CN111287194A - Recyclable foundation pit support structure using inclined steel sheet piles and its support method - Google Patents

Abstract

The invention discloses a recyclable foundation pit support structure using inclined steel sheet piles, comprising steel sheet support row piles, the steel sheet support row piles comprising a plurality of steel sheet piles inserted into soil bodies, the steel sheet piles comprising a pile body, and the steel sheet piles on the piles. One end of the pile body that is inserted into the soil body is the pile tip and the other end is the pile tail. The steel sheet pile is composed of trapezoidal channel steel. There are locks on both sides in the width direction of the steel sheet piles, and the locks pass between the adjacent steel sheet piles. Occlusal connection; the pile tails of all steel sheet piles are fixed with the crown beam; all steel sheet piles are inserted into the soil body inclined to the direction of gravity and inclined to the inside of the foundation pit. It can improve the effect of foundation pit support, and is better suitable for the support of ultra-deep and super-large foundation pits in soft soil areas. The invention has simple construction and shortened construction period; the use of steel sheet piles can provide necessary safety, is not restricted by weather conditions, and can reduce the requirements for space, and has good interchangeability; after use, the steel sheet piles can be recycled and reused, saving energy funds.

Description

Recyclable foundation pit support structure using inclined steel sheet piles and its support method

technical field

The invention relates to the technical field of construction foundation pits, in particular to a foundation pit support method using recyclable inclined steel sheet piles.

Background technique

Pile row support is one of the most widely used foundation pit support forms in China. Compared with the underground diaphragm wall, the pile row structure has many advantages, such as simple construction technology, low cost and flexible layout. The spaced pile row type support is suitable for situations where there is no groundwater or precipitation outside the pit is allowed, and it can also be used in weak water-bearing strata when a water-stop curtain is set or a side-by-side continuous wall is formed with other mixed piles.

The currently used row piles are all vertical piles, which have many shortcomings in the foundation pit support, which affects the application of the row piles. First of all, the displacement of the pile top at the same excavation depth is large, and the internal force is large, which causes a large deformation of the ground behind the pile and endangers the surrounding environment. Secondly, when the strength of the pile is not enough, it is easy to cause the slope protection pile to break and cause the foundation pit to become unstable. Third, the use of vertical piles makes the excavation depth of the foundation pit smaller. When the excavation depth is large, the piles are prone to overturning damage, so the support structure needs a larger section and insertion depth.

Compared with precast concrete piles, the use of steel sheet piles for foundation pit support has the following advantages: steel sheet piles are simple to construct and have a short construction period; for construction tasks, the space requirements can be reduced; steel sheet piles can be reused after use. Can be recycled and reused, saving money.

SUMMARY OF THE INVENTION

In view of the above-mentioned prior art, the present invention proposes a recyclable foundation pit support structure using inclined steel sheet piles and a support method thereof, which are suitable for using a single row of inclined piles for foundation pit support and are expected to recycle the piles to reduce the cost. foundation pit support project. The invention is simple in construction, shortens construction period and saves money.

In order to solve the above technical problems, the present invention proposes a recyclable foundation pit support structure using inclined steel sheet piles, including steel plate support row piles, and the steel plate support row piles include a plurality of steel sheet piles inserted into the soil. The steel sheet pile includes a pile body, and the end of the pile body at the end of the pile body that is inserted into the soil body is a pile tip, and the other end is a pile tail. The steel sheet pile is composed of trapezoidal channel steel. There are locks on the sides, and the adjacent steel sheet piles are connected by locking; the pile tails of all the steel sheet piles are fixed with the crown beam; α is in the range of 0° to 30°, but not including 0°, so that the steel sheet pile supporting row is inclined to the inside of the foundation pit.

Further, the inclination angle is preferably α=15° to 20°.

The length of the steel sheet piles along the edge direction of the foundation pit to be excavated is L, and the pile spacing of the steel sheet piles along the edge direction of the foundation pit to be excavated is H, where H=2˜2.5L.

The cross section of the crown beam is a square with side length A, A>0.6L.

The cross section of the crown beam is a rectangle, the long side of the rectangle is B, the short side is C, and the direction of the short side C coincides with the direction of gravity, B>0.6L.

