CN114134903B - Deep and large foundation pit soil body advanced reinforcement method in soft soil area based on horizontal freezing method - Google Patents
Deep and large foundation pit soil body advanced reinforcement method in soft soil area based on horizontal freezing method Download PDFInfo
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- CN114134903B CN114134903B CN202111512611.0A CN202111512611A CN114134903B CN 114134903 B CN114134903 B CN 114134903B CN 202111512611 A CN202111512611 A CN 202111512611A CN 114134903 B CN114134903 B CN 114134903B
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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
- E02D3/00—Improving or preserving soil or rock, e.g. preserving permafrost soil
- E02D3/11—Improving or preserving soil or rock, e.g. preserving permafrost soil by thermal, electrical or electro-chemical means
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Abstract
The invention provides a horizontal freezing method-based advanced reinforcement method for a deep and large foundation pit soil body in a soft soil area, which comprises the following steps: leveling a construction site, constructing a surrounding structure around a foundation pit, constructing a shaft supporting structure, and excavating a soil body in a shaft; when the design bottom surface of the first layer of freezing and reinforcing area is excavated, horizontally driving freezing pipes to two sides of the design bottom surface of the first layer of freezing and reinforcing area until the position of the foundation pit enclosure structure, arranging freezing equipment, and continuing excavating; and repeating the steps, arranging a freezing pipe and freezing equipment after excavating to the bottom surface of the last layer of freezing and reinforcing area, starting to freeze the soil layer, and constructing the concrete horizontal support of the foundation pit. The method changes the conventional vertical freezing method into the horizontal freezing method, is used for the advanced reinforcement of the deep and large foundation pit soil body in the soft soil area, can improve the advanced reinforcement efficiency of the foundation pit soil body, improves the reinforcement effect of the foundation pit, realizes green and low-carbon construction, and reduces the influence of the freezing pipe on the excavation operation of the foundation pit.
Description
Technical Field
The invention belongs to the technical field of foundation pit reinforcement, and particularly relates to an advanced reinforcement method for a deep and large foundation pit soil body in a soft soil area based on a horizontal freezing method.
Background
In the foundation pit engineering of a soft soil area, in order to enhance the stability of a foundation pit supporting system, effectively control the deformation of the foundation pit supporting system, a nearby road, a pipeline and a building (structure) in the process of excavating a foundation pit, and create conditions for field construction and earthwork excavation, the foundation pit soil body is usually considered to be reinforced. Usually, modes such as cement soil mixing piles, high-pressure jet grouting piles, grouting, precipitation and the like are adopted, wherein the precipitation is only suitable for silty soil or sandy soil strata. In the foundation pit soil body reinforcement, the common method is to carry out in-situ reinforcement on the soil body at the bottom of the foundation pit, so that the soft soil at the bottom of the foundation pit forms cement soil with higher strength and larger modulus, the horizontal deformation resistance of the soil body at the bottom of the foundation pit is improved, and the foundation pit excavation safety is ensured. However, for the deep and large foundation pit engineering in the soft soil area requiring multiple horizontal supports, the deformation control requirement of the foundation pit supporting structure can not be met only by reinforcing the foundation pit bottom soil body: when the upper layer of soil has been excavated and the next horizontal brace has not been formed, the supporting structure of the foundation pit is deformed beyond the allowable value during the excavation. Therefore, advanced reinforcement of the foundation pit soil within the excavation depth range is also required.
Foundation pit soil body reinforcement is a temporary foundation treatment measure which plays a role during foundation pit excavation construction, and soil bodies located in an excavation depth range only play a role before a horizontal support is not formed, and are excavated and transported outside. The adoption of the traditional foundation treatment measures such as cement soil mixing piles, high-pressure jet grouting piles and the like needs to consume a large amount of cement, lime and other solidification materials, the cement and the lime belong to high-energy-consumption building materials, and a large amount of carbon emission is generated in the production process. Under the carbon peak carbon neutral and large background, the advanced reinforcement method for the foundation pit engineering also puts forward the requirements of more green energy conservation and ecological environmental protection, and the traditional treatment measures face more and more limitations. Meanwhile, the foundation pit soil body reinforcement is usually constructed after the construction of the main structure engineering pile, the surrounding enclosure structure, the in-pit upright post pile and other structures is completed and before the foundation pit is excavated, and the design strength requirement is met before the foundation pit is excavated to the corresponding elevation. Therefore, the construction efficiency and the solidification effect of foundation pit soil reinforcement directly affect the total construction period of engineering construction, and a low-carbon environment-friendly method suitable for advanced reinforcement of deep and large foundation pit soil in soft soil areas needs to be developed to ensure construction safety and can carry out foundation pit soil excavation as soon as possible.
