CN117759034A - Deep foundation pit edge reverse middle-forward and half-reverse construction method - Google Patents

Abstract

The invention discloses a deep foundation pit edge reverse middle forward and half reverse construction method, which relates to the field of underground engineering and comprises the following steps: 1) Constructing a fender pile and a waterproof curtain; 2) The first stage of earth excavation to the bottom of a concrete cushion layer of a beam slab structure of a basement; 3) Excavating the earthwork at the second stage according to two stages of slope releasing, and retaining passive soil back pressure; 4) After the basin-type excavation of the middle area is completed, basement bottom plate cabin-jumping construction and sequential construction of wall column structures are carried out; 5) Erecting a steel pipe support die frame in the bottom plate and the slope-placing area around the bottom plate; 6) After the design strength is reached, dismantling the steel pipe support die frame; 7) Removing the soil moulding bed cushion; 8) Processing gaps between a post-cast basement one-layer wall column structure and a pre-constructed basement one-layer wall column structure; 9) The soil sampling opening is reserved and sealed in a layer of beam plate structure of the basement. The construction technology of the peripheral soil-retaining reverse-acting construction basement and the middle basin-type excavation forward-acting construction basement has mature theoretical basis and successful practical experience.

Description

Deep foundation pit edge reverse middle-forward and half-reverse construction method

Technical Field

The invention relates to the field of underground engineering, in particular to a method for constructing a deep foundation pit by adopting a side reverse middle-forward and half reverse construction method.

Background

With the rapid development of economic construction in China, the urban scale is continuously expanded, and the large-scale development of underground space is increasingly paid attention to. In order to develop and utilize urban underground space to the greatest extent, the areas and excavation depths of foundation pits of many newly-built and under-construction projects are larger and larger, the areas of underground constructions are more than tens of thousands of square meters, projects with several layers of basements are more and more common, and deep foundation pit projects have the characteristics of large area, excavation depth, compact construction period, complex surrounding environment and the like.

The forward construction method and the reverse construction method are mainly adopted in the existing deep foundation pit engineering, the forward construction method is that the whole structure is constructed from bottom to top according to the traditional construction sequence, the whole performance of the control structure can be effectively controlled, the construction is relatively convenient, a large enough ventilation opening and a transport opening are formed, a large amount of large-size steel or concrete is consumed by the temporary supporting member adopted in the forward construction method, the whole rigidity is small, and the stability of a foundation pit and the surrounding basement environment are greatly influenced in the process of dismantling and supporting. In contrast, the reverse construction method is to construct from top to bottom, the structural beam plates are adopted as the horizontal supporting parts of the enclosure structure, the horizontal support method has more advantages in strength and rigidity, the problem of stress concentration during support disassembly is avoided, the problem of unstable state of the underground structure is avoided, in some projects with poor soil conditions and thicker silt soil, the deformation of a foundation pit can be effectively controlled by using the reverse construction method, the influence on the surrounding environment is small, but the defects of high difficulty, high cost, low efficiency and the like of the underground excavation under the structural beam plates which are constructed in advance in the reverse construction method are overcome, and therefore, the traditional reverse construction method can be considered to be further optimally designed.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a forward and half reverse construction method in the side reverse of a deep foundation pit, which combines most of the advantages of forward construction method and traditional reverse construction method, adopts a construction method of reverse construction of a basement by peripheral soil remaining back pressure and forward construction of middle basin excavation, can finish about 70% of earthwork in the middle basin excavation in the whole earthwork construction process, and furthest avoids the defects of the conventional reverse construction method in the undercut of the traditional reverse construction method on the premise of ensuring the supporting quality.

The invention aims at being completed by the following technical scheme: the method for constructing the deep foundation pit by forward and half reverse construction in the edge reverse direction comprises the following steps:

1) Constructing a fender pile and a waterproof curtain, digging a groove at the top of the fender pile to the bottom of the crown beam, and constructing the crown beam;

2) Excavating soil in a peripheral area of the basement to the bottom of a cushion layer of a first-stage beam plate structure of the basement, constructing the first-stage beam plate structure of the basement by adopting a soil moulding bed, constructing the first-stage beam plate structure of the basement by adopting a skip method after the soil moulding bed is constructed, constructing the first-stage beam plate structure of the basement by taking part of the first-stage wall column structure of the basement as a pouring part in advance, and reserving a certain number and size of soil taking openings when constructing the first-stage beam plate structure of the basement so as to excavate soil in the third stage;

3) Digging earthwork around the pit edge at the second stage according to two-stage slope-releasing, reserving passive soil back pressure of the two-stage slope-releasing, driving three rows of pine piles on a second stage platform of the two-stage slope-releasing, and reserving soil in the earthwork of the middle area to form basin-type partition digging;

4) After the basin-type excavation of the middle area is completed, the basement bottom plate cabin-jumping method construction and the basement one-layer wall column structure sequential construction are carried out on the middle area;

5) After the construction of the basement bottom plate structure of the middle basin-type excavation area is finished, erecting a steel pipe formwork support in the basement bottom plate and the secondary slope-releasing area, pouring the slope-releasing areas around to form a plain concrete cushion layer, and after the erection of the steel pipe formwork support, constructing a layer of beam plate structure of the basement of the middle area in a partitioning mode;

6) After the one-layer beam plate structure of the basement reaches the design strength, dismantling the steel pipe support die frame, and performing third-stage underground excavation by utilizing the reserved soil taking openings of the top plate at the periphery of the basement;

7) Removing the soil moulding bed cushion layer after the earth is excavated, and then constructing a basement wall column structure of the basement in the peripheral area of the basement by a bin jump method and constructing the area in a reverse way;

8) Processing gaps between a post-cast basement one-layer wall column structure and a pre-cast part;

9) And closing the reserved soil sampling port of the one-layer beam plate structure of the basement.

In the step 1), the pile and the waterproof curtain are selected according to the excavation depth, the surrounding environment and the geological condition of the foundation pit and by combining with the regional experience, the waterproof is fully considered, the grooving width of the pile top of the pile is 2.0m, the pile top of the pile is chiseled, the crown beam of the pile top of the pile is constructed, the crown beam is poured by reinforced concrete, and the pile and the crown beam form rigid connection.

