first sheet pile wall 1 and the second sheet pile wall 2 are both connected to the hollow steel pipe 61 through the water-blocking component 42. The hollow steel pipe 61 can hold the first sheet pile wall 1 and the second sheet pile wall 2 with the water-blocking component 42 to reduce the risk of the first sheet pile wall 1 and the second sheet pile wall 2 overturning, thereby improving the stability and reliability of the soft soil subgrade structure 10.

[0047] Reference Figure 1 As shown, the hollow steel pipe 61 has a hollow structure inside, which can form a water passage connecting the water inlet hole 611 and the drainage hole 612. The interior of the hollow steel pipe 61 can be filled with a third sand and gravel backfill soil 75. The third sand and gravel backfill soil 75 can support the inner wall of the hollow steel pipe 61 and prevent the hollow steel pipe 61 from being deformed by compression and blocking the water passage connected to the water inlet hole 611, thus avoiding affecting the drainage function of the hollow steel pipe 61. In addition, the third sand and gravel backfill soil 75 will not affect the drainage function of the hollow steel pipe 61. Water blocked by the water-blocking member 42 can be smoothly discharged to the drainage trough 62 through the hollow steel pipe 61.

[0048] In some embodiments, the diameter of the water inlet hole 611 of the hollow steel pipe 61 can be less than 1 cm to prevent the second sand and gravel backfill soil 41 in the backfill layer 4 from entering the hollow steel pipe 61 through the water inlet hole 611, which is beneficial to ensuring the structural stability of the backfill layer 4.

[0049] In other embodiments, a metal mesh may be welded to the hollow steel pipe 61 at the water inlet 611, and two layers of second geotextile may be wrapped around the outside of the metal mesh to prevent the second sand and gravel backfill soil 41 in the backfill layer 4 from entering the hollow steel pipe 61 through the water inlet 611. This helps to ensure the structural stability of the backfill layer 4. At the same time, the second geotextile has good permeability, and water can pass through the second geotextile and enter the hollow steel pipe 61 through the water inlet 611 without affecting the drainage function of the drainage maintenance system 6.

[0050] In some embodiments of the present invention, reference is made to... Figures 1-3 As shown, the water-retaining component 42 includes a first sub-water-retaining component 42a and a second sub-water-retaining component 42b with identical structures. Both the first sub-water-retaining component 42a and the second sub-water-retaining component 42b include a first geogrid, a water-retaining plate, and a second geogrid stacked together. The first geogrid and the second geogrid of the first sub-water-retaining component 42a are connected between the first sheet pile wall 1 and the hollow steel pipe 61, and the first geogrid and the second geogrid of the second sub-water-retaining component 42b are connected between the second sheet pile wall 2 and the hollow steel pipe 61.

[0051] It is understandable that the hollow steel pipe 61 can be used to hold the first sheet pile wall 1 together with the first geogrid and the second geogrid of the first sub-water retaining member 42a, so as to reduce the risk of the first sheet pile wall 1 overturning. Similarly, the hollow steel pipe 61 can be used to hold the second sheet pile wall 2 together with the first geogrid and the second geogrid of the second sub-water retaining member 42b, so as to reduce the risk of the second sheet pile wall 2 overturning. The water retaining plate can be a waterproof plastic plate. The water retaining plate can prevent water from falling into the clay backfill soil 43 of the backfill layer 4, so as to ensure the structural strength of the backfill layer 4, thereby helping to ensure the stability and reliability of the soft soil subgrade structure 10.

