Coastal soft soil foundation cement mixing pile construction method

Abstract

The invention discloses a coastal soft soil foundation cement mixing pile construction method. Soil body data are obtained by performing field investigation on a coastal soft soil foundation, so that a proportioning scheme of a cement-composite cementing material is guided, and a mixing pile is more adaptive to a field environment. The pile position is positioned through a satellite positioning system, and whole-process monitoring of the pile driving process is achieved. And through sampling inspection after pile forming, the pile forming quality of the mixing pile is ensured. The invention relates to the technical field of foundation treatment engineering.

Description

Technical Field

[0001] This invention relates to the field of foundation treatment engineering technology, and in particular to a method for constructing cement mixing piles for coastal soft soil foundations. Background Technology

[0002] Coastal areas are widely covered by typical soft strata such as silt and silty soil. These strata are characterized by high water content, low strength, and high compressibility, which bring serious problems such as large foundation settlement and poor structural stability to the construction of tunnels, roadbeds, and foundation pits, seriously affecting the quality of projects and construction safety.

[0003] When traditional pure cement mixing pile reinforcement technology is applied to this type of coastal soft soil stratum, there are many insurmountable defects: on the one hand, pure cement has poor compatibility with soft soil with high water content and high salinity, which easily leads to problems such as insufficient solidification reaction, insufficient pile integrity, low strength compliance rate or even failure to form, and cannot meet the design requirements for foundation bearing capacity and stability; on the other hand, the construction process relies entirely on manual experience for control, and there is a lack of precise monitoring methods for the entire process from slurry preparation to mixing and pile formation, resulting in low construction efficiency, large quality fluctuations, and difficulty in tracing the root cause of problems.

[0004] The existing technological system has significant shortcomings in addressing the above-mentioned pain points: First, there is a lack of systematic research on the improvement of pile quality in coastal soft soil by cement composite curing agents, and there is a lack of composite cementitious material ratio schemes that have been verified by engineering; Second, an intelligent construction management and control scheme for the complex characteristics of coastal soft soil strata has not yet been formed, and it is impossible to achieve integrated management of accurate pile location, real-time control of construction parameters and dynamic quality monitoring, which makes it difficult to meet the needs of refined construction under complex geological conditions. Summary of the Invention

[0005] This invention aims to at least solve one of the aforementioned technical problems existing in the prior art. To this end, this application proposes a method for constructing cement-mixing piles on coastal soft soil foundations, which is adaptable to the characteristics of coastal soft soil strata, achieves high-quality cement-mixing pile reinforcement, and enables intelligent control throughout the entire process.

[0006] The method for constructing cement mixing piles on coastal soft soil foundations according to embodiments of this application includes the following steps: The underlying distribution and physical and mechanical properties of coastal soft soil foundations were detected, and the soil moisture content, organic matter content and salinity index were analyzed to provide a basis for the composition ratio of piles. The cement-composite cementitious material mix design was determined based on the test results of the coastal soft soil foundation. During construction, the location of each pile is determined based on a satellite positioning system; Drill the mixing drill bit at the designated pile location, and grouting is carried out simultaneously during the drilling process to ensure that the grout is mixed evenly. After the piling is completed, the piling time, pile length, verticality and cement content data are recorded and uploaded to the back-end system for subsequent monitoring, analysis and adjustment. After pile completion, core drilling is used for quality testing to check the integrity of the core sample and its unconfined compressive strength. The compressive strength is required to be no less than 1.0 MPa. After core drilling is completed, the voids are filled with grout to avoid affecting the stability of the foundation.

[0007] The cement-mixing pile construction method for coastal soft soil foundations according to the embodiments of this application has at least the following beneficial effects: Soil data is obtained through on-site investigation of the coastal soft soil foundation, thereby guiding the mixing scheme of cement-composite cementitious materials, making the mixing piles more suitable for the site environment. The pile positions are located using a satellite positioning system, enabling full monitoring of the pile driving process. Sampling inspections after pile completion ensure the quality of the mixing piles.

[0008] According to some embodiments of this application, when determining the cement-composite cementitious material mix ratio scheme, the variable control method is used to compare various mix ratio methods, explore the influence of total admixture, material ratio and water-cement ratio on the pile formation effect, and finally determine the optimal mix ratio scheme suitable for coastal soft soil foundation.

[0009] According to some embodiments of this application, in the process of determining the mix proportion scheme, an indoor simulated pile driving test is first conducted, followed by on-site pile driving verification.

[0010] According to some embodiments of this application, the mixing drill bit includes a drill bit body and multiple blade groups, each blade group including at least two blades symmetrically arranged around the center of the drill bit body, and each blade group is equidistantly distributed along the length direction of the drill bit body.

[0011] According to some embodiments of this application, two adjacent blade groups are staggered.

[0012] According to some embodiments of this application, when stirring the slurry, the blades stir the slurry at the same location more than 82.5 times.

[0013] According to some embodiments of this application, the satellite positioning system monitors the piling location in real time to ensure that the piling location is consistent with the pile position. If the piling location is inconsistent with the pile position, the satellite positioning system issues an alarm to the user.

[0014] According to some embodiments of this application, during grouting, a grout mixer is used to ensure uniform mixing of the grout and to control the grout density to be