RETRO-TRACTION SUPPORT SYSTEM FOR FOUNDATION PIT IN PEAT SOIL STRATE AND METHOD OF CONSTRUCTING SAME

Abstract

The application relates to a back-pull support system for a foundation shaft in a peat soil stratum and a construction method. It relates to the technical field of foundation shaft support in civil engineering. The back-pull support system for a foundation shaft in a peat soil stratum in the present application includes cantilever piles and several groups of steel pipes, wherein each of the cantilever piles includes several pile columns and a head beam fixedly arranged on the upper ends of the pile columns; the side of each of the cantilever piles away from the foundation shaft is provided with a surface layer filled with soil, and all the steel pipes are inserted into the surface layer filled with soil at intervals; each group of steel pipes is connected to the pile columns. Figure to be published with the abstract: Figure 1

Description

Title of the invention: RETRO-TRACTION SUPPORT SYSTEM FOR FOUNDATION PITCHES IN A PEAT SOIL STRATE AND METHOD OF CONSTRUCTING THE SAME Technical field

[0001] The application relates to the technical field of foundation shaft support in civil engineering, and in particular to a back-traction support system for foundation shafts in a peaty soil stratum and a method of constructing the same.

[0002] CONTEXT

[0003] Peat soil, also called peat moss, black earth and humus earth, is a kind of peat. Peat soil is a black or dark brown mineral formed by a large number of plant debris in a submerged environment, deposited in the stratum thousands of years ago and partially decomposed by microorganisms under anaerobic conditions, and is a kind of transition product in the process of plants transforming into peat. The water content of peat soil is very high, generally 85-95%. After natural drying, the water content can be reduced to 25-35%. Peat soil stratum is part of soft foundations and is not easy to combine with concrete.

[0004] In the design of foundation shaft support, cement-earth mixture pile, cement-earth injection pile and spiral long jet mixture pile are usually used. Cement-earth mixture piles (including uniaxial, biaxial or multi-axial) are widely used in foundation shaft support, waterproof treatment of curtains and foundations due to simple construction and low cost. However, in the presence of peaty soil stratum, cement-earth mixture piles cannot be implemented because cement does not react with peaty soil.Cement-earth grouting pile (including single pipe, double pipe and three pipes) is successfully applied in many fields, such as foundation pit support, waterproof treatment of curtains and foundations, but cement-earth grouting pile cannot be implemented in peat soil stratum because cement and peat soil do not react. The technology of spiral long jet mix pile is well applied, and practice has proved that spiral long jet mix pile is a practical and feasible technology in ordinary strata, especially in hard soil, but spiral long jet mix pile cannot be implemented in peat soil stratum because cement does not react with peat soil.

[0005] At present, the injection technology includes sleeve valve and tube injection technology, which is applied in many stratum curtains and foundation pits, but it cannot be implemented in peat soil stratum because cement does not react with peat soil.

[0006] In the related technology, the soil pile with pressure grouting is designed, and the soil curtain pile with pressure grouting is made by using a long auger, a forced mixer and a soil pump, and then combined with reinforced concrete piles, the waterproof support of foundation pits is realized.

[0007] In view of the above technology, due to the limitation of equipment and age, only circular curtain piles can be occlusive with slope protection piles, so it is difficult to ensure the sealing quality due to poor occlusal contact, especially when the foundation pit is deep or the pile is long. Therefore, the applicant of the present application designed a dumbbell-shaped curtain pile, particularly a method for constructing a dumbbell-shaped cement-earth curtain pile in a peat soil stratum (Patent No.: ZL202110565948.1). Combined with reinforced concrete slope protection piles, the purpose of foundation pit support and sealing in a peat soil stratum is realized.As a cantilever pile support system, the deformation of the pile top after excavation is too large, and if it exceeds the control value of the specification and design, it may tip over.

