Construction method of anti-floating anchor rod in moderately weathered rock stratum

Abstract

The invention relates to the technical field of foundation engineering construction, and discloses a construction method of an anti-floating anchor rod in a moderately weathered rock stratum.The construction method comprises the steps that a positioning steel bar is fixed in a soil body at the design position of an anchor rod body, a positioning sleeve is placed on the soil body with the positioning steel bar as the center, and then the positioning sleeve is fixed to the inner side face of the positioning sleeve through a fixing steel bar; the cushion layer is constructed, so that the top face of the cushion layer is flush with an upper opening of the positioning sleeve, then the steel bars and the positioning sleeve are taken out, a positioning hole is formed, an anchor hole is drilled downwards from the positioning hole, and an anchor rod body is put into the anchor hole and grouted; constructing a waterproof layer and a protective layer; the arrangement of the positioning steel bars is a first positioning measure for the positions of the anchor holes, and the arrangement of the positioning holes formed by the positioning sleeves is a second positioning measure for the positions of the anchor holes; two positioning measures are adopted, so that the problem that the anti-floating effect of the structure is affected due to the fact that an anchor hole is prone to deviation is effectively solved; meanwhile, the cushion layer can be protected, and the construction period is shortened.

Description

Technical Field

[0001] The invention relates to the technical field of foundation engineering construction, in particular to a construction method of an anti-floating anchor rod in a medium-weathered rock layer. Background Art

[0002] Anti-floating of underground structures is an important issue in foundation engineering. The focus is on how to resist the buoyancy of groundwater on the structure to ensure the stability and safety of the overall structure. The anti-floating problem of underground projects is widely present in projects such as underground garages, subway stations, sunken squares, basements of super high-rise buildings, and offshore dock platforms. Especially in coastal areas and areas with high groundwater levels, the anti-floating problem of underground projects is more serious. As an important technical means to resist the buoyancy of groundwater and ensure the safety of structures, anti-floating anchor rods can effectively solve the problem of anti-floating of underground projects. Setting up anti-floating anchor rods can limit the deformation of the entire structure and improve the stability and safety of the building. Anti-floating anchor rods have the advantages of strong stratum adaptability, stress dispersion, simple construction, and low cost. Therefore, anti-floating anchor rods are widely used in anti-floating of underground projects.

[0003] For areas with moderately weathered rock formations, the installation of anti-floating anchor rods has the advantages of high pull-out bearing capacity, convenient construction, economic and environmental protection, and small space occupation compared with other anti-floating technical measures. Therefore, the installation of anti-floating anchor rods in areas with moderately weathered rock formations is an important means of anti-floating in underground engineering. However, the construction of anti-floating anchor rods in areas with moderately weathered rock formations still has the following problems that are difficult to solve:

[0004] (1) Positioning is difficult. According to relevant technical standards, the allowable deviation of the anchor hole position of the anti-floating anchor is no more than ±100 mm, and the inclination of the anchor hole is no more than 2% of the anchor hole length. In the positioning of the anchor hole, the commonly used method is to set the steel bar head at the positioning position or to spray paint on the cushion layer at the positioning position. However, the effects of these two positioning methods are poor. During the construction of the anchor hole, the back and forth movement of the drilling rig and the mud that emerges after drilling will cover the positioning hole, which brings great difficulties to the positioning of the anti-floating anchor and easily causes the anti-floating anchor to deviate, thereby affecting the quality of the project.

[0005] (2) In the current positioning method, the anchor hole needs to be constructed starting from the set cushion layer. It is necessary to drill holes on the concrete cushion layer first, and then construct the anchor hole, which increases the construction period of the anti-floating anchor rod. At the same time, when the drill rig drills holes on the cushion layer, the vibration during the operation of the drill rig will cause damage to the cushion layer, resulting in a loose bond between the waterproof layer and the cushion layer during the subsequent construction of the waterproof layer, thereby increasing the risk of water seepage in the underground structure and reducing the waterproof performance of the underground structure. Summary of the invention

[0006] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a construction method for anti-floating anchor rods in medium-weathered rock strata. By setting two positioning measures, the problem that the anchor holes are prone to deviation and thus affect the anti-floating effect of the structure is effectively solved. At the same time, the cushion layer can be protected and the construction period can be shortened.

