Cement mixing pile construction method

Abstract

The invention relates to the technical field of cement mixing pile construction, in particular to a cement mixing pile construction method which comprises the steps that construction preparation is conducted, and a construction process parameter test is conducted according to design requirements; setting out a pile position; digging a groove; a pile machine is in place, and a deep stirring machine is moved to a designated pile position and centered; cement grout is prepared, and the water-cement ratio is strictly controlled and is generally 0.45-0.55; during cement mixing pile construction, parameters such as pile machine perpendicularity, mixing depth and guniting amount should be monitored in real time in the construction process, and the construction quality is ensured; quality inspection is conducted, after construction is completed, core drilling and sampling detection should be conducted according to regulations, the integrity of a pile body, the stirring uniformity degree, the construction length of the pile and whether the unconfined compressive strength meet the design or not are detected, and composite foundation bearing capacity inspection is conducted; various parameters in the construction process of the cement mixing pile are detected, construction is adjusted on the basis, and the construction reliability is improved.

Description

Technical Field

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

[0002] Cement-soil mixing piles are a method for reinforcing saturated soft clay low foundations. They use cement as a curing agent and forcefully mix the soft soil and curing agent deep in the foundation through a special mixing machine. A series of physical and chemical reactions between the curing agent and the soft soil are used to harden the soft soil into a high-quality foundation with integrity, water stability and a certain strength. The existing cement-mixing pile construction method relies on the experience of construction personnel, and the construction quality cannot be effectively guaranteed. There is a lack of corresponding remedial measures for construction problems, which affects the reliability of construction. Summary of the invention

[0003] The purpose of the present invention is to solve the shortcomings in the prior art and to propose a cement mixing pile construction method.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions: A cement mixing pile construction method, comprising: Step 1: Construction technology preparation, equipment, site preparation and test preparation. Before the full construction starts, a test pile should be carried out, and the construction process parameter test should be carried out according to the design requirements; Step 2: Pile position setting out. The surveyor shall carry out relevant measurement and setting out work such as the mixing pile position, original ground elevation, hole elevation, etc. according to the design and construction drawings, and make measurement and setting out records and pile layout drawings; Step 3: Dig the trench. Before construction, the water in the trench must be removed to prevent the water from seeping in and affecting the strength of the cement-soil mixing pile. Step 4: Put the pile driver in place, move the deep mixer to the designated pile position, align it, use the walking system of the pile driver to move it to the designated position, use the tower to lift the mixing pile driver to put it in place, level it, and adjust it in the center; Step 5: Prepare cement slurry, strictly control the water-cement ratio, generally 0.45-0.55, and stir the slurry at any time when it enters the spraying pool to ensure that the slurry does not separate; Step 6: During the construction of cement mixing piles, the verticality of the pile driver, mixing depth, shotcrete volume and other parameters should be monitored in real time, and the construction process parameters should be adjusted in time to ensure the construction quality; Step 7, quality inspection. After the construction is completed, core sampling and testing should be carried out as required to test the integrity of the pile body, the uniformity of mixing, the construction length of the pile, whether the unconfined compressive strength meets the design, and the bearing capacity of the composite foundation.

[0005] Preferably, in step 1, the construction process parameters include: a. Determine various technical parameters that meet the design of the single pile shotcrete volume (calculated by cement addition and water-cement ratio), such as drill rod sinking and lifting speed, shotcrete pressure, slurry breaking volume, mixer speed, current entering the bearing layer and drilling speed; b. Determine the resistance to sinking and lifting, and select a reasonable mixing head form, motor power, and the width and inclination of the mixing blades; c. Check whether the mix ratio and water-cement ratio determined by the test are convenient for construction, whether the unconfined compressive strength of the pile body meets the design requirements, and whether the bearing capacity of the composite foundation meets the design requirements; carry out bearing capacity testing on 0.5% of the total number of piles, and only proceed to the next construction process after the test meets the requirements; The construction process parameters are adjusted in time according to the construction pile testing data to ensure the construction quality.