[0008] In view of this situation, the use of internal support will affect the normal use of the foundation pit, which is generally not accepted by the builder and general contractor, and the construction period, cost, difficulty and influence on subsequent projects have many negative effects. The conventional practice is to lock the anchor rod, but the anchor rod with a diameter of 150 mm and a length of 25 m can lock only 2T after calculation, which is too low in terms of cost performance and cannot control the tilting of the support system.

[0009] SUMMARY

[0010] In order to improve the stability and reliability of the foundation shaft support system in a peat soil stratum and to reduce the process costs, the application provides a back-pull support system for a foundation shaft in a peat soil stratum and a method of constructing the same.

[0011] On the one hand, a method of constructing a back-pull support system for foundation wells in a peat soil stratum provided by the application adopts the following technical scheme.

[0012] A method of constructing a back-pull support system for a foundation shaft in a peat soil stratum, including the following steps.

[0013] IF, arranging the cantilever piles: successively casting pile columns and a head beam at a predetermined position on a construction site, where a plurality of pile columns are arranged in rows, and the head beam is fixedly connected to the top of all the pile columns to form the cantilever piles;

[0014] S2, dig the foundation pit: bring in an excavator transport vehicle on a site, and excavate the soil stratum in an area surrounded by the cantilever piles to a predetermined depth to form the foundation pit;

[0015] S3, backfill and dump: backfill part of the earthworks near the piles cantilever in the foundation pit to form a bridge support, so as to ensure the stability of the foundation pit; carry out earthwork in an area on one side of the cantilever piles away from the foundation pit to generate a spilling effect;

[0016] S4, install the steel pipes: measure the positions of the installation piles on a flat site outside a slope top of the foundation pit, where the positions of the setting piles are distributed at intervals in the length direction of the head beam, and installing and fixing a group of the steel pipes at each predetermined setting pile position; and

[0017] S5, connect the steel pipes to the cantilever piles: connect each group of pipes steel to the cantilever piles through steel bars or wire ropes, and the steel pipes generate tensile force on the cantilever piles through the steel bars or wire ropes.

[0018] By adopting the above technical scheme, the problem of large deformation of the pile column and the head beam detected after the excavation of the foundation pit can be solved effectively and timely. On the one hand, the backfilling of the earthwork inside the foundation pit forms a bridge support, on the other hand, the earthwork is carried out on the side opposite to the foundation pit to produce a dumping effect, thus effectively controlling the displacement of the cantilever support system and avoiding dumping accidents.In the present application, the support system with special structure is set up, and the various backfill with thickness of 1.5-3m on the surface is used to ensure uplift resistance and horizontal resistance of the steel pipe, and the steel pipe pulls the pile column and the head beam through the steel bars or wire ropes, thus forming tension on the cantilever piles, so as to balance the active earth pressure, avoid the negative impact on the cost and construction period of the internal support and the subsequent projects, and also overcome the disadvantages of low cost performance and low . poor control of anchor deformation in the peat soil stratum, which is ingenious, practical, fast and economical.

[0019] Optionally, in step S3, the depth of a dumping zone of the cantilever piles excavated in an area remote from the foundation pit is 1 m to 2 m; the width of the dumping zone is 1 to 2 times the depth of the foundation pit.

[0020] By adopting the technical scheme, the depth and width of the dumping area can further ensure the stability of the support system, reduce the displacement of the support system and avoid the occurrence of dumping accidents.

[0021] Optionally, in step S4, the positions of the setting piles are used to drill a deep hole in a ground with a steel drill or a perforator, and inject white lime powder, and insert a wooden stick or the steel bar at the positions of the setting piles to form an obvious sign.

[0022] The position of the setting piles is measured on the flat site on the slope top outside the foundation pit, and the positioning of the piles is carried out with measuring instruments at both ends to prevent the deviation of the position of the setting piles from being rechecked at any time; by adopting the technical scheme, the accuracy and reliability of the installation of the steel pipe positions are ensured.

[0023] Optionally, in step S4, the steel pipes are pushed by an impact pneumatic hammer to the top of the slope, the impact pneumatic hammer and the steel pipes are first used for self-driving, and vibration driving of the impact pneumatic hammer is started when the steel pipes cannot be driven, and the depth of the steel pipes is controlled to reach a designated depth.