[0007] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0008] A construction method for an anti-floating anchor rod in a moderately weathered rock formation comprises the following steps:

[0009] The positioning steel bar is fixed in the soil at the designed position of the anchor rod body, and the positioning sleeve is placed on the soil with the positioning steel bar as the center, and then the positioning sleeve is fixed on the inner side of the positioning sleeve with the fixing steel bar;

[0010] Construct the cushion layer so that the top surface of the cushion layer is flush with the upper end of the positioning sleeve, then remove the steel bars and the positioning sleeve to form a positioning hole, drill an anchor hole downward from the positioning hole, lower the anchor rod body into the anchor hole and inject grout; then construct the waterproof layer and protective layer.

[0011] As a further implementation method, a total station is used to locate the anchor rod according to its designed position, and the bottom end of the positioning steel bar is inserted and fixed in the soil at the positioning position; multiple fixed steel bars are inserted into the soil close to the inner side of the positioning sleeve to ensure that the positioning sleeve does not shift in position.

[0012] As a further implementation method, the height of the positioning sleeve should be consistent with the designed thickness of the cushion layer, and the top ends of the positioning steel bars and the fixing steel bars should be lower than the upper end of the positioning sleeve.

[0013] As a further implementation method, after the cushion layer construction is completed and initially set, a hammer is used to lightly hammer the positioning sleeve to remove it, and then the fixed steel bars and the positioning steel bars are removed to form a positioning hole.

[0014] As a further implementation method, according to the positioning of the positioning hole, a hydraulic down-the-hole drill is used to construct the anchor hole, and the drill hole diameter is smaller than the positioning hole diameter; when the hydraulic down-the-hole drill is constructed on the cushion layer, a waste template is set under its chain wheel as a pad.

[0015] As a further implementation method, when lowering the anchor rods, it is necessary to ensure that the distance between each anchor rod body and the wall of the anchor hole is the same. The grouting is carried out using the reverse pressure grouting method at the bottom of the hole, and the positioning holes are grouted at the same time. The top surface of the grouting body is highly flush with the top surface of the cushion layer.

[0016] As a further implementation method, after the grouting body is completely solidified, the mud generated when the hydraulic down-the-hole drill constructs the anchor hole on the cushion layer is cleaned.

[0017] As a further implementation method, the waterproof layer adopts SBS waterproof membrane.

[0018] As a further implementation, the length of the positioning steel bars and the fixing steel bars is 150 mm.

[0019] As a further implementation method, the protective layer adopts C15 fine stone concrete protective layer.

[0020] The beneficial effects of the present invention are as follows:

[0021] 1. The present invention provides a first positioning measure for the anchor hole position by setting a positioning steel bar, and provides a positioning hole formed by a positioning sleeve as a second positioning measure for the anchor hole position; providing two positioning measures effectively solves the problem that the anchor hole is prone to offset and affects the anti-floating effect of the structure.

[0022] 2. The present invention can form a positioning hole at the cushion layer position by arranging a positioning sleeve, and construct an anchor hole on the basis of the positioning hole. On the one hand, the positioning hole can provide a positioning effect for the drilling of the anchor hole, and on the other hand, the drilling of the anchor hole will not damage the cushion layer. The anchor hole can be drilled directly from the soil position, shortening the construction period of the anti-floating anchor rod, eliminating the situation where the waterproof layer and the cushion layer are prone to loose bonding, and ensuring the waterproof performance of the underground structure.

[0023] 3. The positioning structure of the present invention includes positioning steel bars, fixing steel bars and positioning sleeves, which are reusable. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0025] Figure 1 It is a schematic diagram of the structure of the construction positioning sleeve and the steel bar in an embodiment of the present invention;

[0026] Figure 2 1. is a top view of the structure of the construction positioning sleeve and the steel bar in the embodiment of the present invention;

[0027] Figure 3 It is a front view of the main structure after the anchor hole construction is completed in the embodiment of the present invention;

[0028] Figure 4 It is a front view of the main structure after the anti-floating anchor rod construction is completed in the embodiment of the present invention;

[0029] Figure 5 It is a front view of the positioning sleeve and the steel bar structure principle in the embodiment of the present invention.

[0030] In the figure: the distances or sizes between parts are exaggerated to show the positions of various parts, and the schematic diagram is for reference only.

