In-situ mucky soil deep foundation pit construction method

Abstract

The invention discloses an in-situ mucky soil deep foundation pit construction method. The method comprises the following steps that an area to be treated is divided into a plurality of square blocks and a plurality of layers of step areas; sequentially executing the following operations on each step area in the to-be-treated area from top to bottom: adding a curing agent, stirring, standing, digging out the mucky soil after the mucky soil is cured, and arranging a protective layer; and a curing agent is added into the mucky soil at the bottom of the lowermost step area, standing is conducted after even stirring, and construction is completed after the mucky soil meets the curing strength design requirement. A soil stabilizer is adopted for foundation pit mucky soil solidification, a single process is adopted for construction, and the excavation difficulty is reduced; according to the in-situ mucky soil deep foundation pit construction method, the bottom of a foundation pit and a side slope are solidified, the construction process is simple, and site construction is convenient and fast; the anti-seepage performance of the solidified soil body is remarkably improved, and foundation pit water seepage can be effectively reduced; the solidification time of the solidified soil is short, the project construction period is shortened, and good economic benefits are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of foundation pit treatment and relates to an in-situ silty soil deep foundation pit construction method. Background Art

[0002] Silt soil has a high water content and low bearing capacity, and it is often difficult to carry out deep foundation pit excavation operations on it, especially for deep foundation pits with a depth of ten to fifteen meters. Common treatment methods include pile foundation method, soil replacement method, cement mixing method, caisson foundation method, etc. These methods often have high investments, long construction periods, and complex processes. At the same time, during the excavation of deep foundation pits, the slopes are prone to collapse and groundwater leakage occurs, posing a safety threat to workers and buildings in the foundation pit and affecting the safety of the project.

[0003] In summary, the existing technology has the problems of complex process and high construction cost. Summary of the invention

[0004] The purpose of the present invention is to provide an in-situ silty soil deep foundation pit construction method, which solves the problems of complex process and high construction cost in the prior art.

[0005] The technical solution adopted by the present invention is an in-situ muddy soil deep foundation pit construction method, comprising the following steps: S1. Divide the area to be processed into a number of square blocks and a number of step areas; S2. Perform the following operations in order from top to bottom for each step area in the area to be treated: adding a curing agent, stirring and then letting it stand, digging out the muddy soil after it solidifies, and setting a protective layer; S3. Add curing agent to the silty soil at the bottom of the lowest step area, stir evenly and let it stand. When the silty soil meets the design requirements for curing strength, the construction is completed.

[0006] The present invention is also characterized in that: S2 includes the following steps: S2.1, adding a curing agent to the muddy soil in the area to be treated, stirring evenly and letting it stand, and after the muddy soil in the area to be treated meets the curing strength design requirements, proceed to step S2.2; S2.2. Dig out the solidified soil in the upper step area of ​​the area to be treated from the center to the surrounding areas, and set up the first protective layer, the second protective layer, and the third protective layer of the upper step area respectively; S2.3, adding a curing agent to the muddy soil at the bottom of the excavated step area, stirring evenly and letting it stand, and proceeding to step S2.4 after the muddy soil in the area to be treated meets the curing strength design requirements; S2.4, dig out the solidified soil in the step area to be treated from the center to the surroundings, and respectively set the first protective layer, the second protective layer, and the third protective layer of the step area. When the several layers of step areas divided in step S1 are completed to the lowest step area, step S2.5 is performed; when the several layers of step areas divided in step S1 are not completed to the lowest step area, steps S2.3 to S2.4 are repeated; S2.5. Add the curing agent to the silty soil in the lowest step area, stir evenly and let it stand. After the silty soil in the treated area meets the design requirements of curing strength, dig out the solidified soil in the lowest step area from the center to the surrounding areas, and set the first protective layer and the second protective layer of the lowest step area respectively.

[0007] Several square blocks have the same size; several layers of step areas are stacked in sequence in the vertical direction, the step area depth is three to five meters, and the length and width of the lower step area are five to seven meters smaller than the length and width of the upper step area respectively.

[0008] The mass ratio of the curing agent added to the area to be treated to the silty soil in the area to be treated is 10%-12%.

[0009] The method is characterized in that the first protective layer is a solidified soil wall retained at the upper outer edge of any step area when the solidified soil of the step area is excavated.

