CN114809014A - Construction method of pile-anchor combined supporting structure with unloading pipe shed - Google Patents
Construction method of pile-anchor combined supporting structure with unloading pipe shed Download PDFInfo
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- CN114809014A CN114809014A CN202210530494.9A CN202210530494A CN114809014A CN 114809014 A CN114809014 A CN 114809014A CN 202210530494 A CN202210530494 A CN 202210530494A CN 114809014 A CN114809014 A CN 114809014A
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D17/00—Excavations; Bordering of excavations; Making embankments
- E02D17/02—Foundation pits
- E02D17/04—Bordering surfacing or stiffening the sides of foundation pits
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D15/00—Handling building or like materials for hydraulic engineering or foundations
- E02D15/02—Handling of bulk concrete specially for foundation or hydraulic engineering purposes
- E02D15/04—Placing concrete in mould-pipes, pile tubes, bore-holes or narrow shafts
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D5/00—Bulkheads, piles, or other structural elements specially adapted to foundation engineering
- E02D5/74—Means for anchoring structural elements or bulkheads
- E02D5/76—Anchorings for bulkheads or sections thereof in as much as specially adapted therefor
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A10/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE at coastal zones; at river basins
- Y02A10/23—Dune restoration or creation; Cliff stabilisation
Abstract
The invention discloses a construction method of a pile-anchor combined supporting structure with an unloading pipe shed, and belongs to the technical field of geotechnical engineering supporting. The construction method comprises 1) preparation of construction materials; 2) preparation before construction; 3) constructing a support pile; 4) excavating a soil layer; 5) constructing a prestressed anchor rod; 6) constructing a concrete surface layer; 7) and (5) unloading pipe shed construction. The prestressed anchor rod is arranged on the upper part of the pit wall of the foundation pit; the unloading pipe shed is composed of two layers of grouting steel pipes which are arranged densely and extend into the pit wall of the foundation pit at a smaller inclination angle; according to the invention, the unloading pipe shed is arranged in the middle of the pile anchor structure, so that the dead weight of the upper unstable soil layer is transferred to the stable soil layer far away from the pit wall of the foundation pit, and the problems of limited pile body embedding depth and anchor rod length of the support pile are solved.
Description
Technical Field
The invention belongs to the technical field of geotechnical engineering support, and particularly relates to a construction method of a pile-anchor combined support structure with an unloading pipe shed, which is suitable for deep foundation pit support engineering.
Background
Since the 21 st century, the development of the deep foundation pit support to the high altitude and the underground becomes an important direction for infrastructure construction, and a large amount of deep foundation pit support engineering is generated. At present, the commonly used supporting means for deep foundation pit supporting engineering in northwest areas is mainly a pile-anchor supporting and prestressed anchor rod composite soil nailing wall supporting method. The two supporting means have mature construction technology and high safety, and can effectively control the deformation of the foundation pit. However, the prestressed anchor rod anchoring section often needs to go deep to a certain depth beyond the fracture surface of the foundation pit, and is very easily influenced by the foundation of the adjacent building or passes through the red line of the building; in addition, the foundation pit support is generally a temporary project, and the two common support methods have high manufacturing cost and poor economical efficiency.
Therefore, the deep foundation pit supporting structure with the unloading platform is produced at the same time. For example, the unloading type combined supporting and retaining structure of the Chinese patent CN 112323816A is provided with an unloading plate at a certain depth of a soil layer, and vertical soil pressure at the upper part of the unloading plate is transmitted through a supporting pile or an underground continuous wall and an unloading plate supporting pile, so that lateral soil pressure borne by the supporting pile or the underground continuous wall below an unloading pipe shed is effectively reduced; however, when the unloading plate of the supporting structure is constructed, the upper soil body needs to be excavated and then backfilled, and the requirements of actual engineering cannot be well met. The layered lifting unloading type ground pulling anchor rod of the Chinese patent CN 108842792A is provided with a prestressed anchor rod with certain bending rigidity to form an unloading platform, one end of the anchor rod, which is positioned at a slope, is lifted by adopting a steel strand, and the force transmission direction of the steel strand is changed by a top fixed pulley, so that the anchor rod is anchored in a ground surface stabilized soil layer, and the unloading purpose is achieved. However, according to the Newton's third law (acting force and reacting force), although the direction of the steel strand is changed by the fixed pulley at the top of the slope or the foundation pit, acting forces with downward direction and small difference in magnitude are applied to the additional soil layer, and the unloading effect is not effectively realized; in addition, the anchor rods forming the unloading platform are arranged sparsely, an effective soil arch effect cannot be formed between the anchor rods, the bending rigidity is small, the unloading effect is not obvious, and in addition, the lifting type unloading anchor rods are complex to manufacture and complicated to construct, so that the economic requirement cannot be well met.
