Deep silt stratum elevator shaft foundation pit supporting structure and construction method thereof

Abstract

The application discloses a deep silt stratum elevator shaft foundation pit supporting structure and a construction method thereof, the supporting structure comprises a slope for supporting and a plurality of grid mixing pile walls, the slope is an inclined slope with an inclined angle of the foundation pit side wall, the bottom of the grid mixing pile wall is vertically anchored into a hard soil layer for fixation, the grid mixing pile wall comprises a slope surface grid mixing pile wall arranged in the slope area and a pit bottom grid mixing pile wall arranged at one side of the foundation pit, a reinforcing layer is arranged at the connection position of the slope surface grid mixing pile wall and the pit bottom grid mixing pile wall; the reinforcing layer is a plurality of micro steel pipe piles, each micro steel pipe pile is located at the joint position of the slope surface grid mixing pile wall and the pit bottom grid mixing pile wall, and is mutually engaged with the slope surface grid mixing pile wall on one side and with the pit bottom grid mixing pile wall on the other side, so that the strength of the supporting structure can be ensured, and the engineering cost can be reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of foundation pit excavation support, in particular to a deep silt stratum elevator shaft foundation pit support structure and a construction method thereof. BACKGROUND

[0002] Silt has the characteristics of low shear strength, high sensitivity, high natural water content and high compressibility. When engineering construction is carried out on this soil stratum, improper earth excavation can easily cause lateral flow of silt, resulting in a large external horizontal thrust on the engineering pile, thereby causing horizontal deviation, and even causing necking of the pile body and pile breakage and other engineering accidents. When excavating an elevator shaft foundation pit in a deep silt stratum, a mixing pile gravity retaining wall pile or a steel sheet pile support structure is generally used.

[0003] The mixing pile gravity retaining wall pile is formed by uniformly mixing additives with the original foundation soil, has low construction difficulty, good integrity and low engineering cost, but its strength increases slowly in silt soft soil stratum, and the silt soil causes poor piling effect due to lateral creep of the foundation pit height difference.

[0004] The steel sheet pile has the advantages of slight soil squeezing, rapid support effect, small construction vibration, etc., but its economic cost is high, and after the steel sheet pile is pulled out, a gap is formed in the stratum, which causes the silt soft soil to creep, easily forming a horizontal thrust on the engineering pile, thereby adversely affecting the quality of the engineering pile.

[0005] Therefore, there is a need for an improved method of mixing pile gravity retaining wall pile and steel sheet pile, which is suitable for the excavation and support of a deep silt stratum elevator shaft foundation pit, can ensure the strength of the support structure, and can also control the engineering cost. SUMMARY

[0006] The present application aims to overcome the above-mentioned defects in the prior art, and provides a deep silt stratum elevator shaft foundation pit support structure and a construction method thereof, which can ensure the strength of the support structure and reduce the engineering cost.

[0007] To achieve the above-mentioned purpose, the present application provides a deep silt stratum elevator shaft foundation pit support structure, which comprises a slope for support and a plurality of grid mixing pile walls. The slope is an inclined slope with an inclined angle for the foundation pit side wall. The grid mixing pile wall is fixed by being vertically anchored into the hard soil layer at the bottom. The grid mixing pile wall comprises a slope surface grid mixing pile wall arranged in the slope area and a pit bottom grid mixing pile wall arranged on one side of the foundation pit. A reinforcing layer is arranged at the connection between the slope surface grid mixing pile wall and the pit bottom grid mixing pile wall. The reinforcing layer comprises a plurality of micro steel pipe piles. Each micro steel pipe pile is located at the joint of the slope surface grid mixing pile wall and the pit bottom grid mixing pile wall, and is engaged with the slope surface grid mixing pile wall on one side and with the pit bottom grid mixing pile wall on the other side.

[0008] Preferably, the slope has a slope of 1:1.5.

[0009] Preferably, the slope surface is provided with a concrete layer sprayed by C20 concrete, the thickness of the concrete layer is 80mm, and a steel mesh is laid inside.