As a further technical scheme, in the step 2), the horizontal support system of the basement one-layer beam slab structure is a half reverse construction method, the soil moulding bed is utilized to mainly bear the weight of the basement one-layer beam slab structure, the soil moulding bed must fully consider the total weight of the structure which can be borne by the soil moulding bed in the construction process, the generation of uneven sedimentation is prevented, and the horizontal support system can replace a wood moulding platform template, so that the apparent quality, flatness and the like of concrete can meet the requirement of acceptance regulations;

in the step 2), a basement one-layer top plate soil moulding bed system is designed to be plain soil, a concrete cushion layer, plywood and a basement one-layer top plate from bottom to top;

the basement one-layer frame beam soil moulding bed system without shear walls or frame columns at the beam bottom is designed to be plain soil, a concrete cushion layer, plywood and a basement one-layer frame beam from bottom to top;

the method comprises the steps of designing a soil moulding bed system of a basement one-layer frame beam with an inner shear wall at the beam bottom from bottom to top into plain soil, tamping and leveling a middle coarse sand cushion layer, reserving plywood with a dowel groove, pouring a first inner shear wall part of the basement one-layer frame beam;

the method comprises the steps of designing a soil moulding bed system of a basement one-layer frame beam with an outer shear wall at the beam bottom from bottom to top into plain soil, tamping and leveling a middle coarse sand cushion layer, reserving plywood with a dowel groove, sealing a tongue and groove strip, pouring a part of the basement one-layer outer shear wall in advance, and pouring the basement one-layer frame beam;

the soil moulding bed system of the basement one-layer frame beam is designed to be plain soil from bottom to top, a middle coarse sand cushion layer is tamped and leveled, a plywood with a dowel groove reserved is reserved, a basement one-layer frame column is poured in advance, and the basement one-layer frame beam is arranged;

in the step 2), water stopping tongue and groove strips are arranged on plywood with reserved dowel bar grooves or holes of the underground outdoor shear wall in a penetrating way so as to increase a hydraulic path and realize water stopping;

in the step 2), constructing a part of basement one-layer wall column structure in advance, namely pouring the basement one-layer wall column structure with the height ranging from 500mm to 1000mm below the bottom of the basement one-layer beam plate structure together to form an inverted L-shaped structure;

in the step 2), a basement one-layer beam plate structure is constructed by adopting a skip method, the maximum block size of a skip is less than or equal to 40 meters, the time of skip interval construction is more than or equal to 7 days, and skip joints are arranged and treated according to the requirements of construction joints.

As a further technical scheme, in the step 3), the depth of the back pressure of the secondary slope-releasing passive soil left around the border region in the side reverse direction is 16-18 m, the gradient of the secondary slope-releasing is 1:1.5, three rows of pine piles driven on the second stage platform are required to be arranged in a quincuncial shape, and the soil slope surface is sprayed with a concrete slope protection and is internally provided with a bidirectional reinforcing steel mesh so as to increase the stability of the soil slope.

As a further technical scheme, in the step 4), the basin-type excavation is required to be excavated in layers according to the design requirement, because the first-layer beam plate structure of the basement is constructed during basin-type excavation, in order to prevent stress concentration damage at the internal corner of the first-layer beam plate structure of the basement which is firstly constructed during basin-type excavation, thereby leading to the integral failure of a beam plate supporting system, H-shaped steel is required to be additionally arranged at the corners of the first-layer beam plate structure of the four basements for reinforcement, and the H-shaped steel is fixed with the first-layer beam plate structure of the basement by planting ribs;

in the step 4), the basement bottom plate of the middle basin-type excavation area and a basement one-layer wall column structure are constructed according to the conventional normal method flow.

As a further technical scheme, in the step 5), the steel pipe support frame system of the basement bottom plate area of the middle basin-type excavation area is designed into a one-layer beam plate structure of the basement of the middle basin-type excavation area from bottom to top, namely plain soil, the basement bottom plate, the steel pipe support frame, wood purlin, plywood and the basement of the middle basin-type excavation area; the steel pipe formwork support system of the secondary slope-releasing area is designed to be a one-layer beam slab structure of a basement of the secondary slope-releasing area from bottom to top, comprising plain soil, a concrete cushion layer, a steel pipe support frame, wood beams, plywood and the like.

As a further technical scheme, in the step 6), in order to facilitate the earth excavation and the vertical transportation of construction materials in the reverse construction stage, and simultaneously meet the requirements of natural ventilation and lighting, a reserved soil taking port is reasonably arranged according to the plane arrangement characteristics of the beam slab support and the support stress condition, and the length and the width of the reserved soil taking port are set as a column spanning distance;

in the step 6), the underground excavation is required to excavate in layers, the excavation depth of each layer is not more than 2m, the reserved soil taking opening is excavated, the earthwork of the reserved soil taking opening is excavated, the reserved soil taking opening is excavated to the periphery, the forklift is used for carrying the distal earthwork to the lower part of the reserved soil taking opening, the top plate is turned over by the excavator, the earthwork is transported by the dump truck, the reserved soil taking opening is excavated to the position above a concrete cushion layer by 500mm, and the disturbance of soil under the soil is reduced.

As a further technical scheme, in the step 7), the construction mode of the soil moulding bed is different from that of the steel pipe support mould frame, because the concrete cushion layer of the soil moulding bed is directly and tightly combined with earthwork needing to be excavated, when the soil moulding bed is constructed, the concrete cushion layer is divided into small blocks with the thickness of not more than 4.5m multiplied by 4.5m by using two layers of plywood, reinforcing steel meshes are arranged in the range of 2m multiplied by 2m in the center of each block, and reinforcing steel bar drag hooks are arranged in the center of each block, when the soil moulding bed is dismantled, the pick hooks the reinforcing steel bar drag hooks to pull the concrete cushion layer, so that the whole body of each concrete cushion layer falls off, the concrete cushion layer is prevented from being firmly adhered to a layer of beam slab structure of a basement, and the potential safety hazards of falling of the concrete cushion layer and the plywood are eliminated; the undetached concrete cushion layer is detached by adopting the impact of the back of the excavator bucket or manually detached by using a pneumatic pick;

