Structure and Method for Preloading of Ultra-Soft Silt with No Drainage Layer and Ultra-High Reinforced Structure

Abstract

This invention provides a structure and method for preloading ultra-high reinforced bodies with no drainage layer in the treatment of ultra-soft silt. The treatment structure includes a reinforced working cushion layer, a drainage-resistant reinforced structure, and an ultra-high reinforced surcharge structure layer. The reinforced working cushion layer includes manufactured sand and type A geocells. The drainage-resistant reinforced structure includes non-woven geotextile, a permeable membrane, and a multi-layer composite drainage grid. The composite drainage grid replaces the medium-coarse sand drainage layer, and the vertical plastic drainage board is directly connected to the middle layer of composite drainage grid. The ultra-high reinforced surcharge structure layer includes non-woven geotextile, construction waste, type B geocells, and mineral powder. In the design calculation, the recently filled soil below the drainage-resistant reinforced structure is considered as an additional stress load, and the load diffusion effect of the reinforcement is also considered. This method provides excellent foundation treatment results, reduces sand usage, saves costs, and has a clear calculation principle and method, facilitating design and engineering applications, with a very broad prospect for engineering application.

Description

Technical Field

[0001] This invention belongs to the field of ultra-soft silt foundation treatment technology, specifically relating to an ultra-high reinforced body surcharge preloading treatment structure and method suitable for deep ultra-soft silt. Background Technology

[0002] Extremely soft silt has low bearing capacity, high compressibility, high water content, and low strength, making it difficult to meet engineering requirements. Therefore, when encountering this type of soil in engineering construction, foundation treatment is necessary. Due to the low bearing capacity of the top surface of the silt, a working surface cushion layer is usually required to ensure smooth operation of subsequent construction machinery. Extremely soft silt is often treated with surcharge preloading. The common construction process for surcharge preloading reinforcement of extremely soft silt is as follows: laying a layer of woven fabric → laying a working surface cushion layer of fine sand or sea sand → installing vertical plastic drainage boards → laying a horizontal drainage layer of medium-coarse sand → filling with rockfill → preloading and drainage → dynamic compaction; the heads of the plastic drainage boards are buried in the medium-coarse sand cushion layer. Under the action of the overlying surcharge, the water in the silt enters the horizontal medium-coarse sand drainage layer through the channels of the vertical plastic drainage boards and is then drained away. Due to the extreme scarcity of sand resources both domestically and internationally, the cost of fine sand, sea sand, and medium-coarse sand is extremely high, and the supply of sand resources is tight. The existing construction method of surcharge preloading reinforcement for ultra-soft silt results in high cost and long construction period for foundation treatment in similar projects. Moreover, the strength and bearing capacity of the working surface cushion layer of fine sand or sea sand alone is limited, and the subsequent settlement and deformation of construction machinery operations are large. There is an urgent need to find a working surface cushion layer with high bearing capacity.

[0003] In addition, in the existing large-area surcharge preloading settlement calculation process, the vertical additional stress is usually simply equivalent to the unit weight of the surcharge fill material multiplied by the height of the surcharge fill material. There is still controversy as to whether the newly filled soil below the drainage system should be regarded as an additional stress load. Moreover, the calculation of vertical additional stress usually does not consider the load diffusion effect of the reinforcement, which leads to a large difference in the calculation results of vertical additional stress, and thus the settlement calculation results are large compared with the measured results. Summary of the Invention

[0004] To rapidly and effectively treat ultra-soft silt, this invention provides a structure and method for preloading ultra-soft silt with a reinforced body without a drainage layer. This invention includes a reinforced structure for the construction work surface, a reinforced structure for drainage, and an ultra-high reinforced body surcharge structure. A three-layer composite drainage grid replaces the medium-coarse sand drainage layer, and a plastic drainage board is connected to the middle layer of the composite drainage grid. During design calculations, the recently filled soil below the drainage system is considered as an additional stress load, and the load diffusion effect of the reinforcement is also taken into account. This method provides excellent foundation treatment, reduces sand usage, saves costs, and has a clear calculation principle and method, facilitating design and engineering applications.

[0005] To achieve the above-mentioned technical objectives, the present invention provides a preloading treatment structure for ultra-soft silt without drainage layer and ultra-high reinforced body surcharge, the treatment structure including a reinforced body working pad layer, a drainage-proof reinforced body structure and an ultra-high reinforced body surcharge structure layer.

[0006] The reinforced working pad layer includes a woven fabric layer laid on the top surface of the ultra-soft silt layer and a reinforced composite layer located above the woven fabric layer. The reinforced composite layer is composed of a type A geocell and a manufactured sand dredged fill layer.

[0007] The reinforced structure includes a diaphragm membrane, a multi-layer horizontal composite drainage net, and multiple vertical drainage boards. The vertical drainage boards are inserted into the ultra-soft silt layer, and their bottom ends are embedded in the cohesive soil layer at the bottom of the ultra-soft silt layer. The diaphragm membrane is laid on the top surface of the reinforced working pad layer. The multi-layer horizontal composite drainage net is laid sequentially above the diaphragm membrane. The top of the vertical drainage board extends beyond the diaphragm membrane and is connected to the reinforcing material of the intermediate layer of horizontal composite drainage net.

[0008] The ultra-high reinforced surcharge structure layer includes a first non-woven fabric layer laid on the top surface of the drainage and reinforced structure layer, a composite surcharge layer of construction waste and geocells piled on the first non-woven fabric layer, a second non-woven fabric layer laid on the top surface of the composite surcharge layer, and a mineral powder backfill layer piled on top of the second non-woven fabric layer; the composite surcharge layer is composed of a construction waste impact compaction layer and type B geocells.