[0010] Preferably, the slope surface is provided with a concrete layer sprayed by C20 concrete, the thickness of the concrete layer is 80mm, and a steel mesh is laid inside.

[0011] Preferably, the slope surface is provided with a concrete layer sprayed by C20 concrete, the thickness of the concrete layer is 80mm, and a steel mesh is laid inside.

[0012] Preferably, the slope surface is provided with a concrete layer sprayed by C20 concrete, the thickness of the concrete layer is 80mm, and a steel mesh is laid inside.

[0013] The application also provides a deep silt stratum elevator shaft foundation pit supporting construction method, comprising the following steps:

[0014] Step one: level the site, demarcate the construction area according to the preset position of the supporting structure, including the slope construction area and the pit bottom construction area; determine the preset position of each cement mixing pile and the construction sequence, the adjacent two cement mixing piles are overlapped, and the overlapping length is 200mm, which ensures that the cement mixing piles can be overlapped to form a grid type overall structure;

[0015] Step two: position the pile machine, move the pile machine to align with the pile position, the pile position deviation is not greater than 40mm, the pile machine spindle perpendicularity deviation is not greater than 0.5%, and the cement mixing piles are connected from top to bottom to prevent water seepage caused by overlapping errors;

[0016] Step three: prepare the mud, check whether the mud conveying pipe is unobstructed before construction, and determine the construction parameters of the mud pump;

[0017] Step four: construct the cement mixing pile, the mixing pile machine rotates and drills to the bottom design elevation, and then the prepared cement slurry is pressed into the foundation; the slope grid mixing pile wall is empty above the design slope height, and the pit bottom grid mixing pile wall is empty above the design pit bottom height;

[0018] Step five: construction of micro steel pipe pile, the steel pipe used in the micro steel pipe pile is sunk, so that the position of each micro steel pipe pile is located at the interface of adjacent cement mixing piles, and the cement mixing piles are tightly engaged, and then cement mortar is injected into the micro steel pipe pile under high pressure to form the micro steel pipe pile;

[0019] Step six: after the strength of all the cement mixing piles and the micro steel pipe pile meets the strength requirement, the foundation pit is excavated in layers.

[0020] As preferred, in step six, the foundation pit is excavated, and the slope is graded to the bottom of the elevator shaft pit in layers, and the slope of the slope is 1:1.5.

[0021] Compared with the prior art, the beneficial effects of the present application are that:

[0022] The present application adopts slope excavation, which can effectively weaken the creep of silt soil under the action of earth pressure, ensure that the cement mixing pile grows to the required strength, and at the same time, has good pile forming effect; the slope surface grille mixing pile wall is provided, and the bottom thereof is anchored into the hard soil layer to ensure the position stability of the supporting structure and enhance the horizontal resistance and overall stability of the supporting structure; the bottom grille mixing pile wall is provided to improve the soil quality of the foundation pit for subsequent construction; the micro steel pipe pile is used to reinforce and connect between the slope surface grille mixing pile wall and the bottom grille mixing pile wall, which not only ensures the pile forming quality of the cement mixing pile, but also improves the strength and overall stability of the supporting structure; in addition, the micro steel pipe pile is used to replace the commonly used steel sheet pile, the amount of steel material is greatly reduced, the engineering cost is reduced, and after the construction stage is completed, the steel pipe pile does not need to be pulled out, so that there is no gap in the bottom soil to cause the creep of silt soft soil. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0024] Figure 1 It is a plane structure schematic diagram of a deep silt stratum elevator shaft foundation pit supporting structure provided by the present application;

[0025] Figure 2 It is a cross-sectional structure schematic diagram of a deep silt stratum elevator shaft foundation pit supporting structure provided by the present application.

[0026] In the drawings, there are:

[0027] 11, slope surface grille mixing pile wall; 13, bottom grille mixing pile wall; 12, micro steel pipe pile; 22, concrete layer; 21, steel mesh. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be clearly and completely described in combination with the drawings of the embodiments of the present application. Obviously, the described embodiments are one of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0029] Embodiment one

[0030] Please refer to Figure 1 and Figure 2 , the embodiment one of the present application provides a deep silt stratum elevator shaft foundation pit supporting structure.

