Construction method for controllable anchor expansion structure of soft rock-soil layer branch plate

Abstract

The invention discloses a construction method of a soft rock and soil layer branch plate controllable anchor expanding structure, the branch plate controllable anchor expanding structure comprises a shell, a connecting device, an oil pump, a measuring system, an oil cylinder, a piston, an extruding and expanding device and a drill bit, and a fixed support arm and a telescopic support arm are connected through a half gear, a connecting rod and a connecting rod plate; linear motion of the telescopic support arm is realized by the I-shaped slide block through the linear guide rail, and stretching of the squeezing and expanding arm is realized by driving the synchronous belt through the motor. The oil pump injects oil into the oil cylinder through the oil supply pipe, the piston is pushed to outwards push the squeezing and expanding support arm of the squeezing and expanding device, the squeezing and expanding support arm outwards bends to squeeze rock soil on the hole wall to achieve hole diameter expansion, similarly, the oil pump sucks oil from the oil cylinder through the oil return pipe to enable the piston to retract, and the squeezing and expanding device is recovered. The construction method comprises the following steps: (a) drilling to form a hole; (b) extruding and expanding for forming; (c) hole cleaning; (d) anchoring; (e) anchor hole grouting; the construction method is simple in process, high in work efficiency, low in cost, few in used equipment, advanced in technology and better in economic effect.

Description

Technical Field

[0001] The invention belongs to the technical field of squeezing and expanding anchors in soft rock and soil, and in particular relates to a construction method of a controllable expansion anchor structure of a support plate in a soft rock and soil layer. Background Art

[0002] In the traditional geotechnical anchoring technology, the friction resistance between the grouting body and the rock and soil is quite limited in soft rock and soil, such as slope residual layer, water-rich stratum, coal-bearing weathered soil, fault mud zone, or artificial fill soil layer, etc., and the anchoring project often fails due to insufficient pull-out resistance, which in turn causes deformation and damage of the slope project, and even causes serious landslides and other catastrophic accidents, bringing great harm and threats to people's lives, property and production safety. Based on the traditional geotechnical anchoring technology, the geotechnical squeezed expansion anchor technology was developed by drawing on the squeezed expansion branch pile widely used in bridge pile foundations.

[0003] The new type of anchor bolt with extrusion and expansion is designed to give full play to the strength of the rock and soil in the anchor section by setting an extrusion and expansion branch plate in the anchor section, and greatly improves the anchor pull-out resistance by relying on the pressure of the rock and soil around the branch plate. On the basis of the traditional anchor bolt, the new type of anchor bolt with extrusion and expansion is designed with one or more extrusion and expansion entities with enlarged cross-sections in the anchor section of the rod body. Under the action of sliding force or active earth pressure in the slope soil, the soil produces displacement and deformation toward the free surface. Through the synergistic force of the expansion head and the surrounding rock and soil, the bearing capacity of the deep soil below the potential sliding surface is fully mobilized. The main working principle of the extrusion and expansion anchor bolt is to squeeze and compact the soil on the hole wall through the loading of the drilling and extrusion equipment, and then grouting is completed to form an extrusion and expansion branch plate, so as to give full play to the bearing capacity of the anchor bolt end and the bearing capacity of the deep soil. Summary of the invention

[0004] The invention discloses a construction method of a controllable expansion anchor structure of a support plate in a soft rock and soil layer, aiming to provide a new controllable expansion anchor structure and a corresponding construction method.

[0005] To this end, the present invention adopts the following technical solutions:

[0006] A construction method of a controllable expansion anchor structure of a support plate in a weak rock layer, the controllable expansion anchor structure comprises a cylindrical shell, an extruder, a hydraulic system and a drill bit, the drill bit is fixedly connected to the head end of the shell, and the shell is introduced into the anchor hole through the drill bit; the extruder is fixed in the shell, the shell is used to provide protection for the extruder, and rectangular openings are opened on the left and right sides of the shell for the extruder to expand the anchor outside the shell; the hydraulic system is used to provide hydraulic power for the extruder;

[0007] The extruder includes a head-end connector and a tail-end connector that are arranged opposite to each other. The head-end connector is located inside the shell and against the top of the shell, the tail-end connector is located on the upper part of the shell, and the tail-end connector can slide along the inner wall of the shell; two extruder arms that are hingedly connected in a "<" shape are connected between the left side of the head-end connector and the tail-end connector, and two extruder arms that are hingedly connected in a ">" shape are connected between the right side of the head-end connector and the tail-end connector; when the extruder is in the expanded state, the four extruder arms are arranged in a diamond shape, and the ends of the four extruder arms are hinged with pins; the four extruder arms are all telescopic structures, and the length of the extruder arms is extended or shortened by the telescopic structure;

[0008] A piston is connected to the bottom of the tail end connector, and the piston is used to push the tail end connector to move along the shell, thereby driving the four extrusion and expansion arms to extend outward to expand the anchor; the hydraulic system is connected to the piston;

[0009] The construction method comprises the following steps:

[0010] 1) Drilling: After the slope surface is inspected and qualified, the line is measured and the hole position is determined according to the design requirements. The hole position error and anchor hole deflection are controlled within the error range; the geological compass or protractor is used for orientation to ensure that the drilling rig is placed firmly and stably; the air compressor is used for air supply on the drilling machine, and the down-the-hole drilling rig is used for drilling, and the diameter of the drill bit used is not less than the designed hole diameter; to ensure the anchor hole depth, the drilling depth is more than 0.5m greater than the designed depth; the drilling speed is controlled according to the performance of the drilling rig and the anchoring stratum conditions to prevent the hole from twisting and changing in diameter;