[0024] The pneumatic impact hammer is a mature product, with a bracket, which is very light and easy to move by two people. The base of the air compressor that provides wind power is equipped with wheels and can be easily pushed, which is convenient for going back and forth on the construction site, and will be more convenient to use. By adopting the technical scheme, the fixation of steel pipes is more convenient and stable, the stress is more reasonable, and greater uplift resistance is ensured, thus effectively preventing the deformation of cantilever piles.

[0025] Optionally, in step S4, an anchor drill is used to drill holes to the designated depth, the steel pipes are placed, then a cement slurry having a water / cement ratio of 0.4 to 0.45 is injected, and the cement slurry is topped up a second time if necessary.

[0026] By adopting the technical scheme, the steel pipes are fixed after the cement slag is solidified, thus providing better uplift resistance and effectively preventing deformation of the cantilever piles.

[0027] Optionally, between steps S4 and S5, a through hole is first drilled from the side of the cantilever piles away from the foundation pit to a side facing the foundation pit with a Luoyang excavator, so that the through hole communicates with the foundation pit; the through hole is located between two adjacent pile columns and near a position of the head beam; in step S5, the steel bars or wire ropes pass through the through hole and are fixedly connected to the cantilever piles.

[0028] Adopting the technical scheme, after the steel bars or wire ropes pass through the through hole, it is convenient to fix the steel bars or wire ropes by using the connecting mode of the profiled beam or the I-shaped beam, and the steel bars or wire ropes are connected at the position near the upper end of the pile column, which is equivalent to the steel bars or wire ropes being the "head" for pulling the pile column, generating more intelligent skillful force, effectively controlling the displacement of the support system, and greatly reducing the possibility of dumping accidents.

[0029] Optionally, in step S5, a profiled beam or an I-shaped beam is placed under a front head beam of the pile columns, and a through hole is drilled in the profiled beam or the I-shaped beam, and one end of the steel bar or the wire rope passes through the through hole and is fixed to the profiled beam or the I-shaped beam.

[0030] By adopting the technical scheme, it is convenient to connect the steel bar or wire rope to the profiled beam or I-shaped beam, which effectively prevents the profiled beam or I-shaped beam from falling.

[0031] Optionally, in step S5, if the steel bars are used to connect the steel pipes and the cantilever piles, both ends of each of the steel bars are connected by welding, and if the wire ropes are used to connect the steel pipes and the cantilever piles, both ends of the wire ropes are connected by U-shaped clips.

[0032] By adopting the above technical scheme, the welding method is very fast and convenient for the steel bar, simple in construction and low in cost; regarding the wire rope, it has certain flexibility, so when positioning the position of the steel pipe and the through hole, the requirement for accuracy can be appropriately lowered, thereby reducing the construction difficulty and improving the construction efficiency; meanwhile, connecting the cantilever piles with the steel pipe by the wire rope is relatively simple to operate. If the head beam is considered to have good integrity and high strength, the front profiled beam and I-shaped beam can be omitted, and the wire rope can be wound and connected after passing through the through hole. If it is considered that the integrity of the head beam is poor or the strength is not high enough, the grooved steel or I-shaped beam are bound with the head beam as a whole, and the wire rope can be wound and connected after passing through the through hole. The wire rope adopts U-shaped clips to firmly clamp the wound wire rope, and both ends can adopt this type of fixation; the operation is very convenient.

[0033] On the other hand, a back-traction support system for foundation wells in a peaty soil stratum provided by the application adopts the following technical scheme.

[0034] The back-pull support system for a foundation pit in a peat soil stratum is formed by the above construction method, and includes cantilever piles and several groups of steel pipes, wherein each of the cantilever piles includes a plurality of pile columns and a head beam fixedly disposed on the upper ends of the pile columns; one side of each of the cantilever piles away from the foundation pit has a plurality of earth-filled surface layers, and the steel pipes are inserted into the earth-filled surface layers, and each group of the steel pipes is fixedly connected to the pile columns and / or the head beam via steel bars or wire ropes.