[0052] Reference Figure 2-4 As shown, in the left-right direction, the hollow steel pipe 61 is symmetrically provided with a first reinforcing hook 71 and a second reinforcing hook 72 on the left and right sides. The first sheet pile wall 1 is provided with a first reinforcing clamp on the side near the hollow steel pipe 61, and the second sheet pile wall 2 is provided with a second reinforcing clamp 73 on the side near the hollow steel pipe 61. The first reinforcing hook 71 is adapted to connect to the right end of the first geogrid and the second geogrid of the first sub-water retaining member 42a. The first reinforcing clamp is adapted to connect to the left end of the first geogrid and the second geogrid of the first sub-water retaining member 42a, so that the first sub-water retaining member 42a is connected between the first sheet pile wall 1 and the hollow steel pipe 61. The second reinforcing hook 72 is adapted to connect to the left end of the first geogrid and the second geogrid of the second sub-water retaining member 42b. The second reinforcing clamp 73 is adapted to connect to the right end of the first geogrid and the second geogrid of the second sub-water retaining member 42b, so that the second sub-water retaining member 42b is connected between the second sheet pile wall 2 and the hollow steel pipe 61.

[0053] Both the first and second reinforcement clamps 73 can be constructed as boxes with pre-reserved openings. The first and second geogrids of the first sub-water-retaining member 42a can be inserted into the openings of the first reinforcement clamp and mechanically connected by screws and nuts, so as to clamp the first and second geogrids of the first sub-water-retaining member 42a in the vertical direction. This allows the water-retaining member 42 of the first sub-water-retaining member 42a to be clamped by the first and second geogrids, and the first and second geogrids of the second sub-water-retaining member 42b... The grid can be inserted into the holes of the second reinforcing clamp 73 and mechanically connected by screws and nuts to clamp the first geogrid and the second geogrid of the second sub-water barrier 42b in the vertical direction, so that the water barrier 42 of the second sub-water barrier 42b is clamped by the first geogrid and the second geogrid, thereby preventing the water barrier 42 of the first sub-water barrier 42a and the water barrier 42 of the second sub-water barrier 42b from moving around, avoiding the drainage board from sinking into the clay backfill soil 43, and effectively preventing water from entering the clay backfill soil 43.

[0054] In some embodiments of the present invention, reference is made to... Figures 1-3As shown, there are multiple backfill layers 4. A third geogrid 74 is provided between two adjacent backfill layers 4. At least one of the first sheet pile wall 1 and the second sheet pile wall 2 is connected to the third geogrid 74. That is, the first sheet pile wall 1 can be connected to the third geogrid 74, or the second sheet pile wall 2 can be connected to the third geogrid 74, or both the first sheet pile wall 1 and the second sheet pile wall 2 can be connected to the third geogrid 74 to fix the third geogrid 74. The third geogrid 74 can prevent the clay backfill soil 43 in the backfill layer 4 from shifting, thereby helping to ensure the structural stability of the backfill layer 4.

[0055] It is understandable that there are multiple backfill layers 4. The multiple water-retaining components 42 of the multiple backfill layers 4 can stably and reliably hold the first sheet pile wall 1 and the second sheet pile wall 2, reducing the risk of the first sheet pile wall 1 and the second sheet pile wall 2 overturning. This is beneficial to improving the stability and reliability of the soft soil subgrade structure 10. Moreover, the multiple water-retaining components 42 of the multiple backfill layers 4 can block water layer by layer to form a multi-layer water-retaining effect, which can effectively reduce the risk of water entering the clay backfill soil 43, thereby reducing the risk of structural instability of the clay backfill soil 43. In addition, the number of backfill layers 4 can reduce the thickness of the clay backfill soil 43 in a single backfill layer 4, thereby reducing the risk of structural instability of the clay backfill soil 43 and improving the structural strength of the backfill layer 4.

[0056] In this embodiment, refer to Figure 1 and Figure 2 As shown, in the vertical direction, the top surface of the reinforcement layer 3 is flush with the surface of the soft soil foundation 20. The total height of the multiple backfill layers 4 plus the height of the pavement layer 5 is the net height of the soft soil subgrade structure 10. Among them, the tensile strength of the third geogrid 74 is greater than or equal to 100kN / m, the length of the third geogrid 74 is L1, and the net height of the soft soil subgrade structure 10 is L2. L1 and L2 satisfy the following relationship: L1:L2=0.7. That is to say, the length of the third geogrid 74 is 0.7 times the net height of the soft soil subgrade structure 10, which can prevent the clay backfill soil 43 in the backfill layer 4 from shifting and help ensure the structural stability of the backfill layer 4.