At the same time, the present invention also proposes a supporting method for a recyclable foundation pit supporting structure using inclined steel sheet piles, and the steps are as follows:

Step 1. According to the site conditions and calculation analysis, determine the inclination angle α of the steel sheet supporting row piles between 0° and 30°, but not including 0°, and select the length and strength of the steel sheet pile;

Step 2: Dig trenches;

Step 3: In the construction of inclined piles, the steel sheet piles are driven by the single pile driving method one by one, including:

1) Before driving the steel sheet pile, close the groove at the tip of the pile, and coat the lock with butter or other grease;

2) Measuring and positioning the line: release the axis of the steel sheet pile enclosure, and set up guide piles at intervals. The guide pile is directly used as the steel sheet pile, and then the lanyard line is used as the wire, and the wire is used to control the axis of the steel sheet pile during piling;

3) Feeding the piles: Use the inclined pile static press to lift the steel sheet piles, manually straighten them into place, and the positioning error is less than 20mm; control the pile body according to the inclination angle determined in step 1; according to the inclination angle α determined in step 1 and combine the The return depth and equipment height are calculated respectively for the pile position line, the soil entry line and the alignment line; after the pile position is checked and correct, the inclined pile static press is used for sequential construction; during the piling process, two theodolites are used to monitor and control to ensure the safety of the steel sheet pile. inclination angle α;

4) The single piles are continuously driven one by one. During the process of driving the first steel sheet pile and the second steel sheet pile, the position and direction are measured once every 1m of driving, so as to play the role of a guiding model. Immediately after driving to the predetermined depth Use steel bars or steel plates and electric welding of purlin brackets for temporary fixation;

Step 4. Waterproof curtain construction;

Step 5. Crown beam construction;

Step 6. Clean and level the bottom of the foundation pit, and carry out the next construction operation;

Step 7. Use the crawler pile pulling machine to cooperate with the vibrating hammer to pull out the pile; the pile can be pulled out after the foundation construction is completed and the backfilling is completed.

Further, for the layered excavation foundation pit, for different pile support forms, after the crown beam is constructed, repeat the construction process from step 1 to step 5 until the excavation reaches the bottom of the foundation pit; then, go to step 6 and step seven.

Compared with the prior art, the beneficial effects of the present invention are:

Using the foundation pit supporting structure utilizing the recyclable inclined steel sheet pile according to the present invention for foundation pit support can improve the foundation pit supporting effect. For example, it can be better applied to the support of super-deep and super-large foundation pits in soft soil areas. In addition, the present invention has simple construction and shortened construction period; the use of steel sheet piles can provide necessary safety. And for construction tasks, it can reduce the space requirements; the use of steel sheet piles can not be restricted by weather conditions; in the process of using steel sheet piles, it can simplify the complex procedures for checking the performance of materials or systems to ensure their adaptability and interchangeability. Sex is good. Most importantly, sheet piles can be recycled and reused, saving money.

Description of drawings

Fig. 1 is the schematic diagram of prior art foundation pit support method;

Fig. 2 is the schematic diagram of the method for supporting foundation pit with inclined steel plate support piles adopted in the example of the present invention;

Fig. 3 is a schematic diagram of a steel sheet pile lock and its snap connection.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the following embodiments do not limit the present invention by any means.

Before excavating the foundation pit, it is usually necessary to use supporting piles to support the foundation pit to avoid side collapse of the foundation pit and affect the construction of the foundation pit. Figure 1 is a schematic diagram of a commonly used foundation pit support method. Referring to FIG. 1 , the supporting pile structure includes three vertical supporting piles, the supporting piles are steel sheet piles 1 , and the three schematic steel sheet piles 1 can be pressed into the soil one by one. In Fig. 1, the steel sheet pile 1 goes deep below the bottom 3 of the foundation pit to obtain higher support strength. The part of the steel sheet pile 1 below the bottom of the foundation pit accounts for 1-3 times the length of the steel sheet pile 1 to ensure the protection of the foundation pit. effective support. After the steel sheet piles 1 (three are shown in the figure) are pressed into the soil, the crown beam 2 can be fixedly connected to the outside of the three steel sheet piles 1 . The side of the crown beam 2 can support the side of the foundation pit. The row piles formed by the above structure are all vertical piles, which have many disadvantages when carrying out foundation pit support. For example, the pile top with the same excavation depth has a large displacement and a large internal force, which causes a large deformation of the ground behind the pile and endangers the surrounding area. Environment; when the strength of the pile is not enough, it is easy to cause the slope protection pile to break and cause the foundation pit to become unstable; the use of vertical piles makes the excavation depth of the foundation pit smaller, and when the excavation depth is large, the piles are prone to overturning failure, so the support structure requires a larger cross-section and insertion depth. It is not suitable for the support of super-deep and super-large foundation pits in soft soil areas, which affects the application of row piles.

