CN114032928B - Soil nailing wall construction method for pre-reinforcing side slope rock soil body - Google Patents
Soil nailing wall construction method for pre-reinforcing side slope rock soil body Download PDFInfo
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- CN114032928B CN114032928B CN202111309948.1A CN202111309948A CN114032928B CN 114032928 B CN114032928 B CN 114032928B CN 202111309948 A CN202111309948 A CN 202111309948A CN 114032928 B CN114032928 B CN 114032928B
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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
- E02D17/20—Securing of slopes or inclines
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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 soil nailing wall construction method for pre-reinforcing a side slope rock-soil body, which comprises the steps of firstly, drilling holes in the side slope rock-soil body according to a certain angle in the current state of vertical layered horizontal running water construction on the side slope, penetrating the rock-soil body to be excavated, and entering a preset depth in the designed side slope rock-soil body through the side slope design slope; then inserting soil nails into the drilling section in the rock-soil body of the designed slope from the current slope surface orifice of the drilling hole, and grouting and curing the drilling section provided with the soil nails until the drilling hole is strong; and finally excavating a rock and soil body to be excavated according to the layered horizontal running water construction from top to bottom, exposing the slope in a layered manner to finish the operations of hanging a net on the slope and spraying concrete, and repeatedly circulating the above processes to realize the vertical running water construction until the soil nailing wall supporting construction is finished after the first-level slope is excavated in a layered manner. The method can ensure the temporary stability of the designed slope surface after layered excavation, is convenient for the vertical running water construction and the horizontal running water construction to simultaneously improve the construction efficiency, and avoids the phenomenon of construction site construction failure.
Description
Technical Field
The invention relates to the technical field of slope reinforcement, in particular to a soil nailing wall construction method for pre-reinforcing a slope rock-soil body.
Background
The soil nailing wall (So il Nailing Wall) is an in-situ soil reinforcement technology for reinforcing an in-situ rock-soil body by high-strength materials such as steel bars and the like, so that the 'apparent condensing force' and the strength of the in-situ rock-soil body are improved, and a composite material 'apparent gravity retaining wall' with properties greatly different from those of the original rock-soil body is formed by soil nails, a sprayed concrete surface layer and the reinforced rock-soil body, and is widely applied to slope and foundation pit reinforcement engineering.
At present, in China, drilling grouting soil nails are mainly adopted in the process of reinforcing and treating side slopes and foundation pit soil nail walls. The soil nailing wall is constructed according to the principles of 'top-down layered excavation, layered anchoring and layered spraying protection', and the soil nailing wall is timely hung on a net to spray concrete, so that the slope surface cannot be exposed for a long time, and the slope is unstable.
The traditional soil nailing wall is formed by layered and sectional construction, and after the sprayed concrete surface layer above the positions of one layer of soil nails and the soil nails is finished, the soil nails can be excavated to the elevation of the construction surface of the next layer of soil nails. During construction, earthwork above the next soil nail construction surface can be excavated after each soil nail and the corresponding concrete surface layer are completed and reach the strength required by design, and the excavation is forbidden to exceed the next soil nail construction surface. The stress state of the soil nailing wall exceeds the design state due to the over-digging. Engineering accidents such as collapse of a side slope (or a foundation pit) and overlarge displacement caused by over-digging are frequent.
However, since the construction process is the most dangerous stage during construction period from the completion of excavation of a layer of side slope rock-soil body to the completion of the action of the anchor body maintenance, if rainwater and surface water infiltrate during the period, peripheral machines (vehicle running, piling and the like) vibrate, the rock-soil body is excavated and unloaded, and the temporary stability during the construction period of the side slope is difficult to be ensured due to the influence of vibration and other events caused by blasting or earthquake.
In view of the following disadvantages of the current soil nailing wall supporting technology: (1) the soil nailing wall usually adopts layered excavation to expose the slope surface of the side slope, then the exposed design slope surface is drilled, soil nails are inserted, grouting is carried out for strengthening, the slope surface is hung with a net, sprayed concrete is cured for strengthening, and the like, and the process is difficult to realize the rock-soil body excavation concept of 'first support and then excavation'. After a layer of rock-soil body is excavated, the slope stability is difficult to ensure under the disturbance effect of the subsequent construction of the layer; (2) only after the soil nail anchoring body and the slope surface shotcrete of a certain layer reach the strength required by design, the next layer rock-soil body excavation, soil nail construction, slope surface net hanging and shotcrete spraying operation can be carried out, so that the construction period is not facilitated to be shortened; (3) when the side slope is longer, horizontal running water construction is difficult, the construction is generally carried out by adopting the principles of sectional excavation and sectional anchoring in order to ensure the stability of the excavated side slope during construction, the construction efficiency is low, and the construction is easy to carry out the phenomenon of construction failure; (4) if an event which is unfavorable for the stability of a side slope occurs during a certain layered construction period, the temporary stability of the soil nail during the construction period before the soil nail acts is difficult to ensure.