The principle of freezing method for reinforcing stratum is to freeze water in soft soil stratum by using artificial refrigeration technology to increase its strength and stability. If the freezing pipes are arranged at appropriate intervals, the adjacent frozen soil columns are continuously enlarged and connected to form a continuous frozen soil wall or a closed frozen soil structure. A large number of domestic and foreign freezing engineering practices show that the freezing method has the advantages of good safety and reliability, wide application range, good controllability, small pollution, economy, reasonability and the like, and along with the increase of the reinforcement depth, the economy of the freezing method is more obvious compared with a stirring method or a rotary spraying method. Particularly, the largest pollution of freezing construction is that a small amount of slurry is discharged when a freezing pipe is buried in a drill hole, no harmful substance is injected into a stratum in the freezing process, the stratum naturally melts and recovers to the original state after the engineering is finished, and any underground barrier which can obstruct other engineering construction can not be left in the stratum. As a green construction method, the method is very in line with the development trend of low-carbon and environment-friendly geotechnical engineering.
Disclosure of Invention
In order to solve the technical problems in the background art, the invention provides a method for reinforcing the soil body of the deep and large foundation pit in the soft soil area in advance based on a horizontal freezing method, and solves the problems that in the prior art, in the excavation process of the deep and large foundation pit in the soft soil area, a foundation pit supporting structure is easy to deform, the construction efficiency for reinforcing the soil body of the foundation pit is low, and the environment is easily adversely affected.
In order to achieve the purpose, the invention adopts the following technical scheme:
a horizontal freezing method-based advanced reinforcement method for deep and large foundation pit soil bodies in soft soil areas comprises the following steps:
the method comprises the following steps: leveling a construction site, constructing a surrounding structure around a foundation pit, constructing a shaft supporting structure, and excavating a soil body in a shaft;
step two: when the design bottom surface of the first layer of freezing and reinforcing area is excavated, horizontally driving freezing pipes to two sides of the design bottom surface of the first layer of freezing and reinforcing area until the position of the foundation pit enclosure structure, arranging freezing equipment, and continuing excavating;
step three: repeating the second step, arranging freezing pipes and freezing equipment after excavating to the bottom surface of the last layer of freezing and reinforcing area, starting to freeze the soil layer, and constructing a first horizontal support of the foundation pit;
s01: after the first horizontal support is arranged and the lower foundation soil of the second horizontal support reaches the designed freezing thickness and freezing strength, excavating the lower soil body of the first horizontal support in the foundation pit, and then constructing the second horizontal support of the foundation pit;
s02: after the second horizontal support is arranged, unfreezing the soil body of the first layer of freezing reinforcement area at the lower part of the second horizontal support, and pulling out a freezing pipe;
s03: after the lower foundation soil of the third horizontal support reaches the designed freezing thickness and freezing strength, continuing to excavate the lower soil body of the second horizontal support in the foundation pit, and then constructing the third horizontal support of the foundation pit;
s04: the step S02 to the step S03 are repeated until the foundation pit is excavated to the bottom;
s05: and thawing the soil body of the freezing and reinforcing area below the pit bottom, taking out the freezing pipe and the freezing equipment, and backfilling the vertical shaft to be compact to complete the construction of the foundation pit bottom plate.