[0035] Adopting the above technical scheme, the various embankment with a thickness of 1.5 to 3 m on the surface provides uplift resistance and horizontal resistance to the steel pipe, and the steel pipe is involved in the pile column and the head beam through the connector, which exerts tensile force on each of the cantilever piles, thus balancing the active earth pressure, avoiding the cost and construction period of internal support and the negative impact on subsequent projects, and also overcoming the disadvantages of low cost performance and poor deformation control of the anchor in the peat soil stratum. It is an ingenious and practical structure, and also fast and very economical.

[0036] Optionally, each of the steel pipes includes one steel pipe or two steel pipes or three steel pipes, and when each of the steel pipes includes three steel pipes, the three steel pipes are arranged in a regular triangle or an inverted triangle and the upper ends of the three steel pipes are fixedly connected into a whole.

[0037] Adopting the above technical scheme, different numbers of steel pipes are selected according to different geological conditions and tensile strength requirements. If three steel pipes are used, the upper parts of the three steel pipes are connected as a whole with steel cables, and the effect is better.

[0038] To summarize, the application includes at least one of the following beneficial technical effects.

[0039] First, the support system in the present application uses various backfill on the surface to provide uplift resistance to the steel pipes, which overcomes the problem of low uplift resistance of the anchor rods inserted into the peat soil stratum.

[0040] Second, in the present application, the support system pulls the upper position of the pile column with the steel bars or wire ropes, which produces a more intelligent dexterous force, effectively controls the displacement of the support system, and greatly reduces the possibility of dumping accidents.

[0041] Third, the support system in the present application adopts a back-pull structure, which has obvious advantages in cost, construction period and influence on subsequent projects compared with internal support; at the same time, it also overcomes the disadvantages of low cost performance and poor deformation control of bolting in the peat soil stratum, and is more intelligent and convenient, fast and economical.

[0042] Fourth, the method for constructing the support system in the present application has the advantages of simple process, convenient operation and low cost. BRIEF DESCRIPTION OF THE FIGURES

[0043] [Fig.l] is a schematic diagram of the method of constructing the support system in the present application.

[0044] [Fig.2] is a schematic side view of the support system in the present application.

[0045] [Fig.3] is a partially enlarged structural diagram of [Fig.2].

[0046] [Fig.4] is a schematic diagram of the installation and connection structure of each group of steel pipes with a single steel pipe.

[0047] [Fig.5] is a schematic diagram of the installation and connection structure of each steel pipe group with two steel pipes.

[0048] [Fig.6] is a schematic diagram of another installation and connection structure of each steel pipe group with two steel pipes.

[0049] [Fig.7] is a schematic diagram of the installation and connection structure of each steel pipe group with three steel pipes.

[0050] [Fig.8] is a schematic diagram of another installation and connection structure of each steel pipe group with three steel pipes.

[0051] Reference signs:

[0052] 10 cantilever pile; 11 pile column; 12 head beam; 13 through hole;

[0053] 20 steel pipe;

[0054] 30 connector;

[0055] 40 profiled beam.

[0056] DESCRIPTION OF THE INVENTION

[0057] The present application will be described in more detail with reference to [Fig. 1] to 8.

[0058] The foundation shaft support system in the present application may be widely used in foundation pit support of soft foundations, for example, it can be used in foundation pit support of peat soil stratum; compared with the foundation pit support system in peat soil stratum in the prior art, it has an obvious improvement effect. Of course, it is not limited to foundation pit support of soft foundations such as peat soil stratum, but also the support system which is used in other geological conditions but adopts the same technical scheme in the present application is regarded as a scheme equivalent to the technical scheme in the present application.

[0059] As shown in [Fig.l], [Fig.2] and [Fig.3], the back-pull support system for foundation shafts in a peat soil stratum in the present application includes cantilever piles 10 and several groups of steel pipes 20, where each of the cantilever piles 10 includes several pile columns 11 and a head beam 12 fixed to the upper ends of the pile columns 11, and each group of steel pipes 20 is fixedly connected to the pile columns 11 and / or the head beams 12 via the connectors 30. The connectors 30 may be steel bars or wire ropes.

