High-pressure jet grouting pile forming method for water-rich pebble stratum

Abstract

The invention relates to the technical field of high-pressure jet grouting pile forming, in particular to a high-pressure jet grouting pile forming method for water-rich pebble stratum.The method comprises the steps that firstly, a rotary drilling rig is used for guiding a hole, bentonite slurry is added from a hole gap to protect the wall while the rotary drilling rig is used for guiding the hole, and meanwhile part of the bentonite slurry can permeate into the stratum around the pile; after the hole is formed, the rotary drilling rig is moved away to leave a station, the hole is filled with replacement soil 2, and meanwhile slurry is recycled for reuse; drilling to a designed depth along the hole by adopting a jet grouting drilling machine; under the influence of a cavity formed after the drilling and spraying integrated head is lifted up, after pebbles on the hole wall collapse, cement paste diffusion of the degree is easy to achieve; soil body replacement is adopted to maintain the stability of the hole wall after rotary digging of the guide hole, and compared with a down-the-hole hammer guide hole, a temporary protection pipe does not need to be put down; the guide holes are protected by slurry, a part of bentonite slurry permeates into the pebble stratum, and after cement slurry sprayed in a follow-up rotary jet mode is mixed with the bentonite slurry, the groundwater scouring resistance of the bentonite slurry can be improved.

Description

Technical Field

[0001] The invention relates to the technical field of high-pressure rotary jet grouting pile forming, in particular to a high-pressure rotary jet grouting pile forming method for water-rich pebble strata. Background Art

[0002] The jet grouting rig cannot drill in the pebble formation. A pilot hole is required before jet grouting, and the slurry is not fully diffused, so the pile diameter often does not meet the requirements. The currently available method is to use a geological drill or a down-the-hole hammer with a casing to drill the pilot hole, then lower a PVC pipe as a temporary protective pipe, and then lower the jet grouting rig to start the jet grouting operation; however, the currently available method is blocked by the pebble blocks, and the effect of cement slurry diffusion in the pebble layer is much worse than that in the sand layer and soil layer. In addition, the pebble formation has a large permeability coefficient. When there is recharge, the flow rate of groundwater therein is much greater than that of groundwater in the sand layer, which scours the injected cement slurry, causing it to diffuse and be lost with the groundwater, so it needs to be improved. Summary of the invention

[0003] The object of the present invention is to provide a high-pressure jet grouting pile forming method for water-rich pebble strata to solve the problems raised in the above-mentioned background technology.

[0004] To achieve the above object, the present invention provides the following technical solutions: A high-pressure jet grouting pile forming method for water-rich pebble strata comprises the following steps: Step 1: First, use a rotary drilling rig to drill a hole with a diameter of d. While the rotary drilling rig is drilling the hole, add bentonite slurry from the hole gap to protect the wall. At the same time, part of the bentonite slurry will penetrate into the stratum around the pile. Step 2: After the hole is formed, the rotary drilling rig is moved away to make way for the workstation, and then the replacement soil 2 is filled into the hole, and the mud is recovered and reused; Step 3: Use a jet-jet drill to drill along the hole to the designed depth; Step 4, finally, use a high-pressure, high-flow grouting machine to transport cement slurry from the background slurry mixing barrel to the drill-spray head 3 through a high-pressure hose and the hollow drill rod of the drilling rig, and start rotary spraying. While rotary spraying, lift the drill rod and the drill-spray head 3 of the drilling rig. After the drill rod 5 and the drill-spray head 3 are lifted, a cavity is formed in the hole. Under the scouring of the high-pressure, high-flow cement slurry, the pebble layer on the hole wall collapses to form a collapsed mixing zone 1, where the cement slurry is mixed with the collapsed loose pebbles to form a grouting body.

[0005] Preferably, the replacement soil 2 is clay soil or sandy soil.

[0006] Preferably, the drill pipe diameter of the rotary jet drilling rig is 0.8d-0.95d.

[0007] Preferably, the integrated drilling and spraying head comprises a drill bit, the drill bit and the drill rod are hollow inside, and a plurality of spray holes are arranged on the drill bit.

[0008] Compared with the prior art, the present invention has the following beneficial effects: The high-pressure rotary jet pile forming method for water-rich pebble strata can easily achieve such a degree of cement slurry diffusion after the pebble on the hole wall collapses under the influence of the cavity formed after the drilling and jetting integrated head is lifted; in addition, soil replacement is adopted to maintain the stability of the hole wall after rotary drilling and drilling, and compared with drilling with a down-the-hole hammer, no temporary protection pipe needs to be lowered; the drilling hole adopts mud wall protection, and a part of the bentonite mud penetrates into the pebble stratum, and the cement slurry subsequently jetted in is mixed with the mud, so that the mud can increase its ability to resist groundwater scouring. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a schematic diagram of the overall structure of the present invention.

