Deep soft soil pre-pressing treatment method

Abstract

The invention discloses a deep soft soil pre-pressing treatment method which comprises the following steps: firstly, extracting underground water from soft soil in a shallow area within 20 meters through a precipitation pressurizing pipe, and then switching to be connected with pressurizing equipment to pressurize gas in the soft soil in the shallow area; a water storage layer is arranged on the soft foundation ground to conduct sealing performance testing on a sealing film laid on the soft foundation ground, meanwhile, the water storage layer forms stacking loading on soft soil in a shallow layer area, underground water in the shallow layer area is promoted to flow into a plastic drainage plate and be pumped out by a precipitation pressurization pipe, and the gravity of the water storage layer is matched with the precipitation pressurization pipe to conduct gas pressurization on a soil body. Soft soil in a shallow area can be promoted to drain and reinforce, and soft soil in a deep area can be stacked through self gravity, so that underground water in the deep soft soil is extruded into a plastic drainage plate by the shallow soft soil and is conveniently pumped out. By means of the method, the depth of pre-pressing treatment on the soft foundation ground can be increased to be close to 40 m to the maximum from 20 m or below in the prior art, and the foundation reinforcement depth of the soft foundation ground is deeper.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of soft soil preloading, in particular to a deep soft soil preloading treatment method. BACKGROUND

[0002] The Zhongshan City Mao Bay Yong Flood Control Project is one of the key projects to reduce flood damage in Sanxiang Town and Tanzhou Town of Zhongshan City, and one of the important measures is to build Dayongkou Pumping Station as the backbone project of the regulation "down the row". However, the construction area of the pumping station belongs to the Pearl River Delta land-sea interactive sedimentary plain, the beach phase first terrace, the crust is mainly slow subsidence, and the soft soil with a thickness of dozens of meters is deposited. The soft soil is mainly silt and silt soil, which is characterized by high water content, large void ratio, high compressibility, lack of consolidation, weak permeability, high flow deformation, and easy to produce uneven settlement. Therefore, before construction, the soil layer needs to be preloaded to pre-load and drain the soft soil, so as to consolidate the soil layer. At present, the mainstream method for preloading soft soil at home and abroad is the preloading method, the vacuum preloading method and the preloading method, which can only be used for soft soil within 20 meters. Once the depth of soft soil exceeds 20 meters, the mainstream preloading method is insufficient. SUMMARY

[0003] To solve the above problems, the purpose of the present application is to provide a method for preloading treatment of super deep soft soil with a depth of more than 20 meters.

[0004] The technical scheme adopted by the present application to solve the problem is: a deep soft soil preloading treatment method, comprising the following steps: A. flattening the soft ground surface that needs to be reinforced, and establishing a ring-shaped soil cofferdam around the soft ground surface; B. building a wall in the soil layer through clay mixing piles at the edge of the soft ground surface to establish a sealing wall around the side of the soft ground surface; C. arranging the plastic drainage plates at a set interval on the soft ground surface to form an array, the plastic drainage plates are laid from the soft ground surface to the deep layer 20-40 meters away from the surface of the soft ground surface, and the plastic drainage plates are connected with the vacuum pump through the vacuum pipe; D. drilling holes downward at a set interval on the soft ground surface to form an array, and laying the dewatering booster pipes in the soft ground surface through the drilled holes, the laying depth of the dewatering booster pipes is within the shallow layer of 20 meters, and the dewatering booster pipes are first connected with the water pump to pump water; E. laying the air-tight sealing film on the soft ground surface and the soil cofferdam, and burying the end of the sealing film to isolate the soft ground surface from the atmosphere to form a sealed state; F. Water is poured on the sealing film on the soft ground surface to form a water storage layer with a certain height, the water storage layer is used to test the sealing property of the sealing film, and the soft ground surface is pre-pressed by the gravity of the water storage layer, and the sealing film limits the water in the water storage layer from seeping into the soft ground surface; G. The vacuum pump continuously pumps water and air out of the soil of the soft ground surface through the plastic drainage plate; the water pump lowers the underground water level in the soil of the shallow area through the dewatering booster pipe, so that the buoyant weight of the soil changes into the wet bulk density, thereby forming a stack load on the deep area of the soil; when the water cannot be pumped out or the amount of water pumped out is reduced to a specified amount, the dewatering booster pipe is replaced to connect the booster equipment, thereby boosting the soil of the soft ground surface through the dewatering booster pipe, and under the action of the booster gas, the soil will produce micro-cracks, thereby shortening the path distance of water flowing into the plastic drainage plate.