[0057] Reference Figures 1-3As shown, the third geogrid 74 may include a first sub-geogrid 74a and a second sub-geogrid 74b. The first sub-geogrid 74a may be connected to the first sheet pile wall 1 and located between the first sheet pile wall 1 and the hollow steel pipe 61. The second sub-geogrid 74b may be connected to the second sheet pile wall 2 and located between the second sheet pile wall 2 and the hollow steel pipe 61. Specifically, the first sheet pile wall 1 may be provided with a third reinforcing clamp, and the second sheet pile wall 2 may be provided with a fourth reinforcing clamp 76. The third reinforcing clamp is suitable for clamping the first sub-geogrid 74a, and the fourth reinforcing clamp 76 is suitable for clamping the second sub-geogrid 74b, thereby achieving the clamping and fixing of the third geogrid 74. The third reinforcing clamp and the fourth reinforcing clamp 76 may have the same structure as the first reinforcing clamp and the second reinforcing clamp 73.

[0058] In some embodiments of the present invention, reference is made to... Figure 1 As shown, the distance between the water-retaining component 42 and the third geogrid 74 in the vertical direction is H1, which satisfies the relationship: 0.4m≤H1≤0.6m. For example, H1 can be 0.4m, 0.5m, 0.6m, etc., which helps to ensure the structural strength of the backfill layer 4, simplify the structure of the backfill layer 4, and reduce the engineering cost of the soft soil foundation 20.

[0059] Understandably, if H1 < 0.4m, the distance between the water-retaining component 42 and the third geogrid 74 is small, requiring more water-retaining components 42 and the third geogrid 74 in the backfill layer 4, resulting in higher engineering costs and a more complex structure. If H1 > 0.6m, the distance between the water-retaining component 42 and the third geogrid 74 is large, leading to a greater thickness of the clay backfill 43 and a higher risk of structural instability, making it difficult to guarantee the structural strength of the clay backfill 43. In this embodiment, H1 is within the range of 0.4m to 0.6m, providing a moderate distance between the water-retaining component 42 and the third geogrid 74. This allows for the simplification of the backfill layer 4's structure and a reduction in engineering costs while ensuring its structural strength.

[0060] In some embodiments of the present invention, the distance between the hollow steel pipe 61 and the first sheet pile wall 1 is the same as the distance between the hollow steel pipe 61 and the second sheet pile wall 2. This is beneficial to the uniform stress on both sides of the hollow steel pipe 61, reducing the risk of local deformation of the hollow steel pipe 61, thereby improving the stability and reliability of the soft soil subgrade structure 10. Furthermore, the hollow steel pipe 61 is located in the middle of the first sheet pile wall 1 and the second sheet pile wall 2, ensuring that the distance between the hollow steel pipe 61 and the first sheet pile wall 1 and the distance between the hollow steel pipe 61 and the second sheet pile wall 2 are both relatively short. This avoids the hollow steel pipe 61 being too far from either the first sheet pile wall 1 or the second sheet pile wall 2, preventing the drainage path from being too long and preventing water from accumulating in the backfill layer 4, which helps to reduce the risk of structural instability of the backfill layer 4.

[0061] In some embodiments of the present invention, reference is made to... Figure 4 As shown, the hollow steel pipe 61 includes multiple detachably connected hollow sub-steel pipes 613 to facilitate construction. The corresponding number of hollow steel pipes 61 can be laid out according to the height of the soft soil subgrade structure 10 to be constructed, so as to facilitate the construction of soft soil subgrade structures 10 at different heights. The hollow steel pipe 61 has good versatility.

[0062] Reference Figure 4 As shown, the hollow steel pipe 613 may have a joint 6131 and multiple water inlet holes 611. Multiple hollow steel pipes 613 can be detachably connected by nesting and limiting each other through the joint 6131. ​​Multiple water inlet holes 611 can be arranged at intervals along the circumferential direction of the hollow steel pipe 613. Water blocked by the water-blocking member 42 can flow smoothly into the hollow steel pipe 613 through the multiple water inlet holes 611.