[0011] 2) Branch plate extrusion and expansion: Before placing the branch plate, check the hole depth, hole diameter, and depth and position of the branch plate arrangement; before lowering the anchor drilling and extrusion device to the anchor hole, install a rotating reference on the connecting rod, and perform corresponding number of rotational extrusion and expansion according to the bisector line after each extrusion and expansion; the extrusion and expansion operation is carried out from bottom to top, and the anchor hole depth is measured before and after extrusion and expansion; during the extrusion and expansion operation, determine the opening size and width of the extruder in the extrusion and expansion branch plate device according to the relevant design dimensions of the branch, and combine the flow and pressure parameters of the hydraulic system to control the construction process, and extrude and expand the branch according to the designed position and direction;

[0012] 3) Hole cleaning: Use high-pressure air to remove all rock powder and sediment in the anchor hole, especially in the extrusion cavity, to the outside of the hole, so as not to affect the forming effect of the extrusion body after grouting and the bonding strength between the cement mortar and the rock mass on the hole wall;

[0013] 4) Anchoring: After the anchor hole is inspected and qualified, slowly insert the prefabricated anchor rod (cable). When the rod enters the anchor hole, it should be smoothly pushed forward according to the designed inclination and azimuth. It is strictly forbidden to shake, twist and string to prevent jamming in the middle. After inserting the rod, use a steel ruler to measure the remaining length of the rod outside the hole;

[0014] 5) Grouting: The grouting material is cement mortar, and the corresponding mix ratio test is carried out according to the design strength requirements; the anchor rod adopts a one-time grouting method, that is, the bottom grouting method; during the grouting process, the grouting pipe is slowly pulled out from the bottom of the hole, and the grouting can be stopped when grouting occurs at the hole mouth for more than 10 seconds.

[0015] Furthermore, the squeezing and expanding device is composed of four hinged squeezing and expanding arms; each squeezing and expanding arm includes a fixed support arm and a telescopic support arm, the telescopic support arm is slidably connected to the fixed support arm, and the squeezing and expanding arm is extended and retracted by sliding the telescopic support arm.

[0016] Furthermore, a driving member is connected between the fixed arm and the telescopic arm, and the driving member is used to drive the telescopic arm to move back and forth linearly along the fixed arm.

[0017] Furthermore, the two ends of the extrusion and expansion arm are rotatably connected via a pin shaft, and a limiting structure is also provided at both ends of the extrusion and expansion arm, and the limiting structure is used to limit the maximum rotation angle of the extrusion and expansion arm.

[0018] Furthermore, the limiting structure includes half gears located at both ends of the squeezing and expanding arms. When the two squeezing and expanding arms are connected, the corresponding two half gears are meshed, and the meshing rotation angle of the half gears is the maximum rotation angle of the squeezing and expanding arms.

[0019] Further, in the step 2):

[0020] When squeezing and expanding the branch plate, from top to bottom, the oil pump injects oil into the oil cylinder through the oil supply pipe, pushing the piston and then pushing the squeezing and expanding device, thereby achieving squeezing and expanding; at the same time, the squeezing and expanding arm in the squeezing and expanding device is extended and retracted, further expanding the diameter and volume of the branch plate;

[0021] After each branch expansion, the expander should be kept open for no less than 2 minutes to ensure that the rock and soil around the hole are compacted; after the expander is retracted, the interval between the next branch expansion and expansion should be no less than 1 minute; record the start and end time of each branch expansion and the readings of the oil pressure gauge and flow meter; when expanding the disc, calculate the number of brancher rotations based on the designed disc diameter and the width of the expander of the branch disc device, and the overlap width of each branch after each expansion should be greater than 10mm; the angle disc should be kept stably placed and no displacement should occur;

[0022] The time control of each extrusion and expansion should be consistent with the branching operation, and the start and end time of the plate formation and the oil pressure gauge and flow meter readings of each branching stage should be recorded; when the oil volume of the extrusion and expansion branch plate device changes too low or the soil is too dense to complete the extrusion and expansion, the design depth of the branch plate should be slightly adjusted up and down along the direction of the anchor hole. The adjusted branch plate should still be in the soil layer specified in the design and meet the spacing requirements between the branch plates.

[0023] By measuring the difference in oil flow before and after the expansion of the expander, the change in oil volume in the cylinder can be obtained, and the change in the expansion and contraction of the piston can be converted, and then the expansion state of the expander can be converted, based on which the theoretical aperture of the expanded hole can be calculated. However, due to the machining errors of the hydraulic jack (mainly including the cylinder and piston) and the machining errors of the expander and the gap between components, there will be a certain deviation between the theoretical calculated value and the actual value of the above-mentioned expanded hole diameter. Therefore, the theoretical calculated value of the hole diameter should be corrected by the method of no-load calibration or load calibration, that is, the combination of theoretical calculation and equipment calibration is used to accurately measure the expanded hole diameter of the anchor drilling. The calculation method is as follows:

[0024] Assume the total height of the piston is H, the extended height is h, the internal height is Hh, and the cross-sectional area of ​​the piston is s h ; Assume the reading of the oil flow meter is Q 1 , the reading of the return oil flow meter is Q 2 , the change in the amount of oil in the cylinder during oil supply is ΔQ = Q 1 (The flow reading is reset to zero before oil supply, and the reading of the return oil flow meter during oil supply is Q 2 should remain zero); if Fig.10 As shown, assume that the length of a single arm of the expander ABC and DEF is L, that is, AB = BC = DE = EF = L; the slide length of the expander AA' = DD' = h, the single-side expansion width of the expander B'B" = E'E" = v; assume that the initial width of the expander AD = BE = CF = B 1 E″=w. Through the geometric relationship between piston extension and expansion arm diameter, the maximum expansion aperture can be calculated as w′=w+2v.

