CN219045158U - Deep foundation pit composite supporting structure close to high slope under weak stratum condition - Google Patents

Abstract

The utility model relates to a composite supporting structure of a deep foundation pit adjacent to a high side slope under a weak stratum condition, which is adopted aiming at the special working condition that the deep foundation pit is adjacent to the high side slope beside an excavation area of the deep foundation pit. The composite supporting structure comprises a supporting system close to a high side slope and a deep foundation pit supporting system, wherein the supporting system close to the high side slope comprises an existing gravity retaining wall and a miniature recyclable prestressed anchor rod; the deep foundation pit supporting system comprises guard piles, crown beams and prestressed anchor cables. The utility model has the advantages that: the deep foundation pit excavation process is considered to possibly disturb the adjacent high side slope, and the recyclable anchor rod is adopted to temporarily support the high side slope, so that the stability of the high side slope in the foundation pit excavation process is ensured, the damage to the existing gravity retaining wall is reduced, the anchor rod can be recycled after the foundation pit is backfilled, and the support cost is saved. And the deep foundation pit is supported by pile anchors, and the stability of the deep foundation pit in the excavation process can be ensured to the greatest extent by adopting the existing gravity retaining wall.

Description

Deep foundation pit composite supporting structure close to high slope under weak stratum condition

Technical Field

The utility model relates to the field of deep foundation pit excavation supporting, in particular to a deep foundation pit composite supporting structure adjacent to a high side slope under a weak stratum condition.

Background

Nowadays, rail transportation industry rapidly develops, and more cities start building subways. Meanwhile, due to shortage of land, foundation pit construction areas of related supporting facilities of subways such as parking lots, power substations and the like can be close to buildings or high slopes. When the deep foundation pit construction area is adjacent to the existing high side slope, particularly under the weak stratum condition, the stability of the adjacent high side slope can be influenced to a certain extent in the deep foundation pit excavation process, and the probability of foundation pit instability in the deep foundation pit excavation process can be increased due to the existence of the existing high side slope. Therefore, in the construction process of the foundation pit excavation, the side wall of the foundation pit is supported and the adjacent high slope is also subjected to certain temporary reinforcement.

In the prior art, the foundation pit supporting structure mainly only considers adopting various foundation pit supporting structures under different soil types or different construction conditions. Under the condition that the existing high side slope is adjacent, what supporting structure is adopted in the deep foundation pit excavation process can ensure that the foundation pit excavation is smoothly carried out without being disturbed by the existing high side slope. In addition, after the foundation pit construction is completed, the existing adjacent high slope is not required to be additionally supported, so that the condition of material waste and high cost exists when a general slope support structure is selected. This situation has not been considered in the prior art.

Disclosure of Invention

The utility model provides a composite supporting structure of a deep foundation pit adjacent to a high side slope under a weak stratum condition, and based on the problems existing in the prior art, the utility model aims to solve the technical problem of composite supporting of the deep foundation pit adjacent to the high side slope. The method has the advantages that the stability of the high side slope and the deep foundation pit is guaranteed during construction, meanwhile, the damage to the existing gravity retaining wall can be reduced to the greatest extent, the miniature recoverable anchor rod for temporary support of the high side slope can be recovered after backfilling of the foundation pit, the anchor rod can be utilized for multiple times, and the support cost is reduced.

Aiming at the complex working condition of excavation of a deep foundation pit adjacent to a high side slope under a weak stratum condition, the utility model provides a composite supporting structure of the deep foundation pit adjacent to the high side slope under the weak stratum condition, and the composite supporting structure has the following specific technical scheme.

The composite supporting structure comprises a near high slope supporting system and a deep foundation pit supporting system, wherein the near high slope supporting system comprises an existing gravity type retaining wall and a miniature recyclable prestressed anchor rod, the outer part of a rod body of the miniature recyclable prestressed anchor rod is connected with a plastic sleeve through a centering bracket, the miniature recyclable prestressed anchor rod is anchored on a stable soil body through an anchor head, the anchor head is positioned at the tail end of the anchor rod, the anchor head is connected with the rod body through an anchor ring, the anchor head has a recycling function, and the outer end of the rod body is fixed on the existing gravity type retaining wall through a steel beam waist; the deep foundation pit supporting system comprises guard piles, crown beams and prestressed anchor cables.