[0063] In some embodiments of the present invention, reference is made to... Figure 1 As shown, the drainage maintenance system 6 also includes a water collection well 64, which is located in the soft soil foundation 20 outside the backfill space. The water collection well 64 is connected to the drainage channel 62 and is suitable for collecting water discharged from the drainage channel 62.

[0064] Reference Figure 1 As shown, in the left and right direction, both ends of the drainage channel 62 are provided with water collection wells 64. The water collection wells 64 can be made of reinforced concrete with a strength grade greater than or equal to C25. The depth of the bottom of the water collection well 64 is 6m to 8m greater than the location of the drainage channel 62. The bottom of the water collection well 64 can be 8m to 10m from the ground surface to ensure the capacity of the water collection well 64. After the soft soil subgrade structure 10 is put into service, the engineers can periodically pump out the water collected in the water collection well 64.

[0065] In some embodiments of the present invention, reference is made to... Figure 1 As shown, the reinforcement layer 3 may further include a third geotextile 32. A portion of the third geotextile 32 is placed below the first gravel backfill 31, and another portion of the third geotextile 32 is located on the left and right sides of the first gravel backfill 31, wrapping back onto the upper surface of the first gravel backfill 31. Multiple reinforcement layers 3 may be used. During construction, the first gravel backfill 31 is wrapped with the third geotextile 32 on both sides to replace poorly filled soft soil foundation 20, increase the base contact width, and improve the bearing capacity of the soft soil subgrade structure 10. The tensile strength of the third geotextile 32 is not less than 60 kN / m, and the spacing between the third geotextiles 32 of two adjacent reinforcement layers 3 can be 0.5 m to 0.8 m.

[0066] In some embodiments of the present invention, the top of the electrode rod 63 extends 1m to 2m beyond the ground surface to facilitate the connection of the electrode rod 63 to a power source and to facilitate the replacement of the electrode rod 63 by engineers. The bottom of the electrode rod 63 is flush with the bottom of the first sheet pile wall 1 and the second sheet pile wall 2 to protect the first sheet pile wall 1 and the second sheet pile wall 2 from corrosion. The electrode rod 63 can be made of anode materials such as aluminum alloy and magnesium alloy.

[0067] In some embodiments of the present invention, in the vertical direction, the spacing between any two adjacent first reinforcing hooks 71 can be 0.8m to 1.2m, and the spacing between any two adjacent second reinforcing hooks 72 can be 0.8m to 1.2m. That is, the spacing between any two adjacent first sub-water-blocking members 42a is 0.8m to 1.2m, the spacing between any two adjacent second sub-water-blocking members 42b is 0.8m to 1.2m, the spacing between any two adjacent first and third reinforcing clamps can be 0.4m to 0.6m, and the spacing between any two adjacent second and fourth reinforcing clamps can be 0.4m to 0.6m.

[0068] In some embodiments of the present invention, both the first sheet pile wall 1 and the second sheet pile wall 2 can be made of U-shaped steel sheet piles (Larsen steel sheet piles), which can serve as a retaining wall during the construction of the soft soil subgrade structure 10 to prevent the soft soil foundation 20 from collapsing. In addition, U-shaped steel sheet piles have strong durability. After the soft soil subgrade structure 10 is completed, the U-shaped steel sheet piles can serve as a wall surface and prevent the first gravel backfill 31, the second gravel backfill 41, and the clay backfill 43 in the soft soil subgrade structure 10 from collapsing.

[0069] In some embodiments of the present invention, reference is made to... Figure 1 As shown, the soft soil subgrade structure 10 also includes a sheet pile wall cap 8, which is arranged on the top of the first sheet pile wall 1 and the second sheet pile wall 2 to protect the first sheet pile wall 1 and the second sheet pile wall. The sheet pile wall cap 8 is fixedly connected to the top of the first sheet pile wall 1 and the second sheet pile wall 2 by welding.