Disclosure of Invention
In order to solve the problems, the invention provides the soil nailing wall construction method for pre-reinforcing the side slope rock-soil body, which can ensure the temporary stability of the designed side slope surface after layered excavation, is convenient for vertical flow construction and horizontal flow construction to simultaneously improve the construction efficiency and avoids the construction site from the phenomenon of construction shakiness.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
a soil nailing wall construction method for pre-reinforcing a side slope rock-soil body comprises the following steps: firstly, brushing current slope vegetation and loose surface soil layers, measuring and paying off, and drilling holes in a slope rock-soil body according to a certain angle on the current slope by vertical layered horizontal running water construction, wherein the drilling holes penetrate through the rock-soil body to be excavated and enter a preset depth in a designed slope rock-soil body through a slope design slope; then inserting soil nails into the drilling section in the rock-soil body of the designed slope from the current slope surface orifice of the drilling hole, and grouting and curing the drilling section provided with the soil nails until the drilling hole is strong; and finally excavating a rock and soil body to be excavated according to the layered horizontal running water construction from top to bottom, exposing the slope in a layered manner to finish operations such as slope net hanging and concrete spraying operation, and repeatedly circulating the above processes to realize vertical running water construction until the soil nailing wall supporting construction is finished after the layered excavation of the first-stage slope.
Further, the method specifically comprises the following steps:
step one: cleaning current slope vegetation and surface soil layers, and measuring paying-off; and cleaning vegetation and surface loose rock soil on the current slope surface from top to bottom, so that the current slope surface is exposed out of the solid rock soil layer. Then measuring and paying off on the current slope, paying out the positions of the holes, and enabling the horizontal spacing and the vertical spacing of the holes on the designed slope to be about 0.75 m-2 m after the rock-soil body of the excavated square is excavated in a layered manner;
step two: drilling along the current slope trend by vertical layering horizontal line production from top to bottom; drilling holes in the designed slope rock-soil body at a preset angle from a preset hole position on the current slope surface, wherein the drilling holes penetrate through the rock-soil body to be excavated and enter the designed slope rock-soil body through the slope design slope surface to a preset depth, and the length from the slope design slope surface to the hole bottom is preferably 0.5-1.0 time of the height of the soil nailing wall and meets the requirements of each layered stability of the designed slope after layered excavation and the overall stability of the soil nailing wall during the service period after all excavation;
step three: immediately inserting soil nails into the holes after the holes are drilled for grouting until the holes are strong; immediately after each drilling hole is formed, the hole is cleared and soil nails are inserted for grouting to be strong so as to prevent hole collapse. The soil nail should be set up in the drilling section of design slope to hole bottom scope (i.e. design slope drilling section) to make soil nail top surpass the length of design slope surface and should be 80mm ~ 150mm, soil nail should follow current slope opening insertion, with long stick top to design slope drilling section in.
Step four: excavating a first layer of rock and soil mass, hanging a slope surface with a net and spraying concrete; specifically, excavating a first layered rock-soil body along the trend of a side slope along with the horizontal line operation of the soil nail anchoring body maintenance condition from top to bottom, exposing a first layered design slope surface and exposing the top of the layered soil nail, and completing the construction of hanging a net and spraying concrete on the first layered design slope surface along the trend of the side slope on the design slope surface exposed by excavating the layered rock-soil body; the first layered rock-soil body is excavated to a position 500mm below the elevation of the layered soil nails, and overexcavation is strictly forbidden;
step five: digging a next layered rock-soil body, hanging a slope surface with a net, and spraying concrete until the construction of the whole slope soil nailing wall is completed; specifically, after the first layered shotcrete is cured, the next layered rock-soil body is excavated to expose the horizontal running water construction of the slope surface of the second layered design, net hanging on the slope surface of the second layered design, shotcrete is sprayed, curing is to be reinforced, the vertical construction of this step is circulated to complete the excavation, net hanging on the slope surface, shotcrete curing of other layered rock-soil bodies of the excavated side slope to be reinforced, and all the operations of the whole side slope soil nailing wall support construction are completed.
Further, the included angle between the preset drilling angle and the horizontal plane is 5-20 degrees, and the drilling diameter is 70-120 mm.
Further, HRB400 and HRB500 steel bars are selected as soil nails, the diameters of the steel bars are 16-32 mm, and epoxy coatings are required to be arranged on the surfaces of the steel bars in a corrosive environment; the soil nail is provided with a centering bracket within the whole length range, steel bars with diameters of 6-8 mm are selected for welding, the interval is not more than 2m, and the thickness of a soil nail steel bar protection layer is not less than 20mm.