[0009] The preferred technical solution of the present invention: the woven fabric layer uses 150g / m 2 The woven fabric is laid, and the reinforced composite layer includes a bottom A-type geocell, a middle A-type geocell, and a 1-2m thick manufactured sand fill layer. The bottom A-type geocell is located on the top surface of the woven fabric layer, and the middle A-type geocell is located in the middle of the manufactured sand fill layer.

[0010] The preferred technical solution of the present invention is as follows: the vertical drainage board is constructed using a board insertion machine, with the bottom end of the plastic drainage board penetrating the cohesive soil layer by at least 1.0m, and the vertical drainage boards are spaced 0.8 to 1.0m apart in a square arrangement; the diaphragm is made of HDPE diaphragm with a thickness of not less than 1.5mm; the horizontal composite drainage net has three layers, and the vertical drainage board is connected to the reinforcing bars of the middle layer of the horizontal composite drainage net.

[0011] The preferred technical solution of this invention is as follows: the height of the composite fill layer is 3-6m, the bottom and top layers are both construction waste impact compaction layers, and multiple layers of type B geocells are provided in the middle. Each construction waste impact compaction layer is a backfill compaction layer with a thickness of 0.8-1.2m formed by backfilling construction waste with a particle size of no more than 20cm and then impact compacting it. The construction waste is a filler material with a particle size of no more than 20cm formed by crushing granular bricks and cement concrete blocks. The height of the mineral powder backfill layer is 1-3m, and the height of the mineral powder backfill layer is less than the height of the composite fill layer.

[0012] The preferred technical solution of the present invention is as follows: the type A geocell in the reinforced composite layer is a polyester tensile geocell with a tensile strength limit of not less than 180kN / m.

[0013] A preferred embodiment of the present invention is that the density of the HDPE diaphragm is not less than 0.95 g / cm³. 3 The roughness height is not less than 0.3mm, and the yield strength is not less than 25N / mm; the horizontal composite drainage net adopts a 6.3mm thick composite geogrid with a longitudinal water conductivity of not less than 1*10. -3 m 2 / s, longitudinal tensile strength not less than 18kN / m, and mass per unit area not less than 200g / m² 2 .

[0014] The preferred technical solution of the present invention: both the first nonwoven fabric layer and the second nonwoven fabric layer use 300g / m 2 The nonwoven geotextile, wherein the type B geocell is made of polyethylene extruded geocell with a tensile strength limit of not less than 30kN / m.

[0015] To achieve the above-mentioned technical objectives, the present invention also provides a method for preloading ultra-high reinforced body without drainage layer in ultra-soft silt. The method employs the aforementioned preloading structure for ultra-high reinforced body without drainage layer in ultra-soft silt for preloading, and specifically includes the following steps:

[0016] S1. Set the thickness of the composite fill of construction waste and geocells in the ultra-high reinforced surcharge structure layer as h2 and the surcharge height of mineral powder as h1, where h1 is 1-3m, h2 is 3-6m and h 2＞ h1; and combined with the current ground elevation H of the foundation to be treated d Foundation treatment, handover surface elevation H s Based on the requirements and the thickness h3 of the reinforced working pad, the settlement S of the ultra-soft silt soil layer during construction was calculated. t By adjusting the setpoints h1 and h2, the design height h1, h2 and the calculated S are made equal. t The value must meet the following requirements:

[0017] h1+h2+h3>H s -H d

[0018] H d +h1+h2+h3-S t -h1=H s

[0019] In the formula, S t Settlement of ultra-soft silty soil layer during construction period;

[0020] The design values ​​h1 and h2 that meet the above requirements are used as the actual surcharge height of mineral powder and the thickness of the composite surcharge of construction waste and geocells.

[0021] S2. Determine the foundation treatment area, determine the construction zones, and begin construction;

[0022] S3. A foam board is erected on the top surface of the ultra-soft silt layer, and a layer of woven fabric is laid. Then, a layer of A-type geocells is laid on the woven fabric. The connection between the A-type geocells is treated by insertion. After laying, 50cm to 60cm of manufactured sand is blown in. Then, another layer of A-type geocells is laid. The connection between the A-type geocells is treated by insertion. Another 50cm to 60cm of manufactured sand is blown in.

[0023] S4. Lay a layer of diaphragm membrane with a thickness of not less than 1.5mm, and then use a board inserter to install vertical plastic drainage boards. The bottom of the plastic drainage board should penetrate the ultra-soft silt layer and enter the cohesive soil layer by not less than 1.0m. The spacing between the vertical drainage boards is 0.8 to 1.0m, and the top of the board should be higher than the diaphragm membrane. Lay a multi-layer composite geogrid, tie the top of the vertical drainage board to the middle layer of composite geogrid, and then wrap the vertical drainage board with the diaphragm membrane and seal it with the diaphragm membrane on top of the manufactured sand to ensure the water-proof effect.

[0024] S5. Lay a layer of non-woven geotextile on the top surface of the uppermost composite geogrid, and start backfilling construction waste. First, backfill 0.8-1m of construction waste, compact it with impact, lay a layer of type B geocells, then backfill 0.8-1m of construction waste, compact it with impact, and lay another layer of type B geocells. Repeat the above steps until the composite backfill thickness of construction waste and geocells reaches the composite backfill thickness h2 determined in step S1.