[0070] According to an embodiment of the present invention, the soft soil subgrade structure 10 can be formed by alternately filling multiple layers of clay backfill 43 and second sand and gravel backfill 41 on the reinforcement layer 3, and alternately laying water-retaining components 42 and third geogrid 74. The multiple water-retaining components 42, hollow steel pipes 61 and drainage channels 62 in the soft soil subgrade structure 10 can be connected in sequence to form multiple drainage channels, which is beneficial to ensure the drying of the clay backfill 43 inside the soft soil subgrade structure 10 and the rapid drainage and consolidation of the soft soil foundation 20.

[0071] Reference Figure 5As shown, according to another embodiment of the present invention, a construction method for a soft soil subgrade structure, wherein the soft soil subgrade structure is the aforementioned soft soil subgrade structure, the construction method includes:

[0072] Step S1: Construct a drainage maintenance system.

[0073] The process involves positioning and laying out lines on the construction site according to the design plan, excavating trenches in the soft soil foundation, using wooden boards or mud slurry for wall protection, laying steel cages and pouring concrete to form drainage channels and collection wells located on the left and right sides of the drainage channels. After curing, square plastic blind pipes are filled into the drainage channels, and two layers of first geotextile are covered on the top surface of the drainage channels. Metal mesh is welded to the left and right sides of the hollow steel pipes, and two layers of second geotextile are wrapped around the inlet. Two to three sections of hollow steel pipes are inserted perpendicular to the soft soil foundation at the designated positions, with the bottom of the hollow steel pipes contacting the top of the drainage channels. The top of the hollow steel pipes can extend 1.5m to 2m beyond the surface of the soft soil foundation. The inside of the hollow steel pipes is filled with third sand and gravel backfill. Then, electrode rods are driven at a distance of 9.5m to 14.5m from the hollow steel pipes on the left and right sides, with the bottom of the electrode rods contacting the top of the drainage channels, thus completing the construction of the drainage maintenance system.

[0074] Step S2: Connect the electrode rod to the positive terminal of the power supply and the hollow steel pipe to the negative terminal of the power supply to perform electroosmotic consolidation on the soft soil foundation.

[0075] In this system, water in the soft soil foundation located between the two electrode rods flows into the hollow steel pipe under the influence of the potential difference, and can then be guided into a drainage ditch through the hollow steel pipe to drain the water from the soft soil foundation. The power supply can be a DC power supply, and the voltage of the DC power supply can be controlled within the range of 150V~200V. The current density at the construction site is... Within the specified range, the current density at the construction site can be adjusted according to the structural strength of the soft soil foundation. The current density at the construction site is positively correlated with the voltage of the DC power supply. The expected electroosmotic consolidation time is generally not less than three weeks, and can be adjusted according to the strength requirements of the project.

[0076] Step S3: Construct the first sheet pile wall and the second sheet pile wall.

[0077] In the left-right direction, the horizontal distance between the first sheet pile wall and the second sheet pile wall can be 15m to 22.5m. The specific distance can be determined according to the width requirements of the roadbed. After determining the horizontal distance between the first sheet pile wall and the second sheet pile wall, the first sheet pile wall and the second sheet pile wall are driven to 2m to 3m below the surface of the soft soil foundation, and the depth of the first sheet pile wall and the second sheet pile wall in the soft soil foundation is consistent with the depth of the electrode rod in the soft soil foundation. The upper end of the first sheet pile wall and the second sheet pile wall can extend 6m to 8m beyond the surface of the soft soil foundation. Then, the sheet pile wall cap can be welded to the top of the first sheet pile wall and the second sheet pile wall to complete the construction of the first sheet pile wall and the second sheet pile wall.

[0078] Step S4: Install the reinforcement layer, backfill layer and pavement layer in sequence.