[0025]

[0026] or

[0027]

[0028] The size of the extruded hole diameter can also be obtained by regression of the relationship curve between the oil volume change ΔQ in the calibrated oil cylinder and the extruded hole diameter w' through on-site measurement, and the calculation formula is w'=f(ΔQ).

[0029] In order to reduce processing errors and system errors, the method of combining theoretical calculation with equipment calibration can also be used to determine the size of the extruded and expanded aperture. The specific method is as follows:

[0030] Assume the actual extension height of the piston is h * , the actual area of ​​the piston is S * , the piston machining error is S 0 (large is positive, small is negative), then

[0031]

[0032] Assume the piston processing correction factor is k S ,but

[0033]

[0034] That is, the actual overhang height h of the piston is corrected.

[0035] Assume that the actual length of a single extruder is L * , the gap error of the extruder processing is L 0 (large is positive, small is negative), the squeezer correction coefficient is k L , then

[0036]

[0037] The corrected extrusion diameter is

[0038]

[0039] Piston machining correction factor k S and squeezer correction factor k L This can be determined by equipment calibration.

[0040] From formula (1.6), we can get

[0041]

[0042] At the same time, according to formula (1.2), the piston processing correction coefficient k is calculated S for

[0043]

[0044] Available

[0045]

[0046] Then, according to formula (1.7), the squeezer correction coefficient k is calculated: L for

[0047]

[0048] In the formula, Q 1 is the measured reading of the oil flow meter; h * is the actual extension height of the piston, w is the initial width of the expander, L q is the length of a single expander, w * k is the maximum measured extrusion diameter. S and k L Generally, the average value of multiple calibrations is taken.

[0049] Due to the structural characteristics of the squeezed expansion anchor, under the action of vertical tension, the damage of the soil around the anchor is not a simple compression or shear failure, but presents a variety of deformation and failure forms such as compression, sliding, and anchor-soil separation. Under the condition that the parameters such as the disk diameter and disk angle are relatively reasonable, the soil around the squeezed expansion disk often suffers from shear sliding failure. For the sliding failure of the rock and soil, the slip line theory and the principle of virtual work can be used to solve it accordingly;

[0050] Faced with different types and arrangements of squeezed and expanded anchors, their failure forms are often complex and diverse. Therefore, this paper will mainly focus on the bearing characteristics of the anchoring section of the squeezed and expanded anchor and study and analyze the calculation model of the single-plate ultimate bearing capacity;

[0051] 1) Extruded single-plate anchor

[0052] In the vertical bearing process of the squeezed expansion anchor, shear failure or sliding failure may occur due to the different pressure of the overburden. However, in actual engineering applications, shear failure can be avoided by controlling the depth of the overburden on the squeezed expansion plate. Therefore, the bearing capacity of the plate end is usually considered according to the sliding failure of the rock and soil.

[0053] According to the existing research results and relevant design specifications, the calculation mode of the squeezed single-plate anchor can be determined as follows:

[0054]

[0055] In the formula, F 拉 is the ultimate bearing capacity of the squeezed and expanded single-plate anchor; F 盘端 F is the bearing capacity of the disk end; 锚侧 G is the side friction of the anchor rod; 锚 is the deadweight of the anchor; is the ultimate tensile stress of the anchor rod.

[0056] a. Bearing capacity of the plate end

[0057] According to the slip line theory, the soil in the arc line area of ​​the upper plate of the expansion body undergoes slip failure, so the corresponding Prandtl zone slip deformation field can be established.

[0058] The strain field is given by θ = 0, θ = θ and obeys r = R 0 The logarithmic spiral of exp(θtanφ) is surrounded by the corresponding internal work D 1 The calculation expression is

[0059]

[0060] Where D 1 is the internal work generated within the strain field; b is the force width of the expansion plate; c is the cohesion of the soil around the anchor; u 0is the initial displacement; φ is the angle between the boundary line of the logarithmic spiral and the displacement vector; θ is the angle between the expansion disk section and the failure section; r is the radius of the logarithmic spiral; R 0 is the single-side net width of the extruded body; Θ is the angle between the extruded disc section and the anchor rod section.

[0061] Assuming that the soil outside the failure area remains stationary, the boundary line of the logarithmic spiral will become a discontinuous line, and the angle formed between it and the displacement vector is φ. The internal work of the discontinuous line D 2 The expression is

[0062]

[0063] Since r = R 0 e θtanφ , so D 1 =D 2 Total internal strength D 总 for

[0064] D 总 =D 1 +D 2 =bccotφR 0 u 0 [exp(2θtanφ)-1] (2.4)

[0065] In the formula, R 0 It is the maximum disc diameter of the extruded body.

