MJS construction method pile test construction method

Abstract

The invention relates to the technical field of MJS construction method piles, in particular to an MJS construction method pile test pile construction method which comprises the following specific steps: S1, surveying and setting out; s2, obstacle cleaning; s3, guiding holes by a water well drilling machine; s4, connecting a power supply, a data line, each pipeline, the drill bit and an in-ground pressure monitoring display, performing zero clearing under the condition that the drill bit has no load, and ensuring that the pipeline connection is sealed, so that no air exists in the pipe; s5, the host is in place; s6, lowering the drill rod; s7, the drill rod and the drill bit are in butt joint, during butt joint, the condition of a sealing ring is carefully checked, whether the sealing ring is lost or damaged or not and whether the underground pressure is normal or not are checked, and S8, the step S6 and the step S7 are repeated till the drill bit reaches the preset depth and the drill rod is in place. And the cement mixing amount, the construction process, the post-pile-forming quality, the guide hole drilling machine and the MJS equipment which meet the engineering progress and quality requirements cannot be selected in time.

Description

Technical Field

[0001] The invention relates to the technical field of MJS method piles, and in particular to a MJS method pile test pile construction method. Background Art

[0002] ‌‌MJS piles‌, also known as all-round high-pressure jetting, are an improved high-pressure jetting method that aims to solve the slurry discharge and environmental impact problems of the traditional high-pressure jetting method during horizontal jetting construction. The MJS method uses a unique porous tube and a front-end forced slurry suction device to achieve forced slurry discharge in the hole and ground pressure monitoring, and controls the ground pressure by adjusting the forced slurry discharge volume, thereby reducing the possibility of surface deformation during construction and greatly reducing the impact on the environment. This method is not only suitable for horizontal foundation reinforcement and 360° all-round foundation reinforcement, but also for deep foundation reinforcement and underwater construction, with minimal impact on the surrounding environment and foundation disturbance.

[0003] In the prior art, during the construction of MJS method piles, trial pile tests are not carried out, and different drilling and piling tests are required. It is impossible to timely select the cement content, construction technology, pile quality, lead-hole drilling rig and MJS equipment that meet the project progress and quality requirements, and the construction efficiency is low. Therefore, we propose a trial pile construction method for MJS method piles. Summary of the invention

[0004] The purpose of the present invention is to solve the shortcomings existing in the prior art and propose an MJS method pile test pile construction method, which solves the problem that different drilling and piling tests need to be carried out, and the cement content, construction process and pile quality after completion, and the hole drilling rig and MJS equipment that meet the project progress and quality requirements cannot be selected in time.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: A MJS method pile test pile construction method, the specific steps are as follows: S1. Surveying and setting out: Layout the plane dimensions of the pile positions according to the coordinates of the corner points of the on-site construction position to ensure that the distance between the construction piles and the overlap of the piles meet the design requirements; S2. Obstacle clearing: If there are pipelines in the construction area, the construction unit needs to conduct pipeline briefing; according to the information provided by the construction unit, determine the obstacles in the construction area, dig sample trenches, conduct pipeline inspections, and clear surface obstacles on the construction work surface; S3. Water well drilling rig lead hole: Use water well drilling rig to lead hole in advance, the lead hole diameter is 30mm, and the inclination of the hole is checked; S4. Connect the power supply, data cable, various pipelines, drill bit and underground pressure monitoring display, confirm that the drill bit is reset to zero without load, and ensure that the pipeline connection is sealed so that there is no air in the pipe; S5. Main engine in place: Check the operation of the equipment to ensure that the main engine, high-pressure pump, air compressor, mud mixing system, MJS management device, etc. are in normal working condition before putting the main engine in place. After the frame is placed stably, start zeroing; S6. Lowering the drill pipe: lower the drill pipe to the designed depth in the pilot hole. If it is difficult to lower the drill pipe, open the drilling water to carry out normal drilling. S7. When docking the drill rod and drill bit, carefully check the seal ring to see if it is missing or damaged, and whether the ground pressure is normal. S8, repeating steps S6 and S7 until the drill bit reaches a predetermined depth and the drill rod is in place; S9. After the drill bit reaches the predetermined depth, start zeroing to make the "0" scale of the power head, the nozzle, and the white line on the drill rod in the same straight line, and then set the process parameters; S10, clean water spraying: spray at a fixed position, first start the reverse suction of water flow and air, and when confirming that the slurry discharge is normal, open the mud discharge valve, and start the high-pressure pump and main air compressor; S11. Lifting and spraying: When starting the high-pressure cement pump, the pressure should not be too high. It should be gradually increased until the specified pressure is reached. After reaching the specified pressure and confirming that the pressure in the ground is normal, it can be lifted. When the water is switched to cement slurry, the pressure will automatically rise. The pressure can be adjusted only when there is a sudden change in pressure; S12. During construction, closely monitor the ground pressure. When the pressure is abnormal, the size of the slurry discharge valve must be adjusted in time to control the ground pressure within a safe range; S13, segmented disassembly: After lifting a drill rod, the drill rod is disassembled. The cement slurry needs to be switched to water before disassembly. When the pressure of the cement slurry pump tends to decrease, it means that the water flow has reached the nozzle position. At this time, the cement slurry pump, main air, backdraft air and backdraft water flow are turned off; S14. Repeat the above steps until the construction is completed. After the construction is completed, flush and maintain the equipment.