[0010] The width of the first protective layer is one to two meters; one side of the second protective layer contacts the ground or the upper step area, and the other side contacts the lower step area or the solidified area of ​​the foundation pit bottom.

[0011] The method is characterized in that the second protective layer is a solidified soil slope retained at the edge of any step area when the solidified soil in the step area is excavated; the ratio of the vertical height to the horizontal width of the solidified soil slope in the second protective layer is 1:(1-1.5).

[0012] The method is characterized in that the third protective layer is a solidified soil retaining wall set at the lower inner edge of any step area when the solidified soil of the step area is excavated.

[0013] The height of the third protective layer is one meter to one and a half meters, and the width is one meter to two meters; the outer edge of the third protective layer is in contact with the second protective layer, and the inner edge is the same size as the lower step area on the horizontal plane; a number of anchor rods are arranged in the third protective layer for reinforcement; one end of the anchor rod passes through the third protective layer, and the other end is embedded in the first protective layer of the lower step area.

[0014] The design requirements for the solidification strength are that the characteristic bearing capacity of the silty soil after solidification is not less than 200 kPa, the cohesion is not less than 280 kPa, and the permeability coefficient is not greater than 1×10 -8cm / s, and the internal friction angle is 25 to 29 degrees.

[0015] The beneficial effects of the present invention are: using soil solidifier to solidify the muddy soil of the foundation pit, using a single construction process, reducing the difficulty of excavation; solidifying the bottom and slope of the foundation pit, with a simple construction process and convenient on-site construction; the anti-seepage performance of the soil body is significantly improved after solidification treatment, which can effectively reduce water seepage in the foundation pit; the solidification time of the solidified soil is relatively short, saving the construction period and having better economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a structural schematic diagram of a deep foundation pit after construction is completed in an embodiment of the present invention.

[0017] In the figure, 1, ground; 2, first step solidification area; 3, second step solidification area; 4, third step solidification area; 5, anchor rod; 6, first step solidification soil excavation area; 7, second step solidification soil excavation area; 8, third step solidification soil excavation area; 9, foundation pit bottom solidification operation area; 10, first protective layer; 11, second protective layer; 12, third protective layer. DETAILED DESCRIPTION

[0018] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0019] The in-situ silty soil deep foundation pit construction method comprises the following steps: S1. Divide the area to be processed into a number of square blocks and a number of step areas; Several square blocks have the same size; several layers of step areas are stacked in sequence in the vertical direction, the step area depth is three to five meters, and the length and width of the lower step area are five to seven meters smaller than the length and width of the upper step area respectively.

[0020] S2. Perform the following operations in order from top to bottom for each step area in the area to be treated: adding a curing agent, stirring and then letting it stand, digging out the muddy soil after it solidifies, and setting a protective layer; S2.1, adding a curing agent to the muddy soil in the area to be treated, stirring evenly and letting it stand, and after the muddy soil in the area to be treated meets the curing strength design requirements, proceed to step S2.2; S2.2. Dig out the solidified soil in the upper step area of ​​the area to be treated from the center to the surrounding areas, and set up the first protective layer, the second protective layer, and the third protective layer of the upper step area respectively; S2.3, adding a curing agent to the muddy soil at the bottom of the excavated step area, stirring evenly and letting it stand, and proceeding to step S2.4 after the muddy soil in the area to be treated meets the curing strength design requirements; S2.4, dig out the solidified soil in the step area to be treated from the center to the surroundings, and respectively set the first protective layer, the second protective layer, and the third protective layer of the step area. When the several layers of step areas divided in step S1 are completed to the lowest step area, step S2.5 is performed; when the several layers of step areas divided in step S1 are not completed to the lowest step area, steps S2.3 to S2.4 are repeated; S2.5. Add the curing agent to the silty soil in the lowest step area, stir evenly and let it stand. After the silty soil in the treated area meets the design requirements of curing strength, dig out the solidified soil in the lowest step area from the center to the surrounding areas, and set the first protective layer and the second protective layer of the lowest step area respectively.

[0021] The design requirements for the solidification strength are that the characteristic bearing capacity of the silty soil after solidification is not less than 200 kPa, the cohesion is not less than 280 kPa, and the permeability coefficient is not greater than 1×10 -8 cm / s, and the internal friction angle is 25 to 29 degrees.