[0006] Preferably, in step 1, site preparation: the site for mixing pile construction should be leveled in advance, and the surface hard objects and underground obstacles in the construction area must be cleared to facilitate and accurately carry out pile position layout. The low-lying or pond areas of the site should be drained and silted first, and then backfilled with soil and compacted in layers to the leveling elevation, and appropriately rolled. The compaction degree is required to reach 85%, and the roadbed bearing capacity should meet the requirements for the smooth movement of heavy pile drivers and cranes.

[0007] Preferably, in step 4, the pile driver is leveled: when the ground is uneven, a hydraulic balancing device of the pile mixer is used to keep the lifting equipment horizontal so that the mixing shaft remains vertical; After the move is completed, check the positioning. If there is any deviation, correct it in time. During construction, keep the chassis of the pile mixing machine horizontal and the guide frame vertical. The pile driver should be positioned stably and straight. Use a theodolite or plumb bob to observe and ensure the verticality of the drilling rig.

[0008] Preferably, in step 5, the concrete steps of preparing cement slurry are: a. Cement testing: quality and weight testing of cement entering the site; b. Stir the slurry on site, control the mixing of cement slurry by weight ratio method, and use computer automatic batching; c. When mixing, add water first, then add cement according to the mix ratio of the laboratory, and put it into the mixer; d. After fully stirring, put it into the cement slurry storage tank and stir the cement slurry continuously to prevent its segregation; the mud specific gravity meter is placed at the construction site for easy inspection at any time.

[0009] Preferably, in step 6, the cement mixing pile construction steps are: S1 pre-stirring and sinking: Loosen the crane wire rope to allow the mixer to sink along the guide frame to mix and cut the soil; S2 Shotcrete Mixing: The mixer continues to sink, and the slurry pump is turned on 25cm below the ground surface to spray cement slurry into the soil. The cement slurry is pressed into the foundation, and it rotates while spraying. The two sets of blades rotate forward and reverse at the same time to cut and mix the soil. The pile end continues to spray and mix on the spot for more than 10 seconds; S3 lifting stirring: While the grouting is being sprayed and mixed, the pile mixer is lifted; the lifting speed should be controlled within the specified range to ensure uniform mixing. When the pile mixer is lifted to a certain height from the ground or the designed pile top elevation, the grouting is stopped to complete the single pile construction; S4 Repeated mixing: During the repeated mixing process, ensure that the entire pile length is mixed at least once up and down; S5 Pile quality inspection, sampling and maintenance inspection: quality inspection of piles, including pile body integrity inspection, strength inspection, and inspection of the position and verticality of the mixing piles; S6 cleaning: cleaning the residual cement slurry in the mixing head and pipeline; S7 shift: According to the test results after construction, after the shift, adjustments and corrections are made. After it is determined to be qualified, the above steps are repeated to construct the next pile. The unqualified mixing piles are remedial.

[0010] Preferably, the S5 pile quality inspection specifically includes: a. Use measuring instruments and building automation instruments to measure the diameter of the mixing pile, and record and analyze the data; b. Use measuring instruments and building automation instruments to measure the length of the mixing pile to ensure that the pile length meets the design requirements; c. Review the position of the mixing pile to ensure that its position deviation meets the specification requirements; d. Use measuring instruments such as theodolite to test the verticality of the mixing pile to ensure that the verticality error is within the allowable range; e. Static load test: the bearing capacity of the foundation is tested by loading a single pile with a pressure plate of a certain rigidity to measure the bearing capacity of the single pile.

[0011] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention detects various parameters of the construction process of cement mixing piles, and adjusts the construction based on the parameters, thereby improving the construction reliability, ensuring the construction quality of the mixing piles, forming standardized and numerical construction, and facilitating construction management on the construction site; 2. The construction process parameters of the present invention are adjusted in time according to the construction inspection results to improve the qualified rate of finished products. At the same time, remedial measures are taken to deal with the mixing piles with problems to ensure the construction quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1A process flow chart of a cement mixing pile construction method proposed by the present invention; Figure 2 The present invention provides a flow chart for detecting a cement mixing pile construction method. DETAILED DESCRIPTION

[0013] 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, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. 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.