in the step 7), the main steps of the reverse construction of the basement one-layer wall column structure are as follows: (1) basement frame column: reserving a 250mm multiplied by 250mm hole at the top of a template at one side of a basement frame column, supporting a horn mouth for concrete discharging and serving as a vibrating mouth, and forming a 300mm multiplied by 300mm top plate discharging hole at a position 100mm away from the basement frame column on a basement one-layer beam plate structure of the prior construction, wherein concrete is poured into the basement frame column through the top plate discharging hole, a baffle plate and a horn mouth path, and vibrating concrete through the horn mouth; (2) outdoor shear force wall of basement: a 600mm multiplied by 600mm hole is reserved at intervals of 1500mm at the top of a template at one side of the basement outer shear wall close to the crown beam, and a horn mouth is supported, if an outer shear wall side column is met, a horn mouth is required to be arranged separately and used for concrete discharging and also used as a vibrating mouth, concrete is poured into the basement outer shear wall through a baffle plate and a horn mouth path in a fertilizer tank, and meanwhile, concrete is vibrated through the horn mouth; (3) shear wall in basement: for a post-pouring basement shear wall, two rows of 1500mm roof blanking holes of phi 300 are formed in a layer of beam plate structure of a basement which is constructed in advance at a position 100mm away from the basement shear wall, roof blanking holes on two sides of the basement shear wall are in one-to-one correspondence with the horn mouths, concrete is poured into the basement shear wall on two sides of the basement shear wall through reserved roof blanking holes, baffle plates and horn mouth paths, and concrete is vibrated through the horn mouths; the shear wall outside the basement adopts a wall penetrating water stopping bolt which is a separable bolt, and a 50mm multiplied by 3mm steel plate water stopping sheet is welded on the middle part of the screw; the shear wall through-wall bolt in the basement adopts a common bolt.

As a further technical scheme, in the step 8), a gap between a post-cast basement one-layer wall column structure and a pre-cast part is subjected to compaction grouting treatment, and the gap compaction grouting is larger than 10mm, and the concrete steps are as follows: measuring and recording gaps, treating the surfaces of the gaps, burying grouting pipes, sealing the gaps, performing sealing inspection, preparing grouting materials, grouting, curing and cleaning; the micro-gap compaction grouting smaller than 10mm comprises the following specific steps: measuring and recording gaps, treating the surfaces of the gaps, drilling, embedding grouting plugs, closing the gaps, sealing and checking, preparing grouting materials, grouting, curing and cleaning;

in the step 8), firstly observing whether the slurry overflow condition exists in the slurry outlet in the process of compacting grouting, and if not, indicating that grouting is not completed; observing that the reading of the grouting pump pressure needs to reach a pressure value, if the pressure does not reach 0.4Mpa, indicating that the pressure is insufficient, and continuing grouting; after the sealing is carried out for 10 minutes, secondary grouting is carried out on the grouting hole of the grouting hole, and reciprocating injection is carried out to ensure compactness.

As a further technical scheme, in the step 9), each reserved soil taking hole is closed by sequentially constructing according to a normal method procedure after the basement bottom plate is completed.

The beneficial effects of the invention are as follows: from the essence of the side reverse and the middle forward, the construction mode is that the side region is reversed firstly and the middle region is reversed afterwards, so that the construction mode has the advantages of the traditional forward method and the traditional reverse method, and the construction mode is as follows:

1. the side area beam plate structure of the foundation pit supporting system is higher in safety and has rigidity far higher than that of a temporary support of a conventional forward method, so that the supporting structure is smaller in deformation and safer; the construction is carried out in order aiming at the middle area, so that the structure is ensured to be in a safer state, and the integral construction in order has great guarantee on the integral performance of the structure;

2. the method is environment-friendly, material-saving and labor-saving, and omits a temporary support system (temporary upright posts, upright post piles, temporary supports and the like), so that the workload of construction and dismantling of the temporary support system is also omitted, on one hand, the problem of abrupt change of internal force of the support structure in the dismantling support link is avoided, on the other hand, a large amount of building materials and labor cost are saved, and the method is economical and environment-friendly;

3. compared with the traditional reverse construction method, the construction operation environment is greatly improved, the middle part is widely opened, ventilation, lighting, soil emergence and other aspects are greatly improved, most areas are close to the normal operation, in the whole earthwork construction process, about 70% of earthwork can be completed in the middle basin excavation process, the defect of the traditional reverse construction method in the process of subsurface excavation is avoided to the greatest extent, and the construction operation safety is also greatly guaranteed.

Drawings

Fig. 1 is a schematic structural view of the present invention.

Fig. 2 is a flow chart of the construction process of the present invention.

FIG. 3 is a schematic cross-sectional view of a soil matrix node at a beam plate structure in accordance with the present invention.

FIG. 4 is a schematic cross-sectional view of a soil matrix node at an internal shear wall in accordance with the present invention.

FIG. 5 is a schematic plan view of an external shear wall soil matrix node in accordance with the present invention.

FIG. 6 is a schematic cross-sectional view of a soil matrix node at an external shear wall in accordance with the present invention.

Fig. 7 is a schematic plan view of a node of a soil matrix at a frame column in the present invention.

Fig. 8 is a schematic cross-sectional view of a node of a soil matrix at a frame column in accordance with the present invention.

FIG. 9 is a schematic cross-sectional view of the U-shaped drag hook arrangement of the present invention when the earth mold is removed.

Fig. 10 is a schematic plan view of a post-cast frame column top plate reserved concrete casting hole in the invention.

Fig. 11 is a schematic cross-sectional structure of a post-cast frame column flare arrangement in the present invention.

FIG. 12 is a schematic plan view of a post-cast outer shear wall flare arrangement in accordance with the present invention.

FIG. 13 is a schematic cross-sectional view of a post-cast outer shear wall flare arrangement in accordance with the present invention.

FIG. 14 is a schematic cross-sectional view of a post-cast internal shear wall flare arrangement in accordance with the present invention.

Fig. 15 is a schematic view of a basement one-layer wall column structure of a twice-pouring joint according to the present invention.