Optionally, the construction of the shaft supporting structure adopts any one or more of a cement-soil gravity type enclosure wall, a profile steel cement-soil mixing wall and a row pile according to the excavation depth and the foundation soil condition. The plane size of the vertical shaft should meet the requirements of the rig erection and operation space of the horizontal freezing hole drill, and is generally not smaller than 2m. The construction of the vertical shaft is carried out after the construction of the main structure engineering pile is finished, and the pile position of the vertical column pile is preferably avoided.
Optionally, the horizontal freezing method construction comprises three stages: freezing station installation, horizontal freezing pipe construction and stratum freezing. The freezing station comprises a compressor, a condenser and an evaporator which are connected with the compressor, a throttle valve arranged on the condenser, a cooler arranged between the condenser and the evaporator and a brine circulating system.
Optionally, the brine circulating system includes a brine tank, a brine pump connected to the brine tank, and a main brine pipe installed on the brine pump, the main brine pipe is provided with a liquid distribution ring, a freezer and a liquid collection ring, and one side of the brine tank is provided with a main brine pipe. Flow meters are arranged at the inlet and outlet of the brine main pipe of the outgoing path, the brine main pipe of the return path and the freezer.
Optionally, the freezer comprises a freezing pipe, a liquid supply pipe and a liquid return pipe connected with the freezing pipe.
The horizontal freezing pipe construction process sequentially comprises the following steps: drilling horizontal frozen holes → arranging freezers in the frozen holes → connecting the freezers in different frozen holes into a system and connecting with a freezing station. The horizontal freezing pipe construction and the shaft excavation and shaft supporting structure construction are carried out alternately, and the construction organization design is carried out reasonably.
And drilling the horizontal freezing hole by adopting a pipe-following drilling construction technology. When the horizontal freezing hole is drilled, a compass and a theodolite are adopted to find an inclination angle and an azimuth angle. The horizontal freezing hole drilling process must be subjected to inclination measurement and deviation correction so as to ensure the quality of the formed hole of the freezing hole. And after all the drill holes are qualified through inspection, the drilling machine can be detached.
Optionally, the freezing pipe is made of a material with good heat conduction and low-temperature performance, the outer diameter of the freezing pipe is 89-127mm, and the thickness of the pipe wall is more than or equal to 5mm.
Optionally, the configuration of the freezing pipes is determined according to the thickness of a frozen soil layer and the conditions and the construction period of foundation soil, the distance between single rows of freezing pipes is 1.0-2.5m, and the distance between two or more rows of auxiliary freezing pipes is 3m. For soft foundation with high water content and tight construction period, the distance between the freezing pipes is preferably reduced correspondingly.
Optionally, the freezing pipes in the rows are preferably arranged in a plum blossom shape.
Optionally, during the formation freezing period, the temperature and flow of the circulating brine, the temperature of the frozen soil area, the ground frost heaving amount, the deformation of the foundation pit supporting structure and the like are detected and monitored at regular time.
Optionally, after the first horizontal support is arranged, the foundation pit excavation should be performed after the foundation soil at the lower part of the second horizontal support reaches the designed freezing thickness and freezing strength. The excavation of the foundation pit is strictly carried out according to the requirements of layered excavation and strict over excavation prohibition, and the freezing pipeline is protected. After the foundation pit is excavated to the second horizontal support position, the second horizontal support is arranged in time, and meanwhile, appropriate heat preservation measures are taken for the ground.
Optionally, after the second horizontal support is set, the stop time of the freezing equipment can be reasonably determined according to the concrete strength increase rule for the concrete horizontal support, and the concrete horizontal support is naturally thawed. In the thawing process, the monitoring frequency of internal force and deformation of the foundation pit supporting structure is properly encrypted, an axial force monitoring sensor can be arranged in the support if necessary, and a treatment measure can be taken in time when abnormal conditions are found.
Optionally, the enclosure structure around the foundation pit can be an occlusive pile, a profile steel cement soil mixing wall, a steel sheet pile, an underground continuous wall, a freezing wall and other various types. The pit bottom passive area (without excavation) of the foundation pit can be reinforced by adopting the conventional cement-soil stirring method, high-pressure rotary spraying method and other in-situ stirring and reinforcing technologies, and is matched with the horizontal freezing method of an excavation section for advanced reinforcement, or the two methods are flexibly combined for use.