Further, cement paste or cement mortar is adopted as grouting material, and the strength is not lower than 20MPa; when grouting, the grouting pipe is inserted from the current slope opening to the hole bottom and the grouting is carried out from the hole bottom, the distance from the end part (the grouting outlet) of the grouting pipe to the hole bottom is not more than 200mm, the grouting pressure is 0.2MPa, the grouting pipe is pulled out while grouting, the grouting outlet of the grouting pipe is always below the grouting liquid level, the grouting pipe is pulled out to the designed slope position, grouting is stopped, and grouting is carried out 1-2 times before final grouting as required.
Further, in the fourth step, soil nailing wall layer-by-layer excavation height: the soil layer is 0.5 m-2.0 m, and the rock stratum is 1.0 m-4.0 m; one or two layers of reinforcing steel bars are arranged in the sprayed concrete surface layer on the slope design surface, the reinforcing steel bars are HPB 300-grade reinforcing steel bars, the diameter of the reinforcing steel bars is 6-10 mm, the distance is 150-300 mm, and the two-way reinforcing steel bar crossing points of the reinforcing steel bars are in spot welding or steel wire binding connection.
In the fourth step, 2-3 short steel bars are used for fixing each square meter of steel bar net on the slope surface of the design slope exposed by excavation during net hanging, so that the clear distance between the steel bar net and the slope surface of the design slope is not less than 30mm, each steel bar net and other steel bar nets are firmly lapped, the horizontal lapping width is not less than 300mm, the vertical lapping width is not less than 500mm, the steel bar nets are lapped and welded, and the length of a welding line is not less than 10 times of the diameter of the steel bars;
4 reinforcing steel bars are longitudinally and transversely arranged at the outer side of the reinforcing steel bar net at the junction point of the reinforcing steel bar net and the top of the soil nail and are welded with the top of the soil nail, the connection of the reinforcing steel bars is required to meet the requirement of bearing the tension force of the soil nail, when the local part of the sprayed concrete surface layer is not enough in punching bearing capacity under the action of the tension force of the soil nail, the reinforcing steel bars are reinforced by arranging pressure-bearing steel plates, the diameters of the reinforcing steel bars are 14-22 mm, the spacing is the same as the spacing of the soil nails, and when the tensile strength of the soil nail body is fully utilized, the cross-sectional area of the reinforcing steel bars is not less than 1/2 of the cross-sectional area of the soil nail body.
Further, when the thickness of the sprayed concrete surface layer is larger than 120mm, a double-layer reinforcing mesh is required to be arranged, the second layer reinforcing mesh is required to be laid after the first layer reinforcing mesh is covered by sprayed concrete, when the sprayed concrete of the front layer is sprayed for more than 1 hour after the sprayed concrete of the same surface layer is finally solidified for two or more times, the spraying of the next layer of concrete is carried out, and the spraying water wetting of the surface of the sprayed concrete of the front layer is required before the spraying of the next layer of concrete; when the concrete is sprayed, the width of 500mm is reserved at the bottom of each layer of excavation, so that the concrete is not sprayed temporarily, and the vertical lap joint between the upper layered reinforcement mesh and the lower layered reinforcement mesh after the lower layer of rock-soil body is excavated is facilitated.
Further, the method further comprises the following steps: and arranging upward and downward water discharge holes on the design slope in the longitudinal and transverse directions, wherein the horizontal spacing and the vertical spacing of the water discharge holes are 2-3 m, the water discharge angle Kong Ang is 5-10 degrees, the length of the water discharge holes is slightly larger than that of soil nails, and water permeable pipes or perforated polyethylene pipes are arranged in the holes.
Further, after the construction of the side slope soil nailing wall is completed, a water interception ditch is arranged above the top of the slope, and a drainage ditch is arranged at the bottom of the slope, so that the soil nailing wall can intercept surface water to the water interception ditch and drain the surface water out of the influence range of the side slope in the service period, and the problem that the strength of a side slope rock-soil body is reduced due to the infiltration of the surface water so as to endanger the stability of the soil nailing wall is avoided.