FIG. 16 is a schematic plan view of the construction of the present invention by the side-to-side half-to-side reverse construction method.

Reference numerals illustrate: the concrete slab comprises a fender post 1, a crown beam 2, a waterproof curtain 3, a basement one-layer beam slab structure 4, a basement one-layer top plate 41, a basement one-layer frame beam 42, a soil moulding 5, plain soil 51, a concrete cushion 52, plywood 53, plywood 531 with reserved dowel grooves or holes, a brick moulding 54, a hidden beam 55, dowel bars 56, a middle coarse sand cushion 57, a waterproof rabbet 58, a reserved soil taking opening 6, secondary slope-releasing passive soil 7, a loose wood pile 8, a basement bottom plate 9, a basement one-layer wall column structure 10, a pre-pouring part 101, a steel pipe support frame 11, a plain concrete cushion 12, two-layer plywood partition 13, a steel bar draw hook 14, a steel bar mesh 15, a bell mouth 16, a top plate blanking hole 17, a top plate force transmission belt 18, an outer shear wall side column 19, an outer shear wall 20, a basement frame column 21, a fertilizer groove 22, a basement inner wall 23, a waterproof bolt 24, a common bolt 25, a gap 26, a reserved back pressure soil side line 27, a basin excavation forward construction region 28 and a reverse construction region 29.

Detailed Description

The invention will be described in detail below with reference to the attached drawings:

examples: as shown in fig. 1 to 16, the deep foundation pit side reverse middle forward and half reverse construction method comprises a fender pile 1, a crown beam 2, a waterproof curtain 3, a basement one-layer beam slab structure 4, a basement one-layer top plate 41, a basement one-layer frame beam 42, a soil moulding bed 5, plain soil 51, a concrete cushion layer 52, a plywood 53, a plywood 531 with reserved dowel grooves or holes, a brick moulding bed 54, a hidden beam 55, a dowel 56, a middle coarse sand cushion layer 57, a waterproof rabbet 58, a reserved soil taking opening 6, a secondary slope-releasing passive soil 7, a loose wood pile 8, a basement bottom plate 9, a basement one-layer wall column structure 10, a pre-pouring part 101, a steel pipe formwork 11, a plain concrete cushion layer 12, two-layer plywood partition strips 13, a steel bar drag hook 14, a steel bar net 15, a bellmouth 16, a top plate blanking hole 17, a top plate force transmission belt 18, an outer wall column 19, a basement outdoor wall 20, a basement frame column 21, a fertilizer slot 22, a basement inner wall 23, a shear basin 24, a common bolt 25, a slit 26, a reverse pressure line 27 and a reverse excavation region 29.

As shown in fig. 1 to 16, the embodiment provides a deep foundation pit edge reverse middle forward and half reverse construction method, which comprises the following steps:

1) Constructing a fender pile 1 and a waterproof curtain 3, wherein the fender pile 1 is used for jacking and digging a groove to the bottom of a crown beam, and constructing the crown beam 2;

2) Excavating soil in a peripheral area of the basement to the bottom of a cushion layer of a first-stage beam plate structure of the basement, constructing the first-stage beam plate structure 4 of the basement by adopting a soil moulding bed 5, constructing the first-stage beam plate structure 4 of the basement by adopting a skip method after the construction of the soil moulding bed 5 is completed, constructing a part of a first-stage wall column structure 101 of the basement in advance by the construction of the beam plate structure 4, and reserving a certain number and a certain size of soil taking openings 6 when constructing the beam plate structure so as to excavate soil in a third stage;

3) Digging the earthwork around the pit edge at the second stage according to two-stage slope-releasing, reserving the passive soil 7 for the two-stage slope-releasing to back pressure, driving three rows of pine piles 8 on a second stage platform for the two-stage slope-releasing, and reserving the soil in the middle area without digging to form basin-type partition digging;

4) After the basin-type excavation of the middle area is completed, the basement bottom plate 9 of the area is constructed by a skip method, and the basement one-layer wall column structure 10 is constructed sequentially;

5) After the construction of the basement bottom plate 9 structure of the middle basin-type excavation area is finished, erecting a steel pipe support die frame 11 in the basement bottom plate 9 and a secondary slope-releasing area, and after pouring of plain concrete cushion layers 12 in the slope-releasing area around and erecting of the steel pipe support die frame 11, constructing a layer of beam plate structure 4 of the basement in the middle area in a partition mode;

6) After the one-layer beam plate structure of the basement reaches the design strength, dismantling the steel pipe support die frame 11, and carrying out third-stage underground excavation by utilizing the reserved soil taking port 6 of the peripheral top plate of the basement;

7) Removing the cushion layer of the soil moulding bed 5 after the soil is excavated, and then constructing a basement wall column structure 10 of the basement in the peripheral area by a bottom plate 9 skip method and performing reverse construction;

8) Processing gaps between the post-cast basement one-layer wall column structure 10 and the pre-cast part 101;

9) The soil sampling port 6 is reserved for sealing the one-layer beam plate structure of the basement.

Referring to fig. 1, in this embodiment, the selection of the fender post 1 and the waterproof curtain 3 needs to be comprehensively considered according to the excavation depth, the surrounding environment and the geological conditions of the foundation pit and by combining regional experience, and the waterproof is fully considered.

Preferably, the width of the groove at the top of the fender post 1 is about 2.0m, slurry at the top of the fender post 1 is chiseled, then a crown beam at the top of the fender post 1 is constructed, the crown beam 2 is poured by reinforced concrete, and the fender post 1 and the crown beam 2 form a rigid connection.

Preferably, the basement one-layer beam slab structure 4 is a horizontal support system of half reverse construction method, the soil moulding bed 5 is utilized to mainly bear the weight of the basement one-layer beam slab structure 4, whether the soil moulding bed 5 can bear the total weight of the structure or not must be fully considered in the construction process, uneven settlement is prevented, and the wood moulding bed can be replaced, so that the apparent quality, flatness and the like of concrete meet the acceptance specification requirements.

Referring to fig. 3, the soil matrix 5 system of the basement one-layer top plate 41 is designed to be plain soil 51, concrete cushion 52, plywood 53 and the basement one-layer top plate 41 from bottom to top.