[0005] As a further improvement of the above technical solution, the laying density of the dewatering booster pipe is less than the laying density of the plastic drainage plate.

[0006] As a further improvement of the above technical solution, the distance between adjacent dewatering booster pipes is 3 meters, and the distance between adjacent plastic drainage plates is 1 meter.

[0007] As a further improvement of the above technical solution, in step A, the height of the soil cofferdam is 1.5 meters, and the slope of the soil cofferdam is 30-60 degrees.

[0008] As a further improvement of the above technical solution, in step B, the depth of the sealing wall is the same as the depth of the plastic drainage plate.

[0009] As a further improvement of the above technical solution, in step C, the top of all plastic drainage plates is connected to the vacuum pipe through a hand-shaped joint to form a vacuum drainage pipe network.

[0010] As a further improvement of the above technical solution, in step D, the depth of the dewatering booster pipe is 10 to 15 meters.

[0011] As a further improvement of the above technical solution, in step E, the top of the sealing wall is also excavated to form a sealing ditch, and the sealing film is simultaneously laid in the sealing ditch, and the sealing ditch is filled with a filling material for fixing the sealing film.

[0012] As a further improvement of the above technical solution, in step F, the height of the water storage layer is between one-half and three-quarters of the height of the soil cofferdam.

[0013] As a further improvement of the above technical solution, the sealing film is two layers, and a layer of woven geotextile and a layer of non-woven geotextile are sequentially arranged between the sealing film and the soft ground surface from top to bottom.

[0014] The application has the beneficial effects that: the soft ground surface to be constructed is surrounded by establishing a soil cofferdam on the periphery of the soft ground surface, and a sealing wall is formed by building a wall in the soil layer at the edge of the soft ground surface, the underground water exchange between the soft ground surface area to be constructed and the soft ground surface area outside the sealing wall is isolated by the sealing wall, then a sealing film is laid on the surface of the soft ground surface and the soil cofferdam to maintain the sealing property of the soft ground surface, the soft soil of the soft ground surface is vacuum pumped by laying plastic drainage plates downward on the soft ground surface, the plastic drainage plates penetrate into the deep area 20-40 meters away from the surface of the soft ground surface, the plastic drainage plates are connected with the vacuum pump through the vacuum pipe, the soft soil of the soft ground surface is vacuum pumped, the well holes are drilled on the soft ground surface at the set interval to lay the dewatering booster pipes, the dewatering booster pipes are laid in the shallow area within 20 meters and the underground water is pumped out by the water pump, at the same time, the water is poured above the sealing film and the water storage layer of a certain height is formed by the shielding of the soil cofferdam to test the sealing property of the sealing film, if the sealing film is damaged, the bubbles will be generated on the surface of the water storage layer, and the weight of the water storage layer itself will also load the soft ground surface, when the water pump pumps out the water through the dewatering booster pipe to the extent that the water cannot be pumped out or the pumping amount is reduced to the specified amount, the dewatering booster pipe is replaced to connect the booster equipment, the soil body of the soft ground surface is gas boosted by the dewatering booster pipe, in the process of gas boosting the soil body, the soil body will change from the buoyant unit weight to the wet unit weight, which promotes the soil body in the shallow area to drain and consolidate downward to form the load on the soil body in the deep area, and under the action of the boosting gas, the soil body will continuously generate micro cracks, thereby shortening the path distance of the water flow in the soil body to the plastic drainage plate. In this way, the dewatering booster pipe pumps out the underground water in the soft soil in the shallow area within 20 meters, thereby reducing the pore water pressure and promoting the ground reinforcement of the soft soil in the shallow area, at the same time, the water storage layer forms the load on the soft soil in the shallow area in the process of testing the sealing film, which promotes the underground water in the shallow area to flow into the plastic drainage plate and be pumped out by the dewatering booster pipe, at the same time, the water storage layer will generate a certain gravity to promote the soft soil in the shallow area to be extruded downward to form the reinforcement, and the booster equipment is used to boost the gas to the soil body in the shallow area, which makes the soft soil in the shallow area form the load on the soft soil in the deep area through the gravity in the process of downward extrusion and consolidation, promotes the underground water in the deep area to be extruded into the plastic drainage plate by the soft soil in the shallow area, and the water storage layer can ensure to apply a relatively balanced pressure to the soft ground surface. It can be seen that in this state, the underground water in the soft soil in the deep area is not mainly pumped out into the plastic drainage plate by the vacuum pumping process of the vacuum pump, but is extruded into the plastic drainage plate by the soft soil in the shallow area in the form of load, so that the problem that the vacuum pump cannot pump out the underground water from the soft soil in the deep area due to the insufficient vacuum pumping capacity caused by the too high depth can be avoided, thereby facilitating the underground water in the soft soil in the deep area to be pumped out by the vacuum pump. By this method, the depth of the preloading on the soft ground surface can be increased from the traditional 20 meters to the maximum of nearly 40 meters, so that the ground reinforcement depth of the soft ground surface is deeper. Attached Figure Description

[0015] The present invention will be further explained and described below with reference to the accompanying drawings and specific embodiments.

