1. The utility model provides a subway station main part foundation ditch under city complex environment, includes overhead bridge floor (1), pier (2) with set up in main part foundation ditch of overhead bridge floor (1) below, its characterized in that: the main foundation pit comprises a weak sensitive area foundation pit (3) and a strong sensitive area foundation pit (4);

the strong sensitive area foundation pit (4) is arranged in the projection range of the elevated bridge floor (1) towards the ground; the weak sensitive area foundation pit (3) comprises a first weak sensitive area foundation pit (31) and a second weak sensitive area foundation pit (32); the first weak sensitive area foundation pit (31) and the second weak sensitive area foundation pit (32) are arranged on the ground on two sides of the elevated bridge floor (1); a strong sensitive area foundation pit (4) is arranged between the first weak sensitive area foundation pit (31) and the second weak sensitive area foundation pit (32); an intermediate wall (13) is fixedly connected between the strong sensitive area foundation pit (4) and the first weak sensitive area foundation pit (31) and the second weak sensitive area foundation pit (32); the pit walls on two sides of the strong sensitive area foundation pit (4) close to the bridge pier (2) are underground continuous walls (5); the first weak sensitive area foundation pit (31), the second weak sensitive area foundation pit (32), the strong sensitive area foundation pit (4) are internally provided with a reinforcing structure (9), and a first partition wall (10) and a second partition wall (11) are symmetrically embedded in the ground at two sides of the underground continuous wall (5); the bottom end of the underground continuous wall (5) extends into a stable soil layer (6) of the ground bottom, and the first isolation wall (10) is close to the underground continuous wall (5); the top surface of the first isolation wall (10), the top surface of the second isolation wall (11) and the top surface of the pit wall of the strong sensitive area foundation pit (4) are fixedly connected with a crown beam (7) respectively; and a plurality of reinforced concrete plates (8) are fixedly connected to the top surface of the crown beam (7).

2. The subway station main body foundation pit under the urban complex environment as claimed in claim 1, wherein: the reinforcing structure (9) comprises lattice columns (91); the bottom end of the lattice column (91) extends into a stable soil layer (6) of the ground bottom, and a plurality of rotary spraying piles (92) are fixedly connected to the lower portion of the lattice column (91); the jet grouting pile (92) is vertically embedded at the bottom of the strong sensitive region foundation pit (4), and the upper part of the lattice column (91) is fixedly connected with a plurality of layers of supporting units (93); and two ends of the multilayer supporting unit (93) are fixedly connected with the two underground continuous walls (5) respectively.

3. The subway station main body foundation pit under the urban complex environment as claimed in claim 2, wherein: the multi-layer supporting unit (93) comprises a plurality of reinforced concrete supporting layers (931) and a plurality of steel supporting layers (932); two ends of the reinforced concrete supporting layer (931) are fixedly connected with the two underground continuous walls (5) respectively; two ends of the steel supporting layer (932) are fixedly connected with the two underground continuous walls (5) respectively, and the plurality of reinforced concrete supporting layers (931) and the plurality of steel supporting layers (932) are arranged from top to bottom separately.

4. The subway station main body foundation pit under the urban complex environment as claimed in claim 3, wherein: the reinforced concrete supporting layers (931) on the same horizontal plane are arranged in the foundation pit (4) of the strong sensitive area at equal intervals, the intervals are set to be 6m-10m, the steel supporting layers (932) on the same horizontal plane are arranged in the foundation pit (4) of the strong sensitive area at equal intervals, and the intervals are set to be 2m-5 m; the distance between the reinforced concrete support layer (931) and the adjacent steel support layer (932) is 6m-9m, and the distance between the adjacent steel support layers (932) is 2.5m-4 m; the reinforced concrete support layer (931) and the steel support layer (932) are arranged in parallel.

5. The subway station main body foundation pit under the urban complex environment as claimed in claim 2, wherein: the diameter of the jet grouting pile (92) is 800 mm; and the interval between the rotary spraying piles (92) is 600mm, the rotary spraying piles are overlapped by 200mm, and the rotary spraying piles (92) are embedded into the bottom of the strong sensitive area foundation pit (4) by 4 m.