Disclosure of Invention
The invention provides a construction method of a pile-anchor combined supporting structure with an unloading pipe shed, which can form an effective unloading platform, reduce the vertical soil pressure of the soil body at the lower part of the unloading pipe shed and the lateral soil pressure borne by a supporting pile, and further reduce the embedment depth, the internal force and the deformation of the supporting pile; meanwhile, the broken surface of the soil body on the upper part of the unloading pipe wall moves towards the inside of the foundation pit, the length of the anchor rod on the upper part of the pile body is reduced, and the influence of the foundation of the adjacent building or the crossing of the red line of the building is avoided. The structure is convenient and quick to construct, accords with economic and environment-friendly characteristics, and is suitable for deep foundation pit supporting engineering under various environments.
Therefore, the invention adopts the following technical scheme:
a construction method of a pile-anchor combined supporting structure with an unloading pipe shed comprises the following steps:
1) preparation of construction materials:
grouting the steel pipe: determining the size and the number of the grouting steel pipes according to engineering design requirements, arranging circular slurry outlet holes and rhombic slurry outlet holes on the pipe walls of the grouting steel pipes according to requirements, wherein the circular slurry outlet holes are arranged in rows along the length direction of the grouting steel pipes, the rhombic slurry outlet holes are also arranged in rows along the length direction of the grouting steel pipes, and a slurry stopping section without a hole is reserved at the tail of the grouting steel pipes; the diamond-shaped slurry outlet holes at least comprise two rows and are arranged side by side; then, opening external threads at the head end of the grouting steel pipe;
anchor rod waist rail: anchor rod mounting holes corresponding to the anchor rod mounting positions one by one are formed in the anchor rod waist beam;
pipe shed waist rail: determining the number and the size of the pipe shed waist beam and the anchoring plate according to engineering design requirements, wherein grouting steel pipe holes corresponding to the mounting positions of the grouting steel pipes one by one are formed in the pipe shed waist beam; a bolt hole is formed in the corresponding position of the pipe shed waist beam and the support pile; the anchoring plate is also provided with bolt holes;
2) preparation before construction: leveling a field, determining the excavation range and depth of a foundation pit according to a design drawing, and calibrating the position of a support pile;
3) and (3) supporting pile construction: positioning a drilling machine according to the calibration position of the supporting pile in the step 2), excavating and forming holes, adopting slurry to protect walls, hoisting a reinforcement cage, and pouring concrete to form piles;
4) excavating a soil layer: when the strength of the supporting pile reaches or exceeds 75% of the design requirement, excavating a foundation pit, excavating a soil layer to 0.5m below the standard height of the prestressed anchor rod, stopping excavating and finishing the slope;
5) and (3) prestressed anchor rod construction: positioning and paying off on the trimmed slope surface, and determining the installation position of the anchor rod; drilling by a drilling machine, placing an anchor rod body in a drilled hole and performing high-pressure grouting, wherein the grouting pressure is not less than 0.8Mpa, and the interval time between two times of grouting is 2-4 h;
after grouting, fixing anchor rod waist beams on the slope surface along the horizontal direction, wherein anchor rod mounting holes in the anchor rod waist beams correspond to the drilled holes in the step 5) one by one; after the slurry strength of the anchor rod reaches or exceeds 70% of the designed strength, tensioning the anchor rod and locking the anchor rod to the anchor rod waist beam;
6) and (3) concrete surface layer construction: hanging a bidirectional reinforcing mesh on the wall of the excavated foundation pit, spraying concrete in sections, and spraying in each section from top to bottom, wherein a spray head is vertical to a sprayed surface during spraying, and the spraying distance is 0.6-1.0 m;
7) construction of unloading pipe sheds: excavating the foundation pit for the second time, and stopping excavating after the elevation of the unloading pipe shed is 0.5m lower; positioning and paying off the slope surface, and calibrating the positions of the grouting steel pipe, the pipe shed waist beam and the support pile embedded steel bars;
drilling holes by a drilling machine at the position of the marked grouting steel pipe, wherein the holes are used for installing the grouting steel pipe, and the included angle between the axis of each hole and the horizontal plane is 5-15 degrees; the holes are arranged in two rows along the vertical direction of the slope surface of the foundation pit, and the positions of the holes in the two rows are staggered;
implanting steel bars with the quantity required by design at the position of the steel bar implanting position of the calibrated support pile, and welding and fixing the anchoring plates on the steel bars to ensure that all the anchoring plates are positioned on the same plane; fixing the pipe shed waist beam to the anchoring plate through bolts in the horizontal direction, wherein grouting steel pipe holes of the pipe shed waist beam correspond to the drilling machine holes in the step 7) one by one; the two pipe shed waist beams correspond to the two rows of holes respectively;