The embodiment of the invention has the following beneficial effects:
the method comprises the steps of 1) changing a conventional vertical freezing method into a horizontal freezing method through arranging a vertical shaft in a foundation pit, so that a freezing pipe can drill horizontally at different depths of a stratum to form horizontal continuous freezing bodies at different depths, the advanced reinforcement effect of a freezing reinforcement area on a foundation pit support structure is exerted, and the excessive deformation of a deep and large foundation pit support system in a soft soil area is prevented; 2) The horizontal freezing method is applied to the field of advanced reinforcement of foundation pits, can be unfrozen layer by layer along with the excavation process of the foundation pits, is particularly suitable for reinforcement of an excavation section, has small disturbance on an in-situ soil body, has no adverse effect on excavation construction, reduces the consumption of a large amount of high-energy-consumption building materials such as cement and lime, and the like, has wide application range, good controllability, small pollution, economy and reasonability, and has obvious advantages in construction methods such as deeper cement mixing piles and the like.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate embodiment(s) of the invention and together with the description serve to explain the invention and not to limit the invention. In the drawings:
FIG. 1 is a schematic plan view of a grid reinforcement according to an embodiment of the present invention;
FIG. 2 is a schematic plan view of a strip reinforcement according to an embodiment of the present invention;
FIG. 3 is a schematic plan view of a reinforcement area according to an embodiment of the present invention;
FIG. 4 is a schematic view of a reinforced area structure according to an embodiment of the present invention;
FIG. 5 is a schematic view of a plane for advanced reinforcement of a foundation pit soil body according to an embodiment of the present invention;
FIG. 6 is a schematic view of a support according to an embodiment of the present invention;
FIG. 7 is a cross-sectional view of a support according to an embodiment of the present invention;
fig. 8 is a schematic view of a foundation pit bottom structure according to an embodiment of the invention;
fig. 9 is a schematic cross-sectional view illustrating advanced reinforcement of a foundation pit soil body according to an embodiment of the present invention.
Wherein the figures include the following reference numerals:
1-a building enclosure, 2-a reinforcing area, 3-a freezing reinforcing area, 4-a vertical shaft, 5-a foundation pit bottom, 6-a concrete horizontal support, 7-a first horizontal support, 8-a second horizontal support and 9-a third horizontal support.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses.
In order to keep the following description of the embodiments of the invention clear and concise, a detailed description of known functions and known parts of the invention is omitted.
Referring to fig. 1 to 9, in the present embodiment, a method for reinforcing a deep and large foundation pit soil body in a soft soil area in advance based on a horizontal freezing method is provided, including: the method comprises the following steps:
the method comprises the following steps: leveling a construction site, constructing the enclosure structure 1 around the foundation pit, constructing the supporting structure of the vertical shaft 4, and excavating the soil body in the vertical shaft 4. The construction of the vertical shaft 4 supporting structure adopts any one or more of a cement-soil gravity type enclosure wall, a profile steel cement-soil mixing wall and a row pile according to the excavation depth and foundation soil conditions, the plane shape of the vertical shaft 4 can be rectangular or circular, the plane size of the vertical shaft 4 can meet the requirements of the erection and operation space of a drilling machine of a horizontal freezing hole drill, and the plane size is generally not less than 2m. The construction of the vertical shaft 4 is carried out after the construction of the engineering pile of the main structure is finished, and the pile position of the vertical column pile is preferably avoided;
through the vertical shaft 4, freezing pipes can be horizontally arranged at different depth positions of a soft soil area, a strip-shaped frozen soil continuum is formed in the horizontal direction, and a grid-type or strip-pulling-type reinforcing area 2 is formed in a passive area of a foundation pit supporting structure, so that the effect of controlling deformation is achieved during foundation pit excavation;
step two: when the designed bottom surface of the first layer of freezing and reinforcing area 3 is excavated, horizontally driving freezing pipes into two sides of the designed bottom surface of the first layer of freezing and reinforcing area 3 until the position of the foundation pit enclosure structure 1, arranging freezing equipment, and continuing excavation;
