Rock anchor rod structure penetrating through karst cave area

Abstract

The rock anchor rod structure penetrating through the karst cave area comprises an anchoring body, foundation rock, the karst cave area, a soil layer, a cushion layer and a bottom plate, the foundation rock, the karst cave area, the soil layer, the cushion layer and the bottom plate are sequentially arranged from bottom to top, the lower end of the anchoring body is fixed in the foundation rock, and the upper end of the anchoring body is fixed in the bottom plate. The anchoring body comprises a combination column composed of a cross-shaped long and thin steel column and a plurality of anchor rod steel bars, four fixing grooves used for containing the combination column are formed in the cross-shaped long and thin steel column in the circumferential direction of the cross-shaped long and thin steel column, the slenderness ratio of the combination column is not larger than 250, and the cross-shaped long and thin steel column is made of Q235B. The utility model aims to solve the technical problems in the prior art, and provides a rock anchor rod structure penetrating through a karst cave area, which can ensure the rigidity of a rock anchor rod in a deep and thick karst cave range.

Description

Technical Field

[0001] The utility model relates to the technical field of foundation, in particular to a rock anchor structure that passes through a karst cave area. Background Art

[0002] With the increasing number of basement developments, engineering accidents involving anti-floating and stability problems occur frequently. In addition to drainage, interception and weighting, active arrangements of pull-out piles and pull-out anchors can be used to resist the buoyancy of basement water. When the raft foundation meets the bearing capacity of the foundation, anti-floating rock anchors are widely used in engineering anti-floating due to their convenient construction, low cost and flexible arrangement. For some specific geological areas, the existence of underground caves poses certain challenges to engineering design and construction. Anchors in untreated cave areas may weaken the structural performance of anchors under load and environmental erosion, resulting in failure of anti-floating. There are irregular cavities inside the caves, which are filled with various impurities and groundwater. Therefore, the design structure needs to meet the requirements of sustainability and stability, and the stability and operability under construction conditions need to be met during construction. Utility Model Content

[0003] 1. Technical problems to be solved by the utility model

[0004] The utility model aims to solve the technical problems existing in the prior art and provide a rock anchor structure for crossing a karst cave area, which can ensure the rigidity of the rock anchor in a deep karst cave. When the pull-out design value of the anchor is large, a groove structure is added to resist the punching force. A waterproof structure for connecting the anchor and the bottom plate is added so that the rock anchor can exert its pull-out bearing capacity in the rock-embedded section, and ensure the feasibility of construction in the free section and the stability in the karst cave under subsequent use conditions.

[0005] 2. Technical solution

[0006] In order to solve the above problems, the technical solution provided by the utility model is:

[0007] A rock anchor structure for crossing a karst cave area, comprising an anchor body and foundation rock, a karst cave area, a soil layer, a cushion layer and a bottom plate arranged in sequence from bottom to top, wherein the lower end of the anchor body is fixed in the foundation rock, and the upper end of the anchor body is fixed in the bottom plate, and the anchor body comprises a composite column composed of a cross-shaped slender steel column and a plurality of anchor steel bars, the cross-shaped slender steel column is provided with four fixing grooves along its circumferential direction for accommodating the composite column, the slenderness ratio of the composite column is not greater than 250, and the material of the cross-shaped slender steel column is Q235B.

[0008] Optionally, the anchor body further includes a cement mortar protective layer arranged outside the composite column.

[0009] Optionally, a galvanized mesh is provided around the combined column in the cave area.

[0010] Optionally, a water-stopping steel plate is provided in the base plate, and the water-stopping steel plate is sealingly sleeved on the anchor body.

[0011] Optionally, a water-swellable water-stop strip is provided below the water-stop steel plate and around the anchor body.

[0012] Optionally, a plurality of the anchor steel bars are connected to the cross-shaped slender steel column by fillet welds.

[0013] Optionally, a groove is provided on the upper end surface of the cushion layer, and both sides of the groove are sloped at 45°-60°, and structural steel bars are attached along the surface of the groove.