[0031] Among them: 1-fixed steel bars, 2-positioning steel bars, 3-positioning sleeves, 4-cushion layers, 5-soil, 6-positioning holes, 7-anchor holes, 8-protective layers, 9-waterproof layers, 10-grouting bodies, 11-anchor rod bodies. DETAILED DESCRIPTION

[0032] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0033] Embodiment 1

[0034] In a typical embodiment of the present invention, reference is made to Figure 1-Figure 5 As shown, a construction method of an anti-floating anchor in a medium-weathered rock formation comprises the following steps:

[0035] The positioning steel bar is fixed in the soil at the designed position of the anchor rod body, and the positioning sleeve is placed on the soil with the positioning steel bar as the center, and then the positioning sleeve is fixed on the inner side of the positioning sleeve with the fixing steel bar;

[0036] Construct the cushion layer so that the top surface of the cushion layer is flush with the upper end of the positioning sleeve, then remove the steel bars and the positioning sleeve to form a positioning hole, drill an anchor hole downward from the positioning hole, lower the anchor rod body into the anchor hole and inject grout; then construct the waterproof layer and protective layer.

[0037] The first positioning measure for the anchor hole position is to set positioning steel bars, and the second positioning measure for the anchor hole position is to set positioning holes formed by positioning sleeves. By setting two positioning measures, the problem that the anchor hole is prone to offset and affects the anti-floating effect of the structure is effectively solved.

[0038] The main structure of the anti-floating anchor rod construction includes fixed steel bars 1, positioning steel bars 2, positioning sleeves 3, cushion layers 4, soil bodies 5, positioning holes 6, anchor holes 7, protective layers 8, waterproof layers 9, grouting bodies 10, and anchor rod bodies 11.

[0039] The detailed construction steps are as follows:

[0040] Step 1: Position and install the positioning sleeve 3

[0041] like Figure 1 As shown, firstly, a total station is used to locate the anchor rod body 11 according to the designed position, and the positioning steel bar 2 is fixed in the soil 5 at the positioning position, and the fixing depth is 80mm. The positioning steel bar 2 is the first positioning measure for the position of the anchor hole 7. Specifically, the bottom end of the positioning steel bar 2 is inserted into the soil 5, and the depth is 80mm.

[0042] After the installation of the positioning steel bar 2 is completed, the installation of the positioning sleeve 3 begins. With the positioning steel bar 2 as the center point, the positioning sleeve 3 is placed on the soil 5, and then the four fixed steel bars 1 are fixed in the soil 5 close to the inner side of the positioning sleeve 3. The fixing depth is 80 mm. The bottom of the fixed steel bar 1 is also inserted into the soil. The four fixed steel bars 1 limit the position of the positioning sleeve 3 to ensure that the position of the positioning sleeve 3 will not shift during the construction of the cushion layer 4, thereby ensuring that the construction position of the anchor hole 7 is consistent with the design position and will not shift.

[0043] The fixed steel bar 1 and the positioning steel bar 2 are made of HRB335 steel bars with a diameter of 10 mm. The length of the fixed steel bar 1 and the positioning steel bar 2 is determined according to the thickness of the cushion layer 4 in the actual project. It should be noted that one end of the fixed steel bar 1 and the positioning steel bar 2 is fixed in the soil 5, and the other end should be slightly lower than the upper opening of the positioning sleeve 3 and the top surface of the cushion layer 4 to facilitate the construction of the cushion layer 4 and ensure that there will be no safety problems during the construction of the cushion layer 4. The length of the fixed steel bar 1 and the positioning steel bar 2 is preferably 150 mm.

[0044] Step 2: Construction of cushion layer 4

[0045] like Figure 1 and Figure 2 As shown, after the positioning sleeve 3 is installed and fixed, the construction of the cushion layer 4 begins. The cushion layer 4 uses a C15 concrete cushion layer 4 with a thickness of 100 mm. The cushion layer 4 plays the role of leveling the surface, protecting the foundation, and isolating, draining, and antifreezing. It should be noted that the length of the positioning sleeve 3 is the same as the thickness of the cushion layer 4, which is 100 mm. The upper opening of the positioning sleeve 3 is flush with the top surface of the cushion layer 4, as shown in FIG. Figure 1 As shown, to ensure that the upper opening of the positioning sleeve 3 will not extend out of the cushion layer when the cushion layer 4 is closed, thus affecting the construction. The positioning sleeve 3 is made of a U-PVC pipe with a thickness of 3.2 mm, and the outer diameter of the positioning sleeve 3 is larger than the design diameter of the anchor hole 7.

