A method for constructing a MICP-based dense sand layer wall protection and hole leading jet grouting pile

Abstract

The present application relates to the field of microbial rock-soil technology, and more particularly to a construction method for wall protection and hole guiding rotary jet grouting pile planting based on MICP, comprising the following steps: high-pressure rotary jet grouting loose sand layer, MICP slurry drilling hole guiding, precast pile vertical hole pressing, MICP curing period, and precast pile single pile compressive bearing capacity detection. The time effect of MICP reinforced sand layer is fully utilized, the required pile pressing force of the sand layer is reduced in the form of hole guiding and high-pressure rotary jet grouting during construction, MICP fully plays the role of inducing calcium carbonate precipitation after pile pressing, and the soil layer around the pile is bonded and reinforced, thereby greatly increasing the soil strength around the pile and the bonding strength of the pile and the soil around the pile; during hole guiding, MICP is mixed into the circulating slurry to form microbial mud, increase the cementing capacity of the mud, form a cementing layer to protect the hole wall, and prevent the collapse of the dense sand layer.

Description

Technical Field

[0001] This invention relates to the field of microbial geotechnical technology, and in particular to a construction method for dense sand layer wall protection and jet grouting pile installation based on MICP. Background Technology

[0002] In Jiangsu province, deep and dense saturated sandy soil layers are prevalent. Static cone penetration tests can measure a cone strength of up to 15 MPa and a side friction resistance of up to 150 kPa, making it difficult for conventional engineering piles to be successfully driven into these soil layers using existing construction techniques. For industrial or civil buildings under 30 stories, precast piles are generally chosen as the foundation. If the bearing layer is located in dense sandy soil, the final driving force (or penetration depth) is often too high, resulting in insufficient pile strength, making it difficult to drive to the designated position or even causing pile failure. To solve this problem, pile foundation construction units typically use pre-drilled holes to achieve the required pile depth. This involves excavating a small-diameter hole filled with sand and then driving the precast pile through this hole. However, this construction method will cause huge disturbance to the soil layer within the pile driving range. The pile sidewall cannot be firmly bonded and rubbed with the surrounding soil layer, which greatly reduces the bearing capacity of a single pile. Ultimately, the design value of the engineering pile determined during the test pile test is too low and cannot meet the single pile bearing capacity required by the building. At the same time, during construction, the thick sand layer is prone to collapse after the borehole is drilled, which hinders the construction of the pile and causes huge economic waste.

[0003] MICP technology is a biogeological process that utilizes microbial activity to promote calcium carbonate precipitation. This method is environmentally friendly and sustainable, and is widely used in soil stabilization, cement production, and pollution remediation. MICP technology can enhance the structure of loose soil, thereby increasing its load-bearing capacity. Calcium carbonate precipitates form in the soil, binding particles together to form a cement-like structure. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a construction method for dense sand layer wall protection and jet grouting pile planting based on MICP in order to overcome the shortcomings of the prior art.

[0005] The technical solution adopted in this invention is:

[0006] A construction method for MICP-based dense sand layer wall protection and pilot-hole jet grouting pile installation includes the following steps:

[0007] S1. High-pressure jet grouting loose sand layer: Based on the site survey data, at the engineering pile location, high-pressure jet grouting technology is used to uniformly inject MIP grout into the dense sand layer, forming a disturbance zone and a sand layer loosening zone. High-pressure jet grouting breaks up the dense sand layer to form a disturbance zone with a diameter of 700mm, while the diameter of the loosened soil area (sand layer loosening zone) reaches 1200mm, reducing the penetration resistance of precast piles and facilitating the drilling and precast pile pressing.

[0008] S2, MICP slurry drilling pilot hole: At the engineering pile location, a pilot hole is drilled using a drill bit. MICP slurry is added to the mud used for the pilot hole to enhance the binding properties of the mud, form an adhesive layer on the hole wall, protect the dense sand layer, and prevent the well wall from collapsing. MICP slurry forms a microbial slurry with water and clay powder.

[0009] S3. Precast pile driving into the hole: After drilling, the precast pile is driven into the design depth using the hole opening axis as the engineering pile axis, and construction is carried out by static pressure.