step three: repeating the second step, arranging freezing pipes and freezing equipment after excavating to the bottom surface of the last layer of freezing and reinforcing area 3, starting to freeze the soil layer, and constructing a first horizontal support 7 of the foundation pit;
s01: after the first horizontal support 7 is arranged and the foundation soil below the second horizontal support 8 reaches the designed freezing thickness and freezing strength, excavating the lower soil body of the first horizontal support 7 in the foundation pit, and constructing the second horizontal support 8 of the foundation pit;
s02: after the second horizontal support 8 is arranged, unfreezing the soil body of the first layer of freezing and reinforcing area 3 at the lower part of the second horizontal support, and pulling out a freezing pipe;
s03: after the lower foundation soil of the third horizontal support 9 reaches the designed freezing thickness and freezing strength, continuing to excavate the lower soil body of the second horizontal support in the foundation pit, and then constructing the third horizontal support 9 of the foundation pit;
s04: the step S02 to the step S03 are repeated until the foundation pit is excavated to the bottom;
s05: and thawing the soil body of the freezing and reinforcing area below the pit bottom, taking out the freezing pipe and the freezing equipment, and backfilling the vertical shaft 4 to be compact to complete the construction of the foundation pit bottom plate.
The method for arranging the vertical shaft 4 in the foundation pit converts the conventional vertical freezing method into the horizontal freezing method, is used for the advanced reinforcement of the deep and large foundation pit soil body in the soft soil area, can improve the advanced reinforcement efficiency of the foundation pit soil body, improves the reinforcement effect of the foundation pit, realizes green low-carbon construction, and reduces the influence of the freezing pipe on the excavation operation of the foundation pit.
The horizontal freezing method construction of the embodiment comprises three stages: freezing station installation, horizontal freezing pipe construction and stratum freezing. The freezing station comprises a compressor, a condenser and an evaporator which are connected with the compressor, a throttle valve arranged on the condenser, a cooler arranged between the condenser and the evaporator and a brine circulating system; the brine circulating system comprises a brine tank, a brine pump connected with the brine tank and a path-going brine main pipe arranged on the brine pump, wherein a liquid distribution ring, a freezer and a liquid collection ring are arranged on the path-going brine main pipe, a loop brine main pipe is arranged on one side of the brine tank, flow meters are arranged at the inlet and outlet of the path-going brine main pipe, the loop brine main pipe and the freezer, and whether brine leaks in the freezing pipe or not can be observed.
The freezer of this embodiment includes freezing pipe, supply pipe and liquid return pipe that is connected with freezing pipe. The function of heat exchange between low-temperature brine and the stratum can be realized. The horizontal freezing pipe construction process sequentially comprises the following steps: drilling horizontal frozen holes → arranging freezers in the frozen holes → connecting the freezers in different frozen holes into a system and connecting with a freezing station. The construction of the horizontal freezing pipe and the excavation of the vertical shaft 4 and the construction of a vertical shaft supporting structure are carried out alternately, and the construction organization design is carried out reasonably.
And drilling the horizontal freezing hole by adopting a pipe following drilling construction technology. When the horizontal freezing hole is drilled, a compass and a theodolite are adopted to find an inclination angle and an azimuth angle. The horizontal freezing hole drilling process must be subjected to inclination measurement and deviation correction so as to ensure the quality of the formed hole of the freezing hole. And after all the drill holes are qualified through inspection, the drilling machine can be detached.
The outer diameter of the freezing pipe in the embodiment is 89-127mm, the thickness of the pipe wall is more than or equal to 5mm, wherein the freezing pipe is made of a material with good heat conduction and low temperature performance, and a No. 20 low-carbon steel seamless steel pipe is preferably adopted. The freezing pipes are connected by butt welding or screw threads, and after the freezing pipes are installed, a pressure test is carried out according to relevant regulations to ensure that the salt water is not leaked.