the grouting steel pipes penetrate through the reserved grouting steel pipe holes in the waist beam of the pipe shed and are placed into the holes, the rhombic slurry outlet holes of the upper row of grouting steel pipes face downwards, and the rhombic slurry outlet holes of the lower row of grouting steel pipes face upwards; the grouting pipe extends into the grouting steel pipe, high-pressure grouting is carried out at a distance of 50-100mm from the bottom, the grouting pressure is not less than 0.8Mpa, and grouting is stopped when grout returns around the grouting steel pipe; performing secondary slurry supplement within 2 hours after primary slurry injection is completed, and plugging the orifice; after grouting, screwing a nut at the head end of the grouting steel pipe and fixing the grouting steel pipe to the pipe shed waist beam; finally, a batten plate is fixedly connected between the two rows of pipe shed waist beams;
8) continuously excavating a foundation pit soil layer, and constructing a sprayed concrete surface layer in layers according to design requirements until the bottom surface of the designed foundation pit is reached;
9) when the foundation pit is backfilled, the pipe shed waist beam, the nut and the batten plate are disassembled and recovered.
Furthermore, the diameter of the grouting steel pipe is 80-180mm, the diameter of the circular slurry outlet is 10-15mm, the long symmetry axis of the rhombic slurry outlet is 20-30mm, and the short symmetry axis is 10-15 mm.
Further, in the step 7, the interlayer distance between the upper and lower layers of grouting steel pipes is not more than 0.5m, and the distance between the grouting steel pipes on the same layer is 3-5 times of the diameter of the grouting steel pipes.
Further, the pipe shed waist rail is Q235 channel steel, and the web height needs to satisfy the requirement of slip casting steel pipe hole trompil, and the web height is greater than slip casting steel pipe hole aperture promptly, and is greater than 1 time at least. The thicknesses of the web and the flange need to meet the requirements of deformation and bearing capacity, and the specific requirements of deformation and bearing capacity can be obtained according to calculation or experiments.
Furthermore, the diameter of the grouting steel pipe hole on the pipe shed waist beam is 20-30mm larger than that of the grouting steel pipe.
Furthermore, the supporting pile is a cast-in-situ bored pile with a pile bottom expanded head, and the diameter of the expanded head is 1.2-1.5 times of that of the pile body.
Further, in the step 9), the grouting material for blocking the orifice is cement slurry, and the water-cement ratio of the cement slurry is 0.5-0.6.
Further, the diamond-shaped slurry outlet holes comprise 2-4 rows.
The working principle of the invention is as follows:
1. the unloading principle is as follows: the unloading pipe shed consists of two layers of grouting steel pipes which are densely arranged, the distance between the grouting steel pipes on the same layer is 3-5 times of the diameter of the steel pipes, and the soil body between the steel pipes can form an effective soil arch effect, so that the vertical soil pressure on the upper part is completely transmitted to the grouting steel pipes; meanwhile, the tail end of the grouting steel pipe is fixed on a stable soil layer, and the head end of the grouting steel pipe is connected to the pipe shed waist beam through a nut, so that the structure is equivalent to a 'simply supported beam'; therefore, partial dead weight stress of the unstable soil layer is transmitted to the stable soil layer far away from the pit wall of the foundation pit, and the vertical soil pressure of the soil body at the lower part of the unloading pipe shed and the lateral soil pressure borne by the support piles are effectively reduced.
2. Soil layer reinforcement principle: when the grouting steel pipe is subjected to high-pressure grouting, slurry flows out of the slurry outlet hole, and extrudes, splits and fills the hole in the surrounding soil body, so that the strength of the soil body around the grouting steel pipe is effectively improved; meanwhile, compared with the conventional circular grout outlet, the specially-made diamond grout outlet on the grouting steel pipe has the advantages that the grout outlet pressure is higher after high-pressure grouting, the section of grout outlet is sharper, the splitting effect of grout on a soil body is greatly improved, and the depth and the range of grout extruding into the soil body are effectively enhanced; the interval between the upper row of grouting steel pipe layers and the lower row of grouting steel pipe layers is small, the effect of grouting and reinforcing the soil body between the layers in the whole range can be achieved, cement soil with higher strength is formed between the two grouting steel pipe layers, the two rows of grouting steel pipe layers can jointly act, the stress characteristics of 'upper steel pipe compression and lower steel pipe tension' similar to a concrete slab are achieved to a certain extent, the bearing capacity and the rigidity of the unloading pipe shed are greatly improved, and the unloading purpose is achieved.