6. The subway station main body foundation pit under the urban complex environment as claimed in claim 1, wherein: the first partition wall (10) and the second partition wall (11) respectively comprise a plurality of partition piles (12) which are arranged at equal intervals, and the number of the partition piles (12) contained in the first partition wall (10) is smaller than the number of the partition piles (12) contained in the second partition wall (11); the shortest distance between the isolation piles (12) of the first isolation wall (10) and the underground continuous wall (5) is 1.5-2.5 m, and the shortest distance between the isolation piles (12) of the second isolation wall (11) and the underground continuous wall (5) is 6.5-8.5 m; the shortest distance between the isolation piles (12) of the second isolation wall (11) and the bridge foundation of the pier (2) is 6.5-8.5 m.

7. The subway station main body foundation pit under the urban complex environment as claimed in claim 6, wherein: the bottom ends of the isolation piles (12) extend into a stable soil layer (6) of the ground bottom, and all the isolation piles (12) are arranged in parallel; the distance between the adjacent isolation piles (12) of the first isolation wall (10) is 5-6 m; the distance between adjacent isolation piles (12) of the second isolation wall (11) is 0.8-1.5 m.

8. The subway station main body foundation pit under the urban complex environment as claimed in claim 1, wherein: the wall thickness of the underground continuous wall (5) is 0.7-0.9 m, and the bottom end of the underground continuous wall extends into a stable soil layer (6) of the ground bottom.

9. The subway station main body foundation pit under the urban complex environment as claimed in claim 1, wherein: monitoring points are distributed in the range of 3 times of the depth of the strong sensitive area foundation pit (4) at the edge of the pit opening of the strong sensitive area foundation pit (4).

10. The construction method of the main foundation pit of the subway station under the urban complex environment according to the claims 1-9, characterized by comprising the three steps:

partitioning: partitioning and segmenting into a strong sensitive area and a weak sensitive area according to the complexity of the environment where the main foundation pit of the subway station is located;

construction: constructing a weak sensitive area foundation pit and a strong sensitive area foundation pit;

communication: and communicating the foundation pits of the main body of the station.

Background

Along with the rapid development of urban rail transit engineering and the encryption of an operation wire net, the utilization rate of underground space is higher and higher, and in the field of rail transit subway station construction, most of foundation pits are constructed by an open cut method.

The geological conditions of coastal cities are more complex, and soft soil strata in coastal areas have the characteristics of high natural water content, large natural pore ratio, high compressibility, low shear strength, small consolidation coefficient, long consolidation time, high sensitivity, high disturbance, poor water permeability, complex soil layer distribution, large difference of physical and mechanical properties among layers and the like.

The subway station is often arranged in urban areas with large population density, and urban facilities such as elevated bridges, underground pipelines, high-rise buildings and the like are likely to exist in the construction range. The subway station foundation pit has the characteristics of deep excavation depth, long foundation pit length and the like, and various underground pipelines, various buildings, traffic main roads and the like are often densely distributed around the foundation pit, so that the subway station foundation pit has the characteristics of short construction site, tight construction period, complex construction conditions, high environmental protection requirements of peripheral facilities and the like. When the construction of a main foundation pit of a station is carried out in a complex urban environment, displacement variables of an enclosure structure and surrounding ground surface settlement must be strictly controlled, the problems of soil body slippage and the like are avoided, and unnecessary security threats are generated to surrounding buildings, underground pipelines and surrounding residents of the city.

If the construction area is located in a soft soil area, thick-layer soft soil is widely distributed, and the construction area has the characteristics of high natural water content, high compressibility, high sensitivity, high thixotropy, high rheological property, low strength, weak water permeability and the like. The soft soil layer of the proposed site is composed of a first 3b layer of gray muddy clay; ② 2b layer gray mucky soil; ③ 2 layers of gray silty clay; the fourth layer of gray mucky soil is 1 layer of gray mucky soil, and the fourth layer of gray cohesive soil is 2 layers of gray cohesive soil, and the cumulative thickness is about 35-40 m. Soil layers in the excavation range of the foundation pit mainly comprise (a) miscellaneous filling soil, (2) clay, (3 b) silt clay and (2 b) silt clay. The pit bottom soil layer is 2b of silt clay; the soil layer of the wall bottom is clay 2. The whole soil layer is short of 1 layer of silty clay, and simultaneously 1 layer of silt clay is thick and poor in soil quality and is very unfavorable for deformation control in the excavation process of the foundation pit. Meanwhile, a large subway station needs to be built under the urban traffic main bridge, the clearance between a foundation pit and the bridge is only 9.5m, the distance between a foundation pit support structure and a bridge pile foundation is about 14m closest, the construction difficulty is high, and the requirement for protecting the bridge is high, so that new requirements and challenges are provided for subway station construction.