[0066] After the strain field of the failure zone of the upper plate of the expansion body is established, θ = 90 + α, where α is the angle between the cross section of the expansion plate and the horizontal plane. Assume that the ultimate bearing capacity of the soil per unit width of the upper plate of the expansion body is F n , then according to the principle of virtual work, we can get that the external force work is equal to the internal force work, which is

[0067] D 外 =D 内 (2.5)

[0068] Then we can get F n The expression is

[0069] F n =ccotφR 0 [exp(2θtanφ)-1] (2.6)

[0070] In the formula, F n It is the ultimate bearing capacity of soil within unit width of the upper plate of the expansion body.

[0071] Finally, the bearing capacity formula of the disk end is obtained as follows:

[0072]

[0073] F盘端 =π(D+d)ccotφR 0 [exp(2θtanφ)-1] (2.8)

[0074] Where d is the diameter of the equal-section section of the extruded anchor.

[0075] In the process of vertical pull-out bearing, the rock mass on the upper plate of the extrusion expansion body slipped and failed on the basis of shearing. The bearing capacity calculation formula of the extrusion expansion body plate end was derived from the slip line theory, and it was found that the bearing capacity is not only related to the diameter of the extrusion expansion body plate, but also depends on the diameter of the straight hole section with equal cross section and the cohesion and internal friction angle of the rock mass around the extrusion expansion anchor. Compared with the traditional formula, formula (2.8) can better reflect the bearing capacity characteristics of the extrusion expansion body.

[0076] b. Anchor side friction calculation

[0077] Since the rock and soil in a certain range below the expansion plate separate from the anchor and generate tensile stress during the pulling process, the affected range L b The lateral friction resistance within the length should be deducted when calculating the bearing capacity. For the rock and soil above the expansion plate, a compaction effect is produced when it is pulled, which increases the lateral soil pressure on the anchor rod. a The side friction resistance within the length increases accordingly, so the increased side friction resistance can be taken into account by introducing the expansion coefficient γ. By fully considering the interaction mechanism between the rock and soil around the disk and the side friction resistance, the actual effective length L of the side friction resistance is calculated. 0 It can be expressed as

[0078] L 0 =L m -HL b +γ k L d (2.9)

[0079] Where, L m is the length of the anchor rod; H is the height of the extruded body; L d L is the length range of the lateral earth pressure increase caused by the squeezing of the rock and soil mass above the anchor rod; b The length range of the anchor rod that generates tensile stress due to the separation of anchor and soil; γ k For the expansion coefficient, the recommended empirical value is 1.1 to 1.2.

[0080] The calculation expression of the side friction resistance of the squeeze-expanded anchor is:

[0081] F 锚侧 =f 侧 πdL 0 =f 侧 πd(L m -HLb +γ k L d ) (2.10)

[0082] In the formula, f 侧 It is the lateral friction resistance per unit area of ​​the cross-section of the squeezed anchor rod.

[0083] Compared with the previous empirical formula, the calculation length of the lateral friction resistance is not simply the pile length minus the plate height, but fully considers the length range of the lateral earth pressure increase due to the squeezing of the squeezed expansion body, and the length range of the tensile stress caused by the separation of the anchor and soil. Therefore, the calculation of the lateral friction resistance of the squeezed expansion anchor is not only related to the anchor length and the plate height, but also depends on the length affected by the lateral earth pressure on the plate, the length of the tensile stress area under the plate, and the determination of the expansion coefficient.

[0084] c. Anchor deadweight

[0085] The deadweight of the anchor can be expressed as

[0086] G 锚 =G 1 +G 2 (2.11)

[0087] In the formula, G 1 Main anchor weight; G 2 The weight of the extruded disc.

[0088] The weight of the anchor body is

[0089]

[0090] Where γG is the weight of the anchor.

[0091] The weight of the expansion plate is equivalent to the weight of two H / 2 high truncated cones. Let the weight of the truncated cone be G. 0 , whose expression is

[0092]

[0093] Therefore, the self-weight expression of the squeeze-expanded anchor is:

[0094]

[0095] d. Ultimate bearing capacity of single plate anchor

[0096] Combining the above calculation and analysis process, the calculation model of the ultimate bearing capacity of the squeezed single-plate anchor can be obtained as shown in formula (2.1). It is worth noting that in formula (2.1), The expression is

[0097]

[0098] In the formula, It is the ultimate pull-out bearing capacity of the squeeze-expanded anchor; It is the tensile bearing capacity of the concrete in the squeeze-expanded anchor rod; It is the tensile bearing capacity borne by the steel bars in the squeezed and expanded anchor rod.

[0099] The calculation formula is mainly composed of three parts: the disk end bearing capacity, lateral friction resistance and the self-weight of the extruded anchor. Compared with previous relevant empirical formulas, the disk end bearing capacity is calculated using the slip line theory, and the lateral friction resistance introduces the concept of effective length, which makes the calculation model of the extruded anchor bearing capacity more reasonable and further improves the theoretical research on the extruded anchor.

[0100] The beneficial effects of the present invention are:

[0101] 1. Improved bearing capacity. In the process of squeezing and expanding the borehole into a disc cavity, the soil on the hole wall is squeezed and compacted, which increases the soil density, reduces the porosity ratio, and improves the bearing capacity of the soil in the anchoring section. Since the bearing capacity of the expanded head at the end of the rod body can be brought into play, the ultimate bearing capacity of the deep soil can be fully mobilized to significantly improve the pull-out bearing capacity of the anchor rod, reduce the number of anchoring structures accordingly, and save costs.