[0010] S4. MICP curing period: After the precast piles are completed, they are left to stand for 15 days for curing, so that the MICP between the pile and the surrounding soil can fully exert the calcium carbonate precipitation effect, complete the bonding between the pile and the surrounding soil and the reinforcement of the surrounding soil.

[0011] S5. Precast pile single pile compressive bearing capacity test: After the precast pile is cured, a static load test of the single pile compressive strength is carried out. If the test meets the requirements, the precast pile is considered to have been completed and meets the project requirements.

[0012] To reduce the pile driving force in dense sand layers while ensuring the single pile bearing capacity of the precast piles: Utilizing the time separation principle, the time effect of MIP (Micro-Mixed Polymer) reinforcement of sand layers is fully leveraged. During construction, the required pile driving force for the sand layer is reduced through pre-drilling and high-pressure jet grouting. After pile driving, MIP fully induces calcium carbonate precipitation, bonding and reinforcing the surrounding soil layer, significantly increasing the strength of the surrounding soil and the bond strength between the precast pile and the surrounding soil. Simultaneously, during pre-drilling, MIP grout is pumped into the hole as a circulating grout to protect the hole wall and prevent the dense sand layer from collapsing.

[0013] Furthermore, in S1, the concentration of the MICP slurry is 0.75-1.25 mol / L, the rotary jet pressure is 20 MPa, and the solution injection rate is 900±50 L / m.

[0014] The diameter of the disturbed zone D1 is 700 mm, and the diameter of the loosened sand layer zone D2 is 1200 mm.

[0015] Furthermore, in S2, the diameter of the drill bit is 89 mm;

[0016] The concentration of the MIP slurry is 0.75-1.25 mol / L, the amount added is 500 L / m, and the ratio of water, clay powder and MIP slurry is 1:0.5:0.4-0.67.

[0017] Specifically, when the concentration of MIP slurry is 1.0 mol / L, the ratio of water, clay powder and MIP slurry is 1:0.5:0.5.

[0018] Furthermore, in S1, the high-pressure jet grouting depth range is 5m above the top surface of the dense sand layer and the designed position of the pile end; in S2, the drilling pilot hole depth is 5m above the ground and the designed position of the pile end.

[0019] The present invention has the following advantages over the prior art:

[0020] By fully utilizing the time effect of MICP in reinforcing sandy soil layers, the required pile driving force for sandy soil layers is reduced during construction through pre-drilling and high-pressure jet grouting. After pile driving, MICP fully exerts its effect of inducing calcium carbonate precipitation, bonding and reinforcing the soil layer around the pile, greatly increasing the strength of the soil around the pile and the bond strength between the pile and the soil around the pile.

[0021] When drilling, MICP is added to the circulating slurry to form microbial mud, which increases the mud's bonding ability, forms a bonding layer to protect the borehole wall, and prevents the dense sand layer from collapsing. Attached Figure Description

[0022] Figure 1 This is a process flow diagram of the present invention;

[0023] Figure 2 This is a schematic diagram of the high-pressure rotary jet and pilot hole of the present invention.

[0024] The diagram is labeled: 1 - Disturbed area, 2 - Loosened sand layer area. Detailed Implementation

[0025] The embodiments of the present invention are described in detail below. The embodiments are implemented based on the technical solution of the present invention, and detailed implementation methods and specific operation processes are given. However, the protection scope of the present invention is not limited to the following embodiments.

[0026] A construction method for MICP-based dense sand layer wall protection and pilot-hole jet grouting pile installation includes the following steps:

[0027] S1. High-pressure jet grouting to loosen sand layer: Based on the site survey data, at the engineering pile location, high-pressure jet grouting technology is used to uniformly inject MICP grout with a concentration of 0.75-1.25mol / L and an addition amount of 500L / m into the dense sand layer, forming a disturbance zone and a sand layer loosening zone. The high-pressure jet grouting depth range is 5m above the top surface of the dense sand layer and the designed position of the pile end. The high-pressure jet grouting breaks up the dense sand layer to form a disturbance zone with a diameter of 700mm. At the same time, the diameter of the loosened soil area (sand layer loosening zone) reaches 1200mm, reducing the penetration resistance of the precast pile and facilitating the pilot hole and precast pile pressing.

