CN112227380A - Foundation pit support and foundation treatment synergistic effect method, structure and underground structure construction method - Google Patents
Foundation pit support and foundation treatment synergistic effect method, structure and underground structure construction method Download PDFInfo
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- CN112227380A CN112227380A CN202011107282.7A CN202011107282A CN112227380A CN 112227380 A CN112227380 A CN 112227380A CN 202011107282 A CN202011107282 A CN 202011107282A CN 112227380 A CN112227380 A CN 112227380A
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D17/00—Excavations; Bordering of excavations; Making embankments
- E02D17/02—Foundation pits
- E02D17/04—Bordering surfacing or stiffening the sides of foundation pits
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D19/00—Keeping dry foundation sites or other areas in the ground
- E02D19/06—Restraining of underground water
- E02D19/10—Restraining of underground water by lowering level of ground water
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D19/00—Keeping dry foundation sites or other areas in the ground
- E02D19/06—Restraining of underground water
- E02D19/12—Restraining of underground water by damming or interrupting the passage of underground water
- E02D19/18—Restraining of underground water by damming or interrupting the passage of underground water by making use of sealing aprons, e.g. diaphragms made from bituminous or clay material
Abstract
The invention provides a foundation pit supporting and foundation treatment synergistic method and structure, which are used for reinforcing a construction area before foundation pit excavation is carried out in an upper hard and lower soft composite stratum. Determining a foundation pit side line in a construction area, and laying a downcomer well; constructing a precast pile for a passive area of the foundation pit to reinforce the bottom of the foundation pit; laying a waterproof curtain, constructing flexible piles in a passive region of a foundation pit to reinforce the bottom of the foundation pit, constructing foundation pit edge reinforcing bodies along the inner sides of the side lines of the foundation pit, constructing foundation pit inner reinforcing bodies at preset intervals along the longitudinal direction of the foundation pit, and connecting the foundation pit inner reinforcing bodies with the foundation pit edge reinforcing bodies extending along the longitudinal direction of the foundation pit; and attaching the outer side of the foundation pit edge reinforcement body and constructing a fender pile along the side line of the foundation pit. By adopting the synergistic action method and the structure, the technical problem that construction is difficult because construction machinery has to work on a stratum with a soft foundation in the prior art can be solved.
Description
Technical Field
The invention relates to the field of geotechnical engineering, in particular to a foundation pit supporting and foundation treatment synergistic effect method and structure in an upper hard and lower soft composite stratum and an underground structure construction method.
Background
Among the many factors of the underground structure construction environment, the basic geological and engineering geological features are particularly important for the selection of the construction process, especially for engineering construction in complex strata. The composite stratum is formed by two or more different stratums within the excavation section range of underground engineering and in the excavation extension direction. The composite stratum has various types, and in the present specification, the composite stratum refers to a type of combination of different strata in the end face vertical direction, and the upper hard and lower soft composite stratum is one of the strata; on the bearing layer, the stratum structure comprises an upper stratum and a lower stratum with different properties, the upper stratum is mainly a stratum with better water permeability and harder texture such as a fine medium sand layer, and the lower stratum is mainly a stratum with poorer water permeability, high sensitivity and softer texture such as under-consolidated silt.
The method comprises the following steps of carrying out underground structure construction in a composite stratum, for example, carrying out underground structure construction of underground parts of a pipe gallery, an underpass, an airport terminal and a tower, firstly carrying out foundation pit construction, after the foundation pit excavation is finished, constructing the underground structure in the foundation pit, and meeting the requirement of the stability of the foundation pit in the process of foundation pit excavation and underground structure construction. For satisfying foundation ditch stability requirement, in conventional foundation ditch work progress, construct fender pile and passive district reinforcement around the foundation ditch before the foundation ditch excavation usually, then carry out the foundation ditch excavation, carry out foundation treatment in the foundation ditch after the foundation ditch excavation is accomplished and consolidate the basement, then carry out underground structure construction. Because fender pile construction and passive area reinforcement are carried out before foundation pit excavation, the requirement on foundation pit stability in the foundation pit excavation and underground structure construction process can be met.
However, the construction process has defects in the construction of the composite stratum with hard upper and soft lower. The maximum thickness of the upper stratum often cannot meet the requirement of the underground structure on the embedding depth, and the excavation of the foundation pit needs to penetrate through the upper harder stratum and go deep into the lower softer stratum, so that the foundation treatment has to work on a silt layer of the foundation, and because the bearing capacity of the silt layer is low, the construction machinery is difficult to enter the foundation to work, and the foundation reinforcement is very difficult or even impossible to construct.
Disclosure of Invention
The invention aims to provide a foundation pit supporting and foundation treatment synergistic effect method, a foundation pit supporting and foundation treatment synergistic effect structure and an underground structure construction method, and solves the technical problem that construction is difficult or even impossible due to the fact that construction machinery has to work on a foundation with a soft foundation in the prior art.