[0014] Reference Figure 1-2 , a cement mixing pile construction method, comprising: Step 1: Construction preparation: Preparation of construction drawings and plans: Be familiar with and master the design and construction drawings, and fully understand the design intent; prepare relevant construction plans, and submit them to the owner and the supervision unit for approval before implementation; Test preparation: Raw materials are sampled and tested as required, and put into use after passing the retest, and the construction process parameters are determined at the same time; Before the full construction begins, a test pile should be carried out, and the construction process parameter test should be carried out according to the design requirements; the test piles should generally be about ten, and when conditions are limited, each mix ratio should not be less than two. The geological conditions of the test piles should be representative, and the test piles should be consistent with the engineering piles. The cement mixing pile adopts a one-spray and two-mix construction process; a. Determine various technical parameters that meet the design of the single pile shotcrete volume (calculated by cement addition and water-cement ratio), such as drill rod sinking and lifting speed, shotcrete pressure, slurry breaking volume, mixer speed, current entering the bearing layer and drilling speed; b. Determine the resistance to sinking and lifting, and select a reasonable mixing head form, motor power, and the width and inclination of the mixing blades; c. Check whether the mix ratio and water-cement ratio determined by the test are convenient for construction, whether the unconfined compressive strength of the pile body meets the design requirements, and whether the bearing capacity of the composite foundation meets the design requirements; carry out bearing capacity testing on 0.5% of the total number of piles, and only proceed to the next construction process after the test meets the requirements; Preparation for briefing: Convene a meeting of all project department personnel to brief construction personnel and operators on construction technology and safety technology, so that employees can understand the design intent, master the construction essentials and key processes and safe operating procedures, and ensure clear division of labor and responsibilities.

[0015] Site preparation: The site for mixing pile construction should be leveled in advance, and the surface hard objects and underground obstacles (including stones, tree roots and garbage, etc.) in the construction area must be cleared, and the pile position should be accurately marked. The low-lying or pond areas of the site should be drained and silted before backfilling with soil and compacting in layers to the leveling elevation, and appropriate rolling should be carried out, with a compaction degree of 85%. The bearing capacity of the roadbed should meet the requirements for the stable movement of heavy pile drivers and cranes; Equipment preparation: The main construction machinery includes bulldozers, road rollers, crawler single-bucket excavators, crawler cranes, pile mixers, cement slurry preparation systems, mortar pumps, etc.; the testing equipment includes total stations, GPS, theodolites, levels, slump cones, steel ring rulers, and test molds.

[0016] Step 2: Pile position setting: Review the guide points and leveling points handed over by the planning and surveying unit and use them after confirmation; The surveying personnel shall carry out the surveying and setting out of the mixing pile position, original ground elevation, hole elevation, etc. according to the design and construction drawings, and make good records of the surveying and setting out and the pile layout drawings; According to the design requirements, the mixing piles are closely arranged and measured and laid out; the center distance between the mixing piles and the bored piles at the abutment position shall not be less than the specified value. If it cannot be met, the pile position can be appropriately adjusted, and bamboo piles shall be inserted at the position of the mixing piles as marks; after laying out and determining the line, prepare the measurement technology review form and carry out the review and acceptance certification.

[0017] Step 3: Dig trench According to the construction drawings, the construction outline of the cement mixing pile is measured and set on site as the boundary line for trench excavation; In order to prevent cement soil from rising during cement mixing pile construction and affecting construction, a construction trench should be excavated according to the contour line of the cement soil mixing pile on site. The depth of the trench is determined by the amplitude and length of the pile. Set the pile positioning control line at the edge of the trench, and set the pile position marks every 5 meters on the pile positioning control line to ensure that the overlap between piles complies with the specifications and design requirements; Before construction, the accumulated water in the trench must be removed to prevent the accumulated water from seeping in and affecting the strength of the cement-soil mixing pile.