[0025] S6. Lay another layer of non-woven geotextile on the top surface of the uppermost construction waste compaction layer, and start filling mineral powder. After the mineral powder filling height reaches the mineral powder loading height h1 determined in step S1, carry out preloading.

[0026] The preferred technical solution of the present invention: the settlement amount S of the ultra-soft silt soil layer during the construction period in step S1. tThe calculation process is as follows:

[0027] (1) Under the action of overburden load, the reinforced body in the reinforced working cushion layer of the construction work surface undergoes bending deformation, compressive stress is generated in the upper part of the reinforced body, shear force is generated in the geocell filling, and pull-out force is generated in the lower geocell. The load of the horizontal composite drainage network is ignored in the calculation. The vertical shear force τ generated by the reinforced working cushion layer is:

[0028]

[0029] Where: τ—vertical shear force generated by the reinforced working pad layer, in kPa;

[0030] —Internal friction angle of the reinforced working pad layer filler, in °; 25° for manufactured sand;

[0031] K—Passive earth pressure coefficient

[0032] σ v —Self-weight load of the reinforced working pad layer;

[0033] The calculation process for the self-weight load of the reinforced working pad layer is as follows:

[0034] σ v =r3z

[0035] r3—Specific weight of the reinforcing working pad filler, in kN / m³ 3 ;

[0036] z—Vertical elevation of the reinforced working pad layer from top to bottom; The top elevation of the reinforced working pad layer is 0, and the bottom elevation of the reinforced working pad layer is h3;

[0037] The vertical shear force τ′ of the reinforced working pad filler is taken as the average value of the top and bottom surfaces, and the height z of the top surface is taken as 0, which is the self-weight load σ of the top surface of the reinforced working pad. v顶 =0, the vertical shear force τ on the top surface of the reinforced working pad layer 顶 =0, then:

[0038] τ′=1 / 2(τ 顶 +τ 底 )=1 / 2τ 底

[0039]

[0040] σ v底 =r3 h3

[0041] Based on this calculation, we can conclude that:

[0042]

[0043] Where: r3—specific weight of the reinforcing working pad layer filler, in kN / m³ 3；

[0044] h3—Thickness of the reinforced working pad layer, in meters;

[0045] (2) The vertical component T of the material pull-out force generated by the reinforced working pad layer is:

[0046] T = T a ·sinθ

[0047] Where: T—vertical component of the pull-out force generated by the reinforced working pad layer, in kPa;

[0048] T a —The design pull-out force of the geocells used in the manufactured sand layer is 40 kPa for type A geocells;

[0049] θ—Deformation angle of geocells in the manufactured sand layer, 20° for type A geocells;

[0050] (3) Calculate the load diffusion effect p of the construction surface cushion layer:

[0051] p=τ′+T

[0052] Where: p—load diffusion effect of the construction surface cushion layer, unit kPa;

[0053] (4) Considering the reinforcement diffusion effect of the reinforced working pad layer below the vertical drainage board, the additional vertical stress caused by large-area surcharge preloading is:

[0054] ΔP=r1h1+r2h2+r3h3-p

[0055] Where: ΔP—vertical additional stress caused by large-area surcharge preloading, unit kPa;

[0056] r1—Specific density of mineral powder, in kN / m³ 3 ;

[0057] h1—Package height of mineral powder, in meters;

[0058] h2—Thickness of composite fill of construction waste and geocells, in meters;

[0059] r2—Unit weight of construction waste and geocell composite fill material, in kN / m³ 3 ;

[0060] (5) The total settlement of the ultra-soft silt caused by surcharge preloading is:

[0061]

[0062] Where: S—total settlement of ultra-soft silt caused by surcharge preloading, in meters;

[0063] m s —Settlement correction factor, taken as 1.3 to 1.4 for ultra-soft silt;

[0064] E s —Compression modulus of ultra-soft silt, in kPa, taken as 1.3 to 1.4 for ultra-soft silt;

[0065] H—Thickness of the ultra-soft silt layer, in meters.

[0066] (6) After 4-5 months of surcharge preloading, the consolidation degree of the ultra-soft silt layer reaches 85%, and the settlement of the ultra-soft silt layer during the construction period is S. t =0.85*S.

[0067] The preferred technical solution of this invention is as follows: In step S4, the diaphragm is a 1.5mm thick double-textured HDPE diaphragm; the vertical drainage boards are arranged in a square, with the head of each vertical drainage board protruding 5-10cm above the HDPE diaphragm; in step S4, three layers of 6.3mm thick composite geogrid are laid, and the heads of the vertical drainage boards are tied to the reinforcing bars of the middle layer of composite geogrid; in step S5, the non-woven geotextile is selected as 300g / m². 2 Non-woven geotextile.

[0068] The beneficial effects of this invention are:

[0069] (1) This invention improves the surcharge preloading structure for ultra-soft silt and proposes a surcharge preloading structure composed of three reinforcement systems: a reinforced structure for the construction working surface, a reinforced structure for drainage, and an ultra-high reinforced surcharge structure. This forms a fully flexible surcharge preloading structure, which is easy to construct, reduces construction costs, and saves construction time.

[0070] (2) The reinforced structure of the construction working surface of the present invention is composed of manufactured sand and geocells. The geocells have high strength, which is better than geogrids. Compared with fine sand or sea sand, manufactured sand has a lower cost, more sand sources, and higher strength. The reinforced structure of the construction working surface improves the bearing capacity of the cushion layer of the construction working surface and the subsequent settlement deformation of the construction machinery operation is small.