In order to achieve the purpose, the invention provides a foundation pit supporting and foundation treatment synergistic action method, which is used for reinforcing a construction area before excavation of a foundation pit in an upper hard and lower soft composite stratum, and sequentially comprises the following steps:
step 2, constructing a precast pile for a passive area of the foundation pit to reinforce the bottom of the foundation pit;
step 3, laying a waterproof curtain near the outer side of the side line of the foundation pit; constructing flexible piles in a passive area of a foundation pit to reinforce the bottom of the foundation pit, wherein the flexible piles and the precast piles are alternately arranged at intervals along the longitudinal direction or the transverse direction of the foundation pit, constructing foundation pit edge reinforcing bodies along the inner sides of the side lines of the foundation pit, constructing foundation pit inner reinforcing bodies at intervals of a preset distance along the longitudinal direction of the foundation pit, and connecting the foundation pit inner reinforcing bodies with the foundation pit edge reinforcing bodies which extend along the transverse direction of the foundation pit and are connected with the two sides of the foundation pit and extend along the longitudinal direction of;
and 4, attaching the outer side of the foundation pit edge reinforcing body and constructing a fender post along the side line of the foundation pit.
The invention also provides a construction method of the underground structure, which is used for carrying out the construction of the underground structure in the upper hard and lower soft composite stratum and sequentially comprises the following steps:
step 2, constructing a precast pile for a passive area of the foundation pit to reinforce the bottom of the foundation pit;
step 3, laying a waterproof curtain near the outer side of the side line of the foundation pit; constructing flexible piles in a passive area of a foundation pit to reinforce the bottom of the foundation pit, wherein the flexible piles and the precast piles are alternately arranged at intervals along the longitudinal direction or the transverse direction of the foundation pit, constructing foundation pit edge reinforcing bodies along the inner sides of the side lines of the foundation pit, constructing foundation pit inner reinforcing bodies at intervals of a preset distance along the longitudinal direction of the foundation pit, extending the foundation pit inner reinforcing bodies along the transverse direction of the foundation pit and connecting the foundation pit edge reinforcing bodies extending along the longitudinal direction of the foundation pit at two sides of the foundation pit, and constructing a composite soil body in an active area of the;
step 4, attaching the outer side of the foundation pit edge reinforcing body and constructing a fender post along the side line of the foundation pit;
step 6, constructing an underground structure in the foundation pit;
and 7, backfilling soil bodies below the position of the underground structure butt strap, constructing the butt strap, and backfilling a foundation pit.
The invention also provides a foundation pit supporting and foundation treatment synergistic structure, which is used for reinforcing a construction area before excavation of a foundation pit in an upper hard and lower soft composite stratum, wherein the foundation pit has a foundation pit side line, and the foundation pit supporting and foundation treatment synergistic structure comprises:
the waterproof curtain and the dewatering pipe well are arranged in the construction area;
the precast pile is arranged in the passive area of the foundation pit to reinforce the bottom of the foundation pit;
the flexible piles and the precast piles are alternately arranged at intervals along the longitudinal direction or the transverse direction of the foundation pit;
the foundation pit edge reinforcing body is arranged along the inner side of the side line of the foundation pit;
the foundation pit inner reinforcing bodies extend transversely along the foundation pit and are connected with the foundation pit edge reinforcing bodies extending longitudinally along the foundation pit at two sides of the foundation pit;
and the fender post is attached to the outer side of the foundation pit edge reinforcing body and distributed along the side line of the foundation pit.
Compared with the prior art, the invention has the beneficial effects that:
the synergistic structure and the method for the construction of foundation pit support and foundation treatment before foundation pit excavation can ensure the stability of the soil body in the foundation pit area in the foundation pit excavation and after the excavation, the soil body can be effectively consolidated after the water is drained from the upper stratum, the strength is higher, the construction requirement of construction machinery is met, and the problem that the construction machinery is difficult to work on a silt layer is avoided.
Preferably, in the step 3, a composite soil body is constructed in the active area of the foundation pit; and in the step 4, the fender piles are arranged at intervals by adopting long and short piles. The composite soil body is constructed to reinforce and improve the soil body in the active area, so that the soil pressure of a fender pile system can be reduced, and the fender pile mechanism can be optimized; the long piles and the short piles are arranged at intervals, so that a supporting system can be guaranteed to be stable, a large amount of construction materials are saved, and the construction efficiency is improved.
Preferably, the composite soil body at least comprises a first composite soil body unit and a second composite soil body unit; the first composite soil body unit comprises a first pile body and soil bodies between piles borne by the first pile body, the first pile body is close to the side line of the foundation pit, the pile end of the first pile body extends into the bearing layer, and the second composite soil body unit comprises a second pile body and soil bodies between piles borne by the second pile body; the shortest distance between the longitudinal axis of the second pile body and the side line of the foundation pit is greater than the shortest distance between the longitudinal axis of the first pile body and the side line of the foundation pit, and the pile-soil replacement rate of the second composite soil body unit is less than that of the first composite soil body unit.