[0022] The mass ratio of the curing agent added to the area to be treated to the silty soil in the area to be treated is 10%-12%.

[0023] The first protective layer is the solidified soil wall retained at the upper outer edge of any step area when the solidified soil of the step area is excavated.

[0024] The width of the first protective layer is one to two meters; one side of the second protective layer contacts the ground or the upper step area, and the other side contacts the lower step area or the solidified area of ​​the foundation pit bottom.

[0025] The second protective layer is the solidified soil slope retained at the edge of any step area when the solidified soil in the step area is excavated.

[0026] The ratio of the vertical height to the horizontal width of the solidified soil slope in the second protective layer is 1:(1-1.5); The third protective layer is a solidified soil retaining wall set at the lower inner edge of any step area when the solidified soil in the step area is excavated.

[0027] The height of the third protective layer is one meter to one and a half meters, and the width is one meter to two meters; the outer edge of the third protective layer is in contact with the second protective layer, and the inner edge is the same size as the lower step area on the horizontal plane; a number of anchor rods are arranged in the third protective layer for reinforcement; one end of the anchor rod passes through the third protective layer, and the other end is embedded in the first protective layer of the lower step area.

[0028] S3. Add curing agent to the silty soil at the bottom of the lowest step area, stir evenly and let it stand. When the silty soil meets the curing strength design requirements, the construction is completed.

[0029] When the area to be treated is divided into square blocks, if there are areas with large cross-sectional changes, the treatment blocks can be adjusted accordingly to facilitate construction. The present invention divides the area to be treated into blocks, which is conducive to the arrangement of the sequence of on-site operations, facilitates operation control, and avoids repeated or missing solidification; the amount of curing agent used can be selected after comprehensively considering the water content of the silty soil and the type of silt in the area to be treated; the anchor rod parameters are as follows: total height four meters, plane spacing two meters, anchor rod exposed to the ground 0.2 meters, and the steel bar diameter can be 20 mm to 25 mm ribbed secondary steel bars.

[0030] The present invention adds a certain proportion of soil solidifier into the silt, performs in-situ solidification treatment on the silt in the deep foundation pit, excavates the soil in the foundation pit after the solidification treatment, retains a certain range of solidified soil at the edge of the foundation pit as a retaining structure during the excavation process, and finally forms a silty soil deep foundation pit working environment, providing a site for the next step of construction work, and the solidification and excavation are both carried out in a step-by-step manner.

[0031] The present invention adopts a single construction process, reduces construction difficulty, and reduces excavation difficulty; the present invention significantly improves the anti-seepage performance of the soil around the foundation pit, effectively reduces water seepage in the foundation pit, reduces the drainage site of the foundation pit, and ensures the safety of the foundation pit; the solidification time of the solidified soil in the present invention is relatively short, saves construction period, and has better economic benefits.

[0032] Example 1 This embodiment proposes an in-situ muddy soil deep foundation pit construction method, comprising the following steps: S1. Divide the area to be processed into several square blocks and four-layer step areas; S2. Perform the following operations in order from top to bottom for each step area in the area to be treated: adding a curing agent, stirring and then letting it stand, digging out the muddy soil after it solidifies, and setting a protective layer; S2.1, adding a curing agent to the muddy soil in the area to be treated, stirring evenly and letting it stand, and after the muddy soil in the area to be treated meets the curing strength design requirements, proceed to step S2.2; S2.3, adding a curing agent to the muddy soil at the bottom of the excavated step area, stirring evenly and letting it stand, and proceeding to step S2.4 after the muddy soil in the area to be treated meets the curing strength design requirements; S2.4, dig out the solidified soil in the step area to be treated from the center to the surroundings, and respectively set the first protective layer, the second protective layer, and the third protective layer of the step area. When the four-layer step area divided in step S1 is completed to the lowest step area, step S2.5 is performed; when the four-layer step area divided in step S1 is not completed to the lowest step area, steps S2.3 to S2.4 are repeated; S2.5. Add the curing agent to the silty soil in the lowest step area, stir evenly and let it stand. After the silty soil in the treated area meets the design requirements of curing strength, dig out the solidified soil in the lowest step area from the center to the surrounding areas, and set the first protective layer and the second protective layer of the lowest step area respectively.