[0014] Optionally, epoxy resin is provided on the surface of the cross-shaped slender steel column.

[0015] 3. Beneficial effects

[0016] Compared with the prior art, the technical solution provided by the utility model has the following beneficial effects:

[0017] For rock anchors that pass through karst caves, when the karst caves are irregular and have large cavities, the free section of the rock anchor reinforcement is long and has poor stability, and it is difficult to make holes. The utility model adds a long and thin steel column and welds the anchor reinforcement to form a composite column within the karst cave area. For the irregular karst cave area, there is no need to pour a large amount of concrete. The slenderness ratio of the composite column is controlled to utilize its rigidity. When making holes, the rock anchor reinforcement passes through the karst cave cavity area and enters the rock stratum. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic diagram of the structure of a rock bolt structure that passes through a karst cave area proposed in an embodiment of the utility model;

[0019] Figure 2 A cross-sectional schematic diagram of an anchor body in a rock anchor structure that passes through a karst cave area proposed in an embodiment of the utility model;

[0020] Figure 3 A cross-sectional schematic diagram of a cross-shaped long and thin steel column in a rock anchor structure that passes through a karst cave area proposed in an embodiment of the utility model;

[0021] 1. Foundation rock; 2. Karst cave area; 3. Soil layer; 4. Cushion layer; 5. Bottom plate; 6. Waterstop steel plate; 7. Groove; 8. Structural reinforcement; 9. Water-swelling waterstop strip; 10. Anchor body; 11. Cross-shaped long and thin steel column; 12. Anchor reinforcement; 13. Cement mortar protective layer. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solution and advantages of the utility model more clear, the utility model is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. It should be understood that the specific implementation methods described here are only used to explain the utility model and do not limit the protection scope of the utility model.

[0023] It should be noted that when an element is referred to as being "fixed to", "disposed on", "fixed on" or "installed on" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. Further, when an element is considered to be "fixedly connected to" another element, the two may be fixed in a detachable connection manner or in a non-detachable connection manner, such as socketing, snap-on, one-piece fixation, welding, etc., which can be achieved in the prior art and will not be repeated here. When an element is perpendicular or approximately perpendicular to another element, it means that the ideal state of the two is vertical, but due to the influence of manufacturing and assembly, there may be a certain vertical error. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only and do not represent the only implementation method.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art in the technical field of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0025] The “first” and “second” involved in the present utility model do not represent specific quantities and orders, but are merely used to distinguish names.

[0026] Combined with Figure 1-3 A rock anchor structure for crossing a karst cave region in this embodiment comprises an anchor body 10 and foundation rock 1, a karst cave region 2, a soil layer 3, a cushion layer 4 and a bottom plate 5 which are arranged in sequence from bottom to top, wherein the cushion layer 4 and the bottom plate 5 are both cast by concrete, and the anchor body 10 is inserted into the bottom plate 5, the cushion layer 4, the soil layer 3, the karst cave region 2 and the foundation rock 1 in sequence from top to bottom, wherein the lower end of the anchor body 10 is fixed in the foundation rock 1, and the upper end of the anchor body 10 is fixed in the bottom plate 5, and the anchor body 10 comprises a composite column composed of a cross-shaped long and thin steel column 11 and a plurality of anchor rod steel bars 12, wherein the cross-shaped long and thin steel column 11 and the anchor rod steel bars 12 are arranged in parallel, and the radial cross section of the cross-shaped long and thin steel column 11 is a cross shape, as shown in FIG. Figure 3As shown, the cross-shaped slender steel column 11 is provided with four fixing grooves for accommodating the combined column along its circumferential direction, and a number of the anchor steel bars 12 are connected to the cross-shaped slender steel column 11 through fillet welds. The weld grade is level three, and the weld appearance should meet the requirements of level two welds. The slenderness ratio of the combined column is not greater than 250. The material of the cross-shaped slender steel column 11 is Q235B, and its stiffness can ensure stability and normal pull-out bearing capacity under the action of cave fillings and groundwater.