[0071] (3) The water-retaining reinforced structure of the present invention consists of a double-rough HDPE diaphragm membrane and a three-layer composite drainage grid. The plastic drainage board is directly connected to the composite drainage grid. The bottom is water-retaining with a double-rough HDPE diaphragm membrane. The upper and lower surfaces of the diaphragm membrane are rough, which not only serves as a water barrier but also as an anti-slip function, preventing the instability of the ultra-soft silt foundation during the staged loading process.

[0072] (4) The lower part of the ultra-high reinforced surcharge structure of the present invention uses construction waste and geocells, and the upper part uses mineral powder. The strength of the geocells in the ultra-high reinforced surcharge structure is lower than that of the geocells in the subbase of the construction work surface. Under the premise of ensuring the stability of the foundation, the cost of the reinforcement system is saved. The construction waste is selected after crushing and screening, realizing the recycling and reuse of construction waste. The mineral powder is removed after preloading, realizing recycling and reuse, and preventing the mineral powder from causing secondary pollution to the foundation.

[0073] (5) Before construction, the height of the surcharge is determined by the settlement calculation of the large area surcharge preloading. In the calculation process, the newly filled soil below the drainage system is considered as an additional stress load. At the same time, the load diffusion effect of the reinforcement is considered. The load diffusion effect of the reinforcement consists of two parts: the vertical shear force of the reinforcement filler and the pull-out force of the reinforcement material. The calculation method is simple and practical, and the calculation results are in good agreement with the actual measurement results, ensuring the accuracy of the surcharge height calculation and facilitating its promotion and application. Attached Figure Description

[0074] Figure 1 This is a schematic diagram of the ultra-high reinforced body surcharge preloading treatment structure in this invention;

[0075] Figure 2 This is a schematic diagram of the reinforced structure for drainage in this invention;

[0076] Figure 3 This is a schematic diagram illustrating the calculation of the vertical shear force τ generated by the reinforced working pad layer in this invention;

[0077] Figure 4 This is the measured settlement curve of the example.

[0078] Figure 1 In the middle: 1-Super soft silt layer, 2-Woven cloth layer, 3-Reinforced composite layer, 4-Vertical drainage board, 5-Permeability barrier membrane, 6-Horizontal composite drainage net, 7-Cohesive soil layer, 8-First non-woven cloth layer, 9-Composite fill layer, 10-Second non-woven cloth layer, 11-Mineral powder backfill layer. Detailed Implementation

[0079] The present invention will be further described below with reference to the accompanying drawings and embodiments. (See attached drawings) Figures 1 to 4 All accompanying drawings are simplified versions of embodiments and are intended only to clearly and concisely illustrate the embodiments of the present invention. The technical solutions shown in the drawings below are specific solutions of embodiments of the present invention and are not intended to limit the scope of the claimed invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0080] The embodiment provides a super-soft silt, non-drainage layer, ultra-high reinforced body surcharge preloading treatment structure, such as... Figure 1 and Figure 2 As shown, the structure includes a reinforced working cushion layer, a drainage-resistant reinforced structure, and an ultra-high reinforced surcharge structure layer. The reinforced working cushion layer comprises a woven fabric layer 2 laid on top of the ultra-soft silt layer 1 and a reinforced composite layer 3 located above the woven fabric layer 2. The reinforced composite layer 3 is composed of a type A geocell and a manufactured sand fill layer. The woven fabric layer 2 uses 150g / m³... 2 The reinforced composite layer 3 consists of a woven fabric layer 2, a reinforced composite layer 3, and a 1-2m thick layer of manufactured sand fill. The woven fabric layer 2 has a bottom layer of A-type geocells, a middle layer of A-type geocells, and a 1-2m thick layer of manufactured sand fill. The bottom layer of A-type geocells is located on the top surface of the woven fabric layer 2, and the middle layer of A-type geocells is located in the middle of the manufactured sand fill. The A-type geocells in the reinforced composite layer 3 are made of polyester (PET) tensile geocells with a tensile strength limit of not less than 180kN / m.

[0081] In the embodiment, the water-retaining reinforced structure is as follows: Figure 1 and Figure 2 As shown, the system includes a diaphragm membrane 5, a three-layer horizontal composite drainage net 6, and multiple vertical drainage boards 4. The vertical drainage boards 4 are inserted into the ultra-soft silt layer 1, with their bottom ends embedded in the cohesive soil layer 7 at the bottom of the ultra-soft silt layer 1. The diaphragm membrane 5 is laid on top of the reinforced working cushion layer. The multiple layers of horizontal composite drainage net 6 are laid sequentially above the diaphragm membrane 5. The top of each vertical drainage board 4 extends beyond the diaphragm membrane 5 and is connected to the reinforcing material of the middle layer of horizontal composite drainage net 6. The vertical drainage boards 4 are installed using a board-inserting machine, with the bottom end of the plastic drainage board penetrating at least 1.0m into the cohesive soil layer. The vertical drainage boards 4 are spaced 0.8–1.0m apart in a square arrangement. The diaphragm membrane 5 is made of HDPE and has a thickness of not less than 1.5mm. The horizontal composite drainage net 6 has three layers, and the vertical drainage boards 4 are connected to the reinforcing material of the middle layer of horizontal composite drainage net 6. The density of the HDPE diaphragm membrane is not less than 0.95g / cm³. 3 The roughness height is not less than 0.3mm, and the yield strength is not less than 25N / mm; the horizontal composite drainage net 6 adopts a 6.3mm thick composite geogrid with a longitudinal water conductivity of not less than 1*10. -3 m 2 / s, longitudinal tensile strength not less than 18kN / m, and mass per unit area not less than 200g / m² 2 .