3. Supporting: after the foundation pit is excavated, the soil body is not in a static balance state any more, and the existence of the support piles can transmit the unbalanced lateral soil pressure of the soil body within the depth range of the foundation pit to the soil layer below the bottom surface of the foundation pit; the prestressed anchor rod on the upper part of the pile body provides a supporting point for the supporting pile, and the stress state of a cantilever of the supporting pile is changed; the unloading pipe shed of the depth of the middle part of the foundation pit can play a role in arranging dense soil nails simultaneously, the horizontal soil pressure of an unstable soil layer is transmitted to a stable soil layer, a supporting point is given to the supporting pile simultaneously, the deformation and the internal force of the supporting pile are reduced, the three parts are combined to play a role in supporting, and the deformation and the stability of the foundation pit are guaranteed.
The invention has the beneficial effects that:
1. the invention has definite stress, convenient and quick construction, can effectively improve the stability of the foundation pit and control the deformation, has high construction cost and economy, can be suitable for soil layers such as cohesive soil, weakly cemented sandy soil, broken soft rock and the like, and has wide application range;
2. two layers of densely distributed high-pressure grouting steel pipes are arranged in the middle of the foundation pit, so that an effective 'soil arch effect' can be formed between the grouting steel pipes, and the self-weight stress of the upper soil body is transferred to the grouting steel pipes; the tail end of the grouting steel pipe is fixed on a stable soil layer, the head end of the grouting steel pipe is connected with a pipe shed waist beam on the wall of a foundation pit, a specially-made diamond grout outlet hole in the grouting steel pipe effectively improves the splitting effect of grout on a soil body, increases the depth and range of cement grout extruded into an interlayer soil layer, greatly improves the strength of the soil body, and forms an unloading pipe shed with higher bending rigidity, so that the vertical soil pressure of the soil body in an unstable area at the lower part of the unloading pipe shed and the lateral soil pressure of a supporting structure are reduced, and the internal force, deformation and the depth of a fixing end of a pile body can be further reduced;
3. the existence of the unloading pipe shed provides a vertical supporting effect for the upper soil layer, so that the upper soil layer fracture surface deflects towards the inside of the foundation pit, and the length of the free section of the upper prestressed anchor rod is effectively reduced;
4. the unloading pipe shed can also play a role in densely arranging soil nails, restrain the horizontal displacement of an unstable soil body in the slip crack surface and provide a fulcrum for the support pile to reduce the deformation and the internal force of the support pile;
5. the components of the unloading pipe shed are prefabricated components, construction is convenient and rapid, light machinery can meet construction requirements, and construction requirements and construction condition limitation can be reduced; the influence on the surrounding environment is small, and part of components can be recycled, so that the method has the characteristics of economy, greenness and environmental protection.
Drawings
Fig. 1 is a front view of a pile-anchor combined supporting structure of the present invention;
fig. 2 is a sectional view of the pile-anchor combined supporting structure of the present invention;
FIG. 3 is a schematic view of the connection between a grouting steel pipe and a pipe shed waist rail;
FIG. 4 is a front view of a grouting steel pipe;
FIG. 5 is a cross-sectional view of a grouting steel pipe;
FIG. 6 is a schematic structural view of a wale of the pipe shed;
FIG. 7 is a schematic structural view of an anchor plate;
FIG. 8 is a schematic view of the connection of the anchor plate to the support piles;
FIG. 9 is a schematic cross-sectional view of a two-layer grouting steel pipe after high-pressure grouting;
in the figure: the concrete grouting pile comprises supporting piles 1, prestressed anchor rods 2, anchor rod waist beams 3, concrete surface layers 4, steel bar meshes 5, grouting steel pipes 6, circular grout outlet holes 7, diamond-shaped grout outlet holes 8, pipe shed waist beams 9, grouting steel pipe holes 10, nuts 11, bolt holes 12, batten plates 13, anchoring plates 14 and steel bars 15.
Detailed Description
The invention will now be further described with reference to the accompanying drawings and specific examples, which are given by way of illustration and not by way of limitation. All changes, equivalents and modifications that come within the spirit of the invention are desired to be protected.