[0016] Figure 1 This is a schematic diagram illustrating the processing method of this solution. Detailed Implementation

[0017] This section will describe in detail specific embodiments of the present invention. Preferred embodiments of the present invention are shown in the accompanying drawings. The purpose of the drawings is to supplement the textual description with graphics, so that people can intuitively and vividly understand each technical feature and overall technical solution of the present invention, but they should not be construed as limiting the scope of protection of the present invention.

[0018] In the description of this invention, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., are 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 limiting this invention.

[0019] In the description of this invention, "several" means one or more, "more than" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0020] In the description of this invention, unless otherwise explicitly defined, terms such as "set up," "install," and "connect" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0021] Reference Figure 1 A method for preloading deep soft soil includes the following steps: A. Level the soft base surface that needs reinforcement and build a ring-shaped earthen cofferdam 1 around the soft base surface; B. Construct a sealing wall 2 around the soft foundation by building a wall into the soil layer through clay mixing piles at the edge of the soft foundation; C. Plastic drainage boards 3 are laid on the soft base surface at a set interval to form an array. The plastic drainage boards 3 are laid from the soft base surface to a deep area 20 to 40 meters away from the surface of the soft base surface. The plastic drainage boards 3 are connected to the vacuum pump through a vacuum tube. D. Forming downward drilling in array arrangement with set interval on soft ground surface, and laying dewatering booster pipe 4 in soft ground surface through drilled hole, the laying depth of dewatering booster pipe 4 is in shallow area within 20 meters, and pumping water through water pump connecting dewatering booster pipe 4 is performed firstly; E. Laying air impermeable sealing film 5 on soft ground surface and earth cofferdam 1, and carrying out buried treatment on end part, so as to isolate soft ground surface from atmosphere to form sealing state; F. Filling water on sealing film 5 of soft ground surface to form water storage layer 6 with certain height, water storage layer 6 is used for inspecting sealing property of sealing film 5, and preloading is formed on soft ground surface through gravity of water storage layer 6, sealing film 5 limits water of water storage layer 6 from seeping into soft ground surface; G. Vacuum pump continuously pumps water and air from soil of soft ground surface through plastic drainage plate 3; water pump lowers underground water level in soil of shallow area through dewatering booster pipe 4, so that wet bulk density of soil is changed into dry bulk density, so that soil of shallow area forms preloading to soil of deep area, when water cannot be pumped out or pumping amount is reduced to specified amount, dewatering booster pipe 4 is replaced to connect booster equipment, so that soil of soft ground surface is gas boosted through dewatering booster pipe 4, and micro fissure is generated in soil under action of boosted gas, so that path distance of water flow into plastic drainage plate 3 in soil is shortened.