[0046] Step 3: Take out the fixed steel bar 1, the positioning steel bar 2 and the positioning sleeve 3 and form the positioning hole 6

[0047] like Figure 4 As shown, after the cushion layer 4 is constructed and initially solidified, use a hammer to gently hammer the positioning sleeve 3 to remove the positioning sleeve 3, and then take out the fixed steel bar 1 and the positioning steel bar 2 to form a positioning hole 6, which is convenient for the subsequent construction of the anchor hole 7. At the same time, the fixed steel bar 1, the positioning steel bar 2 and the positioning sleeve 3 can be reused. The formed positioning hole 6 is the second positioning measure for the position of the anchor hole 7.

[0048] It should be noted that when the fixed steel bars 1, the positioning steel bars 2 and the positioning sleeves 3 are taken out, it is necessary to ensure that the structure and flatness of the cushion layer 4 will not be damaged to ensure that the cushion layer 4 will not be damaged, to avoid the loose bonding between the waterproof layer 9 and the cushion layer 4 during the subsequent construction of the waterproof layer 9, to reduce the hidden danger of water seepage in the foundation, and to improve the waterproof performance of the foundation.

[0049] Step 4: Construction of anchor hole 7

[0050] like Figure 3 As shown, after the fixed steel bars 1, the positioning steel bars 2 and the positioning sleeves 3 are taken out and the positioning holes 6 are formed, the cushion layer 4 needs to be cured for 7 days. After the cushion layer 4 is cured, the construction of the anchor holes 7 begins.

[0051] In this embodiment, the diameter of the anchor hole 7 is 200 mm, and the diameter of the positioning hole 6 is 250 mm. The diameter of the anchor hole 7 is smaller than the diameter of the positioning hole 6, which can avoid the damage of the cushion layer 4 due to vibration during the construction of the anchor hole 7. The construction of the anchor hole 7 is carried out by a hydraulic down-the-hole drill. Compared with ordinary drilling rigs, the hydraulic down-the-hole drill has the advantages of higher efficiency, stronger adaptability, simple operation, and high safety. It should be noted that when the hydraulic down-the-hole drill is constructed on the cushion layer 4, a waste template must be set under its chain wheel as a pad to ensure that the cushion layer 4 will not be damaged.

[0052] Step 5: Grouting and installing the anchor rod body 11

[0053] After the anchor hole 7 is drilled and cleaned, the anchor rod body 11 is lowered into the anchor hole. During the lowering process, it is necessary to ensure that the distance between each anchor rod body 11 and the wall of the anchor hole 7 is the same. Figure 4 As shown, the specific distance is determined according to the design requirements. In this embodiment, the distance between the anchor rod body 11 and the wall of the anchor hole 7 is 50 mm. After the installation of the anchor rod body 11, grouting is carried out. The grouting adopts the bottom hole reverse pressure grouting method. The grouting pipe is inserted to 300 mm from the bottom of the anchor hole 7. During the grouting process, air is directly discharged from the orifice of the anchor hole 7. When the concentration of the discharged slurry is the same as the concentration of the injected slurry and does not contain bubbles, the grouting is completed.

[0054] It should be noted that the positioning holes 6 should be grouted together during grouting, and at the same time, the top surface of the grouting body 10 should be flush with the top surface of the cushion layer 4 to avoid loose bonding between the waterproof layer 9 and the cushion layer 4 during the subsequent construction of the waterproof layer 9, reduce the risk of water seepage in the foundation, and improve the waterproof performance of the foundation.

[0055] Step 6: Clean the cushion 4

[0056] After the grouting body is completely solidified, the mud generated when the hydraulic down-the-hole drill constructs the anchor hole 7 on the cushion layer 4 is cleaned. It should be noted that when cleaning the mud generated when the hydraulic down-the-hole drill constructs the anchor hole 7 on the cushion layer 4, tools such as shovels and brooms should be used, and small excavators should not be used for cleaning to ensure that the cushion layer 4 will not be damaged, avoid the situation where the waterproof layer 9 and the cushion layer 4 have loose bonding during the subsequent construction of the waterproof layer 9, reduce the hidden danger of water seepage in the foundation, and improve the waterproof performance of the foundation.