[0031] Firstly, the application of the foundation pit and the elevator shaft is introduced. The foundation pit applied in the present application is divided into 16 sections, the total perimeter of the foundation pit is about 466m, the bottom area of the foundation pit is about 12851㎡, and the excavation depth of the foundation pit is about 9.05-11.90m. Among them, the original ground elevation on site is 3.6m (absolute elevation), and the bottom elevation of the raft cushion is-5.45m; the elevator shaft foundation pit has four, the bottom elevation of the foundation pit is-8.3m, the excavation depth of the elevator foundation pit from the bottom of the raft cushion is 2.85m, and the safety level of the foundation pit is first grade. The bottom area of the foundation pit is 12851㎡, and the earthwork excavation amount is about 117000m 3 . As can be seen, the depth of the elevator shaft foundation pit applied in the present application is deep, and it belongs to silt stratum, and the safety level of the foundation pit of the elevator shaft is high, which proves from the side that the overall strength of the supporting structure of the present application is high, the supporting effect is good, and it can be applied to deep silt stratum.

[0032] The foundation pit supporting structure will be described in detail in combination with the drawings, as shown in Figure 1 and Figure 2 , the foundation pit supporting structure comprises a batter for supporting and a plurality of grid mixing pile walls, the batter is an inclined slope with an inclined angle of the foundation pit side wall. In actual operation, the excavator adopts batter excavation, which can effectively reduce the lateral displacement of silt under the action of soil pressure, ensure that the cement mixing pile grows to the required strength, and at the same time, it has good piling effect. In the embodiment, the slope of the batter is 1:1.5; the slope of the batter can also be selected according to the specific situation of the construction site and silt, so as to reduce the lateral displacement of silt, facilitate construction, and shorten the construction period.

[0033] Further, the grid mixing pile wall bottom is vertically anchored into the hard soil layer for fixation, enhancing the horizontal resistance and overall stability of the supporting structure; specifically, the grid mixing pile wall comprises a slope surface grid mixing pile wall 11 arranged in the sloping area and a pit bottom grid mixing pile wall 13 arranged at one side of the foundation pit, a reinforcing layer is arranged at the connection of the slope surface grid mixing pile wall 11 and the pit bottom grid mixing pile wall 13; the reinforcing layer comprises a plurality of micro steel pipe piles 12, each micro steel pipe pile 12 is located at the joint of the slope surface grid mixing pile wall 11 and the pit bottom grid mixing pile wall 13, and is mutually engaged with the slope surface grid mixing pile wall 11 on one side and with the pit bottom grid mixing pile wall 13 on the other side; the micro steel pipe pile 12 not only strengthens the strength of the supporting structure, but also fills the gap at the joint of the slope surface grid mixing pile wall 11 and the pit bottom grid mixing pile wall 13, thereby improving the integrity of the support.

[0034] The present application adopts the supporting mode of the slope and the grid mixing pile wall, and further uses the micro steel pipe pile 12 for reinforcement, thereby improving the overall integrity and strength of the supporting structure, reducing the engineering cost, being safe and economical, and being convenient for application and promotion; the micro steel pipe pile 12 is used to replace the conventional steel sheet pile, thereby reducing the economic cost and avoiding the gap for the creep of the silt soft soil.

[0035] As shown in Figure 2 The slope surface is provided with an inclined concrete layer 22, the concrete layer 22 is sprayed by C20 concrete, the thickness of the concrete layer 22 is 80mm, and a steel mesh 21 is arranged inside the concrete layer 22; the steel mesh 21 can increase the strength and supporting capacity of the concrete layer 22.

[0036] As shown in Figure 1 The slope surface grid mixing pile wall 11 and the pit bottom grid mixing pile wall 13 are both grid-shaped structures formed by a plurality of cement mixing piles mutually connected, the diameter of the cement mixing pile is 700mm, the core spacing of adjacent two cement mixing piles is 500mm, and the adjacent two cement mixing piles are mutually engaged, so that all the cement mixing piles form a wall body, the wall bodies are mutually connected to form a supporting whole, and the supporting structure has higher strength; the grid-type cement mixing pile is a gravity-type retaining wall supporting structure, which can well solve the problem of insufficient bearing capacity of deep silt stratum, is convenient for early construction site arrangement and later foundation pit excavation construction, and can avoid the problems of environmental pollution, soil settlement and cracking around the building, etc.