[0022] The soft ground surface to be constructed is surrounded by establishing a soil cofferdam 1 on the periphery of the soft ground surface, and a sealing wall 2 is formed by building a wall in the soil layer at the edge of the soft ground surface, the underground water exchange between the soft ground surface area to be constructed and the soft ground surface area outside the sealing wall 2 is isolated by the sealing wall 2, then a sealing film 5 is laid on the surface of the soft ground surface and the soil cofferdam 1 to maintain the sealing property of the soft ground surface, the soft soil of the soft ground surface is vacuum pumped by laying plastic drainage plates 3 downward on the soft ground surface, the plastic drainage plates 3 penetrate into the deep area 20-40 meters away from the surface of the soft ground surface, the plastic drainage plates 3 are connected with a vacuum pump through a vacuum pipe to vacuum pump the soft soil of the soft ground surface, the dewatering booster pipes 4 are laid by drilling holes on the soft ground surface at a set interval, the laying depth of the dewatering booster pipes 4 is within the shallow area 20 meters, and the underground water is pumped out by a water pump, at the same time, the sealing property of the sealing film 5 is tested by pouring water above the sealing film 5 and forming a water storage layer 6 of a certain height by the shielding of the soil cofferdam 1, if the sealing film 5 is damaged, bubbles will be generated on the surface of the water storage layer 6, and the weight of the water storage layer 6 itself will also form a surcharge on the soft ground surface, when the water pump pumps out water through the dewatering booster pipes 4 to a certain amount, the dewatering booster pipes 4 are replaced by connecting a booster device, the booster device boosts the soil of the soft ground surface by gas through the dewatering booster pipes 4, in the process of boosting the soil by gas, the bulk weight of the soil will change into the wet bulk weight, which promotes the soil in the shallow area to consolidate downward to form a surcharge on the soil in the deep area, and under the action of the boosting gas, the soil will continuously generate micro-cracks, thereby shortening the path distance of the water flow in the soil to the plastic drainage plates 3. In this way, the dewatering booster pipes 4 pump out the underground water of the soft soil in the shallow area within 20 meters in depth, thereby reducing the pore water pressure and promoting the ground reinforcement of the soft soil in the shallow area, at the same time, the water storage layer 6 forms a surcharge on the soft soil in the shallow area in the process of testing the sealing film 5, which promotes the underground water in the shallow area to flow into the plastic drainage plates 3 and be pumped out by the dewatering booster pipes 4, at the same time, the water storage layer 6 will generate a certain gravity to promote the soft soil in the shallow area to consolidate and extrude downward to form reinforcement, and the booster device boosts the soil in the shallow area by gas, which makes the soft soil in the shallow area form a surcharge on the soft soil in the deep area through its own gravity in the process of consolidation and extrusion, and the water storage layer 6 can ensure to apply a relatively balanced pressure on the soft ground surface. It can be seen that, in this state, the underground water in the soft soil in the deep area is not mainly pumped out into the plastic drainage plates 3 by the vacuum pumping process of the vacuum pump, but is extruded into the plastic drainage plates 3 by the soil in the shallow area in the form of surcharge, therefore, the problem that the vacuum pump cannot pump out the underground water from the soft soil in the deep area due to insufficient vacuum pumping capacity caused by too high depth can be avoided, so it is convenient to pump out the underground water in the soft soil in the deep area by the vacuum pump.Through the method, the depth of the soft ground surface preloading treatment can be increased from the traditional 20 meters to nearly 40 meters, so that the soft ground surface reinforcement depth is deeper.

[0023] In the scheme, considering that the shallow area is provided with the dewatering booster pipe 4 and the plastic drainage plate 3, and the deep area mainly collects underground water by the plastic drainage plate 3, in order to reduce the construction amount, the laying density of the dewatering booster pipe 4 can be preferably less than that of the plastic drainage plate 3. On this basis, the distance between adjacent dewatering booster pipes 4 is preferably 3 meters, and the distance between adjacent plastic drainage plates 3 is preferably 1 meter.

[0024] In the above scheme, preferably in step A, the height of the earth cofferdam 1 is 1.5 meters, and the slope of the earth cofferdam 1 is 45 degrees.

[0025] In the above scheme, preferably in step B, the depth of the sealing wall 2 is the same as that of the plastic drainage plate 3.

[0026] In order to better fix the sealing membrane 5, preferably in step E, the top of the sealing wall 2 is further excavated to form a sealing ditch 7, the sealing membrane 5 is simultaneously laid in the sealing ditch 7, and the sealing ditch 7 is filled with a filling material 8 for fixing the sealing membrane 5, so that the filling material 8 in the sealing ditch 7 is used to compact the sealing membrane 5 and avoid the filling material 8 from moving in the water storage layer 6.

[0027] The top of the plastic drainage plate 3 is drained by arranging a sand cushion layer in the traditional way, but in the scheme, since the water storage layer 6 is arranged on the soft ground surface, in step D, the top of all the plastic drainage plates 3 is connected with the vacuum pipe through the hand-shaped joint to form a vacuum drainage pipe network for drainage.

[0028] In the scheme, the depth of the dewatering booster pipe 4 is preferably 10 to 15 meters, which is the best working depth of the dewatering booster pipe 4.

[0029] In the scheme, the height of the water storage layer 6 is preferably between one half and three quarters of the height of the earth cofferdam 1, and in combination with the height of the earth cofferdam 1 being 1.5 meters, the optimal depth of the water storage layer 6 is 1 meter.

[0030] In the scheme, the sealing membrane 5 is two layers, and between the sealing membrane 5 and the soft ground surface, a layer of woven geotextile and a layer of non-woven geotextile are sequentially arranged from top to bottom, and the two layers of sealing membranes are used to ensure the sealing effect and avoid the water in the water storage layer 6 from seeping into the soft ground surface below, and the layer of woven geotextile and the layer of non-woven geotextile are used to protect the sealing membrane from being pierced by hard blocks in the surface soil.