Therefore, it is urgently needed to develop a main foundation pit of a subway station under an urban complex environment and a construction method thereof, which can deal with the above-mentioned situations.

Disclosure of Invention

The invention aims to provide a subway station main body foundation pit and a construction method under a complex urban environment, and aims to solve the problems in the prior art.

In order to achieve the purpose, the invention provides the following scheme:

the invention provides a main foundation pit of a subway station under a complex urban environment, which comprises an elevated bridge floor, piers and a main foundation pit arranged below the elevated bridge floor, and is characterized in that: the main foundation pit comprises a weak sensitive area foundation pit and a strong sensitive area foundation pit;

the strong sensitive area foundation pit is arranged in the projection range of the viaduct surface facing the ground; the weak sensitive area foundation pit comprises a first weak sensitive area foundation pit and a second weak sensitive area foundation pit; the first weak sensitive area foundation pit and the second weak sensitive area foundation pit are arranged on the ground on two sides of the viaduct face; a strong sensitive area foundation pit is arranged between the first weak sensitive area foundation pit and the second weak sensitive area foundation pit; a middle partition wall is fixedly connected between the strong sensitive area foundation pit and the first weak sensitive area foundation pit and between the strong sensitive area foundation pit and the second weak sensitive area foundation pit respectively; the pit walls on two sides of the foundation pit of the strong sensitive area, which are close to the bridge pier, are underground continuous walls; the first weak sensitive area foundation pit, the second weak sensitive area foundation pit and the strong sensitive area foundation pit are internally provided with a reinforcing structure, and a first partition wall and a second partition wall are symmetrically embedded in the ground at two sides of the underground continuous wall; the bottom end of the underground continuous wall extends into a stable soil layer of the ground bottom, and the first isolation wall is close to the underground continuous wall; the top surface of the first isolation wall, the top surface of the second isolation wall and the top surface of the pit wall of the foundation pit in the strong sensitive area are fixedly connected with crown beams respectively; and the top surface of the crown beam is fixedly connected with a plurality of reinforced concrete plates.

Preferably, the reinforcing structure comprises lattice columns; the bottom end of the lattice column extends into a stable soil layer of the ground bottom, and a plurality of rotary spraying piles are fixedly connected to the lower portion of the lattice column; the jet grouting pile is vertically embedded at the bottom of the foundation pit of the strong sensitive area, and the upper part of the lattice column is fixedly connected with a plurality of layers of supporting units; and two ends of the multilayer supporting unit are fixedly connected with the two underground continuous walls respectively.

Preferably, the multi-layer supporting unit comprises a plurality of reinforced concrete supporting layers and a plurality of steel supporting layers; two ends of the reinforced concrete supporting layer are fixedly connected with the two underground continuous walls respectively; and two ends of the steel supporting layer are fixedly connected with the two underground continuous walls respectively, and the plurality of reinforced concrete supporting layers and the plurality of steel supporting layers are arranged from top to bottom separately.

Preferably, the plurality of reinforced concrete supporting layers on the same horizontal plane are arranged in the foundation pit of the strong sensitive area at equal intervals, the intervals are set to be 6m-10m, and the plurality of steel supporting layers on the same horizontal plane are arranged in the foundation pit of the strong sensitive area at equal intervals, and the intervals are set to be 2m-5 m; the distance between the reinforced concrete support layer and the adjacent steel support layer is 6-9 m, and the distance between the adjacent steel support layers is 2.5-4 m; the reinforced concrete supporting layer and the steel supporting layer are arranged in parallel.