[0060] The stages of concrete construction include:

[0061] SI, arranging cantilever piles 10: successively casting pile columns 11 and head beams 12 at a predetermined position on a construction site, where a plurality of pile columns 11 are arranged in rows, and the head beams 12 are fixedly connected to the tops of all the pile columns 11 to form the cantilever piles 10; pre-construction of the cantilever piles 10 is carried out according to existing related technologies. Pile columns 11 are formed by drilling and casting, and the pile rows are connected into a whole after casting in place of the head beams 12, and cantilever piles 10 are formed. As relatively mature prior art, this is not detailed here.

[0062] S2, digging a foundation pit: an excavator transport vehicle enters the site, and the soil stratum in the area enclosed by each of the cantilever piles is excavated to a predetermined depth to form a foundation pit; after the foundation pit is excavated, if it is detected that the pile columns 11 and the head beam 12 of each of the cantilever piles 10 are excessively deformed, treat the deformation.

[0063] S3, backfill and dump: backfill part of the earthworks near the piles cantilever 10 into the foundation pit to form a bridge support, so as to ensure the stability of the foundation pit; the embankment is not necessarily backfilled along the entire length, but can be backfilled into a "bridge" type, which is more efficient and economical; earthwork is carried out in the area on one side of each of the cantilever piles 10 away from the foundation pit to produce a spilling effect; earth excavation is carried out on the perimeter of the foundation pit, and the spilling depth of the soil stratum should be 1 to 2 m, and the width is 1 to 2 times the depth of the foundation pit.

[0064] S4, install steel pipes: one side of each of the cantilever piles 10 to distance from the foundation pit is provided with a surface layer filled with earth, and the positions of the placing piles are measured on the flat side of the slope top outside the foundation pit, and the positions of the placing piles are distributed at intervals in the length direction of the head beam 12, and a group of steel pipes 20 is installed and fixed at each predetermined placing pile position; in the present application, the steel pipes 20 are inserted into the surface layer filled with earth, and several groups of steel pipes 20 are arranged at intervals in the length direction of the head beam 12.In this step S4, the position of the setting piles is measured on the flat side outside the slope top of the foundation pit, and the positioning of the piles is carried out with measuring instruments at both ends to prevent the position of the setting piles from being rechecked at any time in case of deviation; the position of the setting piles is used to drill a deep hole in the ground with a steel drill or a perforator, inject white lime powder, and insert a wooden stick or a steel bar at the position of the setting piles to form a clear sign, so as to ensure the accuracy and reliability of the steel pipe installation.

[0065] S5, connect the steel pipes to the cantilever piles: each group of steel pipes 20 is connected to the cantilever piles 10 by means of steel bars or steel cables, and the steel pipes exert a tensile force on the cantilever piles 10 by the through steel bars or steel cables, and the tensile force supplied to the cantilever piles 10 is uniformly dispersed.

[0066] Referring to [Fig.4], each group of steel pipes 20 may be a steel pipe 20. The steel pipes 20 are pushed into the soil stratum from the slope top by an impact pneumatic hammer. First, the impact pneumatic hammer and the steel pipes 20 are used for self-driving, and the vibration driving of the impact pneumatic hammer is started when the steel pipes 20 cannot be driven, and the depth of the steel pipes 20 is controlled to reach a designated depth. The impact pneumatic hammer has a stand, which is very light and is lifted by two people, making it easy to move. The base of the air compressor that provides wind power is equipped with wheels, and is easily pushed.If a ground anchor drilling machine is present on site, the anchor drilling machine can be used to drill holes to the design depth, then the steel pipes 20 are placed, then the cement slurry having the water / cement ratio of 0.4 to 0.45 is injected, and the secondary injection is required. The steel pipes 20 can be pushed vertically downward. The lower ends of the steel pipes 20 can be arranged obliquely in the direction of the foundation pit. In this way, the stress of the steel pipe 20 is more reasonable, providing greater uplift resistance, thereby effectively preventing the deformation of the cantilever piles 10. .