Preferably, the system of the basement one-layer frame beam 42 without shear walls or frame column soil moulding bed 5 is designed from bottom to top as plain soil 51, concrete cushion 52, plywood 53 and the basement one-layer frame beam 42.

Referring to fig. 4, a soil moulding bed 5 system with an inner shear wall at the beam bottom of a first-layer frame beam 42 of a basement is designed to be plain soil 51 from bottom to top, a middle coarse sand cushion 57 is compacted and leveled, a dowel groove is reserved in a plywood 53, a first-layer shear wall pouring part 101 of the first-layer frame beam 42 of the basement is formed.

Referring to fig. 5 and 6, a soil moulding bed 5 system with an external shear wall at the beam bottom of a layer of frame beam 42 of the basement is designed to be plain soil 51 from bottom to top, a middle coarse sand cushion 57 is compacted and leveled, a dowel groove is reserved in a plywood 53, a water stop tongue-and-groove 58 is reserved, a first pouring part 101 of the external shear wall of the layer of frame beam 42 of the basement is formed. Preferably, a brick die 54 is arranged between the concrete cushion 52 and the plywood 53, a dowel 56 is reserved in the plywood 53, a hidden beam 55 is arranged in the brick die 54, and the dowel 56 penetrates through the hidden beam 55.

Preferably, a water stop tongue and groove strip 58 is arranged on the reserved dowel groove hole plywood 531 of the outdoor shear wall 20 in a penetrating manner so as to increase the hydraulic path and further play a role in stopping water.

Referring to fig. 7 and 8, the soil moulding bed 5 system of the basement one-layer frame column 42 is designed into plain soil 51 from bottom to top, the middle coarse sand cushion 57 is compacted and leveled, the dowel holes are reserved in the plywood 53, the basement one-layer frame column is poured into the part 101 in advance, and the basement one-layer frame beam 42.

Preferably, the first construction of the partial lower-room one-layer wall pillar structure 10 means that when the basement one-layer beam slab structure 4 is cast, the basement one-layer wall pillar structure with the height ranging from 500mm to 1000mm below the bottom is cast together (as the first casting part 101) to form an inverted-L-shaped structure.

Preferably, the beam plate structure 4 of the peripheral area of one layer of the basement is constructed by adopting a skip method, the maximum block size of the skip is not more than 40 m, the skip interval construction time is not less than 7 days, and the skip joint is arranged and treated according to the requirement of a construction joint.

Preferably, the back pressure depth of the secondary slope-releasing passive soil 7 reserved around the area in the middle of the side reverse direction is 16-18 m, the secondary slope-releasing gradient is preferably 1:1.5, three rows of pine piles 8 arranged on the secondary platform are arranged in a quincuncial manner, and the soil slope surface is preferably sprayed with a concrete slope protection inner matched with a bidirectional reinforcement mesh 15 so as to increase the soil slope stability.

Preferably, the basin-type excavation is required to be excavated in a layered mode according to design requirements, because the first-layer (peripheral area) beam plate structure 4 of the basement is constructed during basin-type excavation, stress concentration damage occurs at the internal corner of the first-layer beam plate structure 4 of the basement, which is constructed in advance during basin-type excavation, so that the whole beam plate supporting system is invalid, H-shaped steel is required to be additionally arranged at the corners of the first-layer beam plate structure 4 of the four basements for reinforcement, and the H-shaped steel is fixed with the first-layer beam plate structure 4 of the basement by planting ribs.

Preferably, the basement floor 9 structure of the intermediate basin excavated area and the basement one-storey wall stud structure 10 are constructed according to a conventional forward construction flow.

Preferably, the steel pipe support frame 11 system of the middle basin type excavation area basement bottom plate 9 area is designed into plain soil 51, the basement bottom plate 9 structure, the steel pipe support frame 11, wood purlin, plywood 53 and the basement one-layer beam plate structure 4 of the middle basin type excavation area from bottom to top.

Preferably, the system of the steel pipe support frame 11 in the secondary slope-releasing area is designed into a primary soil 51, a concrete cushion 52, a steel pipe support frame 11, wood beams, plywood 53 and a basement one-layer beam slab structure 4 in the secondary slope-releasing area from bottom to top.

Preferably, in order to facilitate the vertical transportation of construction materials in the earth excavation at the reverse working stage, and simultaneously meet the requirements of natural ventilation and lighting, the reserved soil taking opening 6 is reasonably arranged according to the plane arrangement characteristics of the beam plate support and the support stress condition, and the long width of the reserved soil taking opening 6 is usually set to be a span column distance.

Preferably, the underground excavation is required to excavate in layers, the excavation depth of each layer is not more than 2m, the reserved soil taking opening 6 is excavated in the earthwork, the reserved soil taking opening 6 is excavated to the periphery, the forklift is used for carrying the distal earthwork to the position below the reserved soil taking opening 6, the top plate is turned over by the excavator, the dump truck is used for transporting earthwork, the reserved soil taking opening 6 is excavated to the position 500mm above the surface of the concrete cushion layer 52, and the disturbance of soil below is reduced.

Referring to fig. 9, the construction mode of the soil matrix 5 is different from that of the steel pipe support frame 11, the concrete cushion 52 of the soil matrix 5 is directly and tightly combined with the earthwork to be excavated, great difficulty is brought to the demolition of the soil matrix 5, during the construction of the soil matrix 5, the concrete cushion 52 is divided into small blocks with the thickness of not more than 4.5mx4.5m by using two layers of plywood, the two layers of plywood are divided into two layers of plywood by using two layers of plywood dividing strips 13, the phi 8@250 reinforcing steel meshes 15 are arranged in the range of 2m x 2m in each division, and round steel U-shaped drag hooks (namely reinforcing steel drag hooks 14) of phi 18 are pre-buried in the center of each division, and when the soil matrix 5 is demolished, the concrete cushion 52 is pulled by using special pick heads so as to pull the concrete cushion 52, so that each concrete cushion 52 can fall off integrally, the concrete cushion 52 is prevented from being firmly adhered to one layer of beam plate structure 4 of a basement, and the safety hazards of concrete cushion 52 and the dropping of the plywood 53 are eliminated. The undetached concrete cushion layer 52 falls off due to the impact of the back of the excavator bucket, and is practically left to be dismantled at last, and is removed by a manual work and an air pick.