[0018] Step 4: Put the pile driver in place, move the deep mixer to the designated pile position and align it.

[0019] Use the walking system of the pile driver to move to the designated position, lay steel plates and roadbed plates under the pile driver, use the tower to lift the mixing pile driver into place, and adjust the center; When the ground is uneven, use the hydraulic balance device of the pile mixer to keep the lifting equipment horizontal and the mixing shaft vertical; at the same time, check the drill rod length and drill bit diameter to ensure that they meet the construction requirements; Before moving, check the front, back, left and right positions clearly. If any obstacles are found, they should be removed in time. After the move, check the positioning. If there is any deviation, correct it in time. During construction, the chassis of the mixing pile machine should be kept horizontal and the guide frame vertical. The pile driver should be in place stably and straight. Use a theodolite or plumb bob to observe and ensure the verticality of the drilling rig. The verticality deviation of the mixing pile shall not be greater than 1%, the pile position deviation shall not be greater than 50mm, and the pile diameter, enlarged head depth and processing depth shall not be less than the design value.

[0020] Pre-construction inspection: Site cleaning: Before the construction of mixing piles, debris, garbage, etc. in the construction area should be cleared to ensure smooth construction.

[0021] Measurement and positioning: According to the design requirements, use measuring instruments to determine the position of the mixing piles and mark them.

[0022] Equipment inspection: Conduct a comprehensive inspection of the pile mixing machine in use to ensure the normal operation of the equipment and avoid affecting the construction progress and quality due to equipment failure.

[0023] Step 5: Prepare cement slurry The water-cement ratio should be strictly controlled, generally 0.45-0.55, preferably 0.5; cement should be sampled, and water should be added through an approved quantitative container; the cement slurry must be fully mixed and evenly, and when using a mortar mixer to make slurry, the mixing time after each addition must not be less than 3 minutes, generally 5 minutes; to improve the workability of cement, an appropriate amount of admixture can be added, especially in summer construction, an appropriate amount of water reducer should be added, such as calcium lignin sulfonate, the general addition amount is 0.2% of the cement dosage.

[0024] Cement mixing piles use 42.5 grade ordinary Portland cement. In addition to cement slurry as the curing agent, external admixtures with properties such as early strength, slow setting, water reduction, and cement saving should be selected according to project needs. Gypsum has both slow setting and early strength functions. The admixture amount should be 2.0% to 3.0% of the cement dosage. Pure gypsum powder should be used as an additive first, and it is required to pass a 0.075mm square hole sieve> 85%; Specific steps: For each batch of cement entering the construction site, the supervisor, Party A, and the construction unit need to weigh the cement tanker together to ensure double control of the weight of the incoming cement.

[0025] Generally, the slurry is mixed on site, and the weight ratio method is used to control the mixing of cement slurry. Computer batching is adopted, and there is a digital display screen in the control room to show the weight of water and cement added each time.

[0026] When mixing, add water first, then add cement according to the laboratory's mix ratio and put it into the mixer.

[0027] After fully mixing, put it into the cement slurry storage tank; the mud density meter should be placed at the construction site for easy inspection at any time.

[0028] Material quality testing: Cement quality testing: Carry out quality inspection on incoming cement to ensure that the strength, stability and other indicators of the cement meet the design requirements.

[0029] Cement dosage control: According to the design requirements, the cement dosage is accurately controlled to ensure the strength and stability of the mixing pile.

[0030] Step 6, cement mixing pile construction, first carry out cast-in-place pile construction, then carry out mixing pile construction, after the construction is completed, carry out cap beam construction. During the construction process, the verticality of the pile driver, mixing depth, shotcrete volume and other parameters should be monitored in real time, and the construction process parameters should be adjusted in time to ensure the construction quality.