[0006] Preferably, in step S3, the error between the center of the hole and the center of the pile position is less than 50 mm, the depth is not less than the designed depth of 1 m, and the verticality error is less than 1 / 200.

[0007] Preferably, when spraying in step S10 and step S11, water is first sprayed upwards for 50 cm with an initial pressure of 10 MPa. After the pressure reaches 20 MPa, the grouting pump is started to deliver clean water into the hole. After the pump volume and pressure are normal, the grouting pump suction pipe can be moved to the slurry storage barrel for grouting. At this time, the water is switched to cement slurry, and the drill rod is lowered back into place and then sprayed upwards for improvement, with the drill rod shaking at an angle of ±90°.

[0008] Preferably, in step S13, during the process of disassembling the drill rod, carefully check the sealing ring and the data cable to see if they are damaged and whether the ground pressure display is normal. If there is any problem, it should be eliminated in time before continuing to spray. After disassembling the drill rod, the drill rod needs to be flushed and maintained in time.

[0009] Preferably, in step S11, slurry needs to be prepared. When preparing the slurry, the water-cement ratio of the cement slurry is 1:1. Each tank of slurry needs to be measured at least once using a specific gravity meter until the specific gravity of the cement slurry is 1.48-1.52; When making slurry, add water first and then cement. The slurry needs to be filtered twice to ensure the purity and uniformity of the slurry. The external slurry storage tank uses a low-speed mixer to stir the slurry to prevent sedimentation; The stirring time should not be less than 15 minutes. Practice has shown that when the water-cement ratio is 1:1, the stone strength is highest after stirring for 1 hour (when the temperature is below 10°C, it should not exceed 5 hours, and when the temperature is above 10°C, it should not exceed 3 hours. The slurry should be discarded if it exceeds the storage time).

[0010] Preferably, the ground should be flat before drilling, and the local soft soil layer should be treated in advance; the deviation of the drilling position shall not be greater than 50mm, the drilling depth shall be greater than 1m of the pile depth, and the requirement that the jet nozzle reaches the designed pile end shall be met, and the drilling depth deviation shall not be greater than 50mm.

[0011] Preferably, when the main drill rod is connected to the drill bit, the sealing ring should be checked for defects; the drill rod should be assembled and lowered in sections, and the verticality of the guide frame and the flatness of the pile driver chassis should be corrected again before each section of the drill rod is connected and drilled.

[0012] Preferably, the spindle rotation speed should be controlled at 3r / min~5r / min, the lifting step spacing should be 25mm, and the pile cutting frequency within the injection range of each step spacing should not be lower than 3r / min.

[0013] Preferably, after the high-pressure mud pump is turned on, clean water should be sprayed first, and then switched to cement slurry after the spraying pressure reaches 20MPa. The construction equipment should have underground pressure monitoring and forced mud discharge systems, and the equipment discharge volume should not be less than 10m3 / h. The underground pressure control coefficient should be 1.3~1.6.