[0067] Referring to [Fig.5] and [Fig.6], each group of steel pipes 20 may also be two steel pipes 20. As a specific embodiment, as shown in [Fig.5], two steel pipes 20 may be vertically arranged side by side; as another specific embodiment, as shown in [Fig.3] and [Fig.5], one of the two steel pipes 20 is vertically arranged and the other is obliquely arranged. The obliquely arranged steel pipe 20 is located between the vertically arranged steel pipe 20 and the foundation pit, and the lower end of the obliquely arranged steel pipe 20 is inclined in the direction of the foundation pit, and the upper end is inclined toward the side of the vertically arranged steel pipe 20.

[0068] Referring to [Fig.7] and [Fig.8], each group of steel pipes 20 may also be three steel pipes 20, and the three steel pipes 20 are connected in a triangle shape, and have a regular triangle or inverted triangle shape. As one specific embodiment, as shown in [Fig.7], three steel pipes 20 may all be vertically arranged; as another specific embodiment, as shown in [Fig.8], the three steel pipes 20 are obliquely arranged, and the upper ends of the three steel pipes 20 are inclined and close to each other, and the upper ends of the three steel pipes 20 are tied and fixed together with steel cables or steel bars, and the three steel pipes 20 are stressed together, so that the effect is better.

[0069] Between the above steps S4 and S5, the through hole 13 is first drilled from the side of each of the cantilever piles 10 away from the foundation pit to the side facing the foundation pit with a Luoyang shovel, so that the through hole 13 communicates with the foundation pit; the through hole 13 is located between two adjacent pile columns 11 and close to the head beam 12. The steel bar or wire rope passes through the through hole 13 and is fixedly connected to the cantilever piles. The side face of the pile columns 11 and / or the head beam 12 facing one side of the foundation pit and located at the hole of the through hole 13 is provided with a profiled beam 40 or an I-shaped beam; one end of the steel bar or wire rope passes through the corresponding through hole 13 and is welded to the corresponding profiled beam 40 or I-shaped beam.In general, the I-shaped beam can be used if greater stiffness is required, and the 40-section beam can be used if less stiffness is required.

[0070] In step S5, if steel bars are used to connect the steel pipes and the cantilever piles, both ends of each of the steel bars are connected by welding and fixing; if the steel pipes and the cantilever piles are connected by wire ropes, both ends of the wire ropes are connected by U-shaped wire rope clips.

[0071] The implementation principle is as follows: the application makes full use of the various backfill with a thickness of 1.5 to 3 m on the surface to provide uplift resistance and horizontal resistance to the steel pipes 20, and the steel pipes 20 are involved in the pile columns 11 and the head beam 12 through the connectors 30, which exerts a tensile force on each of the cantilever piles 10, thus balancing the active earth pressure, avoiding the negative impact of internal support on the construction cost and period and subsequent projects, and also overcoming the disadvantages of low cost performance and poor deformation control in the peat soil stratum, which is ingenious, practical and efficient.

[0072] In the present application, after the steel bars pass through the through hole 13, it is convenient to fix the steel bars or wire ropes by means of welding the profiled beam 40 or the I-shaped beam, and the steel bar or wire rope is connected to the position near the top of the pile column 11, which is equivalent to the steel bars being a "head" for pulling the pile column 11, generating more intelligent skillful force, effectively controlling moving the support system and significantly reducing the possibility of spill accidents.

[0073] Consider as an example a foundation shaft support project of a proposed building having a total design area of about 10,000 m2. In the shear frame structure of the building, the basement burial depth is -6.6 m and the local depth is -5.8 m. The surface elevation is ±0.00, and the local surface is -0.3 m. The design form of the foundation is a pile foundation.

[0074] Main stratum: plain embankment: brownish yellow, grayish yellow, brownish red, etc., moist, mainly composed of soil in a plastic state, with a small amount of gravel, which is a recent embankment with a thickness of about 1.5 to 3 m.

