CN216515616U - Deep foundation pit waterproof combined structure suitable for three-side riverside shallow bedrock stratum containing quicksand - Google Patents

Abstract

The utility model discloses a deep foundation pit waterproof combined structure suitable for a three-side river-facing shallow bedrock stratum containing quicksand, which comprises a foundation pit waterproof combined structure arranged outside an excavation surface of a foundation pit, a foundation pit slope-setting excavation slope surface supporting structure and a slope top cement soil deep-layer stirring pile curtain, wherein a slope top intercepting ditch is arranged outside the slope top cement soil deep-layer stirring pile curtain; the foundation pit water-stop composite structure comprises a slope bottom cement soil deep stirring pile curtain, a high-pressure jet grouting pile and a drilling cast-in-place pile. The utility model provides a waterproof structure of a combined water interception curtain of a secondary slope-making depth reduction, a double-layer cement soil deep mixing pile water interception curtain and a high-pressure jet grouting pile occlusion bored concrete pile; the waterproof combined structure is safe and economical.

Description

Deep foundation pit waterproof combined structure suitable for three-side riverside shallow bedrock stratum containing quicksand

Technical Field

The utility model relates to the technical field of near water-based pit engineering, in particular to a deep foundation pit waterproof combined structure suitable for a shallow bedrock stratum containing quicksand on three sides.

Background

The underground water prevention and control is a key technical problem of river-facing deep foundation pit engineering, and whether underground water control measures are reasonable or not is closely related to multiple aspects of safety, economy, environmental effect and the like of engineering projects.

With the continuous expansion of the construction scale of municipal infrastructure in cities in China, in recent years, foundation pit engineering projects of river rich water shallow bedrock deep quicksand-containing stratum are continuously emerged, for example, in deep foundation pit engineering with numerous dual stratum of water source and soil rock in the stage I of Yangtze river in the plain of Wuhan, the depth of excavation of deep foundation pits in the Chongqing overseas plaza is 27-34 m, the depth of bedrock burial is 2-14 m, the distance from the south to the edge of the Jiangling is only 40m, and the like.

However, during the actual foundation pit engineering design, sections with geological characteristics such as three faces, shallow bedrock, quicksand-containing stratum and the like are occasionally encountered, the three faces of the sections face the river, the difference of the physical mechanics and the water physical characteristics of the water-rich environment of the upper and lower soil rock stratum is obvious, and the unified knowledge and standard on how to prevent and control the underground water is not known in the industry.

Meanwhile, the construction difficulty brought by fresh characteristics such as large excavation span and depth, complex procedure linking difficulty, large supporting engineering quantity, large cross operation influence and the like is solved for the section, and the construction difficulty brought by high underground water level and abundant reserves of three adjacent rivers, shallow bedrock buried depth and near-surface quicksand-containing stratum, high construction period requirement of a flood period of a river channel in a flood period and the like is also solved for urgent needs.

SUMMERY OF THE UTILITY MODEL

The utility model aims to provide a deep foundation pit waterproof combined structure suitable for a three-face river-facing shallow bedrock stratum containing quicksand, so as to solve the problems in the background technology.

In order to achieve the purpose, the utility model provides the following technical scheme:

the deep foundation pit waterproof combined structure is suitable for a three-side river-facing shallow bedrock stratum containing quicksand and comprises a foundation pit excavation surface arranged at the innermost layer, a foundation pit water-stop combined structure arranged outside the foundation pit excavation surface, a slope top cement soil deep mixing pile curtain arranged at the outermost layer and a foundation pit slope-setting excavation slope supporting structure arranged between the foundation pit water-stop combined structure and the slope top cement soil deep mixing pile curtain, wherein the distance between the slope top cement soil deep mixing pile curtain and a river channel is not less than 1m, a slope top intercepting ditch is arranged at the position close to the periphery of the slope top cement soil deep mixing pile curtain, surrounds the slope top cement soil deep mixing pile curtain and is used for removing ground water, the slope top soil deep mixing pile curtain is a pile-shaped reinforcing body formed by uniformly mixing soil, water and cement in the stratum together through a triaxial cement soil mixer, and the bottom end of the slope top cement soil deep mixing pile curtain penetrates through the upper stratum containing quicksand and extends to the lower rock stratum, drilling 2-3m into the rock stratum from the bottom end of the slope top cement soil deep layer stirring pile curtain, and forming a first water-blocking defense line by the slope top cement soil deep layer stirring pile curtain;