Preferably, the composite soil body further comprises a third composite soil body unit, the third composite soil body unit comprises a third pile body and an inter-pile soil body borne by the third pile body, the shortest distance between the longitudinal axis of the third pile body and the side line of the foundation pit is greater than the shortest distance between the longitudinal axis of the second pile body and the side line of the foundation pit, and the pile-soil replacement rate of the third composite soil body unit is less than the pile-soil replacement rate of the second composite soil body unit. The pile-soil replacement rate of the soil body far away from the foundation pit is smaller than that of the soil body near the foundation pit by adjusting the pile-soil replacement rate of the soil body in the active area of the foundation pit, so that a transition effect is achieved for differential settlement of the soil body between the foundation pit and the periphery of a construction area, and the requirement of projects such as airport construction and the like where an underground structure is located on stricter differential settlement of the soil body is effectively met.
Preferably, before the step 2, constructing a cap-off support by using a preset slope height to form a side slope and a cap-off platform, wherein the limited area of the side line of the foundation pit is positioned on the cap-off platform, and the preset slope height is not more than the depth of an upper stratum; and constructing the precast pile, the flexible pile, the foundation pit edge reinforcing body and the foundation pit inner reinforcing body at the cap-picking platform. Compared with other supporting modes, the construction of cap-removing pile support is simpler, and the construction period is shorter; the pile length required by pile bodies such as precast piles, flexible piles, foundation pit edge reinforcing bodies, foundation pit inner reinforcing bodies and the like is reduced in cap-off construction, and a large amount of construction materials are saved.
Preferably, the foundation pit supporting and foundation treatment synergistic structure further comprises a composite soil body arranged in the active area of the foundation pit, and the fender posts are arranged at intervals of long and short posts.
Preferably, the foundation pit supporting and foundation treatment synergistic structure further comprises a cap-picking supporting structure, the cap-picking supporting structure comprises a side slope and a cap-picking platform, the side slope is arranged at a preset slope height, and the preset slope height is not more than the depth of an upper stratum; the foundation pit side line limiting area is located on the cap picking platform, and the precast pile, the flexible pile, the foundation pit edge reinforcing body and the foundation pit inner reinforcing body are arranged at the cap picking platform.
Drawings
In order to illustrate the embodiments of the present invention more clearly, the drawings that are needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious to those skilled in the art that other drawings can be obtained from the drawings without inventive effort.
FIG. 1 is a schematic overall view of a synergistic structure of foundation pit support and foundation treatment in an embodiment of the present invention;
figure 2 is a top view of a synergistic structure of foundation pit support and foundation treatment in an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.
In the following description, the longitudinal direction and the transverse direction of the foundation pit respectively refer to the length direction and the width direction of a plane where the bottom of the foundation pit is located; the longitudinal direction and the transverse direction of the pile body respectively refer to the length direction of the pile body and the direction vertical to the length direction; the inner side and the outer side respectively refer to one side close to the center of the foundation pit and one side far away from the center of the foundation pit; the inner side direction refers to the direction from the center of the foundation pit to the side line of the foundation pit, and the outer side direction refers to the direction from the side line of the foundation pit to the center of the foundation pit; the directions "up", "down", "top", "bottom", etc. are only relative to the orientation of the foundation pit shown in the drawings and vary with the actual orientation of the foundation pit.
The embodiment discloses a foundation pit supporting and foundation treatment synergistic method, which is used for reinforcing a construction area before foundation pit excavation is carried out in an upper hard and lower soft composite stratum, and sequentially comprises the following steps:
step 2, constructing a precast pile for a passive area of the foundation pit to reinforce the bottom of the foundation pit;
step 3, laying a waterproof curtain near the outer side of the side line of the foundation pit; constructing flexible piles in a passive area of a foundation pit to reinforce the bottom of the foundation pit, wherein the flexible piles and the precast piles are alternately arranged at intervals along the longitudinal direction or the transverse direction of the foundation pit, constructing foundation pit edge reinforcing bodies along the inner sides of the side lines of the foundation pit, constructing foundation pit inner reinforcing bodies at intervals of a preset distance along the longitudinal direction of the foundation pit, and connecting the foundation pit inner reinforcing bodies with the foundation pit edge reinforcing bodies which extend along the transverse direction of the foundation pit and are connected with the two sides of the foundation pit and extend along the longitudinal direction of;
and 4, attaching the outer side of the foundation pit edge reinforcing body and constructing a fender post along the side line of the foundation pit.