In order to improve the support effect of foundation pits and be more suitable for the support of ultra-deep and super-large foundation pits in soft soil areas, a recyclable foundation pit support structure using inclined steel sheet piles proposed by the present invention is shown in Figure 2 , the foundation pit supporting structure includes a steel sheet support row pile, the steel sheet support row pile includes a plurality of steel sheet piles 1 inserted into the soil, the steel sheet pile 1 includes a pile body 11, and the steel sheet pile 1 is on the pile One end of the body 11 which is inserted into the soil body is the pile tip 12 and the other end is the pile tail 13. The steel sheet pile 1 is composed of trapezoidal channel steel, and locks 14 are provided on both sides of the steel sheet pile 1 in the width direction. Adjacent steel sheet piles 1 are connected by occlusal joints 14; the pile tails 13 of all steel sheet piles 1 are fixed with the crown beam 2; it is characterized in that, all steel sheet piles 1 are inserted into the soil body inclined to the direction of gravity, and the inclination angle is α, α is in the range of 0° to 30°, but not including 0°, and the preferred angle of inclination is α=15°～20°. Therefore, the steel sheet pile supporting row piles are inclined to the inner side of the foundation pit.

In the present invention, the length of the steel sheet pile 1 along the edge direction of the foundation pit to be excavated is L, and the pile spacing of the steel sheet pile 1 along the edge direction of the foundation pit to be excavated is H, where H=2˜2.5L.

The cross section of the crown beam 2 can be square or rectangular, if it is a square, its side length is A, and A>0.6L. If it is a rectangle, the long side of the rectangle is B, the short side is C, and the direction of the short side C coincides with the direction of gravity, and B>0.6L.

In the foundation pit supporting structure provided by the present invention, the use of steel sheet piles can provide necessary safety, and the use of steel sheet piles can not be restricted by weather conditions; the supporting effect can be improved by arranging the steel sheet support piles in an inclined manner. In addition, because the steel plate support piles are inclined to the inside of the foundation pit, the construction difficulty can be reduced, and the support of the foundation pit can be more uniform.

Utilize the foundation pit support method of the above-mentioned foundation pit support structure provided by the present invention, and the steps are as follows:

Step 1. According to the site conditions and calculation analysis, within the range of the inclination angle α (0° to 30°), determine the optimal inclination angle of the steel sheet row piles, and select the pile length and the strength of the pile body.

Step 2. Excavation of trenches: Excavate trenches with an excavator according to the surrounding line of the foundation pit, and remove underground obstacles. The soil body of the excavated trenches should be treated in time to ensure the normal construction of crown beams and coupling beams.

Step 3: Construction of inclined piles, and steel sheet piles are used for inclined piles. The steel sheet piles are driven by the single pile driving method one by one. The process is as follows:

1) Construction preparations: Before driving the steel sheet pile, close the groove at the tip of the pile to avoid the intrusion of soil, and coat the lock with butter or other grease; The piles should be repaired and corrected. For the steel sheet piles that are bent and deformed, they should be corrected by methods such as hydraulic jack pressing or fire drying.

2) Measuring and positioning the line: The surveyor releases the axis of the steel sheet pile enclosure, and sets up guide piles at certain distances. The guide piles are directly used as the steel sheet piles, and then the lanyard line is used as the wire, and the wire is used to control the axis of the steel sheet pile during piling. .

3) Feeding the piles: Use the inclined pile static press to lift the steel sheet piles, artificially straighten them in place, and control the positioning error to be less than 20mm; the inclined angle determined in step 1 is 0-30°, and the inclined piles are inclined to the inside of the foundation pit. According to the design inclination angle and combined with the depth of return and the height of the equipment, the pile line, the entry line and the alignment line are calculated respectively. After the pile position review is correct, the inclined pile static pressing machine can be constructed in sequence. during the piling process. To ensure the angle of the steel sheet pile. Controlled in both directions with two theodolites.

4) The single piles are continuously driven one by one, and it should be noted that the heights of the pile tops should not be too different. In the process of driving the first sheet pile and the second sheet pile, in order to ensure the accurate position and direction, so as to play the role of a guide model, the position and direction are measured every time 1m is driven, and the position and direction are measured immediately after driving to the predetermined depth. Temporary fixing by electric welding of steel bars or steel plates and purlin brackets;

Step 4. Construction of the water-proof curtain: The construction of the water-proof curtain is carried out at the same time as the construction of the inclined piles. The bottom elevations of the inclined piles are the same.