the foundation pit slope-putting excavation slope surface supporting structure comprises a first-order slope surface, a middle step, a second-order slope surface and a slope bottom step, wherein the first-order slope surface is formed by two levels of slope-putting, the slope top of the first-order slope surface and the top of a curtain of a cement soil deep mixing pile at the slope top are collinear, the surfaces of the first-order slope surface, the middle step and the second-order slope surface are provided with reinforcing mesh sheets, the reinforcing mesh sheets of the first-order slope surface, the middle step and the second-order slope surface are hung through inserted bars, a plurality of inserted bars on each plane are uniformly distributed in a quincunx shape, a layer of concrete covers the outside of each reinforcing mesh sheet, and the reinforcing mesh sheets and the outer ends of the inserted bars are covered by the layer of concrete;

the middle part of the slope bottom step is provided with a slope bottom intercepting ditch which surrounds the foundation pit water stop composite structure and is used for preventing water of a foundation pit slope putting excavation slope surface supporting structure from entering a foundation pit excavation surface;

the foundation pit water-stop combined structure sequentially comprises a slope bottom cement soil deep mixing pile curtain, a high-pressure jet grouting pile and a drilling filling pile from outside to inside, wherein the slope bottom cement soil deep mixing pile curtain is a pile-shaped reinforcing body formed by uniformly mixing soil, water and cement in a stratum by a triaxial cement soil mixer, the bottom end of the slope bottom cement soil deep mixing pile curtain is drilled into a rock stratum for 2-3m, and the slope bottom cement soil deep mixing pile curtain forms a second water-stop defense line;

the high-pressure jet grouting pile is a cylindrical reinforcing body formed by drilling a hole through a high-pressure jet grouting drill bit, the bottom end of the high-pressure jet grouting pile is drilled into a rock stratum for 2-3m, the cast-in-situ bored pile is a cylindrical reinforcing body formed by filling concrete into a reinforcement cage, and the depth of the bottom end of the cast-in-situ bored into the rock stratum is not less than 5 m;

a gap is reserved between adjacent high-pressure jet grouting piles, a gap is reserved between adjacent cast-in-situ bored piles, any high-pressure jet grouting pile is mutually meshed with two cast-in-situ bored piles, and the two circles of cylindrical reinforcing bodies are mutually meshed to form a sealed waterproof curtain to form a third waterproof defensive line;

the foundation pit excavation surface is excavated along the inner wall of the cast-in-situ bored pile, the bottom wall of the foundation pit excavation surface is sealed by cement concrete, and the height of the bottom wall of the foundation pit excavation surface is smaller than the height of the bottom end of the high-pressure jet grouting pile and larger than the height of the bottom end of the cast-in-situ bored pile, so that the foundation pit excavation surface extends to a foundation stratum all the time, and the enclosure strength of the foundation pit excavation surface is ensured;

and the excavation surface of the foundation pit is also provided with a supporting truss structure consisting of a horizontal inner support and a vertical inner support.

The top beam is poured at the inner side wall position of the top of the cast-in-situ bored pile, the waist beam is poured at the inner side wall position of the middle of the cast-in-situ bored pile, the horizontal inner support comprises two groups of parallel horizontal frames, the edge of the upper horizontal frame is inserted into the top beam through a steel bar, the edge of the lower horizontal frame is inserted into the waist beam through a steel bar, and the height of the bottom surface of the waist beam is 0.5-1m greater than that of the soil-rock interface. During construction, support in the level and support in the vertical, the welding and make two sets of levels support and correspond crown beam and waist rail respectively, support edge ligature reinforcing bar as the bar planting and insert in the gap between two drilling bored concrete piles in the level, support a round template to drilling bored concrete pile top and middle part again, including the bar planting pouring with cement, form the cross-section for the round crown beam and the round waist rail of rectangle, form two sections permanent concreting structures, reinforcing bearing structure's steadiness, reduce the quantity of support in the level.