[0033] S3. Add curing agent to the silty soil at the bottom of the lowest step area, stir evenly and let it stand. When the silty soil meets the curing strength design requirements, the construction is completed.

[0034] Example 2 This embodiment proposes an in-situ muddy soil deep foundation pit construction method, comprising the following steps: S1. Divide the area to be processed into several square blocks and five-layer step areas; The sizes of the square blocks are the same; five steps are stacked in sequence in the vertical direction, the step area is four meters deep, and the length and width of the lower step area are six meters smaller than the length and width of the upper step area respectively; S2. Perform the following operations in order from top to bottom for each step area in the area to be treated: adding a curing agent, stirring and then letting it stand, digging out the muddy soil after it solidifies, and setting a protective layer; S2.1, adding a curing agent to the muddy soil in the area to be treated, stirring evenly and letting it stand, and after the muddy soil in the area to be treated meets the curing strength design requirements, proceed to step S2.2; S2.2. Dig out the solidified soil in the upper step area of ​​the area to be treated from the center to the surrounding areas, and set up the first protective layer, the second protective layer, and the third protective layer of the upper step area respectively; S2.3, adding a curing agent to the muddy soil at the bottom of the excavated step area, stirring evenly and letting it stand, and proceeding to step S2.4 after the muddy soil in the area to be treated meets the curing strength design requirements; S2.4, dig out the solidified soil in the step area to be treated from the center to the surroundings, and respectively set the first protective layer, the second protective layer, and the third protective layer of the step area. When the five-layer step area divided in step S1 is completed to the lowest step area, step S2.5 is performed; when the five-layer step area divided in step S1 is not completed to the lowest step area, repeat steps S2.3 to S2.4; S2.5, add the curing agent to the muddy soil in the lowest step area, stir evenly and let it stand. After the muddy soil in the treatment area meets the curing strength design requirements, dig out the solidified soil in the lowest step area from the center to the surrounding areas, and set the first protective layer and the second protective layer of the lowest step area respectively; S3. Add curing agent to the silty soil at the bottom of the lowest step area, stir evenly and let it stand. When the silty soil meets the curing strength design requirements, the construction is completed.

[0035] Example 3 This embodiment proposes an in-situ muddy soil deep foundation pit construction method, comprising the following steps: S1. Divide the area to be processed into several square blocks and four-layer step areas; The sizes of the square blocks are the same; the four steps are stacked in sequence in the vertical direction, the step area is three meters deep, and the length and width of the lower step area are five meters less than the length and width of the upper step area respectively; S2. Perform the following operations in order from top to bottom for each step area in the area to be treated: adding a curing agent, stirring and then letting it stand, digging out the muddy soil after it solidifies, and setting a protective layer; S2.1, adding a curing agent to the muddy soil in the area to be treated, stirring evenly and letting it stand, and after the muddy soil in the area to be treated meets the curing strength design requirements, proceed to step S2.2; The mass ratio of the curing agent added to the area to be treated to the silty soil in the area to be treated is 10%; S2.2. Dig out the solidified soil in the upper step area of ​​the area to be treated from the center to the surrounding areas, and set up the first protective layer, the second protective layer, and the third protective layer of the upper step area respectively; The width of the first protective layer is one meter; the ratio of the vertical height to the horizontal width of the solidified soil slope in the second protective layer is 1:1; the height of the third protective layer is one meter and the width is one meter; S2.3, adding a curing agent to the muddy soil at the bottom of the excavated step area, stirring evenly and letting it stand, and proceeding to step S2.4 after the muddy soil in the area to be treated meets the curing strength design requirements; S2.4, dig out the solidified soil in the step area to be treated from the center to the surroundings, and respectively set the first protective layer, the second protective layer, and the third protective layer of the step area. When the four-layer step area divided in step S1 is completed to the lowest step area, step S2.5 is performed; when the four-layer step area divided in step S1 is not completed to the lowest step area, steps S2.3 to S2.4 are repeated; S2.5, add the curing agent to the muddy soil in the lowest step area, stir evenly and let it stand. After the muddy soil in the treatment area meets the curing strength design requirements, dig out the solidified soil in the lowest step area from the center to the surrounding areas, and set the first protective layer and the second protective layer of the lowest step area respectively; S3. Add curing agent to the silty soil at the bottom of the lowest step area, stir evenly and let it stand. When the silty soil meets the curing strength design requirements, the construction is completed.