[0014] Preferably, the MJS method pile test pile construction method uses ordinary Portland cement of grade not less than 42.5, the cement content should not be less than 40%, the water-cement ratio should be 1.0, the 28-day unconfined compressive strength should be not less than 1.0 MPa, and the permeability coefficient should be less than one times ten to the negative seventh power cm / s.

[0015] Preferably, the MJS method pile test pile construction method adopts skipping pile construction, the skipping pile interval is 4m to 6m, the interval time between adjacent pile construction is not less than 24h, and when unconditional skipping pile construction is used, it should be ensured that the construction interval time of the same section of adjacent pile bodies is greater than 24h.

[0016] Preferably, the number of test piles is three, and the test piles are numbered MJS1, MJS5, and MJS6. The specific parameters of the test piles are shown in the following table:

[0017] Preferably, the specific parameters of the MJS method pile test construction are shown in the following table:

[0018] Preferably, the specific parameters for the quality control of the MJS method pile test pile construction are shown in the following table:

[0019] In summary, the present invention can select cement content, construction technology, pile quality, and whether the borehole drill and MJS equipment meet the project progress and quality requirements through pile testing; It can test the reliability and practicality of various indicators such as mortar mix ratio and unconfined compressive strength, and issue a final mortar mix ratio report; The pile body quality is tested by coring through drilling holes, which provides a basis for optimizing construction parameters and mortar mix ratios, and for testing the pile body quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the process structure of the present invention. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0022] Reference Figure 1 , a MJS method pile test pile construction method, the specific steps are as follows: S1. Surveying and setting out: Layout the plane dimensions of the pile positions according to the coordinates of the corner points of the on-site construction position to ensure that the distance between the construction piles and the overlap of the piles meet the design requirements; S2. Obstacle clearing: If there are pipelines in the construction area, the construction unit needs to conduct pipeline briefing; according to the information provided by the construction unit, determine the obstacles in the construction area, dig sample trenches, conduct pipeline inspections, and clear surface obstacles on the construction work surface; S3. Water well drilling rig lead hole: Use water well drilling rig to lead hole in advance, the lead hole diameter is 30mm, and the inclination of the hole is checked. The error between the hole center and the pile position center is less than 50mm, the depth is not less than the designed depth of 1m, and the verticality error is less than 1 / 200; S4. Connect the power supply, data cable, various pipelines, drill bit and underground pressure monitoring display, confirm that the drill bit is reset to zero without load, and ensure that the pipeline connection is sealed so that there is no air in the pipe; S5. Main engine in place: Check the operation of the equipment to ensure that the main engine, high-pressure pump, air compressor, mud mixing system, MJS management device, etc. are in normal working condition before putting the main engine in place. After the frame is placed stably, start zeroing; S6. Lowering the drill pipe: lower the drill pipe to the designed depth in the pilot hole. If it is difficult to lower the drill pipe, open the drilling water to carry out normal drilling. S7. When docking the drill rod and drill bit, carefully check the seal ring to see if it is missing or damaged, and whether the ground pressure is normal. S8, repeating steps S6 and S7 until the drill bit reaches a predetermined depth and the drill rod is in place; S9. After the drill bit reaches the predetermined depth, start zeroing to make the "0" scale of the power head, the nozzle, and the white line on the drill rod in the same straight line, and then set the process parameters; S10, clean water spraying: spray at a fixed position, first start the reverse suction of water flow and air, and when confirming that the slurry discharge is normal, open the mud discharge valve, and start the high-pressure pump and main air compressor; S11. Lifting and spraying: prepare the slurry. When preparing the slurry, the water-cement ratio of the cement slurry is 1:1. Each tank of slurry needs to be measured at least once using a hydrometer. When the cement slurry has a specific gravity of 1.48-1.52, inject it. When starting the high-pressure cement pump, the pressure should not be too high. It should be gradually increased until the specified pressure is reached. After reaching the specified pressure and confirming that the pressure in the ground is normal, you can start lifting. When water is switched to cement slurry, the pressure will automatically rise. The pressure can be adjusted only when there is a sudden change in pressure. That is, first spray water upwards for 50cm with an initial pressure of 10MPa. When the pressure reaches 20MPa, start the grouting pump to send clean water into the hole. When the pump volume and pressure are normal, the grouting pump suction pipe can be moved to the slurry storage barrel for grouting. At this time, the water is switched to cement slurry, and the drill rod is lowered back into place and starts to spray upwards for improvement. The drill rod is shaken at an angle of ±90°. S12. During construction, closely monitor the ground pressure. When the pressure is abnormal, the size of the slurry discharge valve must be adjusted in time to control the ground pressure within a safe range; S13, segmented disassembly: After lifting a drill rod, disassemble the drill rod. The cement slurry needs to be switched to water before disassembly. When the pressure of the cement slurry pump shows a downward trend, it means that the water flow has reached the nozzle position. At this time, turn off the cement slurry pump, main air, reverse air and reverse water flow. Pay attention to the process of disassembling the drill rod. Carefully check the seal ring and data line to see if they are damaged and whether the underground pressure display is normal. If there is any problem, it should be eliminated in time before continuing to spray. After disassembling the drill rod, the drill rod needs to be flushed and maintained in time; S14. Repeat the above steps until the construction is completed. After the construction is completed, flush and maintain the equipment.