[0031] The diameter of the bidirectional mixing pile is 50cm, and the cement dosage is 60kg / m. The specific amount is subject to the test pile results. The cement slurry preparation must have sufficient time (more than 4 minutes) to ensure the uniform mixing of the cement slurry and the activation of the cement. The water-cement ratio (cement slurry) should be determined according to the parameters of the test pile. The slurry must be stirred at any time when entering the spraying pool to ensure that the slurry does not segregate.

[0032] Cement mixing pile construction: S1 pre-stirring and sinking: After the cooling water circulation of the mixer is normal, start the mixer motor, loosen the crane wire rope, and let the mixer sink along the guide frame to mix and cut the soil. The sinking speed can be controlled by the motor current detection meter, and the working current should not be greater than the rated current; S2 Shotcrete Mixing: The mixer continues to sink, and the slurry pump is turned on 25cm below the ground surface to spray cement slurry into the soil. The two sets of blades rotate forward and reverse at the same time to cut and mix the soil. Before pre-mixing and sinking, the prepared cement slurry is filtered through a sieve and poured into a slurry storage bucket, so that the mortar pump can pump the slurry to the mixing head, press the cement slurry into the foundation, and rotate while spraying. The pile end should continue to spray and stir for more than 10 seconds on site. During the spraying process, the cement slurry is continuously stirred to prevent its segregation; at the same time, the spraying volume and stirring depth are automatically recorded by the computer; The prepared cement slurry must not be segregated and the slurry supply must be continuous; if the slurry is stopped for some reason, corresponding measures should be taken to deal with it, and the overlap of the piles should not be less than 0.5m; S3 lifting stirring While the grouting is being sprayed, the pile mixer is lifted; the lifting speed should be controlled within the specified range to ensure uniform mixing; at the same time, the two sets of blades rotate forward and reverse to mix the cement soil. When the pile mixer is lifted to a certain height from the ground or the designed pile top elevation, such as 50cm, the grouting is stopped to complete the single pile construction; S4 Repeated mixing: In order to improve the strength and stability of the mixing pile, the mixing pile needs to be repeatedly mixed to ensure uniform mixing. According to the design requirements, the mixing sinking and lifting process is repeated many times until the predetermined mixing times and depth are reached; during the repeated mixing process, it should be ensured that the entire pile length is repeatedly mixed at least once; Construction process inspection: Slurry pipe inspection: Regularly check whether the slurry pipe is unobstructed to avoid uneven grouting due to blockage of the slurry pipe, which will affect the quality of the mixing pile.

[0033] Pile length control: The length of the mixing pile is controlled by measuring instruments to ensure that the mixing pile penetrates the predetermined soil layer and guarantees the bearing capacity of the foundation.

[0034] S5 Pile quality inspection: Conduct quality inspection on piles, including pile integrity inspection, strength inspection, and inspection of the position and verticality of the mixing piles; Check the appearance of the mixing pile, including whether the pile body is flat, whether the pile head is smooth, whether there are cracks and defects, etc., to ensure the quality of the mixing pile.

[0035] Pile strength testing includes: a. Light dynamic penetration method: Use a light penetration device to extract cement soil samples from the pile body within 7 days of pile formation, and check the uniformity of the cement soil mixing pile by observing whether the color of the cement soil samples is consistent, whether there are lumps of cement or unmixed soil clumps. At the same time, the uniformity of the mixing pile can also be checked by the number of hammer strikes during the test.

[0036] b. Core sampling method: After a certain age (e.g. 28 days after the formation of cement-soil mixing piles), the length of the pile body, the cement content of each part of the pile body, the uniformity of cement-soil mixing, and the change in the compressive strength of the pile body are checked by drilling and coring. The core sample diameter should not be less than 80mm, and the depth of drilling into the bearing layer should not be less than 3 times the pile diameter and not less than 3m.

[0037] c. Stress wave reflection method: a detection method based on the theory of stress wave propagation in elastic bodies, which can be used to detect the pile body quality of cement-soil mixing piles.