[0036] Example 4 This embodiment proposes an in-situ muddy soil deep foundation pit construction method, comprising the following steps: S1. Divide the area to be processed into several square blocks and six-layer step areas; The sizes of the square blocks are the same; six steps are stacked in sequence in the vertical direction, the step area is five meters deep, and the length and width of the lower step area are seven meters smaller than the length and width of the upper step area respectively; S2. Perform the following operations in order from top to bottom for each step area in the area to be treated: adding a curing agent, stirring and then letting it stand, digging out the muddy soil after it solidifies, and setting a protective layer; S2.1, adding a curing agent to the muddy soil in the area to be treated, stirring evenly and letting it stand, and after the muddy soil in the area to be treated meets the curing strength design requirements, proceed to step S2.2; The mass ratio of the curing agent added to the area to be treated to the silty soil in the area to be treated is 12%; S2.2. Dig out the solidified soil in the upper step area of ​​the area to be treated from the center to the surrounding areas, and set up the first protective layer, the second protective layer, and the third protective layer of the upper step area respectively; The width of the first protective layer is two meters; the ratio of the vertical height to the horizontal width of the solidified soil slope in the second protective layer is 1:1.5; the height of the third protective layer is 1.5 meters and the width is two meters; S2.3, adding a curing agent to the muddy soil at the bottom of the excavated step area, stirring evenly and letting it stand, and proceeding to step S2.4 after the muddy soil in the area to be treated meets the curing strength design requirements; S2.4, dig out the solidified soil in the step area to be treated from the center to the surroundings, and respectively set the first protective layer, the second protective layer, and the third protective layer of the step area. When the six-layer step area divided in step S1 is completed to the lowest step area, step S2.5 is performed; when the six-layer step area divided in step S1 is not completed to the lowest step area, steps S2.3 to S2.4 are repeated; S2.5, add the curing agent to the muddy soil in the lowest step area, stir evenly and let it stand. After the muddy soil in the treatment area meets the curing strength design requirements, dig out the solidified soil in the lowest step area from the center to the surrounding areas, and set the first protective layer and the second protective layer of the lowest step area respectively; S3. Add curing agent to the silty soil at the bottom of the lowest step area, stir evenly and let it stand. When the silty soil meets the curing strength design requirements, the construction is completed.

[0037] Example 5 This embodiment proposes an in-situ muddy soil deep foundation pit construction method, comprising the following steps: S1. Divide the area to be processed into several square blocks and five-layer step areas; The sizes of the square blocks are the same; five steps are stacked in sequence in the vertical direction, the step area is four meters deep, and the length and width of the lower step area are six meters smaller than the length and width of the upper step area respectively; S2. Perform the following operations in order from top to bottom for each step area in the area to be treated: adding a curing agent, stirring and then letting it stand, digging out the muddy soil after it solidifies, and setting a protective layer; S2.1, adding a curing agent to the muddy soil in the area to be treated, stirring evenly and letting it stand, and after the muddy soil in the area to be treated meets the curing strength design requirements, proceed to step S2.2; The mass ratio of the curing agent added to the area to be treated to the silty soil in the area to be treated is 11%; S2.2. Dig out the solidified soil in the upper step area of ​​the area to be treated from the center to the surrounding areas, and set up the first protective layer, the second protective layer, and the third protective layer of the upper step area respectively; The width of the first protective layer is 1.5 meters; the ratio of the vertical height to the horizontal width of the solidified soil slope in the second protective layer is 1:1.25; the height of the third protective layer is 1.25 meters and the width is 1.5 meters; S2.3, adding a curing agent to the muddy soil at the bottom of the excavated step area, stirring evenly and letting it stand, and proceeding to step S2.4 after the muddy soil in the area to be treated meets the curing strength design requirements; S2.4, dig out the solidified soil in the step area to be treated from the center to the surroundings, and respectively set the first protective layer, the second protective layer, and the third protective layer of the step area. When the five-layer step area divided in step S1 is completed to the lowest step area, step S2.5 is performed; when the five-layer step area divided in step S1 is not completed to the lowest step area, repeat steps S2.3 to S2.4; S2.5, add the curing agent to the muddy soil in the lowest step area, stir evenly and let it stand. After the muddy soil in the treatment area meets the curing strength design requirements, dig out the solidified soil in the lowest step area from the center to the surrounding areas, and set the first protective layer and the second protective layer of the lowest step area respectively; S3. Add curing agent to the silty soil at the bottom of the lowest step area, stir evenly and let it stand. When the silty soil meets the curing strength design requirements, the construction is completed.