Compared with the traditional soil nailing wall construction method, the construction method has the following beneficial effects: (1) before excavation, reinforcing and designing a side slope rock-soil body by arranging soil nails in advance through vertical layered horizontal running water, and then carrying out layered excavation and layered horizontal running water for slope protection (hanging a net and spraying concrete), so that the side slope rock-soil body excavation concept of 'firstly supporting then excavating, side excavating and side supporting and being incapable of excavating to the bottom' is realized; (2) the current slope basically tends to be stable in a long-term geological history process, soil nails are constructed on the current slope, and the construction process is relatively safe; (3) the concrete grouting device is convenient for mixed flow production, vertical layered horizontal flow production from top to bottom is drilled on the current slope, soil nails are inserted into the drilled holes immediately, grouting maintenance is to be strong, and after the completion of the maintenance of one layered soil nail anchoring body, the construction flows of the layered rock-soil body, such as excavation, slope screen hanging, concrete spraying and the like can be immediately carried out in a horizontal flow construction mode, and the vertical flow construction and the horizontal flow construction can be simultaneously carried out. The construction process is coherent and compact, so that the construction site is prevented from being subjected to construction work-carrying phenomenon, and the construction progress and the compression period are accelerated; (4) on the premise that the soil nails play a reinforcing role after the soil nail anchoring body maintenance is finished, the stability of the design slope surface exposed by excavation is guaranteed, concrete can be sprayed by hanging a net on the design slope surface immediately after excavation, the design slope surface is sealed early, and the stability of the slope is improved; (5) the soil nails are used for horizontal running water construction on the premise that the soil nails play a reinforcing role after the maintenance of the soil nail anchoring body is completed, a layer of slope rock-soil body is excavated and protected, the defect that the traditional soil nail wall construction needs to be excavated in a segmented mode is avoided, and the construction efficiency is high; (6) because the soil nails can play a role in reinforcing the rock and soil of the side slope in advance before excavation, the stability of the designed slope can be ensured after layered excavation even if the slope of the excavated side slope is set steeper (the steeper slope design can reduce the excavation of the soil amount, reduce the damage of vegetation on the slope, be beneficial to environmental protection and reduce the cost); (7) the method has the advantages that the rock-soil body of the side slope is reinforced in advance, and on the premise of ensuring safety, after the rock-soil body to be excavated is excavated, the pre-stressed anchor rod is conveniently drilled and arranged in the designed slope body again to form a pre-stressed anchor rod composite soil nailing wall to control the deformation of the side slope, so that the stability of the side slope is further improved; (8) pre-reinforcing a side slope rock soil body, directly exposing primary slope design slope surface primary spraying concrete by layered excavation on the premise of ensuring safety, longitudinally and transversely arranging a lattice beam reinforcement cage at the position of the top of a soil nail on the primary slope surface, and casting and tamping the lattice beam concrete to form a full-length bonding type anchor rod combined lattice Liang Bianpo combined retaining structure; (9) the construction method provided by the invention has wide application range, can be applied to reinforcement treatment of general excavated side slopes, and can also be applied to foundation pit supporting engineering, and has strong applicability. The soil nail serving as the soil nail for pre-reinforcing the designed side slope rock-soil body is a main stress member of the soil nail wall, so that the pre-reinforcing operation of the side slope rock-soil body can not increase the cost additionally.
Therefore, the construction method can realize mixed flow construction, improve efficiency, shorten construction period, be safe and reliable in the reinforcement treatment of various rock-soil bodies and excavation side slopes or foundation pits with different heights, is particularly suitable for side slopes and foundation pit support projects with poor slope stability or difficult self-stabilization of the slope after excavation, and is a soil nailing wall construction method of the pre-reinforced side slope rock-soil body, which is worthy of popularization and application.
Drawings
FIG. 1 is a schematic view of a soil nail and centering bracket construction;
in the figure: (a) a soil nail construction schematic; (b) is a cross-sectional view of (a) A-A; and (c) is a structural schematic diagram of the centering bracket.
Fig. 2 is a schematic diagram of a vertical flow construction section of a soil nailing wall.
FIG. 3 is a schematic diagram of a front elevation of a design side slope surface net-hanging shotcrete.
Fig. 4 is a schematic view of a top connection section of the soil nail.
Fig. 5 is a schematic cross-sectional view of the soil nailing wall after construction is completed.
FIG. 6 is a schematic view of a foundation pit layered basin excavation providing a working surface for a predetermined soil nail.
The marks in the figure: 1-current slope surface; 101-first layered excavation of a rock-soil body; 102-second layered excavation of a rock-soil body; 103-third layered excavation of the rock-soil body; 104-fourth layered excavation of the square rock soil body; 2, designing a slope surface; 3-drilling; 4-soil nailing; 401-centering brackets; 5-cement paste or cement mortar anchor; 6-a reinforcing mesh; 7-reinforcing steel bars; 8-spraying a concrete surface layer; 9-a water discharge hole; 10-slope roof intercepting ditches; 11-slope bottom drainage ditch.
Detailed Description
The present invention will be described in further detail with reference to examples in order to make the objects and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
A soil nailing wall construction method for pre-reinforcing a side slope rock-soil body comprises the following steps:
step one, cleaning current slope vegetation and surface soil layers and measuring paying-off; and cleaning vegetation and surface loose rock soil on the current slope surface from top to bottom, so that the current slope surface is exposed out of the solid rock soil layer. Then measuring and paying off on the current slope, paying out the positions of the holes, and enabling the horizontal spacing and the vertical spacing of the holes on the designed slope to be about 0.75 m-2 m after the rock-soil body of the excavated square is excavated in a layered manner;
and secondly, drilling along the trend of the current side slope vertically and horizontally in a layered manner from top to bottom, namely drilling on the current side slope surface at a preset hole position in the designed side slope rock-soil body according to a preset angle, wherein the drilling is required to penetrate through the rock-soil body to be excavated and enter the designed side slope rock-soil body through the side slope design slope surface to a preset depth, the length from the side slope design slope surface to the hole bottom of the drilling is preferably 0.5-1.0 times of the height of the soil nailing wall, and the requirements of each layered stability of the designed side slope after layered excavation and the overall stability of the soil nailing wall during the service period after all excavation are met.