[0037] Further, the slope surface grid mixing pile wall 11 is embedded into the hard soil layer with a depth greater than 4m, and the pile top is flush with the slope surface; the pit bottom grid mixing pile wall 13 is embedded into the hard soil layer with a depth greater than 4m, and the pile top is flush with the bottom surface of the foundation pit.

[0038] As shown in Figure 1As shown, the micro steel pipe pile 12 has a diameter of 200 mm, and the pile core spacing of two adjacent micro steel pipe piles 12 is 500 mm, each micro steel pipe pile 12 is located at the connection of two adjacent cement mixing piles, and is engaged with the cement mixing piles; ensure the quality of the cement mixing pile, and improve the overall stability and strength of the supporting structure.

[0039] The supporting method of the present application solves the common problems in the existing deep silt stratum elevator shaft foundation pit support, ensures safety while reducing cost, and is convenient for application and promotion.

[0040] Example two

[0041] Please refer to Figure 1 and Figure 2 On the basis of example one, the deep silt stratum elevator shaft foundation pit support construction method provided by example two of the present application comprises the following steps:

[0042] Step one: level the site, demarcate the construction area according to the preset position of the supporting structure, including the slope construction area and the pit bottom construction area; determine the preset position of each cement mixing pile and the construction sequence, the two adjacent cement mixing piles are overlapped with each other, and the overlapping length is 200 mm, to ensure that the cement mixing piles can be engaged with each other to form a grid type overall structure;

[0043] Step two: position the pile machine, move the pile machine to align with the pile position, the pile position deviation is not greater than 40 mm, the pile machine main shaft perpendicularity deviation is not greater than 0.5%, and the cement mixing piles are connected from top to bottom to prevent water seepage caused by overlapping errors;

[0044] Step three: prepare the mud, check whether the mud conveying pipe is unobstructed before construction, and determine the mud conveying amount of the slurry pump, the sinking speed of the equipment, and other construction parameters.

[0045] Step four: construct the cement mixing pile, the mixing pile machine rotates and drills to the bottom of the pile, and then the prepared cement slurry is pressed into the foundation; the slope grid mixing pile wall 11 is empty above the design slope height, and the pit bottom grid mixing pile wall 13 is empty above the design foundation pit bottom height;

[0046] Step five: construct the micro steel pipe pile 12, sink the steel pipe used for the micro steel pipe pile 12, so that the position of each micro steel pipe pile 12 is located at the interface of the adjacent cement mixing piles, and is tightly engaged with the cement mixing piles, and then high-pressure cement mortar is poured into the micro steel pipe pile 12 to form the micro steel pipe pile 12;

[0047] Step six: after the strength of all the cement mixing piles and the micro steel pipe pile 12 meets the strength requirement, excavate the foundation pit in layers.

[0048] Further, in the step six, the foundation pit is excavated, and is layered and segmented to be sloped to the bottom of the elevator shaft pit, and the slope of the sloping is 1:1.5.

[0049] The various technical features in the above embodiments can be combined in any manner, as long as the combination of the features does not conflict or contradict.

[0050] The above embodiments are the preferred embodiments of the present application, but the embodiments of the present application are not limited to the above embodiments, and any changes, modifications, substitutions, combinations, simplifications, etc. made without departing from the spirit and principle of the present application shall be equivalent replacement manners and shall be included in the protection scope of the present application.