[0031] The above merely describes the preferred embodiments of the present application, and is not intended to limit the patent scope of the present application. Any equivalent structural changes made according to the content of the present application specification and drawings, or direct or indirect application in other related technical fields are included in the patent protection scope of the present application.

Claims

1. A method for preloading deep soft soil, characterized by, It comprises the following steps: A. Leveling the soft ground surface in need of reinforcement, and establishing a ring-shaped earth cofferdam (1) around the periphery of the soft ground surface; B. Building a sealing wall (2) around the periphery of the soft ground surface by building a wall in the soil layer through clay mixing piles at the edge of the soft ground surface; C. Forming an array arrangement by applying plastic drainage plates (3) at a set interval on the soft ground surface, the plastic drainage plates (3) being laid into deep areas 20-40 meters away from the surface of the soft ground surface from the soft ground surface, and the plastic drainage plates (3) being connected to a vacuum pump through a vacuum pipe; D. Forming an array arrangement by drilling holes at a set interval on the soft ground surface, and laying a dewatering booster pipe (4) into the soft ground surface through the drilled holes, the dewatering booster pipe (4) being laid in a shallow area within 20 meters in depth, and the dewatering booster pipe (4) being connected to a water pump to perform water pumping; E. Laying an air-tight sealing film (5) on the soft ground surface and the earth cofferdam (1), and performing buried pressure treatment on the end portion of the air-tight sealing film (5), so as to isolate the soft ground surface from the atmosphere to form a sealed state; F. Forming a water storage layer (6) of a certain height by pouring water on the air-tight sealing film (5) on the soft ground surface, the water storage layer (6) being used to inspect the sealing property of the air-tight sealing film (5), and the soft ground surface being pre-pressed by the gravity of the water storage layer (6), and the air-tight sealing film (5) limiting the water in the water storage layer (6) from permeating into the soft ground surface; G. The vacuum pump continuously pumps water and air out of the soil of the soft ground surface through the plastic drainage plates (3), the water pump lowers the underground water level in the soil of the shallow area through the dewatering booster pipe (4), so that the floating bulk density of the soil is changed into the wet bulk density, and the soil of the shallow area forms a load on the soil of the deep area, when the dewatering booster pipe (4) cannot pump out water or the amount of pumped water is reduced to a specified amount, the dewatering booster pipe (4) is replaced to be connected to a booster device, so as to perform gas boosting on the soil of the soft ground surface through the dewatering booster pipe (4), and under the action of the boosted gas, the soil will produce micro-cracks, so as to shorten the path distance of water flow in the soil into the plastic drainage plates (3).

2. The deep soft soil pre-pressing treatment method according to claim 1, wherein the laying density of the dewatering booster pipe (4) is less than the laying density of the plastic drainage plate (3).

3. The deep soft soil pre-pressing treatment method according to claim 2, wherein the distance between adjacent dewatering booster pipes (4) is 3 meters, and the distance between adjacent plastic drainage plates (3) is 1 meter.

4. The deep soft soil pre-pressing treatment method according to claim 1, wherein in step A, the height of the earth cofferdam (1) is 1.5 meters, and the slope of the earth cofferdam (1) is 30-60 degrees.

5. The deep soft soil pre-pressing treatment method according to claim 1, wherein in step B, the depth of the sealing wall (2) is the same as the depth of the plastic drainage plate (3).

6. The deep soft soil pre-pressing treatment method according to claim 1, wherein in step C, the top portions of all the plastic drainage plates (3) are connected to the vacuum pipe through hand-shaped joints to form a vacuum drainage pipe network. ​ ​ ​ ​ ​ 7. The method for preloading deep soft soil as claimed in claim 1, wherein the depth of the dewatering booster pipe (4) is 10-15 m.

8. The method for preloading deep soft soil as claimed in claim 1, wherein the top of the sealing wall (2) is further excavated to form a sealing trench (7), the sealing membrane (5) is simultaneously laid in the sealing trench (7), and the sealing trench (7) is filled with a filling material (8) for fixing the sealing membrane (5).

9. The method for preloading deep soft soil as claimed in claim 1, wherein the height of the water storage layer (6) is 1 / 2-3 / 4 of the height of the earth cofferdam (1).

10. The method for preloading deep soft soil as claimed in claim 1, wherein the sealing membrane (5) is two layers, and a layer of woven geotextile and a layer of non-woven geotextile are further arranged between the sealing membrane (5) and the soft ground surface. ​ ​ ​ ​

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