Preferably, the anchor head is composed of a wedge-shaped clamping piece, an anchor ring, a retaining device, an extrusion spring and a bearing plate. An extrusion spring is arranged in a space formed by the anchor ring and the bearing plate, the extrusion spring is respectively connected with the bottom of the anchor ring and the top of the bearing plate, a central hole for a rod body to pass through is reserved in the middle of the anchor ring, the rod body passes through the bearing plate and the central hole of the anchor ring, wedge-shaped clamping pieces are arranged in the middle of the rod body and the anchor ring, the anchor ring and the wedge-shaped clamping pieces are fixedly connected through friction, the rod body passes through the bearing plate, and the end parts of the rod body are fastened and fixed by the wedge-shaped clamping pieces; and a backstop device is arranged between the anchor ring and the side wall of the anchor head.

Preferably, the retaining device is of a zigzag ribbon structure, so that the anchor ring can only move unidirectionally relative to the side wall of the foundation pit, when the anchor ring is in contact with the bearing plate, the anchor ring is in a locking state, and when the anchor rod needs to be recovered, the wedge-shaped clamping piece is still in a free state as the anchor ring is locked by the retaining device and cannot move, and the wedge-shaped clamping piece loses clamping force along with the movement of the rod body, so that the rod body can be pulled out for recovery.

Preferably, the guard piles adopt cast-in-place piles, pile driving is carried out before excavation, the guard piles are horizontally connected through crown beams to form 'row piles', a certain distance is reserved between the guard piles, and the prestressed anchor cables are driven into the guard piles through steel beam waists.

The utility model has the advantages that:

1. the utility model considers the special working condition that the deep foundation pit excavation area is close to the existing high side slope, utilizes the existing gravity retaining wall support, combines the miniature recoverable prestressed anchor rod to carry out temporary support on the close high side slope, and greatly improves the stability of the close side slope during foundation pit excavation. The side slope is prevented from being damaged in the process of excavating the foundation pit, and the influence on the foundation pit excavation engineering caused by the damage, collapse and the like of the side slope can be further prevented.

2. The utility model adopts the miniature recoverable prestressed anchor rod to support the high slope. After the foundation pit is backfilled, the miniature recyclable prestressed anchor rod can be recycled, so that the supporting cost is reduced, and the structure of the existing gravity type retaining wall of the high slope is protected as much as possible.

3. According to the utility model, the pile anchor support formed by the guard piles and the prestressed anchor cables is used for supporting the side wall of the foundation pit, so that the stability of the foundation pit during deep foundation pit excavation is improved.

Drawings

For a clearer description of an embodiment of the utility model or of the prior art, the drawings that are used in the description of the embodiment or of the prior art will be briefly described, it being obvious that the drawings in the description below are only some embodiments of the utility model, and that other drawings can be obtained from them without inventive effort for a person skilled in the art.

Fig. 1: schematic diagram of a composite supporting structure of a deep foundation pit adjacent to a high slope.

Fig. 2: the utility model discloses an anchor head structure schematic diagram with a recovery function.

Fig. 3: the A-A section structure of fig. 2 is schematically shown.

Fig. 4: the utility model discloses a structure schematic diagram of a prestressed anchor cable.

Reference numerals illustrate:

1. existing gravity retaining walls; 2. miniature recoverable prestressed anchor rod; 3. an anchor head; 4. a rod body; 5. a crown beam; 6. a fender post; 7. pre-stress anchor cables; 8. a steel beam waist; 9. deep foundation pit; 10. a plastic sleeve; 11. Centering support; 12. a wedge-shaped clamping piece; 13. an anchor ring; 14. a stopping device; 15. extruding a spring; 16. a carrying plate; 17. an anchor head of the anchor cable; 18. an N1 backing plate; 19. an N2 backing plate; 20. 2[20b double-spliced channel steel.

Detailed Description

It should be noted that, without conflict, the embodiments of the present utility model and features of the embodiments may be combined with each other. For the purpose of making the objects, technical solutions and advantages of the embodiments of the present utility model more apparent, the technical principles and construction processes of the present utility model will be described in detail with reference to the accompanying drawings.

It is apparent that the examples are given only for explaining the present utility model and do not limit the scope of application of the present utility model. The following description of at least one exemplary embodiment is merely exemplary in nature and is in no way intended to limit the utility model, its application, or uses. All other embodiments, which can be made by those skilled in the art based on the embodiments of the utility model without making any inventive effort, are intended to be within the scope of the utility model.