[0038] Pile position deviation, depth deviation, pile diameter, pile length, inclination, etc. must comply with design and specification requirements; the unconfined compressive strength of the pile body shall not be less than the design requirements.

[0039] Dimensional inspection, including: Diameter detection: Use measuring instruments and building automation instruments to measure the diameter of the mixing pile, and record and analyze the data.

[0040] Length detection: The length of the mixing pile is also measured using measuring instruments and building automation instruments to ensure that the pile length meets the design requirements. Position and verticality detection, including: Position detection: Review the position of the mixing pile to ensure that its position deviation meets the specification requirements.

[0041] Verticality detection: Use measuring instruments such as theodolite to detect the verticality of the mixing pile to ensure that the verticality error is within the allowable range.

[0042] Static load test: The bearing capacity of the foundation is tested by loading a single pile with a pressure plate of a certain rigidity to measure the bearing capacity of the single pile.

[0043] S6 Cleaning: Pour an appropriate amount of hot water into the aggregate hopper, turn on the mortar pump, clean the remaining cement slurry in all pipelines until they are basically clean, and clean the debris adhering to the mixing head.

[0044] S7 shift: According to the test results after construction, after the shift, adjustments and corrections are made. After it is determined to be qualified, the above steps are repeated to construct the next pile. The unqualified mixing piles are remedial.

[0045] Remedial treatment of unqualified mixing piles includes: A. Treatment of cold joints in mixing pile construction: The conventional drilling of one hole is changed to drilling two holes to increase the strength and impermeability of the overlap; the speed of lifting and sinking is strictly controlled, and light pressure and slow speed are achieved to improve the quality of the overlap; If the above method cannot meet the requirements, adopt the scheme of adding plain piles on the outside of the retaining piles at the cold joints to prevent eccentric drilling and ensure the effect of the pile filling. The overlap thickness of the plain piles and the retaining piles is about 10cm to ensure the water-stopping effect of the retaining piles.

[0046] B. Measures for dealing with boulders: In general, the mixer is also applicable to pebble formations with a particle size of less than 10 cm. If larger boulders are encountered during the pile-making process, water impact is used to increase the cement content. If the boulders are too large to be flushed out, additional pile reinforcement is used.

[0047] C. Verticality control and correction measures: Accurately locate the plane position of the pile, and place the pile driver strictly according to the plane position of the pile; for skewed pile positions, add piles and make reinforcing piles on the back.

[0048] D. Emergency measures in case of unexpected shutdown: In case of unexpected shutdown, sink the drill rod 1.0m and spray and mix the grout again to prevent broken piles or interlayers. If the engagement of two piles exceeds 24h, increase the grout volume of the second pile by 20%, or add more piles.

[0049] E. Remedial measures for broken piles and splits: If broken piles and splits are found in the construction method piles during the excavation of the foundation pit, grouting is used on the inner side of the excavation and jet jetting is used on the outer side to stop the water. The broken piles and splits are sealed with t=12mm steel plates, and the steel plates are fully welded to the steel sections in the construction method piles.

[0050] Step 7: After the mixing pile is completely completed, the overall quality inspection is carried out. After the construction is completed, the core sampling test is carried out according to the regulations to test the integrity of the pile body, the uniformity of mixing, the construction length of the pile, and whether the unconfined compressive strength meets the design; Composite foundation bearing capacity test: The composite foundation static load test is used to ensure that the composite foundation bearing capacity meets the design requirements.

[0051] Comprehensive assessment and report, taking into account the appearance, strength, verticality, position and other aspects of the mixed pile, to conduct an overall assessment of the quality of the mixed pile to ensure that it meets the design and specification requirements.

[0052] Prepare a cement mixing pile project inspection report based on the inspection results to evaluate and accept the quality of the project; the inspection report should record the inspection methods, data and other contents in detail to provide a basis for the quality assessment of the cement mixing pile project.

[0053] 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.