The configuration of the freezing pipes is determined according to the thickness of a frozen soil layer required and the condition and the construction period of foundation soil, the distance between single-row freezing pipes is 1.0-2.5m, and the distance between double-row and more than double-row auxiliary freezing pipes is 3m; the freezing pipes in the rows are arranged in a plum blossom shape. For soft foundation with high water content and tight construction period, the distance between freezing pipes is preferably correspondingly reduced.
During the formation freezing period, the temperature and flow of circulating brine, the temperature of a frozen soil area, the ground frost heaving amount, the deformation of a foundation pit supporting structure and the like are detected and monitored at regular time.
After the first horizontal brace 7 is arranged, the foundation pit is excavated after the lower foundation soil of the second horizontal brace 8 reaches the designed freezing thickness and freezing strength. The excavation of the foundation pit is strictly carried out according to the requirements of layered excavation and strict over excavation prohibition, and the protection of the freezing pipeline is paid attention to. After the foundation pit is excavated to the position of the second horizontal support 8, the second horizontal support 8 is arranged in time, and meanwhile, appropriate heat preservation measures are taken for the ground.
After the second horizontal support 8 is arranged, the concrete horizontal support 6 can reasonably determine the out-of-service time of the freezing equipment according to the concrete strength increasing rule and naturally unfreeze. In the thawing process, the monitoring frequency of internal force and deformation of the foundation pit supporting structure is properly encrypted, an axial force monitoring sensor can be arranged in the concrete horizontal support 6 if necessary, and a treatment measure can be taken in time when an abnormal condition is found.
Specifically, a deep and large foundation pit adopting 'occlusive piles + inner supports + horizontal freezing advanced reinforcement' in a soft soil area is taken as an example for explanation, and the advanced reinforcement form of the foundation pit soil body is designed into strip-pulling reinforcement. The concrete construction process is as follows:
firstly, leveling the field, constructing the enclosure structure 1 secant piles around the foundation pit, and synchronously and alternately constructing the supporting structure of the vertical shaft 4 and excavating the soil body in the vertical shaft 4. And when the designed bottom surface of the first layer of freezing and reinforcing area 3 is excavated, horizontally driving freezing pipes to two sides until the position of the foundation pit enclosure structure 1, arranging freezing equipment, and then continuously excavating. And (3) excavating to the bottom surface of the last layer of the freezing and reinforcing area 3, arranging a freezing pipe and freezing equipment, then starting to freeze the soil layer, and constructing a first horizontal support 7 of the foundation pit.
After the first horizontal support 7 is arranged and the foundation soil below the second horizontal support 8 reaches the designed freezing thickness and freezing strength, excavating the lower soil of the first horizontal support 7 in the foundation pit, and then constructing the second horizontal support 8 of the foundation pit. And after the second horizontal support 8 is arranged, unfreezing the soil body of the first layer of freezing and reinforcing area 3 at the lower part of the second horizontal support, and pulling out the freezing pipe. And then, after the lower foundation soil of the third horizontal support 9 reaches the designed freezing thickness and freezing strength, continuing to excavate the lower soil body of the second horizontal support 8 in the foundation pit, and then constructing the third horizontal support 9 of the foundation pit. And circulating the steps until the foundation pit is excavated to the bottom. And finally, unfreezing the soil body of the freezing and reinforcing area below the foundation pit bottom 5, taking out freezing equipment such as a freezing pipe and the like, backfilling the vertical shaft 4 to be compact, completing the construction of the bottom plate of the foundation pit, and finishing the freezing and reinforcing of the foundation pit and the excavation and supporting.
Through the mode that sets up shaft 4 in the foundation ditch, change conventional vertical freezing method into horizontal freezing method, make to freeze the pipe and can drill into along the level in different stratum degree of depth departments, form the continuous freezing body of level of different degree of depth departments, the performance freezes the advanced reinforcement effect of reinforcing zone 3 to the excavation supporting structure, prevents that soft soil area deep foundation pit supporting system from taking place too big deformation.
The horizontal freezing method is applied to the field of advanced reinforcement of foundation pits, can be unfrozen layer by layer along with the excavation process of the foundation pits, is particularly suitable for reinforcement of an excavation section, has small disturbance on an in-situ soil body, has no adverse effect on excavation construction, reduces the consumption of a large amount of high-energy-consumption building materials such as cement and lime, and the like, has wide application range, good controllability, small pollution, economy and reasonability, and has obvious advantages in construction methods such as deeper cement mixing piles and the like.