Specifically, the included angle between the preset drilling angle and the horizontal plane is preferably 5-20 degrees, and the drilling diameter is preferably 70-120 mm. The rock-soil layer characteristics are used by adopting pore-forming methods such as a Luoyang shovel, an auger, a percussion drill, a geological drill and the like, and the adopted pore-forming methods can ensure the stability of the pore wall and reduce the disturbance to the pore wall. The mechanical pore-forming technology is suitable for the loose rock layer with easy-to-collapse pores, and the loose rock layer with easy-to-collapse pores is drilled by adopting a heel tube.
Thirdly, immediately drilling holes, and inserting soil nails into the holes for grouting until the holes are strong; immediately after each drilling hole is formed, the hole is cleared and soil nails are inserted for grouting to be strong so as to prevent hole collapse. The soil nails are arranged in a drilling section ranging from the slope surface of the design slope to the hole bottom (namely, the drilling section of the design slope), the length of the tops of the soil nails exceeding the slope surface of the design slope is preferably 80-150 mm, the soil nails are inserted from the current slope opening, and long wood sticks are used for jacking the soil nails into the drilling section of the design slope;
specifically, HRB400 and HRB500 steel bars are preferably selected as soil nails, the diameters of the steel bars are preferably 16-32 mm, and measures such as epoxy coating on the surfaces of the steel bars can be adopted in a corrosive environment; the soil nails are provided with centering brackets within the whole length range, the distance between the centering brackets is not more than 2m, the thickness of the soil nail reinforcing steel bar protection layer is not less than 20mm, and the centering brackets can be welded by reinforcing steel bars with the diameter of 6-8 mm; see fig. 1.
The grouting material can be cement paste or cement mortar, the strength is preferably M30 and is not lower than 20MPa; during grouting, the grouting pipe is inserted from the current slope opening to the hole bottom and is subjected to grouting from the hole bottom, the distance from the end (a grouting outlet) of the grouting pipe to the hole bottom is not more than 200mm, and the grouting pressure is preferably 0.2MPa. And (3) grouting while pulling out the grouting pipe, so that the grouting outlet of the grouting pipe is always below the grouting liquid level, grouting to the designed slope position, pulling out the grouting pipe, stopping grouting, and supplementing the grouting for 1-2 times before final setting of the grouting as required.
Step four: and excavating a first layer of rock and soil mass, hanging a slope surface with a net and spraying concrete. And excavating a first layered rock-soil body along the trend of the side slope along with the maintenance condition of the soil nail anchor body in a horizontal line operation from top to bottom, exposing a first layered design slope surface and exposing the top of the layered soil nail, excavating the first layered rock-soil body to a position 500mm below the elevation of the layered soil nail, and strictly prohibiting overdrawing. And (3) carrying out horizontal line production along the slope trend on the design slope surface exposed by the first layered rock-soil body excavation to finish the construction of hanging a net and spraying concrete on the first layered design slope surface. See fig. 2, wherein the part between the current slope 1 and the design slope 2 is the rock-soil body to be excavated.
Specifically, soil nailing wall layering excavation height: the soil layer is preferably 0.5 m-2.0 m, and the rock layer is preferably 1.0 m-4.0 m.
One or two layers of reinforcing steel meshes and reinforcing steel bars are arranged in the sprayed concrete surface layer on the slope design surface, the reinforcing steel meshes are HPB 300-grade reinforcing steel bars, the diameters of the reinforcing steel bars are 6-10 mm, the spacing is 150-300 mm, and the two-way reinforcing steel bar crossing points of the reinforcing steel meshes are in spot welding or steel wire binding connection.
During hanging, 2-3 short steel bars (the short steel bars are vertically driven into a rock soil body of a side slope) are fixed on a design slope surface exposed by excavation (thin layer concrete can be sprayed immediately after excavation) according to the slope gradient and the stability condition of the rock soil layer, so that the clear distance between the steel bar net and the design slope surface is not smaller than 30mm, each steel bar net and other steel bar nets are firmly lapped, the horizontal lapping width is not smaller than 300mm, the vertical lapping width is not smaller than 500mm, the steel bar net lapping is welded in a lap joint mode, and the length of a welding seam is not smaller than 10 times the diameter of the steel bar.