[0079] Before laying the reinforcement layer, backfill layer and pavement layer, the hollow steel pipe can be added to the design height. Then, the soft soil foundation below the ground surface between the hollow steel pipe and the first sheet pile wall and between the hollow steel pipe and the second sheet pile wall can be excavated and leveled.

[0080] The reinforcement layer can be constructed by: constructing 3 to 4 reinforcement layers. During the construction of each layer, the third geotextile reinforcement is laid flat on the bottom surface of the backfill space, with a 120cm length reserved at both ends. Then, the first sand and gravel backfill is filled on the third geotextile, leveled and compacted until its relative density is greater than 90%. Then, the reserved third geotextile at both ends is wrapped around the third geotextile and the above arrangement is repeated until the top surface of the reinforcement layer is flush with the surface of the soft soil foundation.

[0081] The backfill layer can be laid by alternately filling multiple layers of clay backfill and second sand and gravel backfill on the reinforcement layer. Between the clay backfill and the second sand and gravel backfill, water-retaining components and a third geogrid are laid alternately. Specifically, after the clay backfill is compacted and leveled, water-retaining components are laid on the upper surface of the clay backfill. Then, the second sand and gravel backfill is filled on top of the water-retaining components, and the compaction degree of the second sand and gravel backfill is achieved to 95% using compaction equipment. After compaction and leveling, the third geogrid is laid on top of the second sand and gravel backfill. The above steps are repeated until the entire backfill layer reaches the design height.

[0082] The laying of the pavement layer may include: pouring asphalt concrete pavement on the upper surface of the last backfill layer, checking whether the asphalt concrete pavement meets the design elevation requirements, and putting it into service after the traffic markings are set on the pavement.

[0083] According to the construction method of soft soil subgrade structure according to an embodiment of the present invention, the backfill layer includes a second sand and gravel backfill, a water-retaining component, and a clay backfill arranged sequentially from top to bottom. The use of clay backfill as part of the filling material in the backfill layer can reduce the amount of the first sand and gravel backfill in the backfill layer, thereby saving engineering costs. The water-retaining component can prevent water from falling into the clay backfill, which helps to keep the clay backfill dry, thereby ensuring the structural strength of the backfill layer and the stability of the soft soil subgrade structure.

[0084] In some embodiments of the present invention, the construction method further includes: excavating soft soil on the soft soil foundation outside the soft soil subgrade structure, drying the soft soil to obtain clay backfill soil, and using clay backfill soil in the backfill layer to reduce the amount of second sand and gravel backfill soil, thereby saving project costs.

[0085] The process involves first excavating the calculated volume of earthwork, then mixing the soft soil using a large mixer. After mixing, the soil is sieved to remove large particles. A shed is erected in a location unaffected by electroosmosis, and an impermeable geomembrane is laid on the ground. The sieved soft soil is then laid on the geomembrane. Equipment such as fans can be used to accelerate the drying of the soft soil on the geomembrane, reducing its moisture content to below the plastic limit, thus obtaining clay backfill soil.

[0086] In some embodiments of the present invention, after the soft soil subgrade structure is put into service, the first sheet pile wall and the second sheet pile wall are both connected to the negative terminal of a DC power supply, and the electrode rod is connected to the positive terminal of a DC power supply. The voltage of the DC power supply is not greater than 30V, so as to protect the first sheet pile wall and the second sheet pile wall and prevent them from being corroded. In addition, solar panels can be installed at the first sheet pile wall and the second sheet pile wall to supplement the power supply and reduce energy consumption.