Preferably, the concrete on the surface layers of the first-step slope, the middle step and the second-step slope is sprayed by a cement high-pressure gun, a layer of concrete is sprayed on the surfaces of the slope bottom step and the slope bottom intercepting ditch to prevent surface water from permeating, and the slope bottom step can be provided with no net hanging structure formed by a steel bar net sheet and inserted bars, so that the actual waterproof requirement is met.

Preferably, the high-pressure jet grouting pile is a pure cement cylindrical pile body, and a common jet grouting pile machine does not have the condition of drilling a rock stratum, so that a down-the-hole drilling geological drilling machine is adopted for hole guiding, when the pile bottom elevation is drilled, the jet grouting pile machine is replaced, and the insertion pipe lifting and jet grouting construction are carried out at the hole guiding position. And the contact part of the upper covering soil layer and the lower horizontal rock layer increases the cutting area and the grouting amount by increasing the grouting pressure and slowing down the lifting speed of the drill rod so as to ensure the pile forming quality.

Preferably, a gap is reserved between the high-pressure jet grouting pile and the slope bottom cement soil deep mixing pile curtain, so that construction from inside to outside is facilitated, a cast-in-situ bored pile is constructed in advance, the high-pressure jet grouting pile is constructed, and finally the slope bottom cement soil deep mixing pile curtain is constructed.

Preferably, the diameter of the reinforcement cage in the cast-in-situ bored pile is 30-40cm smaller than the outer diameter of the cast-in-situ bored pile, and the high-pressure jet grouting pile does not contact the reinforcement cage in the cast-in-situ bored pile. The cement cover with the thickness of 15-20cm is arranged outside the reinforcement cage, so that the bored pile can be conveniently drilled along the cement cover outside the reinforcement cage of the bored pile after forming a surrounding pile, the cement sprayed out in a rotary mode after drilling can be conveniently directly hung on the cement cover of the drilled bored pile, an integrated cement curtain structure is formed after occlusion, and the waterproof performance is improved.

In order to adapt to geological conditions of the upper soil and the lower rock, the cast-in-situ bored pile is constructed by sequentially adopting the following steps: and (3) after drilling on a flowing sand layer and a soil-rock boundary layer, drilling into the rock by directly adopting a mud retaining wall pore-forming mode on a bed rock layer, finally, lowering a reinforcement cage, pouring concrete, and after the concrete reaches initial setting strength, pulling out the steel retaining cylinder by adopting a rotary drilling rig through a steel wire rope reserved on the retaining cylinder to obtain the finished cast-in-situ bored pile.

Preferably, the vertical inner support and the horizontal inner support are welded to form an integrated supporting structure after being bound by iron wires, the peripheral edge of the horizontal inner support is respectively embedded with steel bars and is inserted into the side wall of the bored pile, and the bottom end of the vertical inner support is embedded into the bottom wall back cover of the excavation surface of the foundation pit.

Preferably, precipitation wells are further arranged in the excavation face of the foundation pit at equal intervals and used for excavation construction after water drainage in the foundation pit, drainage pipelines are arranged above the precipitation wells, the slope bottom intercepting ditches and the slope top intercepting ditches, and water inside and outside the foundation pit is discharged into a river channel through a water pump.

Compared with the prior art, the utility model has the beneficial effects that:

aiming at the special geological characteristics of deep foundation pit engineering of three-sided river-facing shallow bedrock stratum containing quicksand, the utility model provides a groundwater waterproof structure of a combined water interception curtain of a second-stage slope-making depth reduction, a double-layer cement soil deep mixing pile water interception curtain and a high-pressure jet grouting pile occlusion drilling cast-in-place pile. This waterproof construction is comparatively simple and convenient, but the process is alternately, and the support piece quantity and the construction volume that adopt reduce by a wide margin compared prior art, and the structure that forms comparatively stabilizes, the security is higher, and the whole obvious percolating water condition that does not have of foundation ditch lateral wall takes place, and whole economic nature and practicality are higher.