4 reinforcing steel bars are longitudinally and transversely arranged at the outer side of the reinforcing steel bar net at the junction point of the reinforcing steel bar net and the top of the soil nail and welded with the top of the soil nail, the connection of the reinforcing steel bars and the top of the soil nail meets the requirement of bearing the tension force of the soil nail, and when the local part of the sprayed concrete surface layer is not enough in punching bearing capacity under the action of the tension force of the soil nail, reinforcing measures such as arranging a pressure-bearing steel plate and the like are adopted. The diameter of the reinforcing steel bar is preferably 14-22 mm, the spacing is the same as the spacing of the soil nails, and when the tensile strength of the soil nail rod body is fully utilized, the cross-sectional area of the reinforcing steel bar is not less than 1/2 of the cross-sectional area of the soil nail rod body. See fig. 3 and 4.
When the thickness of the sprayed concrete surface layer is greater than 120mm, a double-layer reinforcing mesh is arranged, the second layer reinforcing mesh is paved after the first layer reinforcing mesh is covered by sprayed concrete, and when the sprayed concrete of the front layer is sprayed for more than 1 hour after final setting of the sprayed concrete of the same surface layer is performed for two or more than two times, the spraying of the next layer of concrete is performed, and the surface of the sprayed concrete of the front layer is sprayed for wetting before the spraying of the next layer of concrete.
The shotcrete construction should follow the following specifications:
(1) The wet spraying process should be selected preferably, and measures for reducing dust should be adopted when the dry spraying process is adopted;
(2) The concrete spraying operation should be carried out in a sectional and sectional manner sequentially, the spraying sequence in the same section should be from bottom to top, the thickness of the sprayed concrete at one time should not be smaller than 40mm and should not be larger than 80mm, the total thickness of the sprayed concrete on the designed slope should be 80 mm-150 mm, and the strength of the sprayed concrete should not be lower than C20;
(3) When spraying, the spray head is vertical to the sprayed surface, and the distance between the spray head and the sprayed surface is preferably 0.6 m-1.0 m;
(4) After the sprayed concrete is finally set for 2 hours, water spraying maintenance is needed.
The sprayed concrete is reserved at the bottom of each layer of excavation face for a period of time with the width of 500mm, so that vertical lap joint between the upper and lower layered reinforcement meshes after the lower layer of rock-soil body is excavated is facilitated.
Step five: and excavating a next layered rock-soil body, hanging a slope surface with a net, and spraying concrete until the construction of the whole slope soil nailing wall is completed. After the first layered sprayed concrete is cured, the next layered rock-soil body is excavated to expose the horizontal running water construction of the slope surface of the second layered design, net hanging on the slope surface of the second layered design, sprayed concrete is cured and is cured, the vertical construction of the step is circulated to complete the excavation, net hanging on the slope surface and curing of the sprayed concrete of other layered rock-soil bodies of the excavated side slope and is cured until all the operations of the whole side slope soil nailing wall supporting construction are completed. See fig. 5.
Further, all the construction operation requirements in the present step can be performed with reference to the requirements of the fourth step.
It is worth noting that in the construction process, the inclined water draining holes are arranged on the design slope in the longitudinal and transverse directions at proper time, the horizontal spacing and the vertical spacing of the water draining holes are preferably 2-3 m, the inclined water draining holes are preferably inclined by 5-10 degrees, the length of the water draining holes is slightly larger than that of soil nails, and water penetrating pipes or perforated polyethylene pipes are arranged in the holes. During the service period, the underground water in the slope body is continuously drained out of the influence range of the slope body through the drain holes, so that the condition that the underground water is accumulated in the slope body to reduce the strength of the slope rock-soil body and increase the hydrostatic pressure to endanger the stability of the soil nailing wall is avoided.
It is worth noting that after the construction of the side slope soil nailing wall is completed, a water interception ditch is arranged above the slope top, and a drainage ditch is arranged at the slope foot, so that the soil nailing wall can intercept surface water to the water ditch and drain the surface water out of the influence range of the side slope in the service period, and the problem that the stability of the soil nailing wall is endangered due to the fact that the strength of the side slope rock-soil body is reduced due to the infiltration of the surface water is avoided.
Notably, to control the risk of high slopes, the soil nailing wall height is limited to not more than 12m. When the side slope is higher, the side slope should be combined with measures such as prestressed anchor rods, miniature piles and the like. When soil nails are arranged in a bedding and rock slope with an unfavorable structural surface, integral anti-slip and shearing stability checking calculation is carried out along the bedding or the unfavorable structural surface, and the soil nails are used in combination with other measures according to checking calculation results. In combination with the topography and geological conditions, the slope is provided with multiple stages when the slope is higher. A platform is arranged between the upper and lower stages of the multi-stage soil nailing wall, the width of the platform is not less than 2m, and the height of each stage of soil nailing wall is not more than 10m.