[0038] Example 6 This embodiment proposes an in-situ muddy soil deep foundation pit construction method, comprising the following steps: S1. Divide the area to be processed into several square blocks and three-layer step areas; The sizes of the square blocks are the same; three steps are stacked in sequence in the vertical direction, the step area is four meters deep, and the length and width of the lower step area are six meters smaller than the length and width of the upper step area respectively; S2. Perform the following operations in order from top to bottom for each step area in the area to be treated: adding a curing agent, stirring and then letting it stand, digging out the muddy soil after it solidifies, and setting a protective layer; S2.1, adding a curing agent to the muddy soil in the area to be treated, stirring evenly and letting it stand, and after the muddy soil in the area to be treated meets the curing strength design requirements, proceed to step S2.2; The mass ratio of the curing agent added to the area to be treated to the silty soil in the area to be treated is 11%; S2.2. Dig out the solidified soil in the upper step area of ​​the area to be treated from the center to the surrounding areas, and set up the first protective layer, the second protective layer, and the third protective layer of the upper step area respectively; The first protective layer is the solidified soil wall retained at the upper outer edge of any step area when the solidified soil of the step area is excavated; The width of the first protective layer is 1.5 meters; the ratio of the vertical height to the horizontal width of the solidified soil slope in the second protective layer is 1:1; The third protective layer has a height of one meter and a width of two meters; S2.3, adding a curing agent to the muddy soil at the bottom of the excavated step area, stirring evenly and letting it stand, and proceeding to step S2.4 after the muddy soil in the area to be treated meets the curing strength design requirements; The design requirements for the solidification strength are that the characteristic bearing capacity of the silt soil after solidification is 250 kPa, the cohesion is 300 kPa, and the permeability coefficient is 1×10 -8 cm / s, the internal friction angle is 27 degrees; S2.4, dig out the solidified soil in the step area to be treated from the center to the surroundings, and respectively set the first protective layer, the second protective layer, and the third protective layer of the step area. When the three-layer step area divided in step S1 is completed to the lowest step area, step S2.5 is performed; when the three-layer step area divided in step S1 is not completed to the lowest step area, steps S2.3 to S2.4 are repeated; S2.5, add the curing agent to the muddy soil in the lowest step area, stir evenly and let it stand. After the muddy soil in the treatment area meets the curing strength design requirements, dig out the solidified soil in the lowest step area from the center to the surrounding areas, and set the first protective layer and the second protective layer of the lowest step area respectively; S3. Add curing agent to the silty soil at the bottom of the lowest step area, stir evenly and let it stand. When the silty soil meets the design requirements for curing strength, the construction is completed.

[0039] like Figure 1 As shown, it is a schematic diagram of the structure after the construction of this embodiment is completed. Starting from the ground 1, the first step solidification area 2, the second step solidification area 3, and the third step solidification area 4 are stacked in sequence from top to bottom in the vertical direction. A foundation pit bottom solidification operation area 9 is arranged below the third step solidification area 4. The first step solidification area 2, the second step solidification area 3, and the third step solidification area 4 are respectively provided with a first step solidification soil excavation area 6, a second step solidification soil excavation area 7, and a third step solidification soil excavation area 8. One side of the second protective layer 11 of the first step solidification area 2 is the first protective layer 10 of the first step solidification area 2, and the other side of the second protective layer 11 of the first step solidification area 2 is the third protective layer 12 of the first step solidification area 2. The first protective layer 10 of the first step solidification area 2 is flush with the ground 1, and a plurality of anchor rods 5 are arranged in the third protective layer 12 of the first step solidification area 2. One end of the anchor rod 5 passes through the third protective layer 12 of the first step solidification area 2 and is vertically inserted into the first protective layer of the second step solidification area.