Drawings

FIG. 1 is a plan view of a building on a foundation pit required by the present invention;

FIG. 2 is a schematic diagram of specific parameters of the excavation structure inside the foundation pit required by the present invention;

FIG. 3 is a schematic view of the overall structure of the deep foundation pit waterproof composite structure suitable for three facing river shallow bedrock stratum containing quicksand provided by the utility model;

FIG. 4 is a partial schematic view of a secondary grade slope-releasing excavation surface in a deep foundation pit waterproof combined structure suitable for three faces of a river shallow bedrock stratum containing quicksand;

FIG. 5 is a top view of the foundation pit water stop composite structure in the deep foundation pit water stop composite structure suitable for three facing river shallow bedrock stratum containing quicksand according to the present invention;

in the figure: the foundation pit excavation face 1, the foundation pit water stop composite structure 2, the slope bottom cement soil deep mixing pile curtain 201, the high-pressure jet grouting pile 202, the drilling cast-in-place pile 203, the slope top cement soil deep mixing pile curtain 3, the foundation pit slope excavation slope supporting structure 4, the first-order slope 401, the middle step 402, the second-order slope 403, the slope bottom step 404, the river channel 5, the slope top intercepting ditch 6, the inserted ribs 7, the slope bottom intercepting ditch 8, the horizontal inner support 9, the vertical inner support 10, the crown beam 11 and the waist beam 12.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments, and all other embodiments obtained by a person of ordinary skill in the art without creative efforts based on the embodiments of the present invention belong to the protection scope of the present invention.

Firstly, referring to actual construction and construction requirements: the project site of the deep foundation pit engineering of the clear three-flushing rainwater storage tank is located in east of a submarine mountain road, west of a Sichuan mountain area, south of a Sili river road, and 28125of a river, and north of the river along the river road. The project site belongs to a wave plain of Jianghuai, has a micro landform of Nan\ 28125and a first-level stage of river, and has small relief. The original land belongs to the green land of the riverside park, and no important buildings (structures) are arranged around the land.

The foundation pit site is formed by encircling three sides of a river through south hole 2812525%, the water depth of the river is about 0.8-2.5 m, and the thickness of a silt layer in the river is about 2.0-2.5 m. The distance from the north side of the foundation pit to the south is 2812545-80 m, the distance from the east side to the river bank is 12-25 m, the distance from the west side to the river bank is 15-21 m, and the distance from the south side to the south of the river is 1.5-7.0 m.

The three-flushing regulation and storage tank deep foundation pit consists of a regulation and storage tank main body rectangular foundation pit, an emptying pump house foundation pit and a management house foundation pit 3, and the whole plane form is in a special shape, wherein the excavation depth of the main body structure foundation pit is 8.4-19.7 m, and the excavation depth of the emptying pump house foundation pit is 19.7-21.2 m; the excavation depth of the foundation pit plane for management is 8.6 m. The deep foundation pit plane composition and related dimensions are shown in fig. 1.

Secondly, analyzing the geological characteristics of the deep foundation pit engineering:

the deep foundation pit engineering of the combined fertilizer cleaning three-flushing regulation and storage tank has the characteristics of common deep foundation pits, such as large excavation span and depth, complex working procedure, large joining difficulty, large supporting engineering quantity, large cross operation influence and the like, and also has three sides

The river-facing underground water level is high, the reserves are rich, the bedrock burial depth is shallow, the near-surface stratum contains quicksand, the construction period of the river channel flood season submerged area is required to be high, and the like.

1) The underground water reserves are abundant three sides face the river deep basal pit groundwater and the river water UNICOM, and groundwater is supplied by the river water, has very stable groundwater source to the river water can supply groundwater constantly, and the groundwater reserves are extremely abundant, bring very big risk for the foundation ditch safety. The hydraulic connection between the underground water and river water is cut off, the underground water is prevented from permeating into the foundation pit, and the relative dryness in the pit is ensured, so that the underground water-retaining foundation pit has a good construction operation environment and is the important factor for preventing and controlling the underground water of the deep foundation pit.