Preferably, the pile diameter of the jet grouting pile is 800 mm; and the distance between the rotary spraying piles is 600mm, the rotary spraying piles are overlapped by 200mm, and the rotary spraying piles are embedded into the bottom of the strong sensitive area foundation pit by 4 m.

Preferably, the first partition wall and the second partition wall respectively comprise a plurality of partition piles arranged at equal intervals, and the number of the partition piles contained in the first partition wall is smaller than the number of the partition piles contained in the second partition wall; the shortest distance between the isolation piles of the first isolation wall and the underground continuous wall is 1.5-2.5 m, and the shortest distance between the isolation piles of the second isolation wall and the underground continuous wall is 6.5-8.5 m; and the shortest distance between the isolation pile of the second isolation wall and the bridge foundation of the pier is 6.5-8.5 m.

Preferably, the bottom ends of the isolation piles extend into a stable soil layer of the ground bottom, and all the isolation piles are arranged in parallel; the distance between adjacent isolation piles of the first isolation wall is 5-6 m; and the distance between adjacent isolation piles of the second isolation wall is 0.8-1.5 m.

Preferably, the underground continuous wall has a wall thickness of 0.7-0.9 m, and the bottom end of the underground continuous wall extends into the soil stabilizing layer of the ground bottom.

Preferably, monitoring points are distributed in the range of 3 times of the depth of the strong sensitive area foundation pit in the edge of the strong sensitive area foundation pit.

A construction method of a main foundation pit of a subway station in an urban complex environment according to claims 1-9, comprising the three steps of:

partitioning: partitioning and segmenting into a strong sensitive area and a weak sensitive area according to the complexity of the environment where the main foundation pit of the subway station is located;

construction: constructing a weak sensitive area foundation pit and a strong sensitive area foundation pit;

communication: and communicating the foundation pits of the main body of the station.

The invention discloses the following technical effects:

the technical scheme can effectively reduce the long edge effect of the long strip foundation pit of the subway station; the influence of the heavy load around the main foundation pit on the horizontal displacement of the main foundation pit and a sensitive building can be effectively reduced; the support shaft force can be ensured not to be lost, and a support system is strengthened; deformation data of the main foundation pit in the bottom folding stage can be reduced; the deformation of the main foundation pit support structure, the peripheral surface subsidence and the deformation of peripheral buildings can be effectively reduced; thereby realizing the self safety of the main foundation pit and the protection of the surrounding complex environment.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.

Fig. 1 is a schematic view of a main view structure of a foundation pit in a strong sensitive area.

Fig. 2 is a schematic front view of a multi-layer supporting unit.

Fig. 3 is a schematic top view of the main foundation pit.

Fig. 4 is a schematic top view of the multi-layered supporting unit.

The high-rise bridge floor-1, the bridge piers-2, the weak sensitive area foundation pits-3, the first weak sensitive area foundation pits-31, the second weak sensitive area foundation pits-32, the strong sensitive area foundation pits-4, the underground continuous wall-5, the stabilized soil layer-6, the crown beams-7, the reinforced concrete slab-8, the reinforced structure-9, the lattice column-91, the jet grouting piles-92, the multilayer supporting units-93, the reinforced concrete supporting layer 931, the steel supporting layer-932, the first isolation wall-10, the second isolation wall-11, the isolation piles-12 and the middle partition-13.

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 of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.

The invention provides a main foundation pit of a subway station under a complex urban environment, which comprises an elevated bridge floor 1, piers 2 and a main foundation pit arranged below the elevated bridge floor 1, wherein the main foundation pit comprises a weak sensitive area foundation pit 3 and a strong sensitive area foundation pit 4;