The utility model provides a technical scheme that: a composite supporting structure for deep foundation pit adjacent to high slope under weak stratum condition. As shown in fig. 1, the composite supporting structure comprises a high slope supporting system and a deep foundation pit supporting system, the high slope supporting system comprises an existing gravity type retaining wall 1 and a miniature recoverable prestressed anchor rod 2, the outer portion of a rod body 4 of the miniature recoverable prestressed anchor rod 2 is connected with a plastic sleeve 10 through a centering bracket 11, the miniature recoverable prestressed anchor rod 2 is anchored on a stable soil body through an anchor head 3, the anchor head 3 is positioned at the tail end of the anchor rod, the anchor head 3 is connected with the rod body 4 through an anchor ring 13, the outer end of the rod body 4 is fixed on the existing gravity type retaining wall 1 through a steel beam waist 8, and the anchor head 3 has a recovery function. As shown in fig. 2, the anchor head 3 is composed of a wedge-shaped clamping piece 12, an anchor ring 13, a retaining device 14, a compression spring 15 and a bearing plate 16. An extrusion spring 15 is arranged in a space formed by the anchor ring 13 and the bearing plate 16, the extrusion spring 15 is respectively connected with the bottom of the anchor ring 13 and the top of the bearing plate 16, a central hole for a rod 4 to pass through is reserved in the middle of the anchor ring 13, the rod 4 passes through the bearing plate 16 and the central hole of the anchor ring 13, a wedge-shaped clamping piece 12 is arranged in the middle of the rod 4 and the anchor ring 13, the anchor ring 13 and the wedge-shaped clamping piece 12 are fixedly connected through friction, the rod 4 passes through the bearing plate 16, and the end part of the rod 4 is fastened and fixed by the wedge-shaped clamping piece 12; a backstop device 14 is arranged between the anchor ring 13 and the side wall of the anchor head 3; the retaining device 14 is of a zigzag ribbon structure, so that the anchor ring 13 can only move unidirectionally, when the anchor ring 13 contacts the bearing plate 16, the anchor ring 13 is in a locking state, and when the anchor rod needs to be recovered, the wedge-shaped clamping piece 12 is still in a free state as the anchor ring 13 is locked by the retaining device 14 and cannot move, and the wedge-shaped clamping piece 12 loses clamping force along with the movement of the rod body 4, so that the anchor rod can be pulled out and recovered. The deep foundation pit supporting system comprises guard piles 6, crown beams 5 and prestressed anchor cables 7. The guard piles 6 are cast-in-place piles, piles are driven before excavation, the guard piles 6 are horizontally connected through the crown beams 5 to form 'row piles', a certain distance is reserved between the guard piles 6, and the pre-stressed anchor cables 7 are driven into the guard piles 6, and the pre-stressed anchor cables 7 are fixed on the guard piles 6 through steel beam waists 8.

Further, the present utility model relates to an existing slope with a neighboring high slope of 11m height in the actual engineering. The high side slope has an existing gravity retaining wall 1.

Further, as shown in fig. 2, the anchor head 3 has a recovering function, and fig. 3 is a cross-sectional view of the shank 4 of the miniature recoverable prestressed anchor rod 2. The anchor head 3 is connected with the rod body 4 through an anchor ring 13, and the wedge-shaped clamping piece 12 fixes the rod body 4 in the anchor ring 13. When the strength of the anchoring body reaches 75% of the design strength, the anchoring body starts to stretch, the rod body moves outwards and drives the anchor ring 13 to move together, the friction force between the wedge-shaped clamping piece 12 and the rod body 4 is increased along with the outward movement, the extrusion spring at the lower half part of the anchor head 3 is compressed until the anchor ring contacts with the bottom bearing plate, and the stretching force is transmitted to the bearing plate and the anchoring body from the rod body at the moment, so that the anchoring force is obtained, and as the retaining device 14 is arranged on the anchor ring 3, the retaining device 14 adopts the retaining principle similar to a binding belt, the anchor ring 13 can only move unidirectionally in the direction of the bearing plate 16 integrally, and is fixed after the anchor ring 13 contacts with the bearing plate 16.