[0102] 2. Reduced anchoring section length. Since the bearing effect of the enlarged head at the end of the anchor rod increases the anchoring load, the anchoring section length can be effectively reduced under the premise of a certain anchoring load. This is more applicable to working conditions where the design length of the anchor rod is limited (such as encroaching on the road red line, close to the foundation of an existing building, etc.).

[0103] 3. Strong adjustability. The position and number of the enlarged heads can be dynamically adjusted according to the physical and mechanical properties of the soil layer and the depth of the potential sliding surface, which increases the optimization space of the anchoring structure and improves the safety reserve.

[0104] 4. Good economic and social benefits. Since the number of anchoring structures is reduced, reinforcement materials can be saved, construction period can be shortened, green energy conservation and environmental protection can be achieved, and obvious economic and social benefits can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0105] Figure 1 It is a structural schematic diagram of the extruder of the present invention;

[0106] Figure 2 It is a structural schematic diagram of the extrusion and expansion arm of the present invention;

[0107] Figure 3 It is a schematic cross-sectional structure diagram of the extrusion and expansion arm of the present invention;

[0108] Figure 4 It is a schematic diagram of the connection structure of the upper and lower extrusion and expansion arms of the present invention;

[0109] Figure 5It is a schematic diagram of the internal driving structure of the extrusion and expansion arm of the present invention;

[0110] Figure 6 It is an enlarged schematic diagram of the driving structure inside the squeezing and expanding arm of the present invention;

[0111] Figure 7 It is an enlarged schematic diagram of the structures such as the synchronous pulley and the associated switch in the squeezing and expanding arm of the present invention;

[0112] Figure 8 Schematic diagram of the controllable anchor rod of the integral support plate of the squeeze expander of the present invention;

[0113] Fig. 9 It is a schematic diagram of the structure of the squeezing and expanding arm of the squeezing and expanding device of the present invention when it is in the state of contraction and expansion;

[0114] Fig.10 It is a schematic diagram of the structure of each point when calculating the extrusion and expansion aperture of the present invention;

[0115] Fig.11 It is the slip deformation field of the Prandtl zone of the soil mass above the extrusion plate of the present invention;

[0116] Fig.12 It is a schematic diagram of the calculation mode of the squeezed and expanded single-plate anchor rod of the present invention;

[0117] Fig.13 It is a flowchart of the construction method of the present invention;

[0118] In the figure: 1. oil pump; 2. oil supply pipe, 3. oil return pipe, 4. oil cylinder, 5. piston, 6. expander; 7. oil supply valve; 8. oil return valve; 9. oil supply meter, 10. oil return meter, 11. oil supply flow meter, 12. oil return flow meter, 13. connector, 14. fixed support arm, 15. telescopic support arm, 16. half gear, 17. connecting plate, 18. linear guide, 19. I-shaped slider, 20. connecting rod, 21. synchronous belt, 22. slide bar, 23. motor, 24. limiter, 25. drill bit, 26. housing, 27. reducer, 28. coupling, 29. associated switch, 30. bevel gear reducer, 31. synchronous pulley. DETAILED DESCRIPTION

[0119] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments:

[0120] A construction method for a controllable expansion anchor structure of a support plate in a soft rock layer, such as Figure 1-3As shown, the controllable expansion anchor structure includes a housing 26, a hydraulic system, an extruder 6 and a drill bit 25. An oil supply pipe 2 and an oil return pipe 3 are arranged in the hydraulic system, and an oil supply valve 7, an oil supply meter 9, an oil supply flow meter 11 and an oil return valve 8, an oil return meter 10, and an oil return flow meter 12 are installed on the oil supply pipeline and the oil return pipeline respectively. The above devices together constitute a hydraulic system, and record the readings of the oil supply meter 9, the oil return meter 10, the oil supply flow meter 11 and the oil return flow meter 12 at each loading and unloading time step, so as to prepare for calculating the extrusion expansion aperture. The oil pump 1 is connected to the oil cylinder 4 through the oil supply pipe 2 and the oil return pipe 3 to form an extrusion expansion control mechanism, and then the piston 5 is connected to the extruder 6 to form a force transmission mechanism.

[0121] like Figure 2 and 3 As shown, the squeezing and expanding device 6 comprises four identical squeezing and expanding arms, the telescopic support arm 15 and the fixed support arm 14 together constitute one squeezing and expanding arm; the two upper squeezing and expanding arms at the upper part and the two lower squeezing and expanding arms at the lower part are arranged symmetrically. The position and connection relationship between the squeezing and expanding arms are as follows: the upper squeezing and expanding arms are hinged with the lower squeezing and expanding arms through the half gear 16, the connecting rod 20 and the connecting plate 17.

[0122] The specific way in which the piston 5 pushes the expander 6 is that the piston 5 pushes the support seat connector 13 so that the connector 13 moves axially, so that the expander 6 is in a relaxed state. The positions and connection relationships among the piston 5, the connector 13 and the expander arm are as follows: the piston 5 is in close contact with the equal contact surfaces of the connector 13, and two hollow special-shaped plates are arranged on both side surfaces of the connector 13; the shape of the hollow special-shaped plates is composed of a rectangle and a semicircular arc, wherein the role of the hollow cylinder is to allow the connecting rod 20 to pass through, and the connecting rod 20 is used to connect the connecting member 13 and the fixed support arm 14, that is, the connecting member 13 and the upper expander arm are connected.