the strong sensitive area foundation pit 4 is arranged in the projection range of the elevated bridge floor 1 towards the ground; the weak sensitive area foundation pit 3 comprises a first weak sensitive area foundation pit 31 and a second weak sensitive area foundation pit 32; the first weak sensitive area foundation pit 31 and the second weak sensitive area foundation pit 32 are arranged on the ground on two sides of the elevated bridge deck 1; a strong sensitive area foundation pit 4 is arranged between the first weak sensitive area foundation pit 31 and the second weak sensitive area foundation pit 32; an intermediate wall 13 is fixedly connected between the strong sensitive area foundation pit 4 and the first weak sensitive area foundation pit 31 and the second weak sensitive area foundation pit 32 respectively; the pit walls on two sides of the foundation pit 4 of the strong sensitive area, which are close to the bridge pier 2, are underground continuous walls 5; the foundation pit 4 of the strong sensitive area is internally provided with a reinforcing structure 9, and the ground at two sides of the underground continuous wall 5 is symmetrically embedded with a first partition wall 10 and a second partition wall 11; the bottom end of the underground continuous wall 5 extends into a stable soil layer 6 of the ground bottom, and the first isolation wall 10 is close to the underground continuous wall 5; the top surfaces of the first partition wall 10, the second partition wall 11 and the strong sensitive area foundation pit 4 are fixedly connected with a crown beam 7 respectively; the top surface of the crown beam 7 is fixedly connected with a plurality of reinforced concrete slabs 8.

Further, the stabilization soil layer 6 of the ground bottom is a stable ground layer capable of providing a large load support for the underground continuous wall 5.

Furthermore, the underground continuous wall 5, the first partition wall 10 and the second partition wall 11 are parallel to each other, so that the arrangement area of the first partition wall 10 and the second partition wall 11 is optimized, and the construction cost is reduced.

Further, an intermediate wall 13 with the thickness of 800mm is arranged between the strong sensitive area foundation pit 4 and the first weak sensitive area foundation pit 31 and the second weak sensitive area foundation pit 32 respectively, so that the effect of assisting the strong sensitive area foundation pit 4 to resist the internal stress of the first weak sensitive area foundation pit 31 and the second weak sensitive area foundation pit 32 is achieved.

Furthermore, the reinforced concrete slab 8, the first partition wall 10, the second partition wall 11 and the crown beam 7 are mutually matched to form a pile-slab-wall door type structure, so that a stable underground environment is provided for the construction of the foundation pit 4 in the strong sensitive area, and a stable support is provided for the construction on the ground.

In a further preferred embodiment, the reinforcing structure 9 comprises lattice columns 91; the bottom surface of the lattice column 91 is abutted against the stabilized soil layer 6, and a plurality of jet grouting piles 92 are fixedly connected to the lower part of the lattice column 91; the jet grouting pile 92 is vertically embedded at the bottom of the strong sensitive area foundation pit 4, and the upper part of the lattice column 91 is fixedly connected with a plurality of layers of supporting units 93; two ends of the multi-layer supporting unit 93 are fixedly connected with the two underground continuous walls 5 respectively.

Further, the strong sensitive area foundation pit 4 is partially or completely arranged in the projection range of the elevated bridge surface 1 towards the ground; the bottom of the strong sensitive area foundation pit 4 in the projection range of the viaduct deck 1 is reinforced only by the jet grouting piles 92, and the bottom of the strong sensitive area foundation pit 4 outside the projection range of the viaduct deck 1 is reinforced by the three-axis stirring piles, wherein the pile diameter of each three-axis stirring pile is 850mm, the distance between every two three-axis stirring piles is 600mm, the three-axis stirring piles are overlapped by 250mm, and the reinforcing depth is 4m below the bottom of the cushion layer. The use of the triaxial mixing pile can realize strong isolation of a water-bearing stratum outside the foundation pit of the strong sensitive area and avoid collapse of the foundation pit of the strong sensitive area;

furthermore, the lattice column 9 is fixedly connected with the plurality of jet grouting piles 92 and the multi-layer supporting units 93 through reinforced concrete plates, so that the flexure resistance of the reinforced structure 9 is improved, and the deformation and failure of the reinforced structure 9 due to the extrusion of geological stress on the foundation pit wall of the strong sensitive area are avoided.

In a further optimized scheme, the multi-layer supporting unit 93 comprises a plurality of reinforced concrete supporting layers 931 and a plurality of steel supporting layers 932; two ends of the reinforced concrete supporting layer 931 are fixedly connected with the two underground continuous walls 5 respectively; two ends of the steel support layer 932 are fixedly connected with the two underground continuous walls 5 respectively, and the plurality of reinforced concrete support layers 931 and the plurality of steel support layers 932 are arranged from top to bottom separately.