The side lines of the foundation pit are usually four line segments enclosing a closed rectangular area, and the closed rectangular area is a limited area of the side lines of the foundation pit. The limited area of the side line of the foundation pit is the area of the foundation pit to be excavated, the excavation range of the foundation pit is mainly influenced by diving, and the local part of the foundation pit is influenced by confined water. The characteristics of strong permeability, good water-rich property and large water quantity of the upper submerged stratum are utilized, and the upper stratum adopts a dewatering well to pump and drain shallow water to control underground water; the diving under the water is poor in water permeability due to the fact that silt clay is mixed in the diving under the water, and a water-stopping curtain is arranged behind the fender post pile to control deep water; underground water control is carried out by matching the pit with a dredging well. Wherein, the waterproof curtain can adopt a triaxial deep layer to stir the pile deeply, the pile end goes deep into the effective water-proof layer, and the construction is carried out by adopting a two-stirring two-spraying and one-hole sleeving method. The drainage blind ditch and the drainage well are arranged in advance at the base position, and the drainage blind ditch is arranged along the periphery of the foundation pit area. The dewatering well and the dewatering well adopt a pipe well for dewatering, and the pipe well can adopt a sand-free concrete filter pipe and is protected by bamboo pieces; the filtering material is filled in the filtering pipe range, a nylon net is wrapped outside the filtering pipe range, and the well mouth is sealed and filled with clay balls. Before the foundation pit is excavated, the surface drainage system and the construction area around the foundation pit are hardened and sealed to avoid surface water accumulation.
The foundation pit edge reinforcement body and the foundation pit inner reinforcement body are three-axis stirring piles, and the pile diameter of the pile body, the pile distance, the distance between the foundation pit inner reinforcement bodies, the reinforcement width and the reinforcement depth of the foundation pit edge reinforcement body and the foundation pit inner reinforcement body are selected according to actual conditions. In some embodiments, the depth of the top and the bottom of the foundation pit is 6m and 11m from the ground surface, the length of the foundation pit is 700m, the net width of the foundation pit is 12m, the pile diameter of the three-axis stirring pile is 0.85m, the pile spacing is 1.2m, the in-pit reinforcing depth is 5m, the width of the in-pit reinforcing pile is 3m, and the in-pit reinforcing bodies are constructed at intervals of 12m in the longitudinal direction of the foundation pit to transversely connect the edge reinforcing bodies of the foundation pit at the two sides.
The soil body area outside the fender post is a foundation pit active area, and the fender post deforms under the action of soil pressure in the foundation pit active area; the area of the soil body on the inner side of the fender post is a passive area of the foundation pit, and the fender post is under the action of soil pressure in the passive area of the foundation pit after being deformed. The precast pile is a rigid pile, the pile length of the precast pile can be set according to the fluctuation of stratum bedrock, the pile end enters the bearing layer, and the pile top is provided with a pile cap. In some embodiments, the foundation pit passive area adopts a precast pile and a cement mixing pile combined composite foundation, the length of the cement mixing pile is smaller than that of the precast pile, and the cement strength meets the requirement of foundation treatment strength. In the embodiment, the synergistic structure and the method for supporting the construction foundation pit and treating the foundation before excavation of the foundation pit can ensure the stability of the soil body in the foundation pit area in the excavation of the foundation pit and after excavation, the soil body can be effectively consolidated after dewatering and drainage of the upper stratum, the strength is higher, the construction requirement of construction machinery is met, and the problem that the construction machinery is difficult to work on a silt layer is avoided.
In some preferred embodiments, a reinforced gravel cushion is laid on top of the pile top to further control settlement deformation. The laying process of the reinforced broken stone cushion layer comprises the steps of laying a layer of reinforced material in the cushion layer from the pile cap upwards after a certain thickness of broken stone is laid, and the reinforced broken stone cushion layer can be provided with a plurality of layers; the reinforced material has enough tensile strength, and common materials such as polypropylene double-pull geogrid and the like can be selected as the reinforced material.
Specifically, after the precast pile construction is finished and before the fender pile construction is carried out, a composite soil body is constructed in the active area of the foundation pit; the construction composite soil body is reinforced and improved by changing the pile-soil replacement rate of the foundation pit active area, so that the soil pressure of the fender pile system can be reduced, and the optimization of the fender pile mechanism is facilitated. In some preferred embodiments, the guard piles are arranged at intervals of long piles and short piles, wherein the long piles have the same pile length as that of the commonly used process for arranging the guard piles by using the long piles under the same conditions, and the short piles are the same as the long piles in other aspects except for the short piles; at least one short pile is arranged between at least two long piles, for example, two short piles are respectively arranged on two sides of each long pile, and one long pile is respectively arranged on two sides of each short pile. Compared with the commonly adopted process of arranging the fender pile by using the long pile completely, the process of replacing a part of the long pile by adopting a certain number of short piles can generate adverse effect on the uplift stability of the foundation pit, but because the foundation pit foundation treatment, the active area reinforcement and the passive area reinforcement work are completed before the fender pile is constructed, the uplift of the foundation pit can be effectively inhibited, and meanwhile, the long pile is replaced by the short pile without influencing the overall stability of the foundation pit, so that the stability of a supporting system can be ensured under the condition that the pile distance and the total pile number are the same, compared with the arrangement of the fender pile by using the long pile completely, a large amount of construction materials can be saved, and the construction efficiency can be improved.