[0123] The fixed arm 14 has a motor 23, a reducer 27, a conical reducer 30, a linear guide 18, and a synchronous belt 21 at the bottom. The various components are connected by a coupling 28. The synchronous pulley 31 is rotated by driving the motor 23, and the trapezoidal gear on the synchronous pulley 31 cooperates with the trapezoidal gear on the gear side of the synchronous belt 21, thereby realizing the linear motion of the synchronous belt 21, and the I-shaped slider 19 connects the linear guide 18 and the synchronous belt 21 to realize the extension of the telescopic arm.

[0124] The upper left and right sides of the "I"-shaped slider 19 are overlapped on the left and right sides of the telescopic extrusion arm 15, and the lower left and right sides are overlapped on the left and right sides of the synchronous belt inside the fixed support arm 14, and the middle is overlapped on the linear guide rail 18 to connect the fixed support arm 14 with the telescopic support arm 15.

[0125] Half of the half gear 16 is a cylindrical structure and the other half is a gear structure, so that the squeezing and expanding arm can move within a fixed range; the two upper limiters 24 limit the telescopic support arm from exceeding the travel range of the linear guide rail, and the two lower limiters 24 prevent the telescopic support arm 15 from colliding with the bottom driving mechanism along the linear guide rail 18; the associated switch 29 is used to adjust the zeroing step when the squeezing and expanding device is used, that is, the squeezing and expanding arm is reset.

[0126] According to the internal morphological changes of the extrusion and expansion device, the bolt drilling extrusion and expansion device can be divided into an expansion state and a recovery state, such as Figure 5 As shown, the solid line state of the squeezer is the recovery state, and the dotted line state is the expansion state. The oil pump sucks oil from the oil cylinder through the return oil pipe to retract the piston, and the squeezer is recovered and restored, thus reaching the recovery state. Similarly, when the oil pump injects oil into the oil cylinder through the oil supply pipe, pushing the piston to move the squeezer of the squeezer outward, the squeezer squeezes the hole wall rock and soil outward to achieve the expansion of the aperture, reaching the expansion state.

[0127] During on-site construction, before the anchor drilling and expansion device is lowered to the anchor hole, a rotating reference device needs to be installed on the connecting rod. After each expansion, a corresponding number of displacement expansions are performed according to the equal division line. Each time the brancher expands, a set of pairs of branches is formed; after rotating 90° and expanding again, a cross branch is formed. If the divider is rotated at a certain angle and overlap width for continuous expansion, an expansion disk can be formed.

[0128] The measurement of the diameter of the anchor hole is one of the key technologies in the construction of the anchor. The measurement of the diameter of the hole is very important, especially during the construction process. At present, the wellbore gauge or ultrasonic borehole gauge is commonly used in similar engineering practices such as the squeezed branch pile. It is expensive, not intuitive, and requires miniaturization of equipment. Moreover, whether it is the wellbore gauge or ultrasonic detection, the measurement is made after the anchor hole is drilled and squeezed, and it is impossible to measure during the construction process, and it is not possible to both ensure quality and guide construction to meet design requirements.

[0129] Therefore, a new method for measuring the diameter of anchor drilling and expansion is proposed, which can not only ensure the quality but also guide the construction. It is simple to operate, intuitive, reliable and easy to use. The anchor drilling and expansion diameter measuring device mainly consists of an oil pump, an oil pipe, an oil meter, a flow meter, an oil cylinder, a piston and an expander. The oil pump fills the oil cylinder with oil through the oil supply pipe, pushes the piston to move the expander outward, and the expander zigzags outward to squeeze the hole wall rock and soil to achieve the expansion of the diameter; similarly, the oil pump sucks oil from the oil cylinder through the return oil pipe to retract the piston and recover the expander. By measuring the difference in oil supply flow before and after the expansion of the expander, the change in oil volume in the oil cylinder can be obtained, thereby converting the expansion change of the piston, and then converting the expansion state of the expander, and the theoretical diameter of the expansion drilling can be calculated based on this. However, due to the machining error of the hydraulic jack (mainly including the oil cylinder and piston) and the machining error of the expander mechanism and the component gap, there will be a certain deviation between the theoretical calculated value and the actual value of the above expansion diameter. Therefore, the theoretical calculated value of the hole diameter should be corrected through no-load calibration or load calibration, that is, the method combining theoretical calculation with equipment calibration should be used to accurately measure the hole diameter of the anchor drilling and expansion.

[0130] The construction sequence of general prestressed anchors is drilling, hole cleaning, anchoring, grouting, tensioning, and locking. The construction sequence of extruded anchors is similar, but compared with ordinary anchors, there is one more process, that is, special extrusion equipment is needed to extrude and expand the anchor holes into branches or discs.

[0131] The construction process of the extruded and expanded anchor rod is as follows: anchor hole positioning → anchor drilling rig placement → guide hole construction → hole cleaning → replacement of the extruded and expanded drill bit → push the drill rod into place → connection of the extruded and expanded oil pump → cyclic extrusion and expansion → secondary hole cleaning → anchor rod manufacturing and installation → anchor hole grouting → end of the extruded and expanded anchor rod construction.

[0132] like Fig.13 As shown, the construction method of the present invention comprises the following steps:

[0133] 1) Drilling

[0134] a. After the slope surface inspection is qualified, the layout shall be measured and the hole position shall be determined according to the design requirements. The hole position error and anchor hole deflection shall be controlled within the error range.

[0135] b. Use a geological compass or protractor to orient and ensure that the drilling rig support is firm and stable.