[0054] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0055] Unless otherwise specifically stated, the relative arrangement of the parts and steps described in these embodiments, numerical expressions and numerical values ​​do not limit the scope of the present invention. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be regarded as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

Claims

1. A cement mixing pile construction method, characterized in that: include: Step 1: Construction technology preparation, equipment, site preparation and test preparation. Before the full construction starts, a test pile should be carried out, and the construction process parameter test should be carried out according to the design requirements; Step 2: Pile position setting out. The surveyor shall carry out relevant measurement and setting out work such as the mixing pile position, original ground elevation, hole elevation, etc. according to the design and construction drawings, and make measurement and setting out records and pile layout drawings; Step 3: Dig the trench. Before construction, the water in the trench must be removed to prevent the water from seeping in and affecting the strength of the cement-soil mixing pile. Step 4: Put the pile driver in place, move the deep mixer to the designated pile position, align it, use the walking system of the pile driver to move it to the designated position, use the tower to lift the mixing pile driver to put it in place, level it, and adjust it in the center; Step 5: Prepare cement slurry, strictly control the water-cement ratio, generally 0.45-0.55, and stir the slurry at any time when it enters the spraying pool to ensure that the slurry does not separate; Step 6: During the construction of cement mixing piles, the verticality of the pile driver, mixing depth, shotcrete volume and other parameters should be monitored in real time, and the construction process parameters should be adjusted in time to ensure the construction quality; Step 7, quality inspection. After the construction is completed, core sampling and testing should be carried out as required to test the integrity of the pile body, the uniformity of mixing, the construction length of the pile, whether the unconfined compressive strength meets the design, and the bearing capacity of the composite foundation.

2. A cement mixing pile construction method according to claim 1, characterized in that: In step 1, the construction process parameters include: a. Determine various technical parameters that meet the design of the single pile shotcrete quantity, calculated by cement addition amount and water-cement ratio, such as drill rod sinking and lifting speed, shotcrete pressure, slurry breaking quantity, mixer speed, current entering the bearing layer and drilling speed; b. Determine the resistance to sinking and lifting, and select a reasonable mixing head form, motor power, and the width and inclination of the mixing blades; c. Check whether the mix ratio and water-cement ratio determined by the test are convenient for construction, whether the unconfined compressive strength of the pile body meets the design requirements, and whether the bearing capacity of the composite foundation meets the design requirements; carry out bearing capacity testing on 0.5% of the total number of piles, and only proceed to the next construction process after the test meets the requirements; The construction process parameters are adjusted in time according to the construction pile testing data to ensure the construction quality.

3. A cement mixing pile construction method according to claim 2, characterized in that: In the step 1, site preparation: the site for mixing pile construction should be leveled in advance, and the surface hard objects and underground obstacles in the construction area must be cleared to facilitate and accurately carry out pile position layout. The low-lying or pond areas of the site should be drained and silted first, and then backfilled with soil and compacted in layers to the leveling elevation, and appropriately rolled. The compaction degree is required to reach 85%, and the roadbed bearing capacity should meet the requirements for the smooth movement of heavy pile drivers and cranes.

4. A cement mixing pile construction method according to claim 1, characterized in that: In step 4, the pile driver is leveled: when the ground is uneven, the hydraulic balancing device of the pile driver is used to keep the lifting equipment horizontal so that the mixing shaft remains vertical; After the move is completed, check the positioning. If there is any deviation, correct it in time. During construction, keep the chassis of the pile mixing machine horizontal and the guide frame vertical. The pile driver should be positioned stably and straight. Use a theodolite or plumb bob to observe and ensure the verticality of the drilling rig.

5. A cement mixing pile construction method according to claim 1, characterized in that: In step 5, the specific steps of preparing cement slurry are: a. Cement testing: quality and weight testing of cement entering the site; b. Stir the slurry on site, control the mixing of cement slurry by weight ratio method, and use computer automatic batching; c. When mixing, add water first, then add cement according to the mix ratio of the laboratory, and put it into the mixer; d. After fully stirring, put it into the cement slurry storage tank and stir the cement slurry continuously to prevent its segregation; the mud specific gravity meter is placed at the construction site for easy inspection at any time.