It is noted that when the foundation pit engineering soil nailing wall is constructed, a working surface is provided for the pre-set soil nailing to reinforce the rock-soil body of the pit wall of the foundation pit, a part of the rock-soil body to be excavated in the range of the foundation pit can be subjected to layered basin-type excavation to expose a relatively gentle artificial current slope 1 to be abutted against the designed slope 2 of the foundation pit, then the method provided by the invention is used for pre-setting the soil nailing to reinforce the rock-soil body of the side wall of the foundation pit on the artificial current slope 1, and then the rest of the rock-soil body to be excavated in layers is subjected to layered excavation again to expose the designed slope 2, so that the flow construction operation of layered slope net hanging and layered concrete spraying is completed; see fig. 6.
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.
Claims (9)
1. A soil nailing wall construction method for pre-reinforcing a side slope rock-soil body is characterized by comprising the following steps of: the method comprises the following steps: firstly, brushing current slope vegetation and surface soil layers, measuring and paying off, and drilling holes in a slope rock-soil body according to a certain angle on the current slope by vertical layered horizontal running water construction, wherein the drilling holes penetrate through the rock-soil body to be excavated and enter a preset depth in a designed slope rock-soil body through a slope design slope; then inserting soil nails into the drilling section in the rock-soil body of the designed slope from the current slope surface orifice of the drilling hole, and grouting and curing the drilling section provided with the soil nails until the drilling hole is strong; finally, excavating a rock-soil body to be excavated according to the layered horizontal running water construction from top to bottom, exposing the slope in layers to design the slope, and completing the operations of hanging the net on the slope and spraying concrete;
the soil nailing wall construction method for the pre-reinforced side slope rock-soil mass specifically comprises the following steps:
step one: cleaning current slope vegetation and surface soil layers, and measuring paying-off; brushing vegetation and surface loose rock soil bodies on the current slope surface from top to bottom to expose the current slope surface from a solid rock soil layer; then measuring and paying off on the current slope, paying out the positions of the holes, and enabling the horizontal spacing and the vertical spacing of the holes on the designed slope to be 0.75 m-2 m after the rock-soil body of the excavated square is excavated in a layered manner;
step two: vertically layering and horizontally drilling holes in a water flowing mode from top to bottom along the trend of the current slope; drilling holes in the designed slope rock-soil body at a preset angle from a preset hole position on the current slope surface, wherein the drilling holes penetrate through the rock-soil body to be excavated and enter the designed slope rock-soil body through the slope design slope surface to a preset depth, and the length from the slope design slope surface to the hole bottom is 0.5-1.0 times of the height of the soil nailing wall and meets the requirements of the layered stability of the designed slope after layered excavation and the overall stability of the soil nailing wall during the service period after all excavation;
step three: immediately inserting soil nails into the holes after the holes are drilled for grouting until the holes are strong; after each drilling hole is formed, the hole is cleaned immediately and soil nails are inserted into the holes for grouting to be strong so as to prevent hole collapse; the soil nails are arranged on a drilling section ranging from the slope surface of the design slope to the hole bottom, namely, a drilling section of the design slope, the length of the tops of the soil nails exceeding the slope surface of the design slope is 80-150 mm, the soil nails are inserted from the current slope opening, and long wood sticks are used for jacking the soil nails into the drilling section of the design slope;
step four: excavating a first layer of rock and soil mass, hanging a slope surface with a net and spraying concrete; specifically, excavating a first layered rock-soil body along the trend of a side slope along with the horizontal line operation of the soil nail anchoring body maintenance condition from top to bottom, exposing a first layered design slope surface and exposing the top of the layered soil nail, and completing the construction of hanging a net and spraying concrete on the first layered design slope surface along the trend of the side slope on the design slope surface exposed by excavating the layered rock-soil body; the first layered rock-soil body is excavated to a position 500mm below the elevation of the layered soil nails, and overexcavation is strictly forbidden;
step five: digging a next layered rock-soil body, hanging a slope surface with a net, and spraying concrete until the construction of the whole slope soil nailing wall is completed; specifically, after the first layered shotcrete is cured, the next layered rock-soil body is excavated to expose the horizontal running water construction of the slope surface of the second layered design, net hanging on the slope surface of the second layered design is completed, the shotcrete is sprayed, the curing is cured to be strong, the vertical construction of the step is circulated to complete the excavation of other layered rock-soil bodies of the excavated side slope, net hanging on the slope surface and the shotcrete curing to be strong, and all operations of the whole side slope soil nailing wall supporting construction are completed.
2. A method of nailed wall construction of a pre-reinforced side slope rock-soil body as claimed in claim 1, wherein: the included angle between the preset angle of the drilling and the horizontal plane is 5-20 degrees, and the diameter of the drilling is 70-120 mm.
3. A method of nailed wall construction of a pre-reinforced side slope rock-soil body as claimed in claim 1, wherein: the soil nails are HRB400 and HRB500 steel bars, the diameter of the steel bars is 16 mm-32 mm, and epoxy coatings are required to be arranged on the surfaces of the steel bars in a corrosive environment; the soil nail is provided with a centering bracket within the whole length range, steel bars with diameters of 6-8 mm are selected for welding, the interval is not more than 2m, and the thickness of a soil nail steel bar protection layer is not less than 20mm.