[0027] As a preferred solution of the present invention, the cross-shaped long and thin steel column 11 has four wings, and the number of wings can also be adjusted to three or other numbers greater than three.

[0028] As a preferred solution of the utility model, the cushion layer 4 is formed by pouring C20 plain concrete. After the foundation pit is excavated to the designed elevation, the cushion layer 4 is first poured to ensure that the bearing layer of the foundation pit is not disturbed, thereby minimizing the disturbance to the original stratum. Pouring the cushion layer 4 before drilling is equivalent to adding an impermeable layer to the soil layer at the bottom of the foundation pit, thereby increasing the effect of resisting the sudden surge of pressurized water at the bottom of the pit.

[0029] As a preferred solution of the present invention, the anchor steel bar 12 extends to the upper end surface of the bottom plate 5 and is bent horizontally.

[0030] As a preferred embodiment of the present invention, the surface of the cross-shaped slender steel column 11 is provided with epoxy resin, and rust, dust and other impurities are removed from the cross-shaped slender steel column 11 and the anchor steel bars 12 to ensure a smooth base surface. Then, epoxy resin is coated on the surface to form a protective layer. After it dries, a second layer of epoxy resin is applied. The coating area of ​​the epoxy resin is 200 mm in length under the cushion layer.

[0031] As a preferred embodiment of the present invention, the anchor body 10 also includes a cement mortar protective layer 13 arranged outside the composite column. The flange length of the cross-shaped slender steel column 11 ensures that the anchor body 10 has a 15 mm cement mortar protective layer 13, that is, the distance from the edge of the anchor body 10 to the edge of the cross-shaped slender steel column 11, so that the slender steel column has a certain anti-corrosion protective layer thickness.

[0032] As a preferred embodiment of the utility model, a galvanized mesh is provided around the composite column in the cave area 2, and the galvanized mesh is used to wrap the anchor steel bar bundle to prevent leakage during grouting. The amount of early strength agent added to the cement slurry is 0.05% of the cement dosage, and high-pressure grouting is used to ensure the grouting hole quality and the construction quality of the anti-floating anchor body 10.

[0033] As a preferred solution of the utility model, a waterstop steel plate 6 is provided in the base plate 5, and the waterstop steel plate 6 is arranged perpendicular to the axial direction of the anchor body 10. The waterstop steel plate 6 is sealingly sleeved on the anchor body 10, and the waterstop steel plate 6 is welded to the cross-shaped long and thin steel columns 11 to achieve fixed connection and sealing. During the use stage, the cross-shaped long and thin steel columns 11 in the cavity can resist the disturbance of the soil layer and the action of groundwater, and at the same time, the connection method between the anchor body 10 and the base plate 5 is increased and improved, and the waterproof structure is optimized.

[0034] As a preferred solution of the utility model, a water-swellable waterstop strip 9 is provided below the waterstop steel plate 6 and around the anchor body 10. The water-swellable waterstop strip 9 is located inside the bottom plate 5 to further improve the waterproof performance.

[0035] As a preferred embodiment of the present utility model, a groove 7 is provided on the upper end surface of the cushion layer 4, and the two sides of the groove 7 are sloped at 45°-60°, and the two sides of the groove 7 are inclined outwardly, and the bottom plate of the bottom plate 5 is embedded in the groove 7. The groove 7 is designed to meet the shear bearing capacity requirements, and structural steel bars 8 are attached along the surface of the groove 7. The structural steel bars 8 are cast and fixed in the bottom plate 5, and the structural steel bars 8 play a role in crack prevention and waterproofing.

[0036] The specific construction method of the rock bolt structure in the cross-karst cave area is as follows:

[0037] 1. Drilling revealed that the limestone distribution area on the site was less stable and that local slurry leakage was serious during drilling. Before construction, the distribution of karst caves was determined by region.