[0082] In the embodiments, such as Figure 1As shown, the ultra-high reinforced surcharge structure layer includes a first non-woven fabric layer 8 laid on the top surface of the drainage reinforced structure layer, a construction waste and geocell composite surcharge layer 9 filled on the first non-woven fabric layer 8, a second non-woven fabric layer 10 laid on the top surface of the composite surcharge layer 9, and a mineral powder backfill layer 11 filled on the second non-woven fabric layer 10; the composite surcharge layer 9 is composed of a construction waste impact compaction layer and type B geocells. The composite fill layer 9 has a height of 3-6m. Its bottom and top layers are both construction waste impact compaction layers, with multiple layers of Type B geocells in between. Each construction waste impact compaction layer is a 0.8-1.2m thick backfill compaction layer formed by backfilling construction waste with a particle size no greater than 20cm and then impact compacting it. The construction waste is filler material with a particle size no greater than 20cm formed by crushing granular bricks and cement concrete blocks. The mineral powder backfill layer 11 has a height of 1-3m, and its height is less than that of the composite fill layer 9. Both the first nonwoven fabric layer 8 and the second nonwoven fabric layer 10 use 300g / m³ material. 2 The nonwoven geotextile, wherein the type B geocell is made of polyethylene extruded geocell with a tensile strength limit of not less than 30kN / m.

[0083] The example describes the preloading of an ultra-high reinforced body on a super-soft silt foundation. Before the preloading, the thickness of the composite fill of construction waste and geocells in the ultra-high reinforced body surcharge structure layer is set as h2, and the surcharge height of mineral powder is set as h1, where h1 is 1-3m, h2 is 3-6m, and h... 2＞ h1; and combined with the current ground elevation H of the foundation to be treated d Foundation treatment, handover surface elevation H s Based on the requirements and the thickness h3 of the reinforced working pad, the settlement S of the ultra-soft silt soil layer during construction was calculated. t By adjusting the setpoints h1 and h2, the design height h1, h2 and the calculated S are made equal. t The value must meet the following requirements:

[0084] h1+h2+h3>H s -H d The surcharge during the construction period is greater than the design load in the later period, indicating that it is an ultra-high surcharge preloading.

[0085] H d +h1+h2+h3-S t -h1=H s .

[0086] The settlement S of the ultra-soft silt soil layer t The calculation process is as follows:

[0087] (1) Under the action of overburden load, the reinforced body in the reinforced working cushion layer of the construction work surface undergoes bending deformation, compressive stress is generated in the upper part of the reinforced body, shear force is generated in the geocell filling, and pull-out force is generated in the lower geocell. The load of the horizontal composite drainage network is ignored in the calculation. The vertical shear force τ generated by the reinforced working cushion layer is:

[0088]

[0089] Where: τ - vertical shear force generated by the reinforced working pad layer, in kPa;

[0090] - Internal friction angle of the reinforcing working pad layer filler, in °; 25° for manufactured sand;

[0091] K - Passive earth pressure coefficient

[0092] σ v - Self-weight load of the reinforced working pad layer;

[0093] The calculation process for the self-weight load of the reinforced working pad layer is as follows:

[0094] σ v =r3z

[0095] r3 - Reinforced working pad filler density, unit kN / m 3 ;

[0096] z - Vertical elevation of the reinforced working pad layer from top to bottom; The top elevation of the reinforced working pad layer is 0, and the bottom elevation of the reinforced working pad layer is h3;

[0097] The vertical shear force τ′ of the reinforced working pad filler is taken as the average value of the top and bottom surfaces, and the height z of the top surface is taken as 0, which is the self-weight load σ of the top surface of the reinforced working pad. v顶 =0, the vertical shear force τ on the top surface of the reinforced working pad layer 顶 =0, then:

[0098] τ′=1 / 2(τ 顶 +τ 底 )=1 / 2τ 底

[0099]

[0100] σ v底 =r3 h3

[0101] Based on this calculation, we can conclude that:

[0102]

[0103] Where: r3 - density of the reinforced working pad filler, in kN / m³ 3 ;

[0104] h3 - Thickness of the reinforced working pad layer, in meters;

[0105] (2) The vertical component T of the material pull-out force generated by the reinforced working pad layer is:

[0106] T = T a ·sinθ

[0107] Where: T - Vertical component of the pull-out force generated by the reinforced working pad layer, in kPa;

[0108] T a - The design pull-out force of the geocells used in the manufactured sand layer is 40 kPa for type A geocells;

[0109] θ - Deformation angle of geocells in the manufactured sand layer, 20° for type A geocells;

[0110] (3) Calculate the load diffusion effect p of the construction surface cushion layer:

[0111] p=τ′+T

[0112] Where: p - load diffusion effect of the construction surface cushion layer, unit kPa;

[0113] (4) Considering the reinforcement diffusion effect of the reinforced working pad layer below the vertical drainage board, the additional vertical stress caused by large-area surcharge preloading is:

[0114] ΔP=r1h1+r2h2+r3h3-p

[0115] Where: ΔP - vertical additional stress caused by large-area surcharge preloading, unit kPa;

[0116] r1 - Mineral powder density, unit kN / m³ 3 ;

[0117] h1—Powder loading height, in meters;

[0118] h2 - Thickness of composite fill of construction waste and geocells, in meters;

[0119] r2 - Unit weight of construction waste and geocell composite fill material, in kN / m³ 3 ;

[0120] (5) The total settlement of the ultra-soft silt caused by surcharge preloading is:

[0121]

[0122] Where: S - total settlement of ultra-soft silt caused by surcharge preloading treatment, in meters;

[0123] m s - Settlement correction factor, 1.3 to 1.4 for ultra-soft silt;

[0124] E s - The compressibility modulus of ultra-soft silt, in kPa, is taken as 1.3 to 1.4 for ultra-soft silt;

[0125] H - Thickness of the ultra-soft silt layer, in meters.