[0075] Peat soil: black and ash mixed with brown, saturated, soft-plastic, high compressibility. The pores are large and extremely dilated, the pore ratio e = 3.01-8.04, with an average of 5.63, the average water content is 268%, and the average organic content is 45.6%. It is a strong peat soil with a burial depth of about 1.5 m and an average thickness of about 6.8 m.

[0076] The composite support scheme for retaining soil and stopping water is designed by combining a reinforced concrete pile with a soil pile with pressure grouting. The diameter of the reinforced concrete slope protection pile is 600 mm, the pile length is 12 m, the pile spacing is 1.2 m, the slope protection pile and the cement-earth curtain pile seal 300 mm, a total of 488 reinforced concrete piles and 488 soil curtain piles with grouting are distributed. After 30 days of construction by two long augers, the construction of 976 piles is completed. After the excavation of the foundation pit, it is found that the reinforced concrete pile is closely combined with the cement-earth pile, and the water-proofing effect is satisfactory, but the pile top displacement is obviously large, and even some monitoring points reach 20 cm.The backfilling is carried out in time for the earthwork to become a bridge type, and then the side away from the foundation pit is unloaded by an excavator, and the dumping depth is about 1.5 m, with 10 m outside the foundation pit. The 20 steel pipes are pushed into the slope crest by a pneumatic impact hammer. The uplift resistance and horizontal strength of the 20 steel pipes provided by the upper embankment with a thickness of 1.5 to 3 m are fully utilized. If the embankment thickness is 3 m, one 20 steel pipe can be used, and if the embankment thickness is 1.5 m, three steel pipes can be arranged in a regular triangle. A through hole 13 is excavated between the spaces of the cantilever piles 10 by a Luoyang excavator, and a through hole is drilled in the profiled beam 40. The steel pipes 20 and the profiled beam 40 are effectively welded with the through steel bars. the through hole 13 and the through hole of the profiled beam 40, thus achieving a firm connection, and successfully completing the foundation pit support task. After comparison, if the scheme of adding an anchor rod and a steel belt beam is adopted, it will cost 1.5 million yuan. The use of this back-pull support system in the present application will cost only 100,000 yuan, which is 15 times the method of adding an anchor rod and a steel belt beam, and the construction period is only one-fifth of that of the scheme with the anchor rod. From this point of view, this back-pull foundation pit support scheme is a fast and very economical method.

[0077] The examples of this specific embodiment are all preferred embodiments of the present application, and the scope of protection of the present application is not limited accordingly, where the same parts are indicated by the same reference numbers. Therefore, all equivalent changes made according to the structure, form and principle of the present application are to be included within the scope of protection of the present application.

Claims

1. Claims A method of constructing a back-pull support system for a foundation shaft in a peat soil stratum, wherein the construction method comprises the following steps: • IF, arranging cantilever piles (10): successively casting pile columns (11) and a head beam (12) at a predetermined position on a construction site, where a plurality of pile columns (11) are arranged in rows, and the head beam (12) is fixedly connected to the top of all the pile columns (11) to form the cantilever piles (10); • S2, dig the foundation pit: bring in a vehicle transporting an excavator to a site, and excavating the soil stratum in an area surrounded by the cantilever piles (10) to a predetermined depth to form the foundation pit; • S3, backfill and dump: backfill part of the earthwork near the cantilever piles (10) in the foundation pit to form a bridge support, so as to ensure the stability of the foundation pit; carrying out the earthwork in an area on one side of the cantilever piles (10) away from the foundation pit to generate a spilling effect; • S4, install steel pipes (20): measure positions of the setting piles on a flat site outside a slope top of the foundation pit, where the positions of the setting piles are distributed at intervals in the length direction of the head beam (12), and installing and fixing a group of the steel pipes (20) at each predetermined setting pile position; and • S5, connect the steel pipes (20) to the cantilever piles (10): Connecting each group of steel pipes (20) to the cantilever piles (10) through steel bars or wire ropes, where the steel pipes (20) generate a tensile force on the cantilever piles (10) through the steel bars or wire ropes.