As shown in fig. 1 and 2, the invention relates to a construction method of a pile-anchor combined supporting structure with an unloading pipe shed, the pile-anchor combined supporting structure comprises a pile-anchor combined structure and the unloading pipe shed, and the pile-anchor combined structure consists of a supporting pile 1, a prestressed anchor rod 2 and a concrete surface layer.
The prestressed anchor rod 2 is arranged at the upper part of the pit wall of the foundation pit, the anchoring section of the prestressed anchor rod is fixed on the stable soil layer, one end of the free section is connected with the anchoring section, and the other end of the free section is anchored on the anchor rod waist beam 3 by an anchorage device; the sprayed concrete surface layer 4 is composed of distributed bidirectional reinforcing mesh sheets 5 and sprayed concrete and is arranged between the supporting piles 1. The unloading pipe shed is composed of two layers of grouting steel pipes 6 which are arranged densely and extend into the wall of a foundation pit, the included angle between each grouting steel pipe 6 and a horizontal line is 5-15 degrees, one end of each grouting steel pipe is provided with a screw, each grouting steel pipe penetrates through a grouting steel pipe hole 10 in a waist beam 9 of the pipe shed to be connected with a nut 11, the other end of each grouting steel pipe extends into a stable soil layer, and then high-pressure grouting is performed on the stable soil layer. The upper and lower layers of grouting steel pipes 6 are arranged in a staggered manner. The pipe shed wale 9 is a channel steel with bolt holes 12 and grouting steel pipe holes 10 and is placed close to the pit wall of the foundation pit in a transverse mode, the two layers of pipe shed wales 9 are connected through gusset plates 13, and two ends of the pipe shed wales 9 are connected with the anchoring plates 14 through bolts respectively. The anchoring plate 14 is a steel plate with bolt holes and is welded and fixed with the steel bars implanted on the support piles 1. The pipe shed wale 9 is thereby indirectly fixed to the support piles 1.
As shown in fig. 1 and 2, the support pile 1 is a cast-in-situ bored pile with a pile bottom enlarged head, and the diameter of the enlarged head is 1.2 to 1.5 times of the diameter of a pile body.
As shown in figure 1, the prestressed anchor rods 2 are positioned at two sides of the support pile 1 and anchored on an anchor rod waist beam 3 formed by double-spliced I-shaped steel through an anchorage device, and the number of the prestressed anchor rods 2 can be increased or decreased according to the actual condition of a foundation pit.
As shown in fig. 3 to 5, the grouting steel pipe 6 is a large-diameter grouting steel pipe 6, which is a seamless steel pipe with a diameter of 80-180mm and a wall thickness of 4-8mm, and the length of the opening at one end of the grouting steel pipe is required to meet the requirement that the grouting steel pipe can be fixed with the pipe shed waist rail 9 by using the nut 11. A circular slurry outlet hole 7 and a rhombic slurry outlet hole 8 are arranged in the full length from a position 300mm away from the cut wire, a slurry stop section of 300mm is reserved at the tail of the steel pipe, and the circular slurry outlet hole 7 and the rhombic slurry outlet hole 8 are both arranged along the length direction of the grouting steel pipe 6; the diameter of the circular slurry outlet 7 is 10-15mm, the pitch is 300mm, the long symmetrical axis of the diamond slurry outlet 8 is 20-30mm, the diamond slurry outlet is arranged along the length direction of the steel pipe, the short symmetrical axis is 10-15mm, and the pitch is 300 mm. The two kinds of slurry outlet holes are uniformly distributed along the circumference of the steel pipe, and at least 2 rows of diamond slurry outlet holes 8 are required to be arranged. The rhombic slurry outlet holes 8 of the upper layer of grouting steel pipes 6 are arranged downwards, and the rhombic slurry outlet holes 8 of the lower layer of grouting steel pipes 6 are arranged upwards. The interlayer distance between the upper layer of grouting steel pipes 6 and the lower layer of grouting steel pipes 6 is not more than 0.5m, and the distance between the grouting steel pipes 6 on the same layer is 3-5 times of the diameter of the grouting steel pipes.
As shown in fig. 6, the pipe shed wale 9 is made of Q235 channel steel, the web height needs to meet the requirement of 10 holes of grouting steel pipe holes, and the thickness of the web and the flange needs to meet the requirements of deformation and bearing capacity. Set up bolt hole 12 on the both ends web of channel-section steel, the bearing capacity requirement that pipe shed waist rail 9 and anchor plate 14 are connected need be satisfied to the quantity of bolt hole 12, and sets up two rows at least and is listed as. According to the number of the grouting steel pipes 6, a grouting steel pipe hole 10 is arranged at the middle upper part of the channel steel web plate, and the diameter of the hole is 20-30mm larger than that of the grouting steel pipe 6; according to the number of the batten plates 13 and the angle between the batten plates 13 and the tubular shed waist beam 9, two rows and two columns of bolt holes are formed in the lower portion of the channel steel web. The hole pitch of all holes of the channel steel web plate needs to be larger than 20mm or the diameter of a bolt.