[0023] It should be noted that the common quality problems and prevention measures of the MJS method pile test construction method are as follows: Common quality problems: uneven strength and necking of cement soil; Cause analysis: The injection method and equipment were not selected according to the geological conditions; The construction was interrupted due to failure of the shotcrete equipment; Improper matching of pipe pulling speed, rotation speed and grouting volume results in uneven pile diameter and different amounts of slurry; The sprayed slurry and the cut soil particles are not mixed evenly and sufficiently; Passing through harder clay soils, necking occurs.

[0024] Treatment method: Choose different shotcrete methods and machines according to design requirements and site conditions; Before spraying, first conduct a grouting and air pressure test. If everything is normal, you can prepare the slurry and prepare for spraying to ensure continuous operation. When preparing the slurry, you must filter it with a sieve; According to the shape of the consolidation body and the homogeneity of the pile body, adjust the nozzle's rotation speed, lifting speed, injection pressure and injection volume; The method of expanding the pile diameter by positioning rotating spraying (without lifting) or repeated spraying at the parts prone to neck shrinkage and the bottom parts that are difficult to inspect; Control the water-cement ratio and consistency of the slurry; Strict requirements are imposed on the processing accuracy, position, shape, diameter, etc. of the nozzle to ensure the spraying effect.

[0025] Common quality problems: difficulty in drilling and sinking pipes, deviation and slurry leakage.

[0026] Cause analysis: There are underground objects, the ground is uneven and the drill rod tilts beyond the standard; The grouting volume is quite different from the actual required volume; If there are large gaps in the stratum and no slurry comes out or the amount of slurry coming out is too large, it is because the effective injection range is not compatible with the grouting volume, and the grouting volume greatly exceeds the slurry required for rotary jet consolidation.

[0027] Treatment method: The pile placement site should be probed, and if there are any underground objects, the pile drilling point should be removed or moved; The site should be leveled before jet grouting, and the verticality deviation of the drill rod should be controlled within 1 / 200; Use side-mouth nozzles to reduce the slurry outlet diameter and improve the spraying capacity, so that the slurry volume is equivalent to the actual required volume and reduce slurry bubbling; Control cement slurry mix ratio; To deal with the phenomenon of slurry bubbling, we can add an appropriate amount of accelerating setting agent into the slurry to shorten the solidification time and make the slurry solidify within a certain range of soil layers. We can also increase the grouting volume in the gaps and continue the rotary spraying after filling the gaps. To deal with the problem of excessive slurry emission, measures are taken to increase the injection pressure, appropriately reduce the nozzle aperture, and speed up the lifting and rotation speeds.

[0028] Common quality problem: The top of the consolidated body is concave.