For the forming of the strip-drawing type and grid type reinforced soil, the horizontal freezing method can carry out horizontal freezing reinforcement at planes with any depth according to design requirements, and compared with a vertical reinforcing construction method, the strip-drawing grid reinforced soil of each layer can be more uniform, continuous and flexible, and the reinforcing quality is more reliable.
The present invention is not limited to the above specific support scheme. Specifically, the enclosure structure around the foundation pit can be an occlusive pile, a section steel cement soil mixing wall, a steel sheet pile, an underground continuous wall, a freezing wall and other types. The passive area (without excavation) of the pit bottom of the foundation pit can be reinforced by adopting the conventional cement-soil stirring method, high-pressure jet grouting method and other in-situ stirring and reinforcing technologies, and the advanced reinforcement is matched with the horizontal freezing method of the excavation section, or the two methods are flexibly combined for use.
It should be noted that the terms "first," "second," and the like in the description and claims of this application and in the accompanying drawings are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the application described herein are capable of operation in other sequences than those illustrated or described herein.
In the description of the present invention, it is to be understood that the orientation or positional relationship indicated by the orientation words such as "front, rear, upper, lower, left, right", "lateral, vertical, horizontal" and "top, bottom", etc. are usually based on the orientation or positional relationship shown in the drawings, and are only for convenience of description and simplicity of description, and in the case of not making a reverse description, these orientation words do not indicate and imply that the device or element being referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore, should not be considered as limiting the scope of the present invention; the terms "inner and outer" refer to the inner and outer relative to the profile of the respective component itself.
Claims (10)
1. A horizontal freezing method-based advanced reinforcement method for deep and large foundation pit soil bodies in soft soil areas is characterized by comprising the following steps: the method comprises the following steps:
the method comprises the following steps: leveling a construction site, constructing an enclosure structure (1) around a foundation pit, constructing a supporting structure of a vertical shaft (4), and excavating a soil body in the vertical shaft (4);
step two: when the designed bottom surface of the first layer of freezing and reinforcing area (3) is excavated, horizontally driving freezing pipes into two sides of the designed bottom surface of the first layer of freezing and reinforcing area (3) until the foundation pit support structure (1), arranging freezing equipment, and continuously excavating;
step three: repeating the second step, arranging freezing pipes and freezing equipment after excavating to the bottom surface of the last layer of freezing and reinforcing area (3), starting to freeze a soil layer, and constructing a first horizontal support (7) of the foundation pit;
s01: after the first horizontal support (7) is arranged and the foundation soil below the second horizontal support (8) reaches the designed freezing thickness and freezing strength, excavating the soil below the first horizontal support (7) in the foundation pit, and constructing the second horizontal support (8) of the foundation pit;
s02: after the second horizontal support (8) is arranged, unfreezing the soil body of the first layer of freezing and reinforcing area (3) at the lower part of the second horizontal support, and pulling out a freezing pipe;
s03: after the foundation soil at the lower part of the third horizontal support (9) reaches the designed freezing thickness and freezing strength, continuing to excavate the soil at the lower part of the second horizontal support (8) in the foundation pit, and then constructing the third horizontal support (9) of the foundation pit;
s04: the step S02 to the step S03 are repeated until the foundation pit is excavated to the bottom;
s05: and unfreezing the soil body in the freezing and reinforcing area below the pit bottom, taking out the freezing pipe and the freezing equipment, and backfilling the vertical shaft (4) to be compact to complete the construction of the bottom plate of the foundation pit.
2. The advanced reinforcement method for the deep and large foundation pit soil body in the soft soil area based on the horizontal freezing method as claimed in claim 1, characterized in that: and the construction of the supporting structure of the vertical shaft (4) adopts one or two of a cement-soil gravity type enclosure wall and a profile steel cement-soil mixing wall according to the excavation depth and the foundation soil condition.