[0126] (6) After 4-5 months of surcharge preloading, the consolidation degree of the ultra-soft silt layer reaches 85%, and the settlement of the ultra-soft silt layer during the construction period is S. t =0.85*S.

[0127] The results of the above calculations are shown in Tables 1 to 3, where Table 1 shows the calculation parameters of the ultra-high surcharge preloading treatment structure in the embodiment:

[0128] Table 1 Calculation parameters for ultra-high surcharge prestressed reinforced structures

[0129] r1(kN / m3) h1(m) r2(kN / m3) h2(m) r3(kN / m3) h3 φ(°) θ(°) 23 2 20 4 18.5 1 25 20

[0130] Table 2 shows the calculation results of the additional stress of ultra-high surcharge preloading in the embodiments:

[0131] Table 2 Calculation values ​​of additional stress from ultra-high surcharge preloading

[0132] K(kPa) τ′(kPa) T(kPa) p(kPa) ΔP(kPa) 2.46 10.63 13.68 24.31 120.19

[0133] Table 3 shows the settlement calculation results for ultra-high surcharge preloading in the examples:

[0134] Table 3 Calculated Settlement Values ​​for Ultra-High Burrowing Preloading

[0135] ms Es(kPa) H(m) S(m) St(m) 1.35 2000 20 1.62 1.38

[0136] In the embodiment, the elevation H of the top surface of the silt d The elevation of the foundation treatment handover surface is 0.00m. s The value is 3.62m. Based on the calculation results in Tables 1 to 3, the following requirements are met:

[0137] H d +h1+h2+h3-S t -h1=0+2+4+1-1.38-3=3.62m

[0138] h1+h2+h3>H s -H d

[0139] Therefore, the ore powder loading height is determined to be 2m; the composite filling thickness of construction waste and geocells is determined to be 4m; after determining the above filling parameters, construction can be carried out according to the following steps:

[0140] S1. Determine the foundation treatment area, determine the construction zones, and begin construction;

[0141] S2. Lay foam boards on top of the ultra-soft silt layer and then lay a layer of 150g / m³ foam. 2 Weave fabric, then lay a layer of A-type geocells on the woven fabric. The connection between the A-type geocells is made by interlocking. After laying, fill with 50cm of manufactured sand, then lay another layer of A-type geocells. The connection between the A-type geocells is made by interlocking. Fill with another 50cm of manufactured sand.

[0142] S4. Lay a 1.5mm thick double-textured HDPE diaphragm membrane, and then use a plate inserter to install plastic vertical drainage boards. The bottom of the plastic drainage board should penetrate the ultra-soft silt layer and enter the cohesive soil layer by at least 1.0m. The vertical drainage boards should be spaced 0.8 to 1.0m apart, arranged in a square, and the top of the board should be 5 to 10cm above the HDPE diaphragm membrane.

[0143] S5 lays three layers of composite geogrid, binds the top of the vertical drainage board to the middle layer of composite geogrid, and then wraps the vertical drainage board with a pore-proof membrane and welds it to the pore-proof membrane on top of the manufactured sand to ensure the water-proof effect.

[0144] S6. Lay a layer of 300g / m² on top of the uppermost composite geogrid. 2 Non-woven geotextile, start backfilling construction waste, first backfill 1m of construction waste, impact compaction, lay a layer of type B geocell, then backfill 1m of construction waste, impact compaction, then lay a layer of type B geocell, repeat the above steps to make the composite pile thickness of construction waste and geocell 4m, and lay three layers of polyethylene geocell.

[0145] S6. A third 300g / m³ layer is laid on top of the top layer of compacted construction waste. 2 Non-woven geotextile, 2m of mineral powder backfill, full-load preloading for 4 months, and actual measurement of settlement during construction period, as detailed below. Figure 3 As shown, the measured settlement during the construction period after 4 months of preloading was 1.39m, which is close to the calculated value St = 1.38m; this indicates that the calculation method described above has high accuracy. After the foundation treatment reached the preloading unloading conditions, the mineral powder was removed, and 300g / m³ of concrete was removed. 2 Non-woven geotextile.

[0146] The method described in this invention has excellent effects in reinforcing ultra-soft silt, reduces sand usage, saves costs, has clear calculation principles and methods, is easy to design and engineering applications, is simple to construct, and has a very broad prospect for engineering applications.

[0147] In summary, the content of this invention is not limited to the above-described embodiments. Those skilled in the art can easily propose other embodiments within the technical guiding principles of this invention, but such embodiments are all included within the scope of this invention.