Specifically, the composite soil body at least comprises a first composite soil body unit and a second composite soil body unit; the first composite soil body unit comprises a first pile body and soil bodies between piles borne by the first pile body, the first pile body is close to the side line of the foundation pit, the pile end of the first pile body extends into the bearing layer, and the second composite soil body unit comprises a second pile body and soil bodies between piles borne by the second pile body; the shortest distance between the longitudinal axis of the second pile body and the side line of the foundation pit is greater than the shortest distance between the longitudinal axis of the first pile body and the side line of the foundation pit, and the pile-soil replacement rate of the second composite soil body unit is less than that of the first composite soil body unit.
The pile-soil replacement rate is the ratio of the pile volume to the unit volume of the composite soil body. The distance from the longitudinal axis of the pile body to the side lines of the foundation pit is equal to the distance from the point of the longitudinal axis of the pile body on the plane where the four side lines of the foundation pit are located to the side lines of the foundation pit, and the shortest distance from the longitudinal axis of the pile body to the side lines of the foundation pit is the minimum value of a plurality of distances from the longitudinal axis of the pile body to the side lines of the foundation pit.
The longitudinal axis of the first pile body and the longitudinal axis of the adjacent second pile body are mutually symmetrical relative to the interface of the first composite soil body unit and the second composite soil body unit; when the first composite soil body unit is used as the innermost composite soil body unit, the volume of the part of the first composite soil body unit on the inner side of the first pile body is not larger than the volume of the part of the first composite soil body unit on the outer side of the first pile body; when the second composite soil body unit is used as the outermost composite soil body unit, the volume of the part of the second composite soil body unit inside the second pile body is not less than the volume of the part of the second composite soil body unit outside the second pile body. The first pile body and the second pile body can adopt common pile types such as a triaxial stirring pile, a uniaxial deep stirring pile and the like, and the pile diameter is selected according to actual requirements. The composite soil body can comprise one or more first pile bodies, and the shortest distances between the longitudinal axes of the first pile bodies and the side lines of the foundation pit are respectively approximately the same; the composite soil body can comprise one or more second pile bodies, and the longitudinal axes of the second pile bodies are approximately the same as the shortest distance between the side lines of the foundation pit respectively.
The pile-soil replacement rate can be adjusted by changing the slenderness ratio of the pile bodies in the composite soil body unit. In some embodiments, the first composite soil mass unit and the second composite soil mass unit have the same volume, the pile diameters of the first pile body and the second pile body are arranged to be the same, and the pile length of the first pile body is longer than that of the second pile body; in other embodiments, the first composite soil mass unit and the second composite soil mass unit have the same volume, the pile length of the first pile body and the pile length of the second pile body are the same, and the pile diameter of the first pile body is larger than that of the second pile body.
Specifically, the composite soil body further comprises a third composite soil body unit, the third composite soil body unit comprises a third pile body and an inter-pile soil body borne by the third pile body, the shortest distance between the longitudinal axis of the third pile body and the side line of the foundation pit is greater than the shortest distance between the longitudinal axis of the second pile body and the side line of the foundation pit, and the pile-soil replacement rate of the third composite soil body unit is less than the pile-soil replacement rate of the second composite soil body unit.
The longitudinal axis of the second pile body and the longitudinal axis of the adjacent third pile body are symmetrical with each other relative to the interface of the second composite soil body unit and the third composite soil body unit. The third pile body can adopt common pile types such as a triaxial stirring pile, a uniaxial deep stirring pile and the like, and the pile diameter is selected according to actual requirements. The composite soil body can comprise one or more third pile bodies, and the shortest distance between the longitudinal axis of each third pile body and the side line of the foundation pit is approximately the same.
The pile soil replacement rate can be adjusted by changing the pile spacing. In some embodiments, the pile length and the pile diameter of the second pile body and the third pile body are the same, the distance from the longitudinal axis of the first pile body to the longitudinal axis of the adjacent second pile body is smaller than the distance from the longitudinal axis of the second pile body to the longitudinal axis of the adjacent third pile body, so that the volume of the part, on the inner side of the second pile body, of the second soil body unit is smaller than the volume of the part, on the outer side of the second pile body, of the second soil body unit, the volume of the part, on the outer side of the second pile body, of the second soil body unit is the same as the volume of the part, on the inner side of the third pile body, of the third soil body unit, the volume of the part, on the inner side of the third pile body, of the third soil body unit is not smaller than the volume of the part, on the outer side of the third pile body, and therefore, the volume of the third composite soil body unit is larger than the volume of the second soil body, so. Similarly, at this time, the pile-soil replacement rate of the second composite soil body unit is smaller than that of the first composite soil body unit.