Furthermore, servo systems are additionally arranged at two ends of the steel support layer 932 in the projection range of the viaduct, so that the situation that the supporting force at two ends of the steel support layer 932 is reduced due to the fact that the side wall of the foundation pit 4 in the strong sensitive area collapses outwards in the soil of the side wall of the foundation pit 4 in the strong sensitive area at two ends of the steel support layer 932 because of the high-load pier 2 and the soft geological environment can be avoided, and therefore the whole reinforcing structure 9 fails.

In a further optimization scheme, a plurality of reinforced concrete supporting layers 931 on the same horizontal plane are arranged in the strong sensitive area foundation pit 4 at equal intervals, the intervals are set to be 6m-10m, and a plurality of steel supporting layers 932 on the same horizontal plane are arranged in the strong sensitive area foundation pit 4 at equal intervals, and the intervals are set to be 2m-5 m; the distance between the reinforced concrete support layer 931 and the adjacent steel support layer 932 is 6m-9m, and the distance between the adjacent steel support layers 932 is 2.5m-4 m; the reinforced concrete support layer 931 and the steel support layer 932 are arranged in parallel.

In a further optimization scheme, the diameter of the jet grouting pile is 92 mm; the distance between the adjacent jet grouting piles 92 is 600mm, the jet grouting piles are overlapped by 200mm, and the jet grouting piles 92 are embedded into the bottom of the foundation pit 4 of the strong sensitive area by 4 m.

In a further optimization scheme, the first partition wall 10 and the second partition wall 11 respectively comprise a plurality of partition piles 12 which are arranged at equal intervals, and the number of the partition piles 12 contained in the first partition wall 10 is smaller than the number of the partition piles 12 contained in the second partition wall 11; the shortest distance between the isolation piles 12 of the first isolation wall 10 and the underground continuous wall 5 is 1.5m-2.5m, and the shortest distance between the isolation piles 12 of the second isolation wall 11 and the underground continuous wall 5 is 6.5m-8.5 m; the shortest distance between the insulation piles 12 of the second insulation wall 11 and the abutment of the pier 2 is 6.5m to 8.5 m.

Furthermore, the top end of the isolation pile 12 exceeds the bearing platform 2m of the pier 2, so that subsequent construction operation is conveniently carried out on the top end of the isolation pile 12.

In a further optimized scheme, the bottom ends of the isolation piles 12 extend into the stable soil layer 6 of the ground bottom, and all the isolation piles 12 are arranged in parallel; the distance between adjacent isolation piles 12 of the first isolation wall 10 is 5m-6 m; the spacing between adjacent insulation piles 12 of the second insulation wall 11 is 0.8m to 1.5 m.

In a further optimized scheme, the wall thickness of the underground continuous wall 5 is 0.7-0.9 m, and the bottom end of the underground continuous wall extends into a stable soil layer 6 of the ground bottom.

In a further optimization scheme, monitoring points are distributed in the range of 3 times of the depth of the strong sensitive area foundation pit 4 at the edge of the pit mouth of the strong sensitive area foundation pit 4.

Furthermore, monitoring points arranged right below the bottom of the foundation pit 4 in the strong sensitive area comprise various sensors and are electrically connected with an external monitoring processor; the monitoring of settlement of the ground surface and the pipeline around the foundation pit of the strong sensitive area and the foundation pit of the weak sensitive area can be realized, the ground level monitoring outside the pit, the vertical horizontal displacement monitoring of the foundation pit of the strong sensitive area and the foundation pit of the weak sensitive area, the horizontal displacement and settlement monitoring of the pile top of the isolation pile 12 and the jet grouting pile 92, the vertical horizontal displacement monitoring of the soil body outside the foundation pit of the strong sensitive area and the foundation pit of the weak sensitive area, the force monitoring of a supporting shaft, and the horizontal displacement and settlement monitoring of a 2-column pier.