Claims

1. An in-situ muddy soil deep foundation pit construction method, characterized in that: The following steps are involved: S1. Divide the area to be processed into a number of square blocks and a number of step areas; S2. Perform the following operations in order from top to bottom for each step area in the area to be treated: adding a curing agent, stirring and then letting it stand, digging out the muddy soil after it solidifies, and setting a protective layer; S3. Add curing agent to the silty soil at the bottom of the lowest step area, stir evenly and let it stand. When the silty soil meets the design requirements for curing strength, the construction is completed.

2. The in-situ muddy soil deep foundation pit construction method according to claim 1, characterized in that: The S2 comprises the following steps: S2.1, adding a curing agent to the muddy soil in the area to be treated, stirring evenly and letting it stand, and after the muddy soil in the area to be treated meets the curing strength design requirements, proceed to step S2.2; S2.

2. Dig out the solidified soil in the upper step area of ​​the area to be treated from the center to the surrounding areas, and set up the first protective layer, the second protective layer, and the third protective layer of the upper step area respectively; S2.3, adding a curing agent to the muddy soil at the bottom of the excavated step area, stirring evenly and letting it stand, and proceeding to step S2.4 after the muddy soil in the area to be treated meets the curing strength design requirements; S2.4, dig out the solidified soil in the step area to be treated from the center to the surroundings, and respectively set the first protective layer, the second protective layer, and the third protective layer of the step area. When the several layers of step areas divided in step S1 are completed to the lowest step area, step S2.5 is performed; when the several layers of step areas divided in step S1 are not completed to the lowest step area, steps S2.3 to S2.4 are repeated; S2.

5. Add the curing agent to the silty soil in the lowest step area, stir evenly and let it stand. After the silty soil in the treated area meets the design requirements of curing strength, dig out the solidified soil in the lowest step area from the center to the surrounding areas, and set the first protective layer and the second protective layer of the lowest step area respectively.

3. The in-situ muddy soil deep foundation pit construction method according to claim 2, characterized in that: The sizes of several square blocks are the same; several layers of step areas are stacked in sequence in the vertical direction, the depth of the step area is three to five meters, and the length and width of the lower step area are five to seven meters smaller than the length and width of the upper step area.

4. The in-situ muddy soil deep foundation pit construction method according to claim 3 is characterized in that: The mass ratio of the curing agent added to the area to be treated to the silty soil in the area to be treated is 10%-12%.

5. The in-situ muddy soil deep foundation pit construction method according to claim 4, characterized in that: The first protective layer is a solidified soil wall retained at the upper outer edge of any step area when the solidified soil in the step area is excavated.

6. The in-situ muddy soil deep foundation pit construction method according to claim 5, characterized in that: The width of the first protective layer is one to two meters; one side of the second protective layer contacts the ground or the upper step area, and the other side contacts the lower step area or the solidified area of ​​the bottom layer of the foundation pit.

7. The in-situ muddy soil deep foundation pit construction method according to claim 4, characterized in that: The second protective layer is a solidified soil slope retained at the edge of any step area when the solidified soil in the step area is excavated; the ratio of the vertical height to the horizontal width of the solidified soil slope in the second protective layer is 1:(1-1.5).

8. The in-situ muddy soil deep foundation pit construction method according to claim 4, characterized in that: The third protective layer is a solidified soil retaining wall provided at the lower inner edge of any step area when the solidified soil of the step area is excavated.

9. The in-situ muddy soil deep foundation pit construction method according to claim 8, characterized in that: The height of the third protective layer is one meter to one and a half meters, and the width is one meter to two meters; the outer edge of the third protective layer is in contact with the second protective layer, and the inner edge is the same size as the lower step area on the horizontal plane; a number of anchor rods are arranged in the third protective layer for reinforcement; one end of the anchor rod passes through the third protective layer, and the other end is embedded in the first protective layer of the lower step area.

10. The in-situ muddy soil deep foundation pit construction method according to any one of claims 1 to 9, characterized in that: The design requirements for the curing strength are that the characteristic bearing capacity of the silty soil after curing is not less than 200 kPa, the cohesion is not less than 280 kPa, and the permeability coefficient is not greater than 1×10 -8 cm / s, and the internal friction angle is 25 to 29 degrees.

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