In each composite soil body unit, the upper load is jointly born by the pile body and the soil body between the piles born by the pile body, the higher the pile soil replacement rate is, the higher the load born by the pile body is, the smaller the integral compression modulus of the composite soil body unit is, and the smaller the settlement is. The pile-soil replacement rate of the soil body in the active area of the foundation pit is adjusted, so that the pile-soil replacement rate of the soil body far away from the foundation pit is smaller than that of the soil body near the foundation pit, a transition effect is achieved for differential settlement of the soil body between the foundation pit and the periphery of a construction area, and the requirement of projects such as airport construction and the like where an underground structure is located on more strict differential settlement of the soil body is effectively met. Therefore, those skilled in the art can easily understand that when more composite soil units with different distances from the side line of the foundation pit need to be arranged in the construction process, the composite soil units with proper pile-soil replacement rate can still be obtained through the adjustment of the method.
Specifically, before the step 2, a preset slope height is used for constructing a cap-removing support to form a side slope and a cap-removing platform, the limited area of the side line of the foundation pit is located on the cap-removing platform, the preset slope height is not more than the depth of an upper stratum, and the precast pile, the flexible pile, the foundation pit edge reinforcing body and the foundation pit inner reinforcing body are constructed at the cap-removing platform.
The range of the side slope and the cap-removing platform covers the main construction area of the foundation pit, including the active area and the passive area of the foundation pit. In some preferred embodiments, the composite soil mass is constructed at a decapping platform.
On one hand, because the upper stratum is hard, the side slope and the cap-removing platform have stronger stability, the requirements of foundation pit reinforcement and excavation construction can be met, and compared with other support methods, the cap-removing pile support construction is simpler and the construction period is shorter; on the other hand, the pile length required by pile bodies such as precast piles, flexible piles, foundation pit edge reinforcing bodies, foundation pit inner reinforcing bodies and the like is reduced in cap-off construction, and a large amount of construction materials are saved.
The embodiment discloses an underground structure construction method, which is used for carrying out underground structure construction in a hard upper soft lower soft composite stratum and sequentially comprises the following steps:
step 2, constructing a precast pile for a passive area of the foundation pit to reinforce the bottom of the foundation pit;
step 3, laying a waterproof curtain near the outer side of the side line of the foundation pit; constructing flexible piles in a passive area of a foundation pit to reinforce the bottom of the foundation pit, wherein the flexible piles and the precast piles are alternately arranged at intervals along the longitudinal direction or the transverse direction of the foundation pit, constructing foundation pit edge reinforcing bodies along the inner sides of the side lines of the foundation pit, constructing foundation pit inner reinforcing bodies at intervals of a preset distance along the longitudinal direction of the foundation pit, extending the foundation pit inner reinforcing bodies along the transverse direction of the foundation pit and connecting the foundation pit edge reinforcing bodies extending along the longitudinal direction of the foundation pit at two sides of the foundation pit, and constructing a composite soil body in an active area of the;
step 4, attaching the outer side of the foundation pit edge reinforcing body and constructing a fender post along the side line of the foundation pit;
step 6, constructing an underground structure in the foundation pit;
and 7, backfilling soil bodies below the position of the underground structure butt strap, constructing the butt strap, and backfilling a foundation pit.
The underground structure may be a common underground structure such as a pipe gallery, underpass, underground portion of terminal building and tower. In some embodiments, as shown in fig. 1, as the excavation of the excavation proceeds, two supports 8 are provided at the depths of the top and middle of the excavation, respectively, to increase the stability of the excavation. Although the supports are shown as described above, it will be appreciated that the number and location of the support arrangements may be adjusted according to the needs of the actual project.
And after the soil body under the position of the underground structure slab is backfilled to the position of the slab, carrying out slab construction and backfilling the foundation pit. The foundation pit backfill can be made of stone chips, gravel soil, plain soil in the ground and the like. The method of laying geosynthetic material in the backfill soil body below the underground structure butt strap, laying geosynthetic material in a certain range of backfill top surface extension and the like can be adopted, so that the differential settlement between foundation pit backfill and the periphery is reduced.
As shown in fig. 1 and 2, the present embodiment discloses a synergistic structure of a foundation pit support and a foundation treatment, which is used for reinforcing a construction area before excavation of a foundation pit in a composite stratum with hard upper and soft lower layers,
a waterproof curtain 21 and a downcomer well 22 arranged in the construction area;
the precast pile 31 is arranged in the foundation pit passive area 12 to reinforce the bottom of the foundation pit;
the flexible piles 32 are arranged in the foundation pit passive area 12 to reinforce the bottom of the foundation pit, and the flexible piles 32 and the precast piles 31 are alternately arranged at intervals along the longitudinal direction or the transverse direction of the foundation pit;
the foundation pit edge reinforcing body 41 is arranged on the inner side along the foundation pit side line 11;
the foundation pit inner reinforcing bodies 42 are distributed at intervals of a preset distance along the longitudinal direction of the foundation pit, and the foundation pit inner reinforcing bodies 42 extend transversely along the foundation pit and are connected to the foundation pit edge reinforcing bodies 41 extending longitudinally along the foundation pit at two sides of the foundation pit 1;
and the fender post 5 is attached to the outer side of the foundation pit edge reinforcing body 41 and distributed along the foundation pit sideline 11.