[0057] Step 7: Construction of waterproof layer 9 and protective layer 8

[0058] After the cushion layer 4 is cleaned, the waterproof layer 9 and the protective layer 8 are constructed. It should be noted that the protective layer 8 should be constructed immediately after the waterproof layer 9 is laid to prevent the waterproof layer 9 from being damaged by debris such as gravel, thereby affecting the waterproof effect of the entire foundation. The waterproof layer 9 uses a 4mm thick SBS waterproof membrane, which has the advantages of high tensile strength and elongation, good corrosion resistance, good weather resistance, and strong anti-aging ability. At the same time, it has a certain self-healing ability and can repair tiny punctures by itself. When hard objects puncture or embed into the waterproof layer 9, the SBS waterproof membrane will automatically combine with these hard objects to maintain good waterproof performance, so it can be used as a good basic waterproof measure. The protective layer 8 uses a C15 fine stone concrete protective layer with a thickness of 15mm.

[0059] Step 8: Waterproof the nodes

[0060] After the waterproof layer 9 and the protective layer 8 are constructed, the connection nodes between the anchor rod body 11 and the waterproof layer 9 and the protective layer 8 are waterproofed. By setting water-swellable waterproofing strips and pouring non-curing waterproof coatings, the gaps and pores between the anchor rod body 11 and the waterproof layer 9 and the protective layer 8 are filled and sealed, reducing the hidden danger of water seepage in the foundation and improving the waterproof performance of the foundation. After the node waterproofing is completed, the entire construction process is completed.

[0061] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A construction method for anti-floating anchor rods in medium-weathered rock formations, characterized in that: The steps include: The positioning steel bar is fixed in the soil at the designed position of the anchor rod body, and the positioning sleeve is placed on the soil with the positioning steel bar as the center, and then the positioning sleeve is fixed on the inner side of the positioning sleeve with the fixing steel bar; Construct the cushion layer so that the top surface of the cushion layer is flush with the upper end of the positioning sleeve, then remove the steel bars and the positioning sleeve to form a positioning hole, drill an anchor hole downward from the positioning hole, lower the anchor rod body into the anchor hole and inject grout; then construct the waterproof layer and protective layer.

2. The construction method of an anti-floating anchor in a medium-weathered rock formation according to claim 1, characterized in that: Use a total station to locate the anchor rod according to its designed position, insert the bottom end of the positioning steel bar into the soil at the positioning position and fix it; use multiple fixing steel bars to insert them into the soil close to the inner side of the positioning sleeve to ensure that the positioning sleeve does not shift in position.

3. The construction method of an anti-floating anchor in a medium-weathered rock formation according to claim 2, characterized in that: The height of the positioning sleeve should be consistent with the design thickness of the cushion layer, and the fixed top ends of the positioning steel bars and the fixed steel bars should be lower than the upper end of the positioning sleeve.

4. The construction method of an anti-floating anchor in a medium-weathered rock formation according to claim 1, characterized in that: After the cushion layer construction is completed and initially solidified, use a hammer to hammer the positioning sleeve to remove it, and then take out the fixed steel bars and positioning steel bars to form positioning holes.

5. The construction method of an anti-floating anchor in a medium-weathered rock formation according to claim 4, characterized in that: According to the positioning of the positioning hole, the anchor hole is constructed by using a hydraulic down-the-hole drill, and the diameter of the drill hole is smaller than the diameter of the positioning hole; when the hydraulic down-the-hole drill is constructed on the cushion layer, a waste template is set under its chain wheel as a pad.

6. The construction method of an anti-floating anchor in a medium-weathered rock formation according to claim 1, characterized in that: When lowering anchor rods, it is necessary to ensure that the distance between each anchor rod body and the wall of the anchor hole is the same. Grouting is carried out using the reverse pressure grouting method at the bottom of the hole, and the positioning holes are grouted at the same time. The top surface of the grouting body is flush with the top surface of the cushion layer.

7. The construction method of an anti-floating anchor in a medium-weathered rock formation according to claim 6, characterized in that: After the grouting body is completely solidified, the mud generated when the hydraulic down-the-hole drill constructs the anchor hole on the cushion layer is cleaned.

8. The construction method of an anti-floating anchor in a medium-weathered rock formation according to claim 1, characterized in that: The waterproof layer adopts SBS waterproof membrane.

9. The construction method of an anti-floating anchor in a medium-weathered rock formation according to claim 1, characterized in that: The length of the positioning steel bars and the fixing steel bars is 150 mm.

10. The construction method of an anti-floating anchor in a medium-weathered rock formation according to claim 1, characterized in that: The protective layer is made of C15 fine stone concrete.

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