As shown in fig. 7 and 8, the anchoring plate 14 is a Q235 steel plate, the thickness of which needs to meet the bearing capacity requirement, and the number and arrangement of bolt holes at two ends need to be matched with the pipe shed wale 9. The middle part of the anchoring plate 14 is welded with a reinforcing steel bar 15 implanted into the pile body, the diameter of the reinforcing steel bar 15 and the strength of a welding seam need to meet the requirement of bearing capacity, and the reinforcing steel bar 15 is at least arranged in two rows and two columns.
The concrete construction steps of the invention are as follows:
1) preparation of construction Material
Grouting the steel pipe 6: determining the size and the number of the grouting steel pipes 6 according to engineering design requirements, forming circular slurry outlet holes 7 and rhombic slurry outlet holes 8 on the pipe walls of the grouting steel pipes 6 according to requirements, wherein the circular slurry outlet holes 7 and the rhombic slurry outlet holes 8 are distributed along the length direction of the grouting steel pipes 6, and a slurry stopping section without a hole is reserved at the tail of the grouting steel pipe 6; the diamond-shaped slurry outlet holes 8 comprise two rows in parallel; then, opening external threads at the head end of the grouting steel pipe 6;
anchor rod waist rail 3: anchor rod mounting holes corresponding to the anchor rod mounting positions one by one are formed in the anchor rod waist beam 3;
pipe shed wale 9: grouting steel pipe holes 10 corresponding to the mounting positions of the grouting steel pipes 6 one by one are formed in the pipe shed waist beam 9; the corresponding position of the pipe shed waist beam 9 and the support pile 1 is also provided with a bolt hole.
2) Preparation before construction: and (5) leveling the field, determining the excavation range and depth of the foundation pit according to a design drawing, and calibrating the position of the support pile 1.
3) And (3) constructing a support pile 1: and (3) positioning a drilling machine according to the calibration position of the support pile 1 in the step 2), excavating and forming holes, adopting slurry to protect walls, hoisting a reinforcement cage, and pouring concrete to form a pile.
4) Excavating a soil layer: and when the strength of the supporting pile 1 reaches or exceeds 75% of the design requirement, excavating a foundation pit, excavating a soil layer to 0.5m below the elevation of the prestressed anchor rod 2, stopping excavating, and finishing the slope.
5) And (3) construction of the prestressed anchor rod 2: positioning and paying off on the trimmed slope surface, and determining the installation position of the anchor rod; drilling by a drilling machine, placing an anchor rod body and performing high-pressure grouting, wherein a plastic sleeve needs to be sleeved on a free section of the anchor rod, the tail end of a grouting pipe is 50-100mm away from the bottom of a hole, so that smooth grouting return of the bottom of the hole is ensured, and the grouting pressure is not less than 0.8 Mpa; the interval time of the two times of grouting is 2-4 h;
after grouting is finished, fixing the anchor rod waist beam 3 on the slope surface along the horizontal direction, wherein anchor rod mounting holes in the anchor rod waist beam 3 correspond to the drilled holes in the step 5) one by one; and after the strength of the anchor rod slurry reaches or exceeds 70% of the designed strength, tensioning the anchor rod and locking the anchor rod to the anchor rod waist beam 3.
6) And (3) concrete surface layer construction: and hanging a bidirectional reinforcing mesh 5 on the wall of the excavated foundation pit, and spraying concrete in sections, wherein the concrete is sprayed in each section from top to bottom. When spraying, the spray head and the sprayed surface should be kept vertical, the spraying distance is 0.6-1.0m, and the sprayed concrete should be sprayed for curing after final setting for 2 hours. The thickness tolerance of the sprayed concrete is +/-10 mm.