Specifically, the foundation pit supporting and foundation treatment synergistic structure further comprises a composite soil body arranged in the foundation pit active area 13, and the fender posts 5 are arranged at intervals of long and short posts.
Specifically, the composite soil body at least comprises a first composite soil body unit and a second composite soil body unit; the first composite soil body unit comprises a first pile body 61 and the soil body between piles borne by the first pile body 61, the first pile body 61 is close to the side line 11 of the foundation pit, the pile end of the first pile body 61 goes deep into the bearing layer, and the second composite soil body unit comprises a second pile body 62 and the soil body between piles borne by the second pile body 62; the shortest distance between the longitudinal axis of the second pile body 62 and the side line 11 of the foundation pit is greater than the shortest distance between the longitudinal axis of the first pile body 61 and the side line 11 of the foundation pit, and the pile-soil replacement rate of the second composite soil body unit is less than that of the first composite soil body unit.
Specifically, the composite soil body further includes a third composite soil body unit, the third composite soil body unit includes a third pile body 63 and an inter-pile soil body borne by the third pile body 63, a shortest distance between a longitudinal axis of the third pile body 63 and the side line 11 of the foundation pit is greater than a shortest distance between a longitudinal axis of the second pile body 62 and the side line 11 of the foundation pit, and a pile-soil replacement rate of the third composite soil body unit is less than a pile-soil replacement rate of the second composite soil body unit.
Specifically, the foundation pit supporting and foundation treatment synergistic structure further comprises a cap-picking supporting structure, the cap-picking supporting structure comprises a side slope 71 and a cap-picking platform 72, the side slope 71 is arranged at a preset slope height, and the preset slope height is not more than the depth of an upper stratum; the limited area of the foundation pit sideline 11 is positioned on the cap removing platform 72, and the precast pile 31, the flexible pile 32, the foundation pit edge reinforcing body 41 and the foundation pit inner reinforcing body 42 are arranged at the cap removing platform 72.
It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all 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.
Claims (11)
1. A foundation pit supporting and foundation treatment synergistic effect method is used for reinforcing a construction area before foundation pit excavation is carried out in an upper hard and lower soft composite stratum, and sequentially comprises the following steps:
step 1, determining a foundation pit side line in a construction area, and laying a downcomer well;
step 2, constructing a precast pile for a passive area of the foundation pit to reinforce the bottom of the foundation pit;
step 3, laying a waterproof curtain near the outer side of the side line of the foundation pit; constructing flexible piles in a passive area of a foundation pit to reinforce the bottom of the foundation pit, wherein the flexible piles and the precast piles are alternately arranged at intervals along the longitudinal direction or the transverse direction of the foundation pit, constructing foundation pit edge reinforcing bodies along the inner sides of the side lines of the foundation pit, constructing foundation pit inner reinforcing bodies at intervals of a preset distance along the longitudinal direction of the foundation pit, and connecting the foundation pit inner reinforcing bodies with the foundation pit edge reinforcing bodies which extend along the transverse direction of the foundation pit and are connected with the two sides of the foundation pit and extend along the longitudinal direction of;
and 4, attaching the outer side of the foundation pit edge reinforcing body and constructing a fender post along the side line of the foundation pit.
2. The foundation pit supporting and foundation treatment synergistic effect method according to claim 1, wherein in the step 3, a composite soil body is constructed in the active area of the foundation pit; and in the step 4, the fender piles are arranged at intervals by adopting long and short piles.
3. The method of claim 2, wherein the composite soil comprises at least a first composite soil element and a second composite soil element; the first composite soil body unit comprises a first pile body and soil bodies between piles borne by the first pile body, the first pile body is close to the side line of the foundation pit, the pile end of the first pile body extends into the bearing layer, and the second composite soil body unit comprises a second pile body and soil bodies between piles borne by the second pile body; the shortest distance between the longitudinal axis of the second pile body and the side line of the foundation pit is greater than the shortest distance between the longitudinal axis of the first pile body and the side line of the foundation pit, and the pile-soil replacement rate of the second composite soil body unit is less than that of the first composite soil body unit.
4. The method of claim 3, wherein the composite soil further comprises a third composite soil unit, wherein the third composite soil unit comprises a third pile and an inter-pile soil borne by the third pile, wherein the shortest distance between the longitudinal axis of the third pile and the side line of the foundation pit is greater than the shortest distance between the longitudinal axis of the second pile and the side line of the foundation pit, and wherein the pile-soil replacement rate of the third composite soil unit is less than the pile-soil replacement rate of the second composite soil unit.
5. The foundation pit support and foundation treatment synergistic effect method according to claim 1-4, wherein before the step 2, a cap removing support is constructed at a preset slope height to form a side slope and a cap removing platform, the limited area of the foundation pit side line is positioned on the cap removing platform, and the preset slope height does not exceed the depth of an upper stratum; and constructing the precast pile, the flexible pile, the foundation pit edge reinforcing body and the foundation pit inner reinforcing body at the cap-picking platform.