Referring to fig. 10-14, the main steps of the reverse construction of a basement one-layer (peripheral area) wall stud structure 10 are as follows:

preferably, a 250mm×250mm hole is reserved at the top of a template at one side of the basement frame column 21 and a bell mouth 16 is supported for concrete discharging and is also used as a vibrating mouth, a 300mm×300mm top plate discharging hole 17 is formed on a layer of top plate 4 of the basement in advance, which is 100mm away from the frame column, and concrete is poured into the basement frame column 21 through the top plate discharging hole 17, a baffle plate and the bell mouth 16, and meanwhile, the concrete is vibrated through the bell mouth.

Preferably, 600mm×600mm holes are reserved at intervals of 1500mm at the top of the template at one side of the basement outer shear wall 20 close to the crown beam 2 and horn mouths 16 are supported, if the outer shear wall side columns 19 are required to be provided with a single horn mouth 16 for concrete discharging and vibrating mouths, concrete is poured into the basement outer shear wall 20 through the baffle plates and paths of the horn mouths 16 in the fertilizer slot 22, and meanwhile, the concrete is vibrated through the horn mouths; as shown in fig. 12, a roof strap 18 is provided between the crown beam 2 and the outer shear wall jambs 19.

Preferably, if the shear wall 23 is a post-cast basement, two rows of phi 300@1500mm top plate blanking holes 17 are formed on a layer of top plate 4 of the basement in advance construction at a position 100mm away from the basement shear wall 23, the top plate blanking holes 17 on two sides of the basement shear wall 23 are in one-to-one correspondence with the horn mouths 16, concrete is poured into the basement shear wall 23 on two sides of the basement shear wall 23 through the top plate blanking holes 17, the baffle plates and the paths of the horn mouths 16, and meanwhile, concrete is vibrated through the horn mouths.

Preferably, the basement outer shear wall 20 adopts M14 through-wall water stop bolts 24, which are specially made separable bolts, and 50mm multiplied by 3mm steel plate water stop sheets are welded at the middle part of the screw; the shear wall 23 in the basement adopts M14 common bolts 25.

Referring to fig. 15, the gap 26 between the post-cast basement one-layer wall stud structure 10 and the pre-constructed basement one-layer wall stud structure (i.e., the pre-cast portion 101) is subjected to a compaction grouting treatment.

Preferably, the construction steps of the gap compaction grouting with the thickness of more than 10mm are as follows: measuring and recording gaps, treating the surfaces of the gaps, burying grouting pipes, sealing the gaps, performing sealing inspection, preparing grouting materials, grouting, curing and cleaning.

Preferably, the construction steps of the micro-gap compaction grouting smaller than 10mm are as follows: measuring and recording gaps, treating the surfaces of the gaps, drilling, embedding grouting plugs, closing the gaps, sealing and checking, preparing grouting materials, grouting, curing and cleaning.

Preferably, in the compaction grouting process, firstly observing whether the overflow condition of the grouting liquid exists in a grouting hole or other positions, and if not, indicating that grouting is not completed; observing that the reading of the grouting pump pressure needs to reach a pressure value, if the pressure does not reach 0.4Mpa, indicating that the pressure is insufficient, and continuing grouting; after the sealing is carried out for 10 minutes, secondary grouting is carried out on the grouting hole of the grouting hole, and reciprocating injection is carried out to ensure compactness.

Preferably, as shown in fig. 16, a schematic plan view of a side-reverse middle-forward half-reverse construction is shown, with the inside of the reserved counterpressure soil side line 27 serving as a basin-type excavation forward region 28, and the outside of the reserved counterpressure soil side line 27 serving as a reverse construction region 29. Meanwhile, each reserved soil taking opening 6 is closed by sequentially constructing according to a normal method program after the basement bottom plate 9 is completed.

The construction technology of the peripheral soil-retaining reverse-acting construction basement and the intermediate basin-type excavation forward-acting construction basement has mature theoretical basis and successful practical experience, and the arrangement of the soil with a certain width around the foundation pit in the reverse-acting stage can reduce the deformation of the support piles, improve the stability of the foundation pit, and compared with the construction by singly adopting the forward-acting method or the reverse-acting method, the construction technology is more economical, reasonable and efficient, can greatly shorten the construction period and save the construction cost.

It should be understood that equivalents and modifications to the technical scheme and the inventive concept of the present invention should fall within the scope of the claims appended hereto.

Claims (10)

1. The construction method for the side reverse middle forward and half reverse construction of the deep foundation pit is characterized by comprising the following steps of:

1) Constructing a fender post (1) and a waterproof curtain (3), wherein the fender post (1) is used for jacking and digging a groove to the bottom of a crown beam (2), and constructing the crown beam (2);

2) Excavating soil in a peripheral area of the basement to the bottom of a cushion layer of a first-stage basement layer beam plate structure (4), constructing the first-stage basement layer beam plate structure (4) by adopting a soil moulding bed (5), constructing the first-stage basement layer beam plate structure (4) by a skip method after the soil moulding bed (5) is constructed, constructing the first-stage basement layer beam plate structure (4) by using a part of a first-stage basement layer wall column structure (10) in advance, and taking the first-stage basement layer beam plate structure as a first-pouring part (101), and reserving a certain number and a certain size of reserved soil taking openings (6) when constructing the first-stage basement layer beam plate structure (4) so as to excavate soil in a third stage;

3) Digging earthwork around the pit edge at the second stage according to two-stage slope-releasing, reserving the back pressure of the passive soil (7) for the two-stage slope-releasing, driving three rows of loose wood piles (8) on a second stage platform for the two-stage slope-releasing, and reserving the soil in the middle area without digging to form basin-type partition digging;

4) After the basin-type excavation of the middle area is completed, the basement bottom plate (9) of the area is constructed by a bin-jump method, and a basement one-layer wall column structure (10) is constructed sequentially;

5) After the construction of the basement bottom plate (9) structure of the middle basin-type excavation area is finished, erecting a steel pipe support die frame (11) in the basement bottom plate (9) and the secondary slope-releasing area, pouring the surrounding slope-releasing area to form a plain concrete cushion layer (12), and after the erection of the steel pipe support die frame (11), constructing a basement one-layer beam plate structure (4) of the middle area in a partition mode;

6) After the one-layer beam slab structure (4) of the basement reaches the design strength, dismantling the steel pipe support die frame (11), and performing third-stage underground excavation by utilizing the reserved soil taking openings (6) of the peripheral top plate of the basement;

7) Removing the cushion layer of the soil moulding bed (5) after the soil is excavated, and then constructing a basement wall column structure (10) of the basement in the peripheral area of the basement by a bin-jump method and constructing the area in a reverse way;

8) Processing gaps between a post-cast basement one-layer wall column structure (10) and a pre-cast part (101);

9) And closing the reserved soil taking opening (6) of the one-layer beam plate structure (4) of the basement.