2) The excavation scale of the deep foundation pit of the shallow bedrock stratum containing the flowing sand of the large three-faced river with the large quantities of foundation pit supporting measures is large, the excavation depth is large, and a strong peripheral enclosing structure and a plurality of inner support systems are often needed to be adopted in the excavation process of the foundation pit to ensure the safety of the foundation pit. A reasonable underground water prevention and control scheme for the deep foundation pit is to closely combine foundation pit supporting measures for comprehensive consideration, and reduce the supporting measures as much as possible on the premise of ensuring the safety of the foundation pit and underground water control so as to save the construction cost of engineering projects, accelerate the construction progress and improve the comprehensive benefits.

3) The construction period is tight, the procedure connection difficulty is large, and the construction site is closely adjacent to south 28125and river in the west, north and east. The river water level changes greatly along with seasons, and the river water level is higher in summer; in winter, the river water level is lower, the amplitude of flood and dry water level is 4-6 meters, and the rise and fall time is about 48 hours. In the river flood season, the position of a foundation pit is in a submergence period in 6 months every year, the construction period is short, and the connection difficulty between working procedures is large.

4) The principle of underground water prevention and control measures is as follows: the deep foundation pit of the three-face near-river shallow bedrock stratum containing quicksand has the remarkable characteristics of abundant underground water reserves, large construction difficulty of engineering facilities around the foundation pit and large quantity of foundation pit supporting measures. The underground water prevention and control needs to form a continuous closed curtain system which is tightly combined with the bedrock at the bottom from top to bottom around the foundation pit so as to cut off the hydraulic connection between the underground water of the foundation pit and the river; and when the conditions permit, a half-slope excavation scheme is preferably adopted so as to reduce the number of supporting measures and the construction implementation difficulty.

Scheme design: the excavation length of a deep foundation pit of a clear three-flushing regulating storage tank is 88-100 m, the width is 58-70 m, the depth is 18.4-21.2 m, 3-4 horizontal inner supports and a plurality of vertical supports are required to be arranged for straight slope excavation; if proper semi-slope excavation is carried out, the number of horizontal supports can be greatly reduced, and the lengths of vertical supports, building envelopes and the like and the corresponding construction implementation difficulty can be reduced. Therefore, the periphery of the deep foundation pit of the clear three-stroke storage tank is subjected to slope excavation at 7.0m below the ground, 4 horizontal inner supports are reduced to 2 horizontal inner supports, and the length of the vertical supports, the length of the building enclosure and the like are correspondingly reduced by 7 m.

The excavation scheme of the foundation pit semi-slope setting is as follows: 1 slope ratio design, two-stage excavation platforms are arranged, the excavation height of each stage platform is 3.5m, C20 plain concrete with the thickness of 800mm is sprayed on the slope surface, phi 8 @ 200 x 200 steel ribs are arranged in the platform, phi 12 @ 1500 x 1500 steel ribs with the length of 2.0m are implanted on the vertical slope surface in a quincunx mode, phi 50PVC water filter pipes are arranged at the slope positions, drainage ditches and water collection wells are arranged on the outer sides of the slope tops of the slopes, and surface water outside the pits is prevented from flowing into the foundation pits, as shown in figure 2.

Thirdly, concrete construction process:

the final waterproof structure obtained by the comprehensive prevention and control measure scheme of the deep foundation pit engineering groundwater of the clear three-flushing regulation and storage tank is shown in figure 3;

according to the characteristics of high underground water level and large reserve of the deep foundation pit of the clear three-stroke storage tank, large soil discharge amount of foundation pit excavation, high risk of precipitation excavation in the foundation pit and the like. Before the foundation pit slope excavation operation is implemented, firstly, a floor type waterproof curtain of a cement soil deep layer pile with the periphery closed and the pile bottom embedded with a weathered rock stratum of 2.0-3.0 m is applied to the position, close to the slope, of the top of the slope, and is used as a ground water prevention and control water stop measure during the foundation pit slope excavation period, and meanwhile, the floor type waterproof curtain is used as a main water stop measure in the direction of a soil-out slope roadway during the earth transportation during the whole foundation pit excavation period and is a first defense line for controlling the ground water of the deep foundation pit of the storage regulation pool.

After the foundation pit slope-laying excavation operation is completed, a bored pile, a high-pressure jet grouting pile and a cement deep mixing pile are sequentially constructed at the slope bottom close to the side wall of the foundation pit from inside to outside, and flow process is performed to accelerate the engineering implementation progress, as shown in fig. 4.