When the miniature recoverable pre-stressed anchor rod 2 of the temporary support needs to be recovered after the foundation pit is backfilled, firstly, the fixation of the steel beam waist 8 is released, the pre-stress is removed, inward thrust is exerted on the outer end of the miniature recoverable pre-stressed anchor rod 2, the anchor ring 13 cannot move along with the rod body 4 continuously due to the existence of the retaining device 14, the wedge-shaped clamping piece 12 loosens, the rod body 4 is separated from the anchor ring 13, and the miniature recoverable pre-stressed anchor rod 2 can be recovered at the moment.

The deep foundation pit supporting system adopts pile anchor supporting consisting of guard piles 6 and prestressed anchor cables 7. The structure of the prestressed anchor cable 7 is shown in fig. 4, and the pile anchor support is combined with an anti-slide pile support method and an anchor rod support method, which integrate the support principles of the anti-slide pile and the anchor cable, namely, the anti-slide force for preventing the foundation pit slope from sliding downwards is mainly derived from the anchoring force provided by the prestressed anchor cable 7 and the anti-slide force provided by the anti-slide pile. The pile anchor support mainly comprises a guard pile 6, a prestressed anchor rope 7, a concrete surface layer and the like, and is mainly characterized in that anchor rods are adopted to replace an inner support of a foundation pit support, and anchor pulling force is provided for supporting row piles so as to reduce displacement and internal force of the supporting row piles and control deformation of the foundation pit within an allowable range.

The present utility model may be further configured in a preferred example to:

1. and (5) slope support construction.

As shown in fig. 1, the side slope support system of this example includes an existing gravity type retaining wall 1 and a miniature recoverable prestressed anchor rod 2, the miniature recoverable prestressed anchor rod 2 is buried perpendicular to the existing gravity type retaining wall 1 and a stable soil body, the anchor rod includes a rod body 4, an anchor head 3 with a retaining device 14 connected with the rod body 4, the rod body 4 is connected with a plastic sleeve 10 through a centering bracket 11, and the outer end of the rod body 4 is fixed on the existing gravity type retaining wall 1 through a steel beam waist 8. The anchor head 3 is a sealing device, the anchor head 3 has a recycling function to ensure recycling of the anchor rod after backfilling of the foundation pit, and the anchor head 3 in the example comprises a wedge-shaped clamping piece 12, an anchor ring 13, a backstop device 14, an extrusion spring 15, a bearing plate 16 and other structures.

By combining the structure of the anchor rod, the utility model firstly drills a lower inclined hole with a certain size in soil body by using a drilling machine when the side slope is supported, the first distance is 2.0m from the top of the slope, and 1 track is arranged every 2.5m later, and the horizontal distance of the recyclable prestressed anchor rod 7 is 1.5m. The miniature recoverable prestressed anchor rod 2 and the grouting pipe are sent into a hole together, then grouting is carried out, cement slurry and the anchor rod body 4 are not in direct contact due to the existence of the plastic sleeve 10, grouting is stopped after the cement slurry reaches the designed grouting depth, tensioning is started when the anchor strength reaches 75% of the designed strength, and after the prestress of 20kN is applied according to the requirement, the steel beam waist 8 formed by channel steel is fixed on the wall surface of the existing gravity retaining wall 1. And when the deep foundation pit 9 is backfilled, the anchor rod can be recovered through the recoverable anchor head 3 at the end of the anchor rod.

2. And (5) construction of the fender post.

(1) The guard piles 6 adopt the supporting piles with the diameter of 1200mm@1700 mm: the main reinforcement adopts 24C 25 steel bars, the spiral stirrups adopt A12@150mm to arrange, a C20 stiffening hoop is arranged along the inner diameter of the pile body every 2m, and the concrete strength grade is C30. The construction is mainly carried out by rotary drilling, the drilling machine is used for hole forming construction, and clay or high-quality mud wall protection is selected.

(2) And (3) bottom cleaning: ensuring the flatness of the base surface and no virtual slag before the construction of the fender post 6.

(3) Measuring and positioning and paying off: marking the position of the pile core and marking the size and position of the pile diameter by using red paint.