6. A cement mixing pile construction method according to claim 1, characterized in that: In step 6, the cement mixing pile construction steps are: S1 pre-stirring and sinking: Loosen the crane wire rope to allow the mixer to sink along the guide frame to mix and cut the soil; S2 Shotcrete Mixing: The mixer continues to sink, and the slurry pump is turned on 25cm below the ground surface to spray cement slurry into the soil. The cement slurry is pressed into the foundation, and it rotates while spraying. The two sets of blades rotate forward and reverse at the same time to cut and mix the soil. The pile end continues to spray and mix on the spot for more than 10 seconds; S3 lifting stirring: While the grouting is being sprayed and mixed, the pile mixer is lifted; the lifting speed should be controlled within the specified range to ensure uniform mixing. When the pile mixer is lifted to a certain height from the ground or the designed pile top elevation, the grouting is stopped to complete the single pile construction; S4 Repeated mixing: During the repeated mixing process, ensure that the entire pile length is mixed at least once up and down; S5 Pile quality inspection, sampling and maintenance inspection: quality inspection of piles, including pile body integrity inspection, strength inspection, and inspection of the position and verticality of the mixing piles; S6 cleaning: cleaning the residual cement slurry in the mixing head and pipeline; S7 shift: According to the test results after construction, after the shift, adjustments and corrections are made. After it is determined to be qualified, the above steps are repeated to construct the next pile. The unqualified mixing piles are remedial.

7. A cement mixing pile construction method according to claim 6, characterized in that: The S5 pile quality inspection specifically includes: a. Use measuring instruments and building automation instruments to measure the diameter of the mixing pile, and record and analyze the data; b. Use measuring instruments and building automation instruments to measure the length of the mixing pile to ensure that the pile length meets the design requirements; c. Review the position of the mixing pile to ensure that its position deviation meets the specification requirements; d. Use measuring instruments such as theodolite to test the verticality of the mixing pile to ensure that the verticality error is within the allowable range; e. Static load test: the bearing capacity of the foundation is tested by loading a single pile with a pressure plate of a certain rigidity to measure the bearing capacity of the single pile.

8. A cement mixing pile construction method according to claim 6, characterized in that: The remedial treatment of the unqualified mixing piles specifically includes: A. Treatment of cold joints in mixing pile construction: The conventional drilling of one hole is changed to drilling two holes to increase the strength and impermeability of the overlap; the speed of lifting and sinking is strictly controlled, and light pressure and slow speed are achieved to improve the quality of the overlap; If the above method cannot meet the requirements, adopt the solution of adding piles outside the retaining piles at the cold joints to prevent eccentric drilling and ensure the effect of pile filling. The overlap thickness of the piles and the retaining piles is about 10cm to ensure the water-stopping effect of the retaining piles. B. Treatment measures for isolated boulders: Generally, the mixer is also applicable to pebble formations with a particle size of less than 10 cm. If larger isolated boulders are encountered during the pile-making process, water impact is used to increase the cement content. If the isolated boulders are too large to be flushed out, pile reinforcement is used. C. Verticality control and deflection correction measures: accurately locate the plane position of the pile, and the pile driver is placed strictly according to the plane position of the pile; for the deflected pile position, add piles and add reinforcement piles on the back; D. Emergency measures in case of unexpected shutdown: In case of unexpected shutdown, sink the drill pipe 1.0m and spray and mix again to prevent pile breakage or interlayer. If the engagement of two piles exceeds 24h, increase the slurry volume of the second pile by 20% or add more piles; E. Remedial measures for broken piles and splits: If broken piles and splits are found in the construction method piles during the excavation of the foundation pit, grouting is used on the inner side of the excavation, and jet jetting is used on the outer side to stop water. The broken piles and splits are sealed with steel plates, and the steel plates are fully welded to the steel sections in the construction method piles.

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