The process is as follows:

1) Positioning: The deep mixer reaches the designated pile position and aligns.

2) Pre-mixing and sinking: After the cooling water circulation of the deep mixer is normal, start the motor of the mixer, loosen the sling of the mixer, and let the mixer stir and cut the soil along the guide frame and sink.

3) Preparation of cement slurry: When the deep mixer sinks to a certain depth, it starts to mix the cement slurry according to the mixing ratio determined by the design, and pours the cement slurry into the collecting hopper before grouting.

4) Lifting and mixing: After the deep mixer sinks to the design depth, turn on the mortar pump to press the cement slurry into the foundation, and rotate while spraying, and at the same time lift the deep mixer in strict accordance with the lifting speed determined by the design.

5) Repeat up and down mixing: When the deep mixer is lifted to the top elevation of the design depth, the cement slurry in the hopper should be just emptied. In order to mix the soft soil and the cement slurry evenly, the mixer can be sunk into the soil while rotating again, and the mixer can be lifted out of the ground after reaching the designed reinforcement depth.

6) Cleaning: Clean the remaining cement slurry in all pipelines, and clean the soft soil adhering to the mixing head.

7) Shift: Move the deep mixer to the next pile position and repeat the above steps.

Step 5. Crown beam construction: The process is as follows:

1) The crown beam earthwork shall be excavated by mechanical partitions. First, the first layer of earthwork shall be excavated to the design pile top elevation of the supporting pile. After removing the remaining soil, the pile head floating slurry shall be removed to the design elevation. The concrete on the top surface of the pile core shall be chiseled. Treatment and removal of scum at the top of the pile. If the strength of the pile head concrete at the design elevation fails to meet the design requirements, it must continue to be demolished until the quality of the concrete meets the design requirements, and it is poured together when the concrete of the crown beam at the elevation section is insufficient.

2) The soil between the piles is artificially leveled to the bottom elevation of the crown beam, and compacted and compacted.

3) After the pile head is broken, the reinforcement can be made according to the section reinforcement of the crown beam. Rebar cutting and binding errors ensure that the design and construction specifications are met. Reinforcing bars should be reserved for the joint part of the crown beam segmented pouring.

4) Check the elevation of the crown beam and install the formwork. When the formwork is supported, it is necessary to ensure that the formwork is stable and firm to prevent the formwork from being deformed when the concrete is poured. The size of the formwork section is made according to the crown beam section.

5) Complete the reinforcement works. Longitudinal reinforcement is best to use HRB335 or HRB400 steel, stirrups and tie bars should use HPB300 and HRB335 steel. The diameter of the side longitudinal bars should not be less than 20mm, and the spacing should not be greater than 200mm; the diameter of the top and bottom longitudinal bars should not be less than 20mm, and the spacing should not be greater than 300mm; the diameter of the stirrups should not be less than 8mm, and the spacing should not be greater than 250mm; the diameter of the tie bars should be Use 6 to 12mm, and the spacing should not be greater than 500mm.

6) Complete the concrete pouring and curing. The concrete strength grade should not be lower than C25, and the anchoring of the main reinforcement of the row piles into the crown beam should not be less than 35d (d is the diameter of the reinforcement).

For the foundation pit excavated in layers, for different pile support forms, repeat the above steps until the excavation reaches the bottom of the foundation pit.

Step 6. Clean and level the bottom of the foundation pit, and carry out the next construction operation;

Step 7. Use the crawler pile pulling machine to cooperate with the vibrating hammer to pull out the pile; after the foundation construction is completed and the backfilling is completed, the pile can be pulled out. The process is as follows:

1) Remove the crown beam.

2) Vibration. First, clamp the head of the steel sheet pile with a pile driver and vibrate it for 1 min to 2 min to loosen the soil around the steel sheet pile and produce "liquefaction" to reduce the friction force of the soil on the pile.

3) Vibrate. When pulling out the pile, pay attention to the load of the pile driver. When it is found that it is difficult to pull up or cannot be pulled out, the pile should be stopped. First vibrate for 1min-2min, then hammer down 0.5-1.0m and then vibrate upwards. Repeatedly, the pile can be pulled out. Pull out.

The foundation pit support method provided by the invention can reduce the space requirements for construction tasks; in the process of using steel sheet piles, it can simplify the complex procedures for checking the performance of the material system to ensure good adaptability and interchangeability. . Most importantly, sheet piles can be recycled and reused, saving money.