4. A method of nailed wall construction of a pre-reinforced side slope rock-soil body as claimed in claim 1, wherein: the grouting material adopts cement paste or cement mortar, and the strength is not lower than 20MPa; when grouting, the grouting pipe is inserted from the current slope opening to the hole bottom and is subjected to grouting from the hole bottom, the distance from the grouting outlet at the end part of the grouting pipe to the hole bottom is not more than 200mm, the grouting pressure is 0.2MPa, the grouting pipe is pulled out while grouting, the grouting outlet of the grouting pipe is always below the grouting liquid level, the grouting pipe is pulled out to the designed slope position, grouting is stopped, and grouting is carried out 1-2 times before final grouting is carried out according to requirements.
5. A method of nailed wall construction of a pre-reinforced side slope rock-soil body as claimed in claim 1, wherein: in the fourth step, soil nailing wall layer-by-layer excavation height: the soil layer is 0.5 m-2.0 m, and the rock stratum is 1.0 m-4.0 m; one or two layers of reinforcing steel bars are arranged in the sprayed concrete surface layer on the slope design surface, the reinforcing steel bars are HPB 300-grade reinforcing steel bars, the diameter of the reinforcing steel bars is 6-10 mm, the distance is 150-300 mm, and the two-way reinforcing steel bar crossing points of the reinforcing steel bars are in spot welding or steel wire binding connection.
6. A method of nailed wall construction of a pre-reinforced side slope rock-soil body as claimed in claim 1, wherein: in the fourth step, when the net is hung, each square meter of reinforcing steel bar net is fixed on the design slope surface exposed by excavation through 2-3 short reinforcing steel bars, so that the clear distance between the reinforcing steel bar net and the design slope surface is not less than 30mm, each piece of reinforcing steel bar net and other reinforcing steel bar nets are firmly lapped, the horizontal lapping width is not less than 300mm, the vertical lapping width is not less than 500mm, the reinforcing steel bar net lap joint adopts lap joint welding, and the welding seam length is not less than 10 times of the diameter of the reinforcing steel bars;
4 reinforcing steel bars are longitudinally and transversely arranged at the outer side of the reinforcing steel bar net at the junction point of the reinforcing steel bar net and the top of the soil nail and welded with the top of the soil nail, the connection of the reinforcing steel bars and the top of the soil nail is required to meet the requirement of bearing the tension force of the soil nail, when the local part of the sprayed concrete surface layer is not enough to bear the punching bearing force under the action of the tension force of the soil nail, a pressure-bearing steel plate is arranged for reinforcing, the diameter of the reinforcing steel bars is 14-22 mm, the distance between the reinforcing steel bars and the soil nail is the same, and when the tensile strength of the soil nail body is fully utilized, the cross-sectional area of the reinforcing steel bars is not less than 1/2 of the cross-sectional area of the soil nail body.
7. A method of nailed wall construction of a pre-reinforced side slope rock-soil body as claimed in claim 1, wherein: when the thickness of the sprayed concrete surface layer is greater than 120mm, a double-layer reinforcing mesh is required to be arranged, a second layer of reinforcing mesh is required to be laid after the first layer of reinforcing mesh is covered by sprayed concrete, and when the sprayed concrete of the front layer is sprayed for more than 1 hour after final setting of the sprayed concrete of the same surface layer is required to be sprayed for two times or more than two times, the spraying of the next layer of concrete is required to be carried out, and the spraying water on the surface of the sprayed concrete of the front layer is required to be wetted before the spraying of the next layer of concrete; when the concrete is sprayed, the width of 500mm is reserved at the bottom of each layer of excavation surface, so that the concrete is not sprayed temporarily, and the vertical lap joint between the upper and lower layered reinforcement meshes after the lower layer of rock-soil body is excavated is facilitated.
8. A method of nailed wall construction of a pre-reinforced side slope rock-soil body as claimed in claim 1, wherein: further comprises: and arranging upward and downward water discharge holes on the design slope in the longitudinal and transverse directions, wherein the horizontal spacing and the vertical spacing of the water discharge holes are 2-3 m, the water discharge angle Kong Ang is 5-10 degrees, the length of the water discharge holes is slightly larger than that of soil nails, and water permeable pipes or perforated polyethylene pipes are arranged in the holes.
9. The soil nailing wall construction method of the pre-reinforced side slope rock-soil body of claim 1, which is characterized in that: after the construction of the side slope soil nailing wall is completed, a water interception ditch is arranged above the top of the side slope, and a drainage ditch is arranged at the bottom of the side slope, so that the soil nailing wall can intercept surface water to the water interception ditch and drain the surface water outside the influence range of the side slope during the service period, and the problem that the strength of the side slope rock-soil body is reduced due to the infiltration of the surface water so as to endanger the stability of the soil nailing wall is avoided.
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