(4) Burying a protective barrel: the pile casing is made of steel plates with the diameter of between 1.20 and 1.40 meters and the height of 1.70 meters and is 5 to 8 millimeters. In order to increase rigidity and prevent deformation, stiffening ribs are welded on the upper and lower ports of the pile casing and the outer side of the middle part respectively. The bottom of the pile casing is buried in 1.5 meters under the ground, and the top of the pile casing is 0.2 meter higher than the ground. The pile casing is generally buried by adopting an excavation burying method, namely, after a soil layer of the pile casing to be buried is excavated or manually excavated by a special drilling bucket, the pile casing is placed in the soil layer. The burying should be accurate, horizontal, vertical and stable, and the periphery of the protective cylinder should be backfilled with clay and tamped. The calibration of the pile center position after the pile casing is in place is also critical, a cross reinforcement frame can be welded on the pile casing mouth after the pile casing is arranged, a hammer is hung at the center of the cross frame, the pile casing is naturally lowered, whether the pile casing coincides with the pile center is checked, the accurate installation position of the pile casing is checked, and after the pile casing is in place, the outside excavation seam is backfilled in a layered manner. If the protection sleeve is installed by adopting a pressing method, the protection sleeve rolling opening should be prevented during pressing.

(5) And (3) positioning a drilling machine: and (5) erecting a drilling frame, adjusting, lifting the drill bit, and slowly placing the drill bit into the casing. Starting a winch to hoist the drill plate, filling square timber below the drill plate base, leveling the drilling machine, aligning the drilling hole, installing the drill plate, and requiring the center of the drill plate to be on a plumb line with a hoisting pulley on a drill frame, wherein the position deviation of the drill rod is not more than 2 cm.

(6) Drilling: preferably, a rotary drilling rig provided with a heavy machine lock drill rod can be selected for drilling, so that the construction efficiency of a dense stratum is ensured. And checking the diameter-keeping device of the drill bit before forming the hole, and timely replacing the drill bit with exceeding abrasion during the construction process. In the pore-forming, construction is carried out according to parameters determined by construction, and when the rotary drilling rig drills to reach rock and the rock is not moved, the percussion drilling rig is used for drilling the rock layer below the rotary drilling rig until the design depth is reached.

(7) Hole cleaning: and after drilling to the designed hole depth, testing the slurry index, and if the slurry index exceeds the standard, adjusting through slurry replacement. And then placing the bottom-cleaning drill bit into a hole bottom to clean the hole, and fishing out sediment. The hole cleaning adopts a gas lift method. When the hole is cleaned, the mud surface in the hole should not be lower than 1.0 meter below the hole opening and be higher than the ground water level by more than 1.0-1.5 meters. And after the hole cleaning is finished, the self-checking is qualified, and then the hole depth measurement is carried out together with a supervision engineer to serve as a basis for measuring sediment before casting.

(8) Hanging and placing a reinforcement cage: when the reinforcement cage is in the hole, the reinforcement cage is hoisted by a 25-ton crane. When the reinforcement cage is installed, two-point hoisting is adopted. The first lifting point is arranged at the lower part of the framework, and the second lifting point is arranged between the middle point and the upper third point of the length of the framework. When the reinforcement cage is hung into the hole, the hole diameter is aligned, the reinforcement cage is kept vertical, the reinforcement cage is slowly hung into the hole, and the reinforcement cage is slowly hung into the hole and is not suitable for left and right rotation and does not swing to collide with the hole wall. If the blocking is met, stopping the descending, and finding out the reason for processing. Do not raise and drop and force down. After the reinforcement cage is positioned, concrete is poured within 6 hours, so that the hole collapse is prevented.

(9) Secondary bottom cleaning: after the reinforcement cage is arranged, a non-shrinkage hydrological measuring rope and a standard measuring hammer are required to be adopted to measure the sediment value, and pile holes exceeding the control range are required to be subjected to secondary bottom cleaning. Preferably, the secondary bottom cleaning adopts a gas lift method, and a pouring conduit is arranged immediately after the secondary bottom cleaning is qualified for underwater concrete pouring.

(10) The guide pipe is arranged below: the pile foundation concrete is poured by adopting a slurry-down vertical lifting guide pipe method, a circular spiral quick joint guide pipe is selected, the upper end of the circular spiral quick joint guide pipe is connected with a pouring funnel, and the circular spiral quick joint guide pipe is suspended by a crane or a drilling machine, so that the guide pipe can vertically move up and down during pouring and pulling. The connection between the guide pipes is provided with a sealing ring. The catheters are placed down in sequence, and the descending order of the catheters, the number of each catheter and the length of each catheter are recorded. When the guide pipe is arranged downwards, the collision of the steel reinforcement cage is prevented, the guide pipe supporting frame is made of profile steel, and the supporting frame is supported on the drilling platform and used for supporting the suspension guide pipe. After all the concrete is put into the hole, the concrete is put at the bottom of the hole so as to check the length and the depth of the guide pipe, and then lifted by 15-30 cm to start pouring the underwater concrete. The dismantling conduit is hoisted during concrete pouring using a rig or crane.