3. The advanced reinforcement method for the deep foundation pit soil body in the soft soil region based on the horizontal freezing method as claimed in claim 1, characterized in that: and (3) adopting row piles according to the excavation depth and the foundation soil condition in the construction of the supporting structure of the vertical shaft (4).
4. The advanced reinforcement method for the deep foundation pit soil body in the soft soil region based on the horizontal freezing method as claimed in claim 1, characterized in that: the horizontal freezing method construction comprises three stages: installing a freezing station, constructing a horizontal freezing pipe and freezing a stratum; the freezing station comprises a compressor, a condenser and an evaporator connected with the compressor, a throttle valve arranged on the condenser, a cooler arranged between the condenser and the evaporator and a brine circulating system.
5. The method for the advanced reinforcement of the soil body of the deep and large foundation pit in the soft soil region based on the horizontal freezing method as claimed in claim 4, wherein: the brine circulating system comprises a brine tank, a brine pump connected with the brine tank and a path-going brine main pipe arranged on the brine pump, wherein a liquid distribution ring, a freezer and a liquid collection ring are arranged on the path-going brine main pipe, and a loop brine main pipe is arranged on one side of the brine tank; and flow meters are arranged at the inlet and outlet of the path-removing brine main pipe, the loop brine main pipe and the freezer.
6. The method for the advanced reinforcement of the soil body of the deep and large foundation pit in the soft soil region based on the horizontal freezing method according to claim 5, wherein: the freezer comprises a freezing pipe, a liquid supply pipe and a liquid return pipe which are connected with the freezing pipe.
7. The method for the advanced reinforcement of the soil body of the deep and large foundation pit in the soft soil region based on the horizontal freezing method as claimed in claim 6, wherein: the horizontal freezing pipe construction process sequentially comprises the following steps: drilling horizontal frozen holes → arranging freezers in the frozen holes → connecting the freezers in different frozen holes into a system and connecting with a freezing station.
8. The advanced reinforcement method for the deep foundation pit soil body in the soft soil region based on the horizontal freezing method as claimed in claim 7, characterized in that: the horizontal freezing hole drilling adopts a pipe-following drilling construction technology, and inclination measurement and deviation correction must be carried out in the horizontal freezing hole drilling process.
9. The advanced reinforcement method for the deep and large foundation pit soil body in the soft soil area based on the horizontal freezing method as claimed in claim 8, wherein: the distance between the single row of freezing pipes is 1.0-2.5m, the distance between the double rows and the auxiliary freezing pipes above the double rows is 3m, and the freezing pipes among the rows are arranged in a plum blossom shape.
10. The advanced reinforcement method for the deep foundation pit soil body in the soft soil region based on the horizontal freezing method as claimed in claim 1, characterized in that: and after the second horizontal support (8) is arranged, for the concrete horizontal support (6), the operation stopping time of the freezing equipment is determined according to the concrete strength increasing rule, and the concrete horizontal support is naturally thawed.
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| JP4093670B2 (en) * | 1999-02-23 | 2008-06-04 | 株式会社大林組 | Dismantling method of underground structure |
| CN105926636B (en) * | 2016-05-13 | 2018-03-20 | 中国矿业大学 | Deep Foundation Pit Frozen back cover construction method |
| CN105951860A (en) * | 2016-06-24 | 2016-09-21 | 北京城建集团有限责任公司 | Slanting freezing bottom-making water stop structure for interior and side faces of underground excavated foundation pit and method |
| CN106013166B (en) * | 2016-06-27 | 2018-07-03 | 中国矿业大学 | Spoke type freezes to dig the construction method that formula excavates ultra-deep foundation pit outward |
| CN109723065B (en) * | 2019-02-26 | 2023-11-03 | 济南轨道交通集团有限公司 | Reinforcing device and deep foundation pit local freezing reinforcing construction method in water-rich gravel stratum |
| CN113089680B (en) * | 2021-04-16 | 2022-02-11 | 中国矿业大学 | Method for realizing excavation-following and supporting partitioned excavation of foundation pit by utilizing artificial freezing method |
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