[0029] Cause analysis: After the cement slurry is mixed with the soil, a certain shrinkage effect will occur due to the water separation characteristics of the slurry, resulting in a depression on the top of the consolidated body. The depth of the depression varies with factors such as the water separation characteristics of the soil slurry, the diameter and length of the consolidated body, etc.

[0030] Treatment method: The length of the jet grouting is 0.3 to 1.0 m longer than the design, or after the MJS pile construction is completed, part of the top of the consolidated body is chiseled off, the concave part is filled with concrete or the slurry is directly injected into the jet grouting hole again, or after the jet grouting is completed, drill 0.5 to 1.0 m again within 0.5 to 1.0 m of the top of the solid, lift the rod in situ and grout again for reinforcement.

[0031] Common quality problem: The grouting flow rate remains unchanged, but the pressure drops suddenly.

[0032] Cause analysis: leakage in grouting system.

[0033] Treatment method: Check the leakage in each part and pull out the grouting pipe to check the sealing performance if necessary.

[0034] Common quality problems: The pressure suddenly increases and exceeds the maximum limit, the flow rate is zero, and the pressure does not change after shutdown.

[0035] Cause analysis: Nozzle is clogged.

[0036] Treatment method: Pull out the pipe, remove the drill and clear the nozzle.

[0037] Common quality problem: no return of pulp.

[0038] Cause analysis: There are large gaps in the stratum or unknown holes.

[0039] Treatment method: Increase the grouting volume in the gap area, adopt fixed spraying measures, and continue normal spraying after the gap is filled.

[0040] During the construction of the MJS method pile test pile, the quality inspection of the all-round high-pressure jetting method solid reinforcement should adopt the method of coring. The number of inspection points should not be less than 1% of the number of construction piles, and no less than 3 points. The gaps after the completion of the coring should be filled with grouting. Excavation can only be carried out after passing the inspection.

[0041] The cement content of 45% was tested in the laboratory and combined with the on-site inspection, which was found to be in compliance with the design and specification requirements.

[0042] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A MJS method pile test pile construction method, characterized in that: The specific steps are as follows: S1. Surveying and setting out: Plane size pile positions are set out according to the coordinates of the corner points of the on-site construction location to ensure that the distance between construction piles and the overlap of piles meet the design requirements; S2. Obstacle clearing: If there are pipelines in the construction area, the construction unit needs to conduct pipeline briefing; according to the information provided by the construction unit, determine the obstacles in the construction area, dig sample trenches, conduct pipeline inspections, and clear surface obstacles on the construction work surface; S3. Water well drilling rig hole: Use water well drilling rig to drill the hole in advance, the hole diameter is 30mm, and the inclination of the hole is checked; S4. Connect the power supply, data cable, various pipelines, drill bit and underground pressure monitoring display, confirm that the drill bit is reset to zero without load, and ensure that the pipeline connection is sealed so that there is no air in the pipe; S5. Main engine in place: Check the operation of the equipment to ensure that the main engine, high-pressure pump, air compressor, mud mixing system, MJS management device, etc. are in normal working condition before putting the main engine in place. After the frame is placed stably, start zeroing; S6. Lowering the drill pipe: lower the drill pipe to the designed depth in the pilot hole. If it is difficult to lower the drill pipe, open the drilling water to carry out normal drilling. S7. When docking the drill rod and drill bit, carefully check the seal ring to see if it is missing or damaged, and whether the ground pressure is normal. S8, repeating steps S6 and S7 until the drill bit reaches a predetermined depth and the drill rod is in place; S9. After the drill bit reaches the predetermined depth, start zeroing to make the "0" scale of the power head, the nozzle, and the white line on the drill rod in the same straight line, and then set the process parameters; S10, clean water spraying: spray at a fixed position, first start the reverse suction of water flow and air, and when confirming that the slurry discharge is normal, open the mud discharge valve, and start the high-pressure pump and main air compressor; S11. Lifting and spraying: When starting the high-pressure cement pump, the pressure should not be too high. It should be gradually increased until the specified pressure is reached. After reaching the specified pressure and confirming that the pressure in the ground is normal, it can be lifted. When the water is switched to cement slurry, the pressure will automatically rise. The pressure can be adjusted only when there is a sudden change in pressure; S12. During construction, closely monitor the ground pressure. When the pressure is abnormal, the size of the slurry discharge valve must be adjusted in time to control the ground pressure within a safe range; S13, segmented disassembly: After lifting a drill rod, the drill rod is disassembled. The cement slurry needs to be switched to water before disassembly. When the pressure of the cement slurry pump shows a downward trend, it means that the water flow has reached the nozzle position. At this time, the cement slurry pump, main air, backdraft air and backdraft water flow are turned off; S14. Repeat the above steps until the construction is completed. After the construction is completed, flush and maintain the equipment.