(11) And (3) concrete pouring: and (5) pouring underwater concrete by adopting a slurry down-lifting conduit method. And the water-proof rubber ball method is adopted for casting. Before the pipe is cast, a sufficient amount of concrete should be prepared for casting. Before casting, an isolating rubber ball slightly smaller than the inner diameter of the guide pipe is placed in the guide pipe to serve as an isolating body for isolating slurry and concrete.

Once the pouring is started, the pouring should be continuously carried out without interruption. In the pouring process, the depth of the guide pipe embedded into the concrete is not less than 2.0 meters, and is not more than 6 meters, so that the guide pipe is conveniently pulled out of the concrete surface. The depth of the concrete surface in the pile hole is measured every 30 minutes, and the disassembly work of the guide pipe is guided. In the casting process, the situation of the orifice is closely noted, if the steel reinforcement cage floats upwards, the casting should be stopped slightly, meanwhile, a weight is pressed on the steel reinforcement cage, and the casting is continued within the time of not exceeding the specified interruption. The rising speed of the concrete surface is controlled to be more than 2 meters per minute. During pouring, the mud displaced by the concrete is discharged into other pile holes or sedimentation tanks under construction through a mud drainage ditch, so that the mud is prevented from overflowing and polluting the environment. The concrete should be poured continuously, the elevation of the poured pile top should be 0.5m higher than the elevation of the designed pile top to ensure the strength of the concrete, the redundant part should be chiseled before the concrete construction of the bearing platform, and the pile head should have no loose layer. The integral steel casing of the wellhead below the ground or pile top is pulled out immediately after the concrete is poured.

3. And (5) constructing the prestressed anchor cable.

The prestress anchor cable 7 is made of low-relaxation prestress steel strands, wherein the prestress anchor cable is 3 multiplied by 7 phi 5, and the design value of the steel strands is 1860kN. The prestressed anchor cable 7 is woven on site while drilling, the inner anchoring section is corrugated, and the tensioning section is straight. Strand blanking length = anchor section + free stretch section + wale thickness + jack length. The steel strands should be fed strictly according to the design size, and the length error of each strand is not more than 50mm. Marking the free end and the anchoring section in a sub-packaging mode, and processing and manufacturing an anchor rope bracket every 2m for the prestressed anchor rope 7 in the range of the anchoring section. The steel strand of the free section is placed into a plastic pipe (or wrapped with a plastic film) and is coated with butter, and after the guide cap is arranged at the anchoring end part, the steel strand is smoothly placed for standby.

The prestressed anchor cable 7 is set to be 2.0m from the ground surface at the first path by adopting a foundation pit supporting anchor cable with the diameter of 3 multiplied by 7 phi 5, and 1 path is set at each depth of 3.0m along the depth of the foundation pit. The horizontal distance between the prestressed anchor cables 7 is 1.7m, namely 1 prestressed anchor cable is arranged between every two piles or every two piles. The prestressed anchorage cable 7 has lengths 13m, 15m, 17m and 19m and effective anchoring lengths 6m, 7m, 10 and 11m. The prestressed anchorage cable 7 is connected with the horizontal layer of 2[20b double-spliced channel steel 20. And M30 cement slurry is adopted for grouting. The tension anchoring forces are 250kN and 260kN.

(1) Drilling and positioning: and a measurer finds the set elevation about 1m below the anchor cable elevation according to the drawing, discharges the anchor cable elevation position of the layer, marks with red paint and ensures the position to be accurate.