The floor type waterproof curtain of the cement soil deep mixing pile is formed by embedding a weathered rock stratum of 2.0-3.0 m into the pile bottom of the cement soil deep mixing pile at the bottom of the slope along the outer side of the foundation pit, and is a second defense line for underground water prevention and control in foundation pit excavation; the cast-in-situ bored pile is simultaneously used as a foundation pit enclosure structure, and the section size and the rock-socketed depth of the cast-in-situ bored pile are calculated and determined according to the design of the foundation pit enclosure pile; the high-pressure jet grouting pile is arranged on the outer side of the cast-in-situ bored pile, the pile bottom is embedded into the middle weathered rock stratum of 2.0-3.0 m, the high-pressure jet grouting pile is meshed with the cast-in-situ bored pile to form a waterproof curtain, and the waterproof curtain is a third defense line for preventing and controlling underground water during foundation pit excavation, and is shown in figure 5.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the utility model, the scope of which is defined in the appended claims and their equivalents.

Claims (7)

1. The deep foundation pit waterproof combined structure suitable for a three-side river-facing shallow bedrock quicksand-containing stratum comprises a foundation pit excavation surface (1) arranged at the innermost layer, a foundation pit water-stop combined structure (2) arranged outside the foundation pit excavation surface (1), a slope top cement soil deep mixing pile curtain (3) arranged at the outermost layer and a foundation pit slope-slope excavation supporting structure (4) arranged between the foundation pit water-stop combined structure (2) and the slope top cement soil deep mixing pile curtain (3), and is characterized in that the slope top cement soil deep mixing pile curtain (3) is not less than 1m away from a river channel (5), a slope top intercepting ditch (6) is arranged near the periphery of the slope top cement soil deep mixing pile curtain (3), the slope top intercepting ditch (6) surrounds the slope top cement soil deep mixing pile curtain (3) and is used for removing ground water, and the slope top cement soil deep mixing pile curtain (3) is a triaxial cement soil mixer is used for mixing soil and water in the stratum The bottom end of the slope top cement soil deep mixing pile curtain (3) penetrates through a flowing sand-containing soil layer at the upper part and extends to a rock stratum at the lower part, the bottom end of the slope top cement soil deep mixing pile curtain (3) is drilled into the rock stratum for 2-3m, and the slope top cement soil deep mixing pile curtain (3) forms a first water-blocking defense line;

the foundation pit slope-setting excavation slope surface supporting structure (4) comprises a first-step slope surface (401), a middle step (402), a second-step slope surface (403) and a slope bottom step (404), wherein the first-step slope surface (401) is formed by slope setting of an upper step and a lower step, the top of the first-step slope surface (401) is collinear with the top of a cement soil deep mixing pile curtain (3), reinforcing mesh sheets are arranged on the surfaces of the first-step slope surface (401), the middle step (402) and the second-step slope surface (403), the reinforcing mesh sheets of the first-step slope surface (401), the middle step (402) and the second-step slope surface (403) are suspended through inserted bars (7), a plurality of inserted bars (7) on each plane are uniformly distributed in a quincunx shape, a layer of concrete covers the outside the reinforcing mesh sheets, and the outer ends of the reinforcing mesh sheets and the inserted bars (7) are covered by the layer of concrete;

the middle part of the slope bottom step (404) is provided with a slope bottom intercepting ditch (8), the slope bottom intercepting ditch (8) surrounds the exterior of the foundation pit water-stopping combined structure (2), and the slope bottom intercepting ditch (8) is used for preventing water of the foundation pit slope-setting excavation slope supporting structure (4) from entering the foundation pit excavation surface (1);

the foundation pit water-stop combined structure (2) sequentially comprises a slope bottom cement soil deep mixing pile curtain (201), a high-pressure jet grouting pile (202) and a drilling filling pile (203) from outside to inside, the slope bottom cement soil deep mixing pile curtain (201) is a pile-shaped reinforcing body formed by uniformly mixing soil, water and cement in a stratum together through a triaxial cement soil mixer, the bottom end of the slope bottom cement soil deep mixing pile curtain (201) is drilled into the stratum for 2-3m, and the slope bottom cement soil deep mixing pile curtain (201) forms a second water-stop defense line;