2. A MJS method pile test pile construction method according to claim 1, characterized in that: In step S3, the error between the center of the hole and the center of the pile position is less than 50 mm, the depth is not less than the designed depth of 1 m, and the verticality error is less than 1 / 200.

3. A MJS method pile test pile construction method according to claim 1, characterized in that: When spraying in step S10 and step S11, first spray water upwards for 50cm with an initial pressure of 10MPa. After the pressure reaches 20MPa, start the grouting pump to deliver clean water into the hole. After the pump volume and pressure are normal, the grouting pump suction pipe can be moved to the grouting bucket for grouting. At this time, the water is switched to cement slurry. After the drill rod is lowered into place again, it starts to spray upwards for improvement, and the drill rod is shaken at an angle of ±90°.

4. A MJS method pile test pile construction method according to claim 1, characterized in that: In step S13, it is noted that during the process of disassembling the drill rod, the sealing ring and the data line should be carefully checked to see if they are damaged and whether the ground pressure display is normal. If there is any problem, it should be eliminated in time before continuing to spray. After disassembling the drill rod, the drill rod needs to be flushed and maintained in time.

5. A MJS method pile test pile construction method according to claim 1, characterized in that: In the step S11, slurry needs to be prepared. When preparing the slurry, the water-cement ratio of the cement slurry is 1:

1. Each tank of slurry needs to be measured at least once using a specific gravity meter until the specific gravity of the cement slurry is 1.48-1.52; When making slurry, add water first and then cement. The slurry needs to be filtered twice to ensure the purity and uniformity of the slurry. The external slurry storage tank uses a low-speed mixer to stir the slurry to prevent sedimentation; The stirring time should not be less than 15 minutes. Practice has shown that when the water-cement ratio is 1:1, the stone strength is highest after stirring for 1 hour (when the temperature is below 10°C, it should not exceed 5 hours, and when the temperature is above 10°C, it should not exceed 3 hours. The slurry should be discarded if it exceeds the storage time).

6. A MJS method pile test pile construction method according to claim 1, characterized in that: Before drilling a hole, the ground should be flat and the local soft soil layer should be treated in advance; the deviation of the drilling hole position shall not be greater than 50mm, the drilling hole depth shall be greater than 1m of the pile depth, and the requirement that the jet nozzle reaches the designed pile end shall be met. The drilling hole depth deviation shall not be greater than 50mm.

7. The MJS method pile test pile construction method according to claim 1, characterized in that: When the main drill rod is connected to the drill bit, check whether the sealing ring is damaged; the drill rod should be assembled and lowered in sections, and the verticality of the guide frame and the flatness of the pile driver chassis should be corrected again before each section of the drill rod is connected and drilled.

8. The MJS method pile test pile construction method according to claim 1, characterized in that: The spindle rotation speed should be controlled at 3r / min~5r / min, the lifting step spacing should be 25mm, and the pile cutting frequency within the injection range of each step spacing should not be lower than 3r / min.

9. The MJS method pile test pile construction method according to claim 1, characterized in that: After the high-pressure mud pump is turned on, it is advisable to spray clean water first. After the spraying pressure reaches 20MPa, switch to cement slurry. The construction equipment should have underground pressure monitoring and forced mud discharge system, and the equipment discharge volume should not be less than 10m3 / h. The underground pressure control coefficient should be 1.3~1.6.

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