A construction method of a main foundation pit of a subway station under an urban complex environment according to claims 1-9, comprising the three steps of:

partitioning: partitioning and segmenting into a strong sensitive area and a weak sensitive area according to the complexity of the environment where the main foundation pit of the subway station is located;

construction: constructing a weak sensitive area foundation pit and a strong sensitive area foundation pit;

communication: and communicating the foundation pits of the main body of the station.

In one embodiment of the invention, the invention is solved by the following technical scheme, and the method for constructing the main foundation pit of the subway station under the urban complex environment comprises the following steps: partitioning and segmenting into a strong sensitive area and a weak sensitive area according to the complexity of the environment where the main foundation pit of the subway station is located; constructing a weak sensitive area foundation pit (namely a weak sensitive area foundation pit 3) and a strong sensitive area foundation pit (namely a strong sensitive area foundation pit 4) respectively; and the foundation pits of the main body of the station are communicated.

The method comprises the following specific steps:

in order to reduce the influence on the surrounding complex environment during the construction of the subway station foundation pit, a main foundation pit is divided into a plurality of small foundation pits, a weak sensitive area foundation pit 3 is constructed in advance, a strong sensitive area foundation pit 4 is constructed later, and monitoring and measuring work of deformation of surrounding building structures in the construction process of the foundation pits is carried out during the construction.

Wherein, the construction of weak sensitive area foundation ditch 3 includes in proper order: the construction method comprises the following steps of (1) leveling a field, setting a heavy-load sidewalk → constructing an enclosure construction → constructing a pit inner reinforced structure 9 → constructing a crown beam 7 and a first reinforced concrete supporting layer 931 → layering earthwork, installing the reinforced concrete supporting layer 931 and a steel supporting layer 932 → cushion layer, waterproof construction → constructing a bottom plate → constructing a side wall, an upright post, middle plate construction → constructing a side wall, an upright post and a top plate → constructing an outer waterproof layer and a protective layer;

the construction process flow of the strong sensitive area foundation pit 4 sequentially comprises the following steps: the construction method comprises the steps of site leveling, heavy-load pavement setting → underground continuous wall construction → pit inner reinforcing structure 9 construction → construction of foundation range pit outer isolation piles 12 of sensitive buildings → construction of a crown beam 7 and a first reinforced concrete supporting layer 931 → construction of the pit outer isolation piles 12, the crown beam 7 and a reinforced concrete plate 8 → earthwork layering, installation of the reinforced concrete supporting layer 931 and a steel supporting layer 932 → cushion layer, waterproof construction → reinforced concrete plate construction → side wall, upright post, medium plate construction → side wall, upright post, roof construction → outer waterproof and protective layer construction.

Wherein, the strong sensitive area foundation pit 4 needs to be provided with an isolation pile 12 at the periphery of the sensitive building foundation, and the isolation pile 12, the main foundation pit and the reinforcing structure 9 are connected by adopting a crown beam and reinforced concrete plate structure to form a 'pile-plate-wall' door type structure.

The specific construction mode is that the foundation pit 4 of the strong sensitive area is positioned below the viaduct surface 1, the clearance is about 9.5m, the land of the strong sensitive area is leveled, and the passing sidewalk of a heavy-duty vehicle is repaired, so that the transportation of construction equipment and materials is facilitated; the weak sensitive area foundation pit 3 is respectively a first weak sensitive area foundation pit 31 and a second weak sensitive area foundation pit 32, the length of the first weak sensitive area foundation pit 31 is 121m, the excavation depth is 16.8m, and the distance between the pit wall of the first weak sensitive area foundation pit 31 and the nearest elevated bridge pier is about 47.5 m; the length of the second weak sensitive area foundation pit 32 is 140m, the excavation depth is 16.2m, and the distance between the pit wall of the second weak sensitive area foundation pit 32 and the overhead pier is about 31.9 m; the length of the strong sensitive area foundation pit 4 is 88m, the excavation depth is 16.5m, and the distance between the wall of the strong sensitive area foundation pit 4 and the overhead pier is about 14.0 m.