2. The deep foundation pit edge reverse middle forward and half reverse construction method according to claim 1, wherein the method comprises the following steps: in the step 1), the selection of the fender post (1) and the waterproof curtain (3) is comprehensively considered according to the excavation depth, the surrounding environment and the geological conditions of the foundation pit and the combination of regional experiences, the water stop is fully considered, the grooving width of the top of the fender post (1) is 2.0m, the top slurry of the fender post (1) is chiseled, then the crown beam (2) on the top of the fender post (1) is constructed, the crown beam (2) is poured by adopting reinforced concrete, and the fender post (1) and the crown beam (2) form rigid connection.

3. The deep foundation pit edge reverse middle forward and half reverse construction method according to claim 1, wherein the method comprises the following steps: in the step 2), the one-layer beam slab structure (4) of the basement is a horizontal support system of a half reverse construction method, the soil moulding bed (5) is utilized to bear the weight of the one-layer beam slab structure (4) of the basement, the overall weight of the structure can be borne by the soil moulding bed (5) in the construction process, uneven settlement is prevented, and a wood mould platform template can be replaced, so that the apparent mass, flatness and the like of the concrete meet the requirement of acceptance regulations;

in the step 2), the soil moulding bed (5) system of the first layer top plate (41) of the basement is designed to be plain soil (51), concrete cushion (52), plywood (53) and the first layer top plate (41) of the basement from bottom to top;

the system of the soil moulding bed (5) of the basement one layer of frame beam (42) without the shear wall or the frame column at the beam bottom is designed to be plain soil (51), concrete cushion (52), plywood (53) and the basement one layer of frame beam (42) from bottom to top;

the system of a soil moulding bed (5) of a basement one-layer frame beam (42) with an inner shear wall at the beam bottom is designed to be plain soil (51), middle coarse sand cushion layers (57) are tamped and leveled, plywood (53) with reserved dowel grooves, a first pouring part (101) of the inner shear wall of the basement one-layer frame beam (42) from bottom to top;

the method comprises the steps of designing a soil moulding bed (5) system of a basement one-layer frame beam (42) with an outer shear wall at the beam bottom from bottom to top into plain soil (51), tamping and leveling a middle coarse sand cushion layer (57), reserving a plywood (53) with a dowel groove, sealing a water tongue-and-groove strip (58), pouring a basement one-layer outer shear wall first pouring part (101), and pouring a basement one-layer frame beam (42);

the soil moulding bed (5) system of the basement one-layer frame beam (42) is designed to be plain soil (51), middle coarse sand cushion (57) ramming and leveling, plywood (53) with reserved dowel grooves, a basement one-layer frame column pouring part (101) in advance, and the basement one-layer frame beam (42) from bottom to top;

in the step 2), a water stopping tongue-and-groove strip (58) is arranged on a plywood (531) with reserved dowel bar grooves or holes of the basement outer shear wall (20) in a penetrating way so as to increase a hydraulic path and realize water stopping;

in the step 2), the first construction of a part of basement one-layer wall column structure (10) refers to that when the basement one-layer beam plate structure (4) is poured, the basement one-layer wall column structure (10) with the height ranging from 500mm to 1000mm below the bottom is poured together to form an inverted L-shaped structure;

in the step 2), the basement one-layer beam plate structure (4) is constructed by adopting a skip method, the maximum block size of a skip bin is less than or equal to 40 meters, the time of skip bin interval construction is more than or equal to 7 days, and skip bin joints are arranged and treated according to the requirements of construction joints.

4. The deep foundation pit edge reverse middle forward and half reverse construction method according to claim 1, wherein the method comprises the following steps: in the step 3), the back pressure depth of the secondary slope-releasing passive soil (7) reserved around the border area in the side reverse direction is 16-18 m, the gradient of the secondary slope-releasing is 1:1.5, three rows of pine piles (8) which are arranged on the second stage platform are required to be arranged in a quincuncial shape, and the soil slope surface is sprayed with a concrete slope protection and is internally provided with a bidirectional reinforcing steel mesh (15) so as to increase the soil slope stability.

5. The deep foundation pit edge reverse middle forward and half reverse construction method according to claim 1, wherein the method comprises the following steps: in the step 4), the basin-type excavation is required to be excavated in a layered manner according to the design requirement, because the first-layer beam plate structure (4) of the basement is constructed during basin-type excavation, in order to prevent stress concentration damage at the internal corner of the first-layer beam plate structure (4) of the basement which is constructed in advance during basin-type excavation, the whole beam plate supporting system is invalid, H-shaped steel is required to be additionally arranged at the corners of the first-layer beam plate structure (4) of the four basements for reinforcement, and the H-shaped steel is fixed with the first-layer beam plate structure (4) of the basement by planting bars;

in the step 4), the basement bottom plate (9) of the middle basin-type excavation area and the basement one-layer wall column structure (10) are constructed according to the conventional normal method flow.

6. The deep foundation pit edge reverse middle forward and half reverse construction method according to claim 1, wherein the method comprises the following steps: in the step 5), a steel pipe formwork support (11) system in a basement bottom plate (9) area of the middle basin excavation area is designed to be plain soil (51), the basement bottom plate (9), the steel pipe formwork support (11), wood purlin, plywood (53), and a layer of beam plate structure (4) of the basement of the middle basin excavation area from bottom to top; the steel pipe support die frame (11) system of the secondary slope-releasing area is designed to be plain soil (51), concrete cushion (52), steel pipe support die frame (11), wood purlin, plywood (53) and a layer of beam plate structure (4) of the basement of the secondary slope-releasing area from bottom to top.