Claims

1. A preloading and surcharge treatment structure for ultra-soft silt without a drainage layer and with ultra-high reinforced body, characterized in that: The treatment structure includes a reinforced working pad layer, a drainage reinforced structure, and an ultra-high reinforced surcharge structure layer; the reinforced working pad layer includes a woven fabric layer (2) laid on the top surface of the ultra-soft silt layer (1) and a reinforced composite layer (3) located above the woven fabric layer (2); the reinforced composite layer (3) is composed of a type A geocell and a machined sand filling layer. The reinforced structure includes a diaphragm (5), a multi-layer horizontal composite drainage net (6), and multiple vertical drainage boards (4). The vertical drainage boards (4) are inserted into the ultra-soft silt layer (1), and their bottom ends are embedded in the cohesive soil layer (7) at the bottom of the ultra-soft silt layer (1). The diaphragm (5) is laid on the top surface of the reinforced working pad layer. The multi-layer horizontal composite drainage net (6) is laid sequentially above the diaphragm (5). The top of the vertical drainage board (4) extends above the diaphragm (5) and is connected to the reinforcing material of the intermediate layer horizontal composite drainage net (6). The ultra-high reinforced surcharge structure layer includes a first non-woven fabric layer (8) laid on the top surface of the drainage reinforced structure layer, a construction waste and geocell composite surcharge layer (9) filled on the first non-woven fabric layer (8), a second non-woven fabric layer (10) laid on the top surface of the composite surcharge layer (9), and a mineral powder backfill layer (11) filled on the top surface of the second non-woven fabric layer (10); the composite surcharge layer (9) is composed of a construction waste impact compaction layer and type B geocells; The reinforced composite layer (3) includes a bottom layer of type A geocells, a middle layer of type A geocells, and a 1-2m thick layer of manufactured sand. The bottom layer of type A geocells is located on the top surface of the woven fabric layer (2), and the middle layer of type A geocells is located in the middle of the manufactured sand layer. The composite fill layer (9) has a height of 3-6m. Its bottom and top layers are both construction waste impact compaction layers, and multiple layers of type B geocells are provided in the middle. Each layer of construction waste impact compaction layer is formed by backfilling construction waste with a particle size of no more than 20cm and then impact compacting it, with a thickness of 0.8-1m. The 2m backfill compaction layer is formed by crushing granular bricks and cement concrete blocks into filler with a particle size not greater than 20cm. The height of the mineral powder backfill layer (11) is 1-3m, and the height of the mineral powder backfill layer (11) is less than the height of the composite fill layer (9). The A-type geocell in the reinforced composite layer (3) is a polyester tensile geocell with a tensile strength limit of not less than 180kN / m. The B-type geocell is a polyethylene extrusion geocell with a tensile strength limit of not less than 30kN / m.

2. The preloading and surcharge treatment structure for ultra-soft silt without drainage layer and ultra-high reinforced body according to claim 1, characterized in that: The woven fabric layer (2) uses 150g / m 2 The woven fabric was laid out.

3. The preloading and surcharge treatment structure for ultra-soft silt without drainage layer and ultra-high reinforced body according to claim 1, characterized in that: The vertical drainage board (4) is constructed using a board insertion machine. The bottom of the plastic drainage board penetrates the cohesive soil layer by at least 1.0m. The vertical drainage boards (4) are spaced 0.8~1.0m apart and arranged in a square. The diaphragm membrane (5) is made of HDPE and has a thickness of not less than 1.5mm. The horizontal composite drainage net (6) has three layers, and the vertical drainage board (4) is connected to the middle layer of the horizontal composite drainage net (6) by the reinforcing material.

4. The preloading and surcharge treatment structure for ultra-soft silt without drainage layer and ultra-high reinforced body according to claim 3, characterized in that: The density of the HDPE diaphragm is not less than 0.95 g / cm³. 3 The roughness height is not less than 0.3mm, and the yield strength is not less than 25N / mm; the horizontal composite drainage net (6) adopts a 6.3mm thick composite geogrid with a longitudinal water conductivity of not less than 1*10 - 3 m 2 / s, longitudinal tensile strength not less than 18kN / m, and mass per unit area not less than 200g / m² 2 .

5. The preloading and surcharge treatment structure for ultra-soft silt without drainage layer and ultra-high reinforced body according to claim 1, characterized in that: Both the first nonwoven layer (8) and the second nonwoven layer (10) are made of 300g / m 2 Non-woven geotextile.