Although the present invention has been described above in conjunction with the accompanying drawings, the present invention is not limited to the above-mentioned specific embodiments, which are merely illustrative rather than restrictive. Under the inspiration of the present invention, many modifications can be made without departing from the spirit of the present invention, which all belong to the protection of the present invention.

Claims (7)

1. A recoverable foundation pit supporting structure utilizing inclined steel sheet piles comprises steel sheet supporting row piles, the steel sheet supporting row piles comprise a plurality of steel sheet piles (1) inserted into a soil body, each steel sheet pile (1) comprises a pile body (11), one end, located in the soil body to be inserted, of each pile body (11) on each steel sheet pile (1) is a pile tip (12), the other end of each steel sheet pile (1) is a pile tail (13), each steel sheet pile (1) is composed of a trapezoid groove steel, locking notches (14) are formed in two sides of each steel sheet pile (1) in the width direction, adjacent steel sheet piles (1) are connected in an occluded mode through the locking notches (14), the pile tails (13) of all the steel sheet piles (1) are fixed to a crown beam (2), the foundation pit supporting row piles are inclined to the gravity direction, the inclination angle is α and is 0-30 degrees, but the inclination angle of the steel sheet piles does not include 0 degree, and accordingly the foundation pit supporting row piles are inclined to the inner side.

2. The recoverable foundation pit supporting structure using inclined steel sheet piles according to claim 1, wherein α -15 ° to 20 °.

3. The recoverable foundation pit supporting structure using the inclined steel sheet piles according to claim 1, wherein the length of the steel sheet piles (1) in the edge direction of the foundation pit to be excavated is L, the pile spacing of the steel sheet piles (1) in the edge direction of the foundation pit to be excavated is H, and H is 2-2.5L.

4. Recoverable foundation pit supporting construction using inclined steel sheet piles, according to claim 3, characterized in that the cross-section of the top beam (2) is square with a side length A > 0.6L.

5. Recoverable foundation pit supporting construction using inclined steel sheet piles, according to claim 3, characterised in that the cross-section of the top beam (2) is rectangular with the long side B and the short side C, the short side C running in the direction of gravity, B > 0.6L.

6. A method of foundation pit bracing using a recoverable foundation pit bracing structure using inclined steel sheet piles according to claim 1, comprising the steps of:

step one, according to site conditions and calculation and analysis, determining that the inclination angle α of the steel plate supporting row pile is 0-30 degrees but not 0 degree, and selecting the length and the pile body strength of the steel plate pile (1);

step two, digging a groove;

step three, oblique row pile construction, adopting a single-pile one-by-one driving method to drive steel sheet piles, comprising the following steps:

1) sealing a groove opening at the pile tip before the steel sheet pile is driven, and coating grease or other grease at a lock opening;

2) measuring, positioning and paying off: paying out the axis of the enclosure of the steel sheet pile, arranging guide piles at intervals, directly using the steel sheet pile as the guide pile, then hanging a rope line as a lead, and controlling the axis of the steel sheet pile by using the lead during pile driving;

3) the method comprises the following steps of (1) sending a pile, namely, hoisting a steel sheet pile by using an inclined pile static pressure machine, manually righting the steel sheet pile to be in place, controlling a pile body according to the inclination angle determined in the step one, calculating a pile line, an earth penetration line and a counterpoint line according to the inclination angle α determined in the step one and combining the downward returning depth and the equipment height, sequentially constructing by using the inclined pile static pressure machine after the pile position is rechecked, and monitoring and controlling by using two theodolites to ensure the inclination angle α of the steel sheet pile in the pile driving process;

4) continuously driving single piles one by one, measuring the position and the direction once every 1m when the first steel sheet pile and the second steel sheet pile are driven in the process of driving so as to play a role of a guide sample plate, and immediately and temporarily fixing the steel bars or the steel plates and the purlin surrounding support through electric welding after the steel bars or the steel plates are driven to a preset depth;

step four, constructing a waterproof curtain;

step five, constructing the crown beam;

sixthly, cleaning and leveling the bottom of the foundation pit, and performing the next construction operation;

seventhly, adopting a crawler pile pulling machine to be matched with a vibration hammer to pull the pile; and after foundation construction is finished and backfilling is carried out, the pile can be pulled out.

7. The foundation pit supporting method of the recoverable foundation pit supporting structure using the inclined steel sheet piles according to claim 6, wherein for the foundation pit excavated in layers, the construction process of the first to fifth steps is repeated after the construction of the top beam for different row pile supporting forms until the bottom of the foundation pit is excavated; then, step six and step seven are performed.

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