Claims

1. A deep silt ground stratum elevator shaft foundation pit support structure, characterized by: The supporting structure comprises a slope and a plurality of grid mixing pile walls, the slope is an inclined slope with an inclined angle of the pit wall, the bottom of the grid mixing pile wall is vertically anchored into the hard soil layer for fixation, the grid mixing pile wall comprises a slope surface grid mixing pile wall (11) arranged in the slope area and a pit bottom grid mixing pile wall (13) arranged at one side of the pit, a reinforcing layer is arranged at the connection of the slope surface grid mixing pile wall (11) and the pit bottom grid mixing pile wall (13); the reinforcing layer comprises a plurality of micro steel pipe piles (12), each micro steel pipe pile (12) is arranged at the joint of the slope surface grid mixing pile wall (11) and the pit bottom grid mixing pile wall (13), and is engaged with the slope surface grid mixing pile wall (11) on one side and the pit bottom grid mixing pile wall (13) on the other side; The slope is 1:1.5; The slope surface grid mixing pile wall (11) and the pit bottom grid mixing pile wall (13) are both grid structures formed by a plurality of cement mixing piles which are engaged with each other, and adjacent two cement mixing piles are engaged with each other, so that all the cement mixing piles form a wall body; Each micro steel pipe pile (12) is arranged at the joint of two adjacent cement mixing piles and is engaged with the cement mixing piles; The micro steel pipe pile (12) fills the gap at the joint of the slope surface grid mixing pile wall (11) and the pit bottom grid mixing pile wall (13) and improves the integrity of the supporting structure; The diameter of the cement mixing pile is 700 mm, the pile core spacing of adjacent two cement mixing piles is 500 mm, the diameter of the micro steel pipe pile (12) is 200 mm, and the pile core spacing of adjacent two micro steel pipe piles (12) is 500 mm; The bottom of the slope surface grid mixing pile wall (11) is embedded into the hard soil layer with a depth greater than 4 m, and the top is flush with the surface of the slope; the bottom of the pit bottom grid mixing pile wall (13) is embedded into the hard soil layer with a depth greater than 4 m, and the top is flush with the bottom surface of the pit.

2. The deep silt stratum elevator shaft foundation pit support structure according to claim 1, characterized in that: A concrete layer (22) formed by spraying C20 concrete is arranged on the surface of the slope, and the thickness of the concrete layer (22) is 80 mm, and a steel mesh (21) is arranged inside.

3. A construction method of a deep silt stratum elevator shaft foundation pit support, characterized by: The deep thick silt stratum elevator shaft pit supporting structure comprises the deep thick silt stratum elevator shaft pit supporting structure according to any one of claims 1 to 2. Further comprising the following steps: Step one: flatten the site, demarcate the construction area according to the preset position of the supporting structure, including the slope construction area and the pit bottom construction area; determine the preset position of each cement mixing pile and the construction sequence, and adjacent two cement mixing piles are engaged with each other with an overlapping length of 200 mm, so that the cement mixing piles can be engaged with each other to form a grid type overall structure; Step two: position the pile machine, move the pile machine to align with the pile position, the pile position deviation is not greater than 40 mm, the verticality deviation of the pile machine main shaft is not greater than 0.5%, and the cement mixing piles are connected into a whole from top to bottom to prevent water seepage caused by overlapping errors; Step three: prepare the mud, check whether the mud conveying pipe is unobstructed before construction, and determine the construction parameters of the mud pump; Step four: construction of cement mixing pile, the mixing pile machine rotates down the drill, when drilling to the design elevation of the pile bottom, the prepared cement slurry is pressed into the foundation; the slope grid mixing pile wall (11) is empty pile above the design slope height, the pit bottom grid mixing pile wall (13) is empty pile above the design pit bottom height; Step five: construction of micro steel pipe pile (12), the micro steel pipe pile (12) is used for sinking, so that the position of each micro steel pipe pile (12) is located at the interface of adjacent cement mixing piles, and is tightly engaged with the cement mixing piles, and then high-pressure cement mortar is poured into the micro steel pipe pile (12) to form the micro steel pipe pile (12); Step six: after the strength of all cement mixing piles and micro steel pipe piles (12) meets the strength requirement, the foundation pit is excavated in layers; In the step six, the foundation pit is excavated, and the slope is put to the bottom of the elevator shaft pit in layers and sections, and the slope of the slope is 1:1.5.

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