the high-pressure jet grouting pile (202) is a cylindrical reinforcing body formed by drilling through a high-pressure jet grouting drill bit, the bottom end of the high-pressure jet grouting pile (202) is drilled into a rock stratum for 2-3m, the cast-in-situ bored pile (203) is a cylindrical reinforcing body formed by filling concrete into a reinforcement cage, and the depth of the bottom end drilled into the rock stratum is determined according to the stability check calculation of the deep foundation pit and is not less than 3 times of the pile diameter;

a gap is reserved between every two adjacent high-pressure jet grouting piles (202), a gap is reserved between every two adjacent cast-in-situ bored piles (203), any one high-pressure jet grouting pile (202) is meshed with the two cast-in-situ bored piles (203), and the two circles of cylindrical reinforcing bodies are meshed with each other to form a sealed waterproof curtain to form a third waterproof defensive line;

the foundation pit excavation face (1) is excavated along the inner wall of the cast-in-situ bored pile (203), the bottom wall of the foundation pit excavation face (1) is sealed by cement concrete, and the height of the bottom wall of the foundation pit excavation face (1) is smaller than the height of the bottom end of the high-pressure jet grouting pile (202) and larger than the height of the bottom end of the cast-in-situ bored pile (203), so that the foundation pit excavation face (1) extends to a foundation layer all the time, and the enclosure strength of the foundation pit excavation face (1) is ensured;

the foundation pit excavation surface (1) is also provided with a supporting truss structure consisting of a horizontal inner support (9) and a vertical inner support (10);

crown beam (11) have been pour to the inside wall position at drilling bored concrete pile (203) top, waist rail (12) have been pour to the inside wall position at drilling bored concrete pile (203) middle part, support (9) including the horizontal frame of two sets of parallels in the level, the horizontal frame edge on upper portion inserts through the reinforcing bar in crown beam (11), and the horizontal frame edge of lower part inserts through the reinforcing bar in waist rail (12), waist rail (12) bottom surface elevation is higher than 0.5-1m of soil rock interface elevation.

2. The deep foundation pit waterproof composite structure suitable for the quicksand-containing stratum of the shallow bedrock of the three-face river according to claim 1, characterized in that: the concrete on the surface layers of the first-step slope surface (401), the middle step (402) and the second-step slope surface (403) is sprayed by a cement high-pressure gun, and a layer of concrete is sprayed on the surfaces of the slope bottom step (404) and the slope bottom intercepting ditch (8).

3. The deep foundation pit waterproof composite structure suitable for the quicksand-containing stratum of the shallow bedrock of the three-face river according to claim 1, wherein the high-pressure jet grouting pile (202) is a concrete cylindrical pile body.

4. The deep foundation pit waterproof composite structure suitable for the quicksand-containing stratum of the shallow bedrock of the three-side river according to claim 1, wherein the high-pressure jet grouting pile (202) is closely attached to the curtain (201) of the cement soil deep stirring pile at the slope bottom.

5. The deep foundation pit waterproof composite structure suitable for the sand-bearing stratum of the shallow bedrock of the three-side river, according to claim 1, is characterized in that the diameter of a reinforcement cage in the cast-in-situ bored pile (203) is 30-40cm smaller than the outer diameter of the cast-in-situ bored pile (203), and the high-pressure jet grouting pile (202) does not contact the reinforcement cage in the cast-in-situ bored pile (203).

6. The deep foundation pit waterproof combined structure suitable for the quicksand-containing stratum of the shallow bedrock of the three-side river according to claim 1, wherein the vertical inner support (10) and the horizontal inner support (9) are bound by iron wires and then welded to form an integrated supporting structure, the peripheral edges of the horizontal inner supports (9) are respectively embedded with steel bars and inserted into the side wall of the cast-in-situ bored pile (203), and the bottom ends of the vertical inner supports (10) are embedded into the bottom wall back cover of the foundation pit excavation surface (1).

7. The deep foundation pit waterproof composite structure suitable for the quicksand-containing stratum of the shallow bedrock of the three-face river according to claim 1, wherein dewatering wells are further arranged in the foundation pit excavation surface (1) at equal intervals.

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