2. A method of constructing the back-pull support system for foundation pits in a peat soil stratum according to claim 1, wherein, in step S3, the depth of a pouring zone of the cantilever piles (10) excavated in an area away from the foundation pit is 1 m to 2 m; the width of the pouring zone is 1 to 2 times the depth of the foundation pit.

3. A method of constructing the back-pull support system for foundation pits in a peat soil stratum according to claim 1 or 2, wherein, in step S4, the positions of the setting piles are used to drill a deep hole in a soil with a steel drill or a perforator, and inject white lime powder, and insert a wooden stick or the steel bars at the positions of the setting piles to form an obvious sign.

4. A method for constructing the back-pull support system for a foundation pit in a peat soil stratum according to claim 1 or 2, wherein, in step S4, the steel pipes (20) are pushed by a pneumatic impact hammer to the top of the slope, the pneumatic impact hammer and the steel pipes (20) are first used for self-driving, and vibration driving of the pneumatic impact hammer is started when the steel pipes (20) cannot be driven, and the depth of the steel pipes (20) is controlled to reach a designated depth.

5. A method of constructing the back-pull support system for foundation wells in a peat soil stratum according to claim 1 or 2, wherein, in step S4, an anchor drill is used to drill holes to a designated depth, the steel pipes (20) are placed, then a cement slurry having a water / cement ratio of 0.4 to 0.45 is injected, and the cement slurry is supplemented a second time if necessary.

6. A method of constructing the back-pull support system for foundation pits in a peat soil stratum according to claim 1 or 2, wherein, between steps S4 and S5, a through-hole (13) is first drilled from the side of the cantilever piles (10) away from the foundation pit to a side facing the foundation pit with a Luoyang excavator, so that the through-hole (13) communicates with the foundation pit; the hole through hole (13) is located between two adjacent pile columns (11) and near a position of the head beam (12); in step S5, the steel bars or wire ropes pass through the through hole (13) and are fixedly connected to the cantilever piles (10).

7. A method of constructing the back-pull support system for foundation pits in a peat soil stratum according to claim 6, wherein, in step S5, a profiled beam (40) or an I-shaped beam is placed under a front head beam (12) of the pile columns (11), and a through-hole is drilled in the profiled beam (40) or the I-shaped beam, and one end of the steel bar or the wire rope passes through the through-hole and is fixed to the profiled beam (40) or the I-shaped beam.

8. A method of constructing the back-pull support system for foundation pits in a peat soil stratum according to claim 1 or 2, wherein, in step S5, if the steel bars are used to connect the steel pipes (20) and the cantilever piles (10), both ends of each of the steel bars are connected by welding, and if the wire ropes are used to connect the steel pipes (20) and the cantilever piles (10), both ends of the wire ropes are connected by U-shaped clips.

9. A back-pull support system for a foundation pit in a peat soil stratum, wherein the system is constructed by the construction method described in any one of claims 1 to 8, and the support system comprises cantilever piles (10) and a plurality of groups of steel pipes (20), wherein each of the cantilever piles (10) comprises a plurality of pile columns (11) and a head beam (12) fixedly disposed at the upper ends of the pile columns (11); one side of each of the cantilever piles (10) away from the foundation pit has a plurality of surface layers filled with soil, and the steel pipes (20) are inserted into the surface layers filled with soil, and each group of the steel pipes (20) is fixedly connected to the pile columns (11) and / or the head beam (12) via steel bars or steel cables.

10. A back-pull support system for foundation wells in a peat soil stratum according to claim 9, wherein each group of the steel pipes (20) comprises a steel pipe (20) or two steel pipes (20) or three steel pipes (20), and wherein each group of the steel pipes (20) comprises three steel pipes (20), the three steel pipes (20) are arranged in a regular triangle or an inverted triangle, and the upper ends of the three steel pipes (20) are fixedly connected into a whole.

Images