(2) Drilling: a down-the-hole impact drill is used. The drill hole diameter of the anchor cable adopts a drill bit with 150mm, and the drill hole inclination angle is 15 degrees. Before drilling, determining hole sites according to design requirements, and marking, wherein the horizontal hole pitch error of the anchor cable is not more than 50mm, and the vertical hole pitch error is not more than 100mm. The depth of the drilling hole should not be smaller than the design size, and should not be larger than 1% of the design length, and the deflection size of the drilling bottom should not be larger than 3% of the length of the anchor cable. When the drilling machine drills, drill rods required for drilling are placed in order according to the design length of the anchor cable, the drill rods are used up, and the hole depth is right. The depth of the drilling hole exceeds the design length of the anchor cable by about 0.5 m. And after the drilling is finished, the drill rod and the drilling tool are pulled out one by one, and the impactor is cleaned for standby. And (3) rechecking the hole depth by using a polyethylene pipe, blowing the hole by using high-pressure air, and plugging the hole opening by pulling out the polyethylene pipe when the dust in the hole is blown clean and the hole depth is not less than the design length of the anchor cable.

(3) And (3) installing a prestressed anchor cable: before the pre-stressed anchor cable 7 is assembled in the hole, checking whether the number of the pre-stressed anchor cable 7 is consistent with the hole number, and after confirming that the number is correct, cleaning the hole once by high-pressure air, so that the pre-stressed anchor cable 7 can be assembled. The grouting pipe and the prestressed anchor cable 7 are tied together and put into a borehole. The angle of the pre-stressed anchor cable 7 rod body is consistent with the drilling angle, and the delivery force is uniform and does not swing left and right.

(4) Grouting under normal pressure: the grouting liquid adopts M30 cement paste. And (3) grouting by adopting gravity or low pressure (0.4-0.6 MPa), adopting a bottom grouting mode, inserting the bottom end of the guide pipe into the hole bottom (preferably 100-200mm away from the hole bottom), slowly withdrawing the guide pipe at a uniform speed during grouting, and ensuring that the gas in the hole can completely escape through the slurry outlet of the guide pipe under the surface of the slurry in the hole all the time, wherein when the cement slurry flows out from the hole opening, the grouting is full, and stopping grouting.

(5) Installing a waist beam: the waist beam has the function of connecting the prestressed anchor cable 7 into a whole, so that the foundation pit is uniformly stressed, and the anchor cable tensioning in the next step can be normally performed. Adopts a 2[20b double-spliced groove steel waist beam. The upper channel steel and the lower channel steel are fixedly connected by adopting C25 steel bars, the clearance between the upper channel steel and the lower channel steel is 100mm, and the steel strand is ensured to penetrate out. The steel strand is penetrated out of the position and adopts a 200 multiplied by 20 backing plate, and the aperture of the middle opening hole is 50mm.

(6) Stretching the anchor cable: stretching can be performed when the strength of the anchoring body reaches 15.0MPa or 75% of the design strength. Before the pre-stressed anchor cable 7 is stretched, the stretching equipment should be calibrated. Before formal tensioning, 0.1-0.2 times of the design value is needed, and the tension is performed once, so that all parts of the cable are tightly contacted, and the rod body of the anchor cable is completely straight. The anchor cable is formally tensioned, an anchor clamping piece is not installed, the tensioning load is gradually loaded according to 10%, 25%, 50%, 75% and 110% of the designed tension value of the anchor cable, the observation time of each level of load is not less than 5 minutes, and after deformation is stable, the next level of load can be tensioned. After tensioning, the joint of the locking anchor clamp and the anchor cable is smeared with red paint, and if the paint is found to be larger in fault, prestress compensation tensioning is needed.

(7) External protection: after hole sealing and grouting, a 500mm steel strand is reserved from the anchor device, the rest part is cut off, and the outside of the steel strand is coated with a cement mortar protection layer with the thickness not less than 50mm.

(8) And (3) drawing an anchor cable: (1) the detection number should not be less than 5% of the total number of the anchor cables, and the detection number of the anchor cables in the same soil layer should not be less than 3. (2) The test should be performed after the strength of the grouting consolidation body of the anchoring section reaches 15MPa or 75% of the design strength. (3) The detection anchor cable should be selected by adopting a random sampling method. (4) The detection value of the pulling-resistant bearing capacity is determined according to the technical regulations of building foundation pit supporting (JGJ 120-2012). (5) The detection test is carried out according to the acceptance test method of the technical regulations of building foundation pit support. (6) When the detected anchor cable is unqualified, the detection quantity should be enlarged.

On the basis of the technical scheme, the utility model can be improved as follows.