[0136] c. The drilling equipment shall use an air compressor to supply air, and the down-the-hole drill shall be used for drilling. The diameter of the drill bit used shall not be less than the designed hole diameter.

[0137] d. To ensure the anchor hole depth, the drilling depth should be more than 0.5m greater than the design depth.

[0138] e. The drilling speed should be strictly controlled according to the performance of the drilling rig and the conditions of the anchoring stratum to prevent the borehole from twisting and changing in diameter, which may cause difficulties in anchoring or other accidents.

[0139] 2) Branch plate expansion

[0140] a. Before forming branches and trays, the hole depth, hole diameter, and the depth and position of the branch and tray layout should be verified.

[0141] b. Before the anchor drilling and expansion device is lowered to the anchor hole, a rotating reference device needs to be installed on the connecting rod. After each expansion is completed, the corresponding number of rotations and expansions should be performed according to the bisector line.

[0142] c. The extrusion and expansion operation should be carried out from bottom to top, and the anchor hole depth should be measured before and after extrusion and expansion.

[0143] d. During the branching operation, the opening size and width of the expander in the branching plate device should be determined according to the relevant design dimensions of the branch, and the branching should be expanded according to the designed position and direction in combination with the construction process control of the oil pressure gauge and flow meter. After each branching operation, the expander should be kept open for no less than 2 minutes to ensure the compaction of the rock and soil around the hole; after the expander is retracted, the interval between the next branching operation and the expansion operation should be no less than 1 minute. Record the start and end time of each branching operation and the readings of the oil pressure gauge and flow meter.

[0144] e. During the extrusion and expansion operation, the number of brancher rotations should be calculated based on the designed disk diameter and the width of the extrusion and expansion branch disk device. The overlap width of each branch after each extrusion and expansion should be greater than 10mm; the angle disk should be kept stable and not shifted; the brancher should be rotated strictly according to the graduation sequence on the angle disk, combined with the construction process control of the oil pressure gauge and flow meter, to extrude and expand the disk. The time control of each extrusion and expansion should be consistent with the branching operation, and the start and end time of the disk and the oil pressure gauge and flow meter readings at each branching stage should be recorded.

[0145] f. When the oil volume of the extrusion and expansion branch and plate device changes too low or the soil is too dense to complete the extrusion and expansion, the design depth of the branch or plate can be slightly adjusted up and down along the direction of the anchor hole. The adjusted branch and plate should still be in the soil layer specified in the design and meet the spacing requirements between the branches and plates.

[0146] 3) Cleaning holes

[0147] Use high-pressure air to remove all rock powder and sediment in the anchor hole, especially in the extruded cavity, to the outside of the hole to avoid affecting the forming effect of the extruded body after grouting and the bonding strength between the cement mortar and the rock mass on the hole wall.

[0148] 4) Anchor

[0149] After the anchor hole is inspected and qualified, the prefabricated anchor rod (cable) is slowly inserted. When the rod enters the anchor hole, it should be smoothly pushed forward according to the designed inclination and orientation. It is strictly forbidden to shake, twist and string to prevent jamming in the middle. After inserting the rod, use a steel ruler to measure the remaining length of the rod outside the hole.

[0150] 5) Grouting

[0151] Grouting is an important process in the construction of squeezed and expanded anchor rods and is the key to determining the quality of squeezed and expanded anchor rods.

[0152] a. Before grouting, check whether the grouting pipe and exhaust pipe are unobstructed and whether the grouting machine is in good condition.

[0153] b. The grouting material is cement mortar. The corresponding mix ratio test should be carried out according to the design strength requirements. If necessary, appropriate early strength agent can be added.

[0154] c. The anchor rod adopts a one-time grouting method, that is, the bottom hole grouting method; during the grouting process, the grouting pipe is slowly pulled out from the bottom of the hole, and the grouting can be stopped only when grout emerges from the hole mouth for more than 10 seconds.