[0010] The meanings of the numbers in the figure are: 1. Collapsed mixed area; 2. Replaced soil; 3. Drilling and spraying integrated head; 4. Rotary drilling and guide hole wall; 5. Drill rod. DETAILED DESCRIPTION

[0011] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0012] The present invention provides a technical solution: A high-pressure jet grouting pile construction method for water-rich pebble strata, please refer to Figure 1 , including the following steps: Step 1: Use a rotary drilling rig to drill a hole with a diameter of d. Figure 1 The distance between the walls 4 of the rotary drilling holes on both sides is d. When the rotary drilling rig is drilling, bentonite slurry is added from the hole gap to protect the wall and prevent the hole from collapsing. At the same time, part of the bentonite slurry will penetrate into the stratum around the pile. Due to its greater consistency, it can better overcome the stagnation of groundwater flow in place. Step 2: After the hole is formed, the rotary drilling rig is moved away to make way for the workstation, and then the replacement soil 2 is filled into the hole. Specifically, the replacement soil 2 is clay soil or sandy soil, and the mud is recovered and reused; Step 3: Because the soil in the hole is loose, a jet grouting drill can be used to drill along the hole to the designed depth. In order to improve the jet grouting effect, a special spiral large-diameter drill rod is used, with a diameter of 0.8d-0.95d, where d is the diameter of the lead hole; Part of the soil in the hole is squeezed out by the drill rod, and part of it is returned to the surface by the auger. The integrated drilling and spraying head 3 of the present invention comprises a drill bit, the drill bit and the drill rod are hollow inside, and a plurality of spray holes are arranged on the drill bit.

[0013] Step 4: Use a high-pressure, high-flow grouting machine to transport cement slurry from the backstage mixing barrel to the nozzle through a high-pressure hose and the hollow drill rod of the drilling rig, and start rotary spraying, while lifting the drill rod and the nozzle of the drilling rig. After the drill rod and the nozzle are lifted, a cavity is formed in the hole. Under the scouring of the high-pressure, high-flow cement slurry, the pebble layer on the hole wall collapses, forming a collapsed mixing zone 1, where the cement slurry is mixed with the collapsed loose pebbles to form a grouting body with a diameter of D. The cement slurry is mixed with the bentonite slurry that penetrates into the formation in step 1, which can increase the viscosity of the cement slurry and prevent it from being carried away by flowing groundwater.

[0014] In the high-pressure jet grouting pile forming method of the present invention, the diameter d of the lead hole is a larger value, d is not less than 0.6D, and a thicker drill rod is used. After exceeding the lead hole range, it only needs to continue to diffuse 0.2D to reach the designed pile diameter. In comparison, the diameter of the drill rod of a conventional jet grouting drill or the diameter of a small-diameter lead hole is only 0.15D to 0.2D, and the slurry needs to diffuse more than 0.4D after being sprayed out from the drill bit, which is very difficult and the effect is usually not good. With this method, under the influence of the cavity formed after the drilling and spraying integrated head is lifted, this degree of cement slurry diffusion can be easily achieved after the pebbles on the hole wall collapse.

[0015] The present invention adopts soil replacement to maintain the stability of the hole wall after rotary drilling. Compared with drilling with a down-the-hole hammer, it does not need to lower a temporary protection pipe. The hole is protected by mud wall, and a part of the bentonite mud penetrates into the pebble formation. After the cement slurry injected by subsequent rotary jetting is mixed with the mud, its ability to resist groundwater erosion can be increased.

Claims

1. A high-pressure jet grouting pile forming method for water-rich pebble strata, characterized in that: The following steps are involved: Step 1: First, use a rotary drilling rig to drill a hole with a diameter of d. While the rotary drilling rig is drilling the hole, add bentonite slurry from the hole gap to protect the wall. At the same time, part of the bentonite slurry will penetrate into the stratum around the pile. Step 2: After the hole is formed, the rotary drilling rig is moved away to make way for the workstation, and the hole is then filled with replacement soil (2), while the mud is recovered and reused; Step 3: Use a jet grouting drill to drill along the hole to the designed depth; Step 4, finally, a high-pressure, high-flow grouting machine is used to transport cement slurry from the backstage slurry mixing barrel to the drilling and spraying integrated head (3) through a high-pressure hose and a hollow drill rod of the drilling rig, and rotary spraying is started. The drill rod and the drilling and spraying integrated head (3) of the drilling rig are lifted while rotary spraying. After the drill rod (5) and the drilling and spraying integrated head (3) are lifted, a cavity is formed in the hole. Under the flushing of the high-pressure, high-flow cement slurry, the pebble layer on the hole wall collapses, forming a collapsed mixing zone (1), where the cement slurry is mixed with the collapsed loose pebbles to form a grouting body.

2. A high-pressure jet grouting pile forming method for water-rich pebble strata according to claim 1, characterized in that: The replacement soil (2) is clay soil or sandy soil.

3. The high-pressure jet grouting pile forming method for water-rich pebble strata according to claim 1 is characterized by: The drill pipe diameter of the rotary jet drilling rig is 0.8d-0.95d.

4. A high-pressure jet grouting pile forming method for water-rich pebble strata according to claim 1, characterized in that: The integrated drilling and spraying head (3) comprises a drill bit, the drill bit and the drill rod are hollow inside, and a plurality of spray holes are arranged on the drill bit.

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