[0028] S2. MICP grout drilling pilot hole: At the engineering pile location, a pilot hole is drilled using a drill bit with a diameter of 89mm. The drilling mud used for the pilot hole contains MICP grout with a concentration of 0.75-1.25mol / L. The jetting pressure is 20MPa, and the solution injection rate is 900±50L / m. The drilling depth is 5m above the designed position of the pile end from the ground surface. This is to enhance the binding properties of the mud, form an adhesive layer on the hole wall, protect the dense sand layer, and prevent the well wall from collapsing. The MICP grout is mixed with water and clay powder in a ratio of 1:0.5:0.4-0.67 to form a microbial grout.

[0029] S3. Precast pile driving into the hole: After drilling, the precast pile is driven into the design depth using the hole opening axis as the engineering pile axis, and construction is carried out by static pressure.

[0030] S4. MICP curing period: After the precast piles are completed, they are left to stand for 15 days for curing, so that the MICP between the pile and the surrounding soil can fully exert the calcium carbonate precipitation effect, complete the bonding between the pile and the surrounding soil and the reinforcement of the surrounding soil.

[0031] S5. Precast pile single pile compressive bearing capacity test: After the precast pile is cured, a static load test of the single pile compressive strength is carried out. If the test meets the requirements, the precast pile is considered to have been completed and meets the project requirements.

[0032] To reduce the pile driving force in dense sand layers while ensuring the single pile bearing capacity of the precast piles: Utilizing the time separation principle, the time effect of MIP (Micro-Mixed Polymer) reinforcement of sand layers is fully leveraged. During construction, the required pile driving force for the sand layer is reduced through pre-drilling and high-pressure jet grouting. After pile driving, MIP fully induces calcium carbonate precipitation, bonding and reinforcing the surrounding soil layer, significantly increasing the strength of the surrounding soil and the bond strength between the precast pile and the surrounding soil. Simultaneously, during pre-drilling, MIP grout is pumped into the hole as a circulating grout to protect the hole wall and prevent the dense sand layer from collapsing.

Claims

1. A method for constructing a MICP-based dense sand layer retaining wall and hole guide rotary jet grouting pile, characterized in that, The method comprises the following steps: S1, high-pressure rotary jet loose sand layer: according to the site geological exploration data, the MICP slurry is uniformly jetted into the dense sand layer at the engineering pile point by using the high-pressure rotary jet technology to form a disturbance zone and a sand layer loosening zone; S2, MICP slurry drilling guide hole: at the engineering pile point, the guide hole is drilled by a drill bit, the MICP slurry is added into the mud used for the guide hole to enhance the cementation of the mud, a tacky layer is formed on the hole wall to prevent the well wall from collapsing, and the MICP slurry, water and pottery powder form a microbial slurry; S3, precast pile vertical hole pressure: after the guide hole is drilled, the orifice axis is used as the engineering pile axis to press the precast pile to the designed depth, and the construction is performed in a static pressure mode; S4, MICP curing period: after the precast pile construction is completed, the precast pile is cured for 15 days to make the MICP between the pile and the surrounding soil fully play a calcium carbonate precipitation role, and the adhesion between the pile and the surrounding soil and the reinforcement of the surrounding soil are completed; S5, precast pile single-pile compressive bearing capacity detection: after the precast pile curing is completed, the single-pile compressive strength static load test is performed, and the precast pile is completed and meets the engineering requirements after meeting the requirements; In S1, the concentration of the MICP slurry is 0.75-1.25 mol / L, the diameter D1 of the disturbance zone is 700 mm, and the diameter D2 of the sand layer loosening zone is 1200 mm.

2. The construction method according to claim 1, characterized in that, In S1, the rotary jet pressure is 20 MPa, and the solution injection amount is 900±50 L / m.

3. The construction method according to claim 1, characterized in that, In S2, the diameter of the drill bit is 89 mm; The concentration of the MICP slurry is 0.75-1.25 mol / L, the added amount is 500 L / m, and the dosage ratio of water, pottery powder and MICP slurry is 1:0.5:0.4-0.

67.

4. The construction method according to claim 1, wherein, In S1, the high-pressure rotary jet depth range is the top surface of the dense sand layer to 5 m above the designed position of the pile end; In S2, the drilling guide hole depth is from the ground to 5 m above the designed position of the pile end.

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