[0087] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0088] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A soft soil subgrade structure, characterized in that, The soft soil subgrade structure is located on a soft soil foundation (20), and the soft soil subgrade structure includes: A first sheet pile wall (1) and a second sheet pile wall (2) are arranged opposite to each other. Parts of the first sheet pile wall (1) and the second sheet pile wall (2) are buried in the soft soil foundation (20). A backfill space is formed between the first sheet pile wall (1) and the second sheet pile wall (2). A reinforcement layer (3) is provided in the backfill space, and at least a portion of the reinforcement layer (3) is located below the surface of the soft soil foundation (20). The reinforcement layer (3) includes a first sand and gravel backfill soil (31). Backfill layer (4), the backfill layer (4) is provided in the backfill space and located above the reinforcement layer (3), the backfill layer (4) includes a second sand and gravel backfill soil (41), a water-blocking component (42) and a clay backfill soil (43) arranged from top to bottom; A road surface layer (5) is disposed above the backfill layer (4); A drainage maintenance system (6) is provided, comprising a hollow steel pipe (61), a drainage trough (62), and an electrode rod (63). The drainage trough (62) is located below the reinforcement layer (3) and extends to the outside of the first sheet pile wall (1) and the second sheet pile wall (2). The hollow steel pipe (61) passes through the reinforcement layer (3) and the backfill layer (4). The hollow steel pipe (61) has an inlet hole (611) and a drain hole (63). 12) The water inlet (611) is connected to the water-blocking component (42), the drain hole (612) is connected to the drain trough (62), at least part of the electrode rod (63) is buried in the soft soil foundation (20) outside the backfill space, the electrode rod (63) is used to connect to the positive terminal of the power supply, the hollow steel pipe (61) is used to connect to the negative terminal of the power supply, or the first sheet pile wall (1) and the second sheet pile wall (2) are used to connect to the negative terminal of the power supply.

2. The soft soil subgrade structure according to claim 1, characterized in that, Both the first sheet pile wall (1) and the second sheet pile wall (2) are connected to the hollow steel pipe (61) through the water-blocking member (42).

3. The soft soil subgrade structure according to claim 2, characterized in that, The water-blocking component (42) includes a first sub-water-blocking component (42a) and a second sub-water-blocking component (42b) with the same structure. Both the first sub-water-blocking component (42a) and the second sub-water-blocking component (42b) include a first geogrid, a water-blocking plate and a second geogrid stacked together. The first geogrid and the second geogrid of the first sub-water-blocking component (42a) are both connected between the first sheet pile wall (1) and the hollow steel pipe (61); The first geogrid and the second geogrid of the second sub-water barrier (42b) are both connected between the second sheet pile wall (2) and the hollow steel pipe (61).

4. The soft soil subgrade structure according to claim 3, characterized in that, There are multiple backfill layers (4), and a third geogrid (74) is provided between two adjacent backfill layers (4). At least one of the first sheet pile wall (1) and the second sheet pile wall (2) is connected to the third geogrid (74).

5. The soft soil subgrade structure according to claim 4, characterized in that, The distance between the water-blocking component (42) and the third geogrid (74) in the vertical direction is H1, which satisfies the relationship: 0.4m≤H1≤0.6m.

6. The soft soil subgrade structure according to any one of claims 1-5, characterized in that, The distance between the hollow steel pipe (61) and the first sheet pile wall (1) is the same as the distance between the hollow steel pipe (61) and the second sheet pile wall (2).

7. The soft soil subgrade structure according to claim 6, characterized in that, The hollow steel pipe (61) includes a plurality of detachably connected hollow sub-steel pipes (613).

8. The soft soil subgrade structure according to claim 1, characterized in that, The drainage maintenance system (6) also includes a water collection well (64), which is located in the soft soil foundation (20) outside the backfill space and is connected to the drainage channel (62).

9. A construction method for a soft soil subgrade structure, characterized in that, The soft soil subgrade structure is the soft soil subgrade structure according to any one of claims 1-8, and the construction method includes: Construct the aforementioned drainage maintenance system; The electrode rod is connected to the positive terminal of the power supply and the hollow steel pipe is connected to the negative terminal of the power supply to perform electroosmotic consolidation on the soft soil foundation. Construct the first and second sheet pile walls; The reinforcement layer, backfill layer, and pavement layer are laid out in sequence.

10. The construction method for soft soil subgrade structure according to claim 9, characterized in that, The construction method also includes: Soft soil is excavated from the soft soil foundation outside the soft soil subgrade structure and dried to obtain the clay backfill soil.

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