6. The underground structure construction method is used for carrying out underground structure construction in a hard-upper soft-lower soft composite stratum and sequentially comprises the following steps:
step 1, determining a foundation pit side line in a construction area, and laying a downcomer well;
step 2, constructing a precast pile for a passive area of the foundation pit to reinforce the bottom of the foundation pit;
step 3, laying a waterproof curtain near the outer side of the side line of the foundation pit; constructing flexible piles in a passive area of a foundation pit to reinforce the bottom of the foundation pit, wherein the flexible piles and the precast piles are alternately arranged at intervals along the longitudinal direction or the transverse direction of the foundation pit, constructing foundation pit edge reinforcing bodies along the inner sides of the side lines of the foundation pit, constructing foundation pit inner reinforcing bodies at intervals of a preset distance along the longitudinal direction of the foundation pit, extending the foundation pit inner reinforcing bodies along the transverse direction of the foundation pit and connecting the foundation pit edge reinforcing bodies extending along the longitudinal direction of the foundation pit at two sides of the foundation pit, and constructing a composite soil body in an active area of the;
step 4, attaching the outer side of the foundation pit edge reinforcing body and constructing a fender post along the side line of the foundation pit;
step 5, excavating a foundation pit, excavating the limited area of the side line of the foundation pit to a preset depth, and arranging a support in the width direction of the foundation pit;
step 6, constructing an underground structure in the foundation pit;
and 7, backfilling soil bodies below the position of the underground structure butt strap, constructing the butt strap, and backfilling a foundation pit.
7. Excavation supporting and foundation treatment synergism structure for consolidate the construction area before carrying out excavation of foundation ditch in soft composite stratum under last hardness, the foundation ditch has the foundation ditch sideline, excavation supporting and foundation treatment synergism structure include:
the waterproof curtain and the dewatering pipe well are arranged in the construction area;
the precast pile is arranged in the passive area of the foundation pit to reinforce the bottom of the foundation pit;
the flexible piles and the precast piles are alternately arranged at intervals along the longitudinal direction or the transverse direction of the foundation pit;
the foundation pit edge reinforcing body is arranged along the inner side of the side line of the foundation pit;
the foundation pit inner reinforcing bodies extend transversely along the foundation pit and are connected with the foundation pit edge reinforcing bodies extending longitudinally along the foundation pit at two sides of the foundation pit;
and the fender post is attached to the outer side of the foundation pit edge reinforcing body and distributed along the side line of the foundation pit.
8. The foundation pit supporting and foundation treatment cooperative structure as recited in claim 7, further comprising a composite soil body disposed in the active area of the foundation pit, wherein the fender piles are arranged at intervals.
9. The synergistic structure for foundation pit support and foundation treatment as claimed in claim 8, wherein the composite soil comprises at least a first composite soil unit and a second composite soil unit; the first composite soil body unit comprises a first pile body and soil bodies between piles borne by the first pile body, the first pile body is close to the side line of the foundation pit, the pile end of the first pile body extends into the bearing layer, and the second composite soil body unit comprises a second pile body and soil bodies between piles borne by the second pile body; the shortest distance between the longitudinal axis of the second pile body and the side line of the foundation pit is greater than the shortest distance between the longitudinal axis of the first pile body and the side line of the foundation pit, and the pile-soil replacement rate of the second composite soil body unit is less than that of the first composite soil body unit.
10. The synergistic structure for supporting and foundation treatment of a foundation pit of claim 9, wherein the composite soil further comprises a third composite soil unit, the third composite soil unit comprises a third pile and an inter-pile soil borne by the third pile, the shortest distance between the longitudinal axis of the third pile and the boundary of the foundation pit is greater than the shortest distance between the longitudinal axis of the second pile and the boundary of the foundation pit, and the pile-soil replacement rate of the third composite soil unit is less than the pile-soil replacement rate of the second composite soil unit.
11. The foundation pit supporting and foundation treatment synergistic structure as claimed in claims 7-10, further comprising a uncapped supporting structure, wherein the uncapped supporting structure comprises a side slope and an uncapped platform, the side slope is arranged at a preset slope height, and the preset slope height does not exceed the upper stratum depth; the foundation pit side line limiting area is located on the cap picking platform, and the precast pile, the flexible pile, the foundation pit edge reinforcing body and the foundation pit inner reinforcing body are arranged at the cap picking platform.
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| CN114086566A (en) * | 2021-11-10 | 2022-02-25 | 中铁第四勘察设计院集团有限公司 | Long and narrow soft soil foundation pit excavation support and soil transportation method |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114086566A (en) * | 2021-11-10 | 2022-02-25 | 中铁第四勘察设计院集团有限公司 | Long and narrow soft soil foundation pit excavation support and soil transportation method |
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