Claims

1. A construction method for a controllable expansion anchor structure of a support plate in a soft rock layer, characterized in that: The controllable expansion anchor structure includes a cylindrical shell, a squeezer, a hydraulic system and a drill bit, wherein the drill bit is fixedly connected to the head end of the shell, and the shell is introduced into the anchor hole through the drill bit; the squeezer is fixed in the shell, and the shell is used to provide protection for the squeezer, and rectangular openings are provided on the left and right sides of the shell for the squeezer to expand the anchor outside the shell; the hydraulic system is used to provide hydraulic power for the squeezer; The extruder includes a head-end connector and a tail-end connector that are arranged opposite to each other. The head-end connector is located inside the shell and against the top of the shell, the tail-end connector is located on the upper part of the shell, and the tail-end connector can slide along the inner wall of the shell; two extruder arms that are hingedly connected in a "<" shape are connected between the left side of the head-end connector and the tail-end connector, and two extruder arms that are hingedly connected in a ">" shape are connected between the right side of the head-end connector and the tail-end connector; when the extruder is in a stretched state, the four extruder arms are arranged in a diamond shape, and the ends of the four extruder arms are hinged with pins; the four extruder arms are all telescopic structures, and the length of the extruder arms is extended or shortened by the telescopic structure; A piston is connected to the bottom of the tail end connector, and the piston is used to push the tail end connector to move along the shell, thereby driving the four extrusion and expansion arms to extend outward to expand the anchor; the hydraulic system is connected to the piston; The construction method comprises the following steps: 1) Drilling: After the slope surface is inspected and qualified, the line is measured and the hole position is determined according to the design requirements. The hole position error and anchor hole deflection are controlled within the error range; the geological compass or protractor is used for orientation to ensure that the drilling rig is placed firmly and stably; the air compressor is used for air supply on the drilling machine, and the down-the-hole drilling rig is used for drilling, and the diameter of the drill bit used is not less than the designed hole diameter; to ensure the anchor hole depth, the drilling depth is more than 0.5m greater than the designed depth; the drilling speed is controlled according to the performance of the drilling rig and the anchoring stratum conditions to prevent the hole from twisting and changing in diameter; 2) Branch plate extrusion and expansion: Before forming branches and plates, check the hole depth, hole diameter, and depth and position of branch plate arrangement; before the anchor drilling and extrusion and expansion device is lowered to the anchor hole, install a rotating reference on the connecting rod, and perform corresponding number of rotational extrusion and expansion according to the bisector line after each extrusion and expansion; the extrusion and expansion forming operation is carried out from bottom to top, and the anchor hole depth is measured before and after extrusion and expansion; during the extrusion and expansion operation, determine the opening size and width of the extruder in the extrusion and expansion branch plate device according to the relevant design dimensions, and combine the flow and pressure parameters of the hydraulic system to control the construction process, and extrusion and expansion is carried out according to the designed position and direction; 3) Hole cleaning: Use high-pressure air to remove all rock powder and sediment in the anchor hole, especially in the extrusion cavity, to the outside of the hole, so as not to affect the forming effect of the extrusion body after grouting and the bonding strength between the cement mortar and the rock mass on the hole wall; 4) Anchoring: After the anchor hole is inspected and qualified, slowly insert the prefabricated anchor rod (cable). When the rod enters the anchor hole, it should be smoothly pushed forward according to the designed inclination and azimuth. It is strictly forbidden to shake, twist and string to prevent jamming in the middle. After inserting the rod, use a steel ruler to measure the remaining length of the rod outside the hole; 5) Grouting: The grouting material is cement mortar, and the corresponding mix ratio test is carried out according to the design strength requirements; the anchor rod adopts a one-time grouting method, that is, the bottom grouting method; during the grouting process, the grouting pipe is slowly pulled out from the bottom of the hole, and the grouting can be stopped when grouting occurs at the hole mouth for more than 10 seconds.

2. The construction method of a controllable expansion anchor structure of a branch plate in a soft rock layer according to claim 1 is characterized in that: The squeezing and expanding device is composed of four squeezing and expanding arms that are hinged; each squeezing and expanding arm includes a fixed support arm and a telescopic support arm, the telescopic support arm is slidably connected in the fixed support arm, and the squeezing and expanding arm is telescoped by sliding the telescopic support arm.

3. The construction method of a controllable expansion anchor structure of a branch plate in a soft rock layer according to claim 2 is characterized in that: A driving member is also connected between the fixed arm and the telescopic arm. The driving member drives the synchronous belt to move, driving the "I"-shaped slider connecting the fixed arm and the telescopic arm to move back and forth in a straight line, so that the telescopic arm moves back and forth in a straight line along the fixed arm, thereby realizing the contraction of the squeezing and expanding arm.

4. The construction method of a controllable expansion anchor structure of a branch plate in a soft rock layer according to claim 1 is characterized in that: The two ends of the extrusion and expansion arm are rotatably connected through a pin shaft, and a limiting structure is also provided at both ends of the extrusion and expansion arm, and the limiting structure is used to limit the maximum telescopic length of the extrusion and expansion arm.

5. The construction method of a controllable expansion anchor structure of a support plate in a soft rock layer according to claim 4 is characterized in that: The limiting structure includes half gears located at both ends of the squeezing and expanding arms. When the two squeezing and expanding arms are connected, the corresponding two half gears are meshed, and the meshing rotation angle of the half gears is the maximum rotation angle of the squeezing and expanding arms.

6. The construction method of a controllable expansion anchor structure of a branch plate in a soft rock layer according to claim 1 is characterized in that: In the step 2): When squeezing and expanding the branch plate, from top to bottom, the oil pump injects oil into the oil cylinder through the oil supply pipe, pushing the piston and then pushing the squeezing and expanding device, thereby achieving squeezing and expanding; at the same time, the squeezing and expanding arm in the squeezing and expanding device is extended and retracted, further expanding the diameter and volume of the branch plate; After each branch expansion, the expander should be kept open for no less than 2 minutes to ensure that the rock and soil around the hole are compacted; after the expander is retracted, the interval between the next branch expansion and expansion should be no less than 1 minute; record the start and end time of each branch expansion and the readings of the oil pressure gauge and flow meter; when expanding the disc, calculate the number of brancher rotations based on the designed disc diameter and the width of the expander of the branch disc device, and the overlap width of each branch after each expansion should be greater than 10mm; the angle disc should be kept stably placed and no displacement should occur; The time control of each extrusion and expansion should be consistent with the branching operation, and the start and end time of the plate formation and the oil pressure gauge and flow meter readings of each branching stage should be recorded; when the oil volume of the extrusion and expansion branch plate device changes too low or the soil is too dense to complete the extrusion and expansion, the design depth of the branch or plate should be slightly adjusted up and down along the direction of the anchor hole. The adjusted branch plate should still be in the soil layer specified in the design and meet the spacing requirements between the branch plates.

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