[0038] 2. When the base is excavated to the bottom layer, 300mm is reserved and the bottom is manually cleaned to the designed elevation. If there is pressurized water gushing out of the cave, the cushion layer in other areas shall be poured first. In the area with large water gushing, the pressurized water load in the cave shall be unloaded by setting up drainage ditches and water collection wells. Blind ditches shall be set up to drain the water, and gravel shall be laid on the top of the PVC water pipe with dense d30, and then the cushion layer shall be poured. When constructing the anti-floating anchor grouting, pumping and drainage shall be stopped to avoid the formation of dynamic water pressure to disperse the mud.

[0039] 3. Position the anchor rods on the plane, arrange the sequence reasonably and use the jump method. Construct the area without caves first to avoid disturbing the slender composite columns in the cave area. Construct the anchor rods in the cave area later. When drilling, use an air machine under a pressure of 10-12Mpa to discharge the unstable filling wall in the cave. When drilling through the cave, the speed should be 0.6m / min for strong weathering and 0.5m / min for medium weathering.

[0040] 4. After cleaning and removing the rust on the cross-shaped long and thin steel column, apply two layers of epoxy resin for corrosion protection, the length is 200mm below the cushion layer, and use engineering glue to seal. After installation and vertical positioning, secondary grouting is used. In order to improve the early strength, triethanolamine early strength agent is added to the cement slurry M30, the water-cement ratio is not less than 0.5, and the grouting pressure is not less than 2Mpa.

[0041] 5. The grouting port is sealed with cement slurry. When the primary slurry strength reaches 50Mpa, secondary grouting is used, and the cross-shaped long and thin steel column is welded with the anchor steel bar and the water-stop steel plate. The size of the water-stop steel plate is 30mmx30mmx10. A steel bar hole is opened on the water-stop steel plate, and the rock anchor steel bar passes through the water-stop steel plate and is bent upward to the top of the bottom plate.

[0042] The above schematically describes the present invention and its implementation methods, which are not restrictive. The drawings show only one implementation method of the present invention, and the actual structure is not limited thereto. Therefore, if ordinary technicians in this field are inspired by it and design structural methods and embodiments similar to the technical solution without creativity without departing from the purpose of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A rock bolt structure for crossing a karst cave area, characterized by: It includes an anchor body and foundation rock, a karst cave area, a soil layer, a cushion layer and a bottom plate arranged in sequence from bottom to top, the lower end of the anchor body is fixed in the foundation rock, the upper end of the anchor body is fixed in the bottom plate, the anchor body includes a composite column composed of a cross-shaped slender steel column and a plurality of anchor steel bars, the cross-shaped slender steel column is provided with four fixing grooves along its circumferential direction for accommodating the composite column, the slenderness ratio of the composite column is not greater than 250, and the material of the cross-shaped slender steel column is Q235B.

2. A rock bolt structure for crossing a karst cave area according to claim 1, characterized in that: The anchor body also includes a cement mortar protective layer arranged outside the composite column.

3. A rock bolt structure for crossing a karst cave area according to claim 2, characterized in that: A galvanized mesh is provided in the cave area surrounding the combined columns.

4. A rock bolt structure for crossing a karst cave area according to claim 1, characterized in that: A water-stopping steel plate is arranged inside the bottom plate, and the water-stopping steel plate is sealingly sleeved on the anchor body.

5. A rock bolt structure for crossing a karst cave area according to claim 4, characterized in that: A water-swellable water-stop strip is provided below the water-stop steel plate and around the anchor body.

6. A rock bolt structure for crossing a karst cave area according to any one of claims 1 to 5, characterized in that: A plurality of anchor rod reinforcements are connected to the cross-shaped long and thin steel columns through fillet welds.

7. A rock bolt structure for crossing a karst cave area according to any one of claims 1 to 5, characterized in that: The upper end surface of the cushion layer is provided with a groove, the two sides of the groove are sloped at 45°-60°, and structural steel bars are attached along the surface of the groove.

8. A rock bolt structure for crossing a karst cave area according to any one of claims 1 to 5, characterized in that: The surface of the cross-shaped long and thin steel column is provided with epoxy resin.

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