Then, transporting away earth and stone in the foundation pit 4 of the strong sensitive area by using equipment, and constructing an underground continuous wall 5 on two opposite pit walls of the foundation pit 4 of the strong sensitive area, which are close to the bridge pier 2, wherein the underground continuous wall extends from the top end of the pit wall of the foundation pit 4 of the strong sensitive area to an underground stable soil layer 6; then, constructing a reinforcing structure 9 in the foundation pit 4 of the strong sensitive area between the two underground continuous walls 5, specifically, reinforcing the pit bottom by adopting high-pressure jet grouting piles 92 within the projection range of the viaduct, wherein the pile diameter of the high-pressure jet grouting piles 92 is 800mm, the spacing of the high-pressure jet grouting piles 92 is 600mm, the high-pressure jet grouting piles are lapped by 200mm, and the reinforcing depth is 4m below the pit bottom of the foundation pit 4 of the strong sensitive area; and (3) adopting a triaxial mixing pile to reinforce the pit bottom outside the projection range of the viaduct, wherein the pile diameter of the triaxial mixing pile is 850mm, the distance between the triaxial mixing pile and the pit bottom is 600mm, the triaxial mixing pile and the pit bottom are overlapped by 250mm, and the reinforcing depth is 4m below the pit bottom of the foundation pit in the strong sensitive area. The use of the triaxial mixing pile can realize effective isolation of the aquifer outside the foundation pit 4 in the strong sensitive area and avoid collapse of the foundation pit 4 in the strong sensitive area;

the support body system of strong sensitive area foundation ditch 4 is five vertical supports, the first is that the cross-section is 800mm 1000mm reinforced concrete supporting layer 931, the second is that the cross-section is phi 800 mm's steel brace layer 932 (adopt servo in the overhead bridge projection scope), the third is 800mm 1000mm reinforced concrete supporting layer 931, the fourth is phi 800 steel brace layer 932 (adopt servo in the overhead bridge projection scope), the fifth is phi 800 steel brace layer 932 (adopt servo in the overhead bridge projection scope).

In the technical scheme, a first isolation wall 10 and a second isolation wall 11 are arranged between the wall of the strong sensitive area foundation pit 4 and the bridge pier, the diameter phi of each isolation pile 12 is 800mm, the distance between the first isolation wall 10 and the wall of the strong sensitive area foundation pit 4 is 1100mm, the distance between the first isolation wall 10 and the second isolation wall 11 is 4950mm, the distance between the second isolation wall 11 and the bridge foundation of the bridge pier 2 is 7700mm, and the length of each isolation pile 12 is 33 m. The top of the isolation pile 12 is provided with a crown beam 7 with the cross section of 800mm multiplied by 800mm, and simultaneously, a reinforced concrete plate 8 is connected with the crown beam 7 of the main foundation pit to form a portal structure of pile-plate-wall.

The monitoring points are distributed in the range of 3 times of the depth of the strong sensitive area foundation pit 4 at the edge of the strong sensitive area foundation pit 4, the monitoring is carried out in the construction process, and the monitoring items comprise: monitoring the settlement of the ground surface and pipelines around the foundation pit of the strong sensitive area and the foundation pit of the weak sensitive area, monitoring the water level outside the pit, monitoring the vertical horizontal displacement of the foundation pit of the strong sensitive area and the foundation pit of the weak sensitive area, monitoring the horizontal displacement and settlement of the pile tops of the isolation pile 12 and the jet grouting pile 92, monitoring the vertical horizontal displacement of the soil outside the foundation pit of the strong sensitive area and the foundation pit of the weak sensitive area, monitoring the force of a supporting shaft, and monitoring the horizontal displacement and settlement of the column 2 of the pier. Through monitoring each parameter of geological environment around the strong sensitive area foundation pit 4, the implementation of having realized grasping the construction environment has avoided leading to the stagnation of construction progress because of the sudden change of geological environment, even collapses and does over again.

In the description of the present invention, it is to be understood that the terms "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on those shown in the drawings, are merely for convenience of description of the present invention, and do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and thus, are not to be construed as limiting the present invention.

The above-described embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solutions of the present invention can be made by those skilled in the art without departing from the spirit of the present invention, and the technical solutions of the present invention are within the scope of the present invention defined by the claims.