7. The deep foundation pit edge reverse middle forward and half reverse construction method according to claim 1, wherein the method comprises the following steps: in the step 6), in order to facilitate the earth excavation and the vertical transportation of construction materials in the reverse construction stage, and simultaneously meet the requirements of natural ventilation and lighting, a reserved soil taking opening (6) is reasonably arranged according to the plane arrangement characteristics of the beam plate support and the support stress condition, and the length and the width of the reserved soil taking opening (6) are set to be a column spanning distance;

in the step 6), the underground excavation is required to excavate in layers, the excavation depth of each layer is not more than 2m, the reserved soil taking opening (6) is excavated, the earthwork of the reserved soil taking opening (6) is excavated, the reserved soil taking opening (6) is excavated to the periphery, the forklift is used for transferring the far-side earthwork to the position below the reserved soil taking opening (6), the top plate is turned over by the excavator, the dump truck is used for transporting earthwork, and the reserved soil taking opening (6) is excavated to the position above the surface of the concrete cushion layer (52) by 500mm, so that the disturbance of soil below is reduced.

8. The deep foundation pit edge reverse middle forward and half reverse construction method according to claim 1, wherein the method comprises the following steps: in the step 7), the soil moulding bed (5) is dismantled in a construction mode different from that of the steel pipe support mould frame (11), because the concrete cushion layer (52) of the soil moulding bed (5) is directly and tightly combined with earthwork needing to be excavated, when the soil moulding bed (5) is constructed, the concrete cushion layer (52) is divided into small blocks with the thickness of not more than 4.5mX4.5m by using two layers of plywood, a reinforcing mesh (15) is arranged in the range of 2m X2 m in the center of each block, a reinforcing steel bar drag hook (14) is embedded in the center of each block, when the soil moulding bed (5) is dismantled, a pick is used for hooking the reinforcing steel bar drag hook (14) to pull the concrete cushion layer (52), so that the whole body of each concrete cushion layer (52) falls off, the concrete cushion layer (52) is prevented from being firmly adhered with a layer beam slab structure (4) of a basement, and the safety hazards of falling of the concrete cushion layer (52) and the plywood (53) are eliminated; the undetached concrete cushion layer (52) is detached by adopting the impact of the back of the excavator bucket or is detached by using a pneumatic pick manually;

in the step 7), the reverse construction of the basement one-layer wall column structure (10) comprises the following steps: (1) basement frame column (21): reserving 250mm multiplied by 250mm holes at the top of a template at one side of a basement frame column (21) and supporting a horn mouth (16) for concrete discharging and serving as a vibrating mouth, and arranging a 300mm multiplied by 300mm top plate discharging hole (17) at a position which is 100mm away from the basement frame column (21) on a layer of beam plate structure (4) of a basement in advance construction, wherein concrete is poured into the basement frame column (21) through the top plate discharging hole (17), a baffle plate and a path of the horn mouth (16), and meanwhile, vibrating concrete through the horn mouth (16); (2) basement outer shear wall (20): a 600mm multiplied by 600mm hole is reserved at intervals of 1500mm at the top of a template at one side of the basement outer shear wall (20) close to the crown beam (2) and a horn mouth (16) is supported, if an outer shear wall side column (19) is met, a horn mouth (16) is required to be arranged separately for concrete blanking and is also used as a vibrating mouth, concrete is poured into the basement outer shear wall (20) through a baffle plate and a path of the horn mouth (16) in a fertilizer groove (22), and meanwhile, concrete is vibrated through the horn mouth; (3) shear wall (23) in basement: for a post-pouring basement shear wall (23), two rows of 1500mm roof blanking holes (17) of phi 300 are formed in a position, which is 100mm away from the basement shear wall (23), of a beam plate structure (4) of a basement for previous construction, the roof blanking holes (17) on two sides of the basement shear wall (23) are in one-to-one correspondence with the horn mouths (16), and concrete is poured into the basement shear wall (23) through reserved roof blanking holes (17), baffles and paths of the horn mouths (16) on two sides of the basement shear wall (23), and meanwhile, concrete is vibrated through the horn mouths (16); the shear wall (20) outside the basement adopts a wall penetrating water stopping bolt (24) which is a separable bolt, and a 50mm multiplied by 3mm steel plate water stopping sheet is welded at the middle part of the screw; the shear wall (23) in the basement is provided with a through-wall bolt by adopting a common bolt (25).

9. The deep foundation pit edge reverse middle forward and half reverse construction method according to claim 1, wherein the method comprises the following steps: in the step 8), the gap between the post-cast basement one-layer wall column structure (10) and the pre-cast part (101) is subjected to compaction grouting treatment, and the gap is more than 10mm in compaction grouting, and the concrete steps are as follows: measuring and recording gaps, treating the surfaces of the gaps, burying grouting pipes, sealing the gaps, performing sealing inspection, preparing grouting materials, grouting, curing and cleaning; the micro-gap compaction grouting smaller than 10mm comprises the following specific steps: measuring and recording gaps, treating the surfaces of the gaps, drilling, embedding grouting plugs, closing the gaps, sealing and checking, preparing grouting materials, grouting, curing and cleaning;

in the step 8), firstly observing whether the slurry overflow condition exists in the slurry outlet in the process of compacting grouting, and if not, indicating that grouting is not completed; observing that the reading of the grouting pump pressure needs to reach a pressure value, if the pressure does not reach 0.4Mpa, indicating that the pressure is insufficient, and continuing grouting; after the sealing is carried out for 10 minutes, secondary grouting is carried out on the grouting hole of the grouting hole, and reciprocating injection is carried out to ensure compactness.

10. The deep foundation pit edge reverse middle forward and half reverse construction method according to claim 1, wherein the method comprises the following steps: in the step 9), each reserved soil taking opening (6) is closed by sequentially constructing according to a normal method program after the basement bottom plate (9) is completed.