6. A method for preloading and surcharge treatment of ultra-soft silt without drainage layer ultra-high reinforced body, characterized in that: The treatment method employs the ultra-soft silt without drainage layer ultra-high reinforced body surcharge preloading treatment structure as described in any one of claims 1 to 5, and specifically includes the following steps: S1. Set the thickness of the composite fill of construction waste and geocells in the ultra-high reinforced surcharge structure layer as h2 and the surcharge height of mineral powder as h1, where h1 is 1-3m, h2 is 3-6m and h 2＞ h1; and combined with the current ground elevation H of the foundation to be treated d Foundation treatment, handover surface elevation H s Based on the requirements and the thickness h3 of the reinforced working pad, the settlement S of the ultra-soft silt soil layer during construction was calculated. t By adjusting the setting value h 1、 h2 makes the design height h 1、 h2 and calculated S t The value must meet the following requirements: ； ； In the formula, S t Settlement of ultra-soft silty soil layer during construction period; The design value h that meets the above requirements 1、 h2 represents the actual loading height of mineral powder and the thickness of the composite filling of construction waste and geocells in the actual loading. S2. Determine the foundation treatment area, determine the construction zones, and begin construction; S3. A foam board is erected on the top surface of the ultra-soft silt layer, and a layer of woven fabric is laid. Then, a layer of A-type geocells is laid on the woven fabric. The connection between the A-type geocells is treated by insertion. After laying, 50cm to 60cm of manufactured sand is blown in. Then, another layer of A-type geocells is laid. The connection between the A-type geocells is treated by insertion. Another 50cm to 60cm of manufactured sand is blown in. S4. Lay a layer of diaphragm membrane with a thickness of not less than 1.5mm, and then use a board inserter to install vertical plastic drainage boards. The bottom of the plastic drainage board should penetrate the ultra-soft silt layer and enter the cohesive soil layer by not less than 1.0m. The spacing between the vertical drainage boards is 0.8~1.0m, and the top of the board should be higher than the diaphragm membrane. Lay a multi-layer composite geogrid, and tie the top of the vertical drainage board to the middle layer of composite geogrid. Then wrap the vertical drainage board with the diaphragm membrane and seal it with the diaphragm membrane on top of the manufactured sand to ensure the water-proof effect. S5. Lay a layer of non-woven geotextile on the top surface of the uppermost composite geogrid, and start backfilling construction waste. First, backfill 0.8-1m of construction waste, compact it with impact, lay a layer of type B geocells, then backfill 0.8-1m of construction waste, compact it with impact, and lay another layer of type B geocells. Repeat the above steps until the composite backfill thickness of construction waste and geocells reaches the composite backfill thickness h2 determined in step S1. S6. Lay another layer of non-woven geotextile on the top surface of the uppermost construction waste compaction layer, and start filling mineral powder. After the mineral powder filling height reaches the mineral powder loading height h1 determined in step S1, carry out preloading.

7. The method for preloading and surcharge treatment of ultra-soft silt without drainage layer and ultra-high reinforced body according to claim 6, characterized in that, The settlement amount S of the ultra-soft silt soil layer during the construction period in step S1. t The calculation process is as follows: (1) Under the action of overburden load, the reinforced body in the reinforced working cushion layer of the construction work surface undergoes bending deformation, the upper part of the reinforced body generates compressive stress, the filler in the geocell generates shear force, and the lower geocell generates pull-out force. The load of the horizontal composite drainage network is ignored in the calculation process; the vertical shear force τ generated by the reinforced working cushion layer is: ； Where: τ—vertical shear force generated by the reinforced working pad layer, in kPa; φ—Internal friction angle of the reinforced working pad filler, in °; 25° for manufactured sand; K — Passive earth pressure coefficient ; σ v —Self-weight load of the reinforced working pad layer; The calculation process for the self-weight load of the reinforced working pad layer is as follows: ； r3—Specific weight of the reinforcing working pad filler, in kN / m³ 3 ; z—Vertical elevation of the reinforced working pad layer from top to bottom; The top elevation of the reinforced working pad layer is 0, and the bottom elevation of the reinforced working pad layer is h3; The vertical shear force τ´ of the reinforced working pad filler is taken as the average value of the top and bottom surfaces, and the height z of the top surface is taken as 0, which is the self-weight load σ of the top surface of the reinforced working pad. v顶 =0, vertical shear force τ on the top surface of the reinforced working pad layer 顶 =0, then: τ´=1 / 2(τ 顶 +t 底 )=1 / 2τ 底； ； σ v底= r3 h3 Based on this calculation, we can conclude that: ; Where: r3—specific weight of the reinforcing working pad layer filler, in kN / m³ 3； h3—Thickness of the reinforced working pad layer, in meters; (2) The vertical component T of the material pull-out force generated by the reinforced working pad layer is: ； Where: T—vertical component of the pull-out force generated by the reinforced working pad layer, in kPa; T a —The design pull-out force of the geocells used in the manufactured sand layer is 40 kPa for type A geocells; θ—Deformation angle of geocells in the manufactured sand layer, 20° for type A geocells; (3) Calculate the load diffusion effect p of the construction surface cushion layer: ； Where: p—load diffusion effect of the construction surface cushion layer, unit kPa; (4) Considering the diffusion effect of the reinforced working pad layer below the vertical drainage board, the additional vertical stress caused by large-area surcharge preloading is: ； Where: ΔP—vertical additional stress caused by large-area surcharge preloading, unit kPa; r1—Specific gravity of mineral powder, in kN / m³ 3 ; h1—Powder loading height, in meters; h2—Thickness of composite fill of construction waste and geocells, in meters; r2—Unit weight of construction waste and geocell composite fill material, in kN / m³ 3 ; (5) The total settlement of the ultra-soft silt caused by surcharge preloading is: ; Where: S—total settlement of ultra-soft silt caused by surcharge preloading, in meters; m s —Settlement correction factor, taken as 1.3~1.4 for ultra-soft silt; E s —Compression modulus of ultra-soft silt, in kPa, 1.3~1.4 for ultra-soft silt; H—Thickness of the ultra-soft silt layer, in meters; (6) After 4-5 months of surcharge preloading, the consolidation degree of the ultra-soft silt layer reaches 85%, and the settlement of the ultra-soft silt layer during the construction period is: .

8. The method for preloading and surcharge treatment of ultra-soft silt without drainage layer and ultra-high reinforced body according to claim 6, characterized in that: In step S4, a 1.5mm thick double-textured HDPE diaphragm is used. The vertical drainage boards are arranged in a square, with the head of each board protruding 5-10cm above the HDPE diaphragm. In step S4, three layers of 6.3mm thick composite geogrid are laid, and the heads of the vertical drainage boards are tied to the reinforcing bars of the middle layer of composite geogrid. In step S5, a 300g / m² nonwoven geotextile is used. 2 Non-woven geotextile.

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