Further, pile type of the guard piles 6 can adopt engaged piles, the engaged piles are partially embedded in the circumference between adjacent concrete row piles, and reinforcement cages are arranged in piles which are constructed in the follow-up sequence in an opposite mode, so that the integral continuous waterproof and soil-retaining guard structure with good seepage-proofing effect is formed. The arrangement mode of the piles is that one pile is not reinforced, and the super retarding plain concrete piles (A piles) and one reinforced concrete pile (B piles) are arranged at intervals. During construction, the pile A is firstly constructed, the pile B is then constructed, and the construction of the pile B is completed after the concrete of the pile A is initially set and before final setting. And the piles A and B are constructed by adopting a full sleeve drilling machine, and concrete at the intersection part of the adjacent piles A is cut off, so that occlusion is realized.

The beneficial effects of adopting the further scheme are as follows: aiming at the characteristic of a multi-water-rich weak stratum region, the occluding pile has good seepage-proofing effect, does not need to increase auxiliary water-saving curtain lamp waterproof measures, reduces supporting cost, and has high pore-forming speed and high pile-forming efficiency.

The foregoing is only a preferred embodiment of the present utility model, but the scope of the present utility model is not limited thereto, and any person skilled in the art, who is within the scope of the present utility model, should make equivalent substitutions or modifications according to the technical scheme of the present utility model and the inventive concept thereof, and should be covered by the scope of the present utility model.

Claims (4)

1. The composite supporting structure is characterized by comprising a high slope supporting system and a deep foundation pit supporting system, wherein the high slope supporting system comprises an existing gravity type retaining wall (1) and a miniature recoverable prestressed anchor rod (2), the outer part of a rod body (4) of the miniature recoverable prestressed anchor rod (2) is connected with a plastic sleeve (10) through a centering bracket (11), the miniature recoverable prestressed anchor rod (2) is anchored on a stable soil body through an anchor head (3), the anchor head (3) is positioned at the tail end of the anchor rod, the anchor head (3) is connected with the rod body (4) through an anchor ring (13), the anchor head (3) has a recovery function, and the outer end of the rod body (4) is fixed on the existing gravity type retaining wall (1) through a steel beam waist (8); the deep foundation pit supporting system comprises guard piles (6), crown beams (5) and prestressed anchor cables (7).

2. The composite supporting structure for the deep foundation pit adjacent to the high slope under the weak stratum condition according to claim 1, wherein the anchor head (3) is composed of a wedge-shaped clamping piece (12), an anchor ring (13), a retaining device (14), an extrusion spring (15) and a bearing plate (16); an extrusion spring (15) is arranged in a space formed by the anchor ring (13) and the bearing plate (16), the extrusion spring (15) is respectively connected with the bottom of the anchor ring (13) and the top of the bearing plate (16), a central hole for a rod body (4) to pass through is reserved in the middle of the anchor ring (13), the rod body (4) passes through the bearing plate (16) and the central hole of the anchor ring (13), a wedge-shaped clamping piece (12) is arranged in the middle of the rod body (4) and the anchor ring (13), the anchor ring (13) and the wedge-shaped clamping piece (12) are fixedly connected through friction, the rod body (4) passes through the bearing plate (16), and the end part of the rod body is fastened and fixed by the wedge-shaped clamping piece (12); a retaining device (14) is arranged between the anchor ring (13) and the side wall of the anchor head (3).

3. The composite supporting structure for deep foundation pit adjacent to high slope under the condition of weak stratum according to claim 2, wherein the retaining device (14) is of a zigzag ribbon structure, so that the anchor ring (13) can only move unidirectionally relative to the side wall of the foundation pit, when the anchor ring (13) is contacted with the bearing plate (16), the anchor ring (13) is in a locking state, and when the anchor rod needs to be recovered, the wedge-shaped clamping piece (12) is still in a free state due to the fact that the anchor ring (13) is locked by the retaining device (14) and cannot move, and the wedge-shaped clamping piece (12) loses clamping force along with the movement of the rod body (4), so that the rod body (4) can be pulled out for recovery.

4. The deep foundation pit composite supporting structure adjacent to a high side slope under the condition of a weak stratum according to claim 1, wherein the guard piles (6) are cast-in-place piles, piles are driven before excavation, the guard piles (6) are horizontally connected through crown beams (5) to form 'row piles', a certain distance is reserved between the guard piles (6), pre-stressed anchor cables (7) are driven into the guard piles (6), and the pre-stressed anchor cables (7) are fixed on the guard piles (6) through steel beam waists (8).

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