7) Construction of unloading pipe sheds: and (4) excavating the foundation pit for the second time, stopping excavating after the height mark of the unloading pipe shed is 0.5m, positioning and paying off, and calibrating the positions of the grouting steel pipe 6, the pipe shed waist beam 9 and the support pile 1 in bar planting. And (3) adopting a drilling machine to form a hole, wherein the allowable deviation values of the hole depth and the hole diameter are +/-50 mm and +/-5 mm respectively. And (3) implanting steel bars 15 with the quantity required by design at the steel bar implanting position of the calibrated support pile 1, welding the anchoring plate 14 with the implanted steel bars 15, and further connecting the prefabricated pipe shed waist beam 9 with the anchoring plate 14 through bolts. And then, the grouting steel pipe 6 penetrates through a grouting steel pipe hole 10 reserved on a pipe shed waist beam 9 and is placed into the drilled hole, the allowable deviation of the position of the grouting steel pipe 6 is 100mm, and the allowable deviation of the inclination angle is 3 degrees. The grouting pipe extends into the grouting steel pipe 6, high-pressure grouting is carried out at a distance of 50-100mm from the bottom, the grouting pressure is not less than 0.8Mpa, grouting is stopped until grout return appears around the steel pipe, secondary grout supplement is carried out within 2 hours after primary grouting is completed, an orifice is blocked, the grouting material is cement paste, and the water-cement ratio of the grout is preferably 0.5-0.6. After grouting, screwing the nut 11 at the end of the grouting steel pipe 6 with the screw, and fixing the end; and finally, a batten plate 13 is connected and fixed between the two rows of tubular shed waist beams 9, and the batten plate 13 can be connected with the tubular shed waist beams 9 through bolts.
9) And continuously excavating the soil layer, and constructing the sprayed concrete surface layer 4 layer by layer according to the design requirement until the bottom surface of the designed foundation pit is reached.
10) When the foundation pit is backfilled, the pipe shed waist beam 9, the nut 11 and the batten plate 13 which are connected through the bolts are disassembled and recovered.
Claims (8)
1. A construction method of a pile-anchor combined supporting structure with an unloading pipe shed is characterized by comprising the following steps:
1) preparation of construction materials:
grouting the steel pipe: determining the size and the number of the grouting steel pipes (6) according to engineering design requirements, arranging circular slurry outlet holes (7) and rhombic slurry outlet holes (8) on the pipe walls of the grouting steel pipes (6) according to requirements, arranging the circular slurry outlet holes (7) in rows along the length direction of the grouting steel pipes (6), arranging the rhombic slurry outlet holes (8) in rows along the length direction of the grouting steel pipes (6), and leaving slurry stopping sections without holes at the tail of the grouting steel pipes (6); the rhombic slurry outlet holes (8) at least comprise two rows and are arranged side by side; then, opening external threads at the head end of the grouting steel pipe (6);
anchor rod waist rail: anchor rod mounting holes corresponding to the anchor rod mounting positions one by one are formed in the anchor rod waist beam (3);
pipe shed waist rail: determining the number and the size of a pipe shed waist beam (9) and an anchoring plate (14) according to engineering design requirements, wherein grouting steel pipe holes (10) which correspond to the mounting positions of grouting steel pipes (6) one by one are formed in the pipe shed waist beam (9); a bolt hole (12) is formed at the position corresponding to the position of the pipe shed waist beam (9) and the support pile (1); the anchoring plate (14) is also provided with bolt holes;
2) preparation before construction: leveling a field, determining the excavation range and depth of a foundation pit according to a design drawing, and calibrating the position of a support pile (1);
3) and (3) supporting pile construction: positioning a drilling machine according to the calibration position of the supporting pile (1) in the step 2), excavating to form a hole, adopting slurry to protect a wall, hoisting a reinforcement cage, and pouring concrete to form a pile;
4) excavating a soil layer: when the strength of the supporting pile (1) reaches or exceeds 75% of the design requirement, excavating a foundation pit, excavating a soil layer to 0.5m below the elevation of the prestressed anchor rod (2), stopping excavating and finishing the slope;
5) and (3) prestressed anchor rod construction: positioning and paying off on the trimmed slope surface, and determining the installation position of the anchor rod; drilling by a drilling machine, placing an anchor rod body in a drilled hole and performing high-pressure grouting, wherein the grouting pressure is not less than 0.8Mpa, and the interval time between two times of grouting is 2-4 h;
after grouting is finished, fixing the anchor rod waist beam (3) on the slope surface along the horizontal direction, wherein anchor rod mounting holes in the anchor rod waist beam (3) correspond to the drilled holes in the step 5) one by one; after the slurry strength of the anchor rod reaches or exceeds 70% of the designed strength, tensioning the anchor rod and locking the anchor rod to the anchor rod waist beam (3);
6) and (3) concrete surface layer construction: hanging a bidirectional reinforcing mesh (5) on the wall of the excavated foundation pit, spraying concrete in sections, wherein the concrete is sprayed in each section from top to bottom, a spray head is vertical to a sprayed surface during spraying, and the spraying distance is 0.6-1.0 m;
7) construction of unloading pipe sheds: excavating the foundation pit for the second time, and stopping excavating after the elevation of the unloading pipe shed is 0.5m lower; positioning and paying off on the slope surface, and calibrating the positions of the grouting steel pipe (6), the pipe shed waist beam (9) and the embedded steel bars of the support piles (1);
drilling holes by a drilling machine at the position of the calibrated grouting steel pipe (6), wherein the holes are used for installing the grouting steel pipe (6), and the included angle between the axis of each hole and the horizontal plane is 5-15 degrees; the holes are arranged in two rows along the vertical direction of the slope surface of the foundation pit, and the positions of the holes in the two rows are staggered;
reinforcing steel bars (15) with the quantity required by design are implanted at the positions where the reinforcing steel bars are implanted in the calibrated support piles (1), and anchoring plates (14) are welded and fixed on the reinforcing steel bars (15) to ensure that the anchoring plates (14) are positioned on the same plane; fixing the pipe shed waist beam (9) to the anchoring plate (14) through bolts in the horizontal direction, wherein the grouting steel pipe holes (10) of the pipe shed waist beam (9) correspond to the drilling machine holes in the step 7 one by one; the two pipe shed waist beams (9) are respectively corresponding to the two rows of holes;
the grouting steel pipes (6) penetrate through the reserved grouting steel pipe holes (10) in the pipe shed waist beam (9) and are placed into the holes, the rhombic slurry outlet holes (8) of the upper row of grouting steel pipes (6) face downwards, and the rhombic slurry outlet holes (8) of the lower row of grouting steel pipes (6) face upwards; the grouting pipe extends into the grouting steel pipe (6) and performs high-pressure grouting at a distance of 50-100mm from the bottom, the grouting pressure is not less than 0.8Mpa, and grouting is stopped after grout returns around the grouting steel pipe (6); performing secondary slurry supplement within 2 hours after primary slurry injection is completed, and plugging the orifice; after grouting, screwing a nut (11) at the head end of the grouting steel pipe (6) and fixing the grouting steel pipe to the pipe shed waist beam (9); finally, a batten plate (13) is fixedly connected between the two rows of pipe shed waist beams (9);
8) continuously excavating a foundation pit soil layer, and constructing a sprayed concrete surface layer (4) layer by layer according to design requirements until the bottom surface of the designed foundation pit is reached;
9) when the foundation pit is backfilled, the pipe shed waist beam (9), the nut (11) and the batten plate (13) are disassembled and recovered.
2. The construction method of a pile-anchor combined supporting structure with an unloading pipe shed, according to claim 1, characterized in that the diameter of the grouting steel pipe (6) is 80-180mm, the diameter of the circular grout outlet (7) is 10-15mm, the long symmetry axis of the rhombic grout outlet (8) is 20-30mm, and the short symmetry axis is 10-15 mm.
3. The construction method of a pile-anchor combined supporting structure with an unloading pipe shed as claimed in claim 1, wherein in the step 7, the distance between the upper and lower layers of grouting steel pipes (6) is not more than 0.5m, and the distance between the grouting steel pipes (6) on the same layer is 3-5 times of the diameter of the grouting steel pipes.
4. The construction method of the pile-anchor combined supporting structure with the unloading pipe shed as claimed in claim 1, wherein the pipe shed waist beam (9) is a Q235 channel steel, the height of the web plate needs to meet the requirement of opening a grouting steel pipe hole (10), and the thickness of the web plate and the thickness of the flange need to meet the requirements of deformation and bearing capacity.
5. The construction method of the pile-anchor combined supporting structure with the unloading pipe shed as claimed in claim 4, wherein the diameter of the grouting steel pipe hole (10) on the pipe shed waist beam (9) is 20-30mm larger than that of the grouting steel pipe (6).
6. The construction method of the pile-anchor combined supporting structure with the unloading pipe shed as claimed in claim 1, wherein the supporting pile (1) is a cast-in-situ bored pile with a pile bottom enlarged head, and the diameter of the enlarged head is 1.2-1.5 times of the diameter of a pile body.
7. The construction method of a pile-anchor combined supporting structure with an unloading pipe shed as claimed in claim 1, wherein in the step 9), the grouting material for blocking the orifice is cement slurry, and the water cement ratio of the cement slurry is 0.5-0.6.
8. The construction method of a pile-anchor combined supporting structure with an unloading pipe shed is characterized in that the rhombic grout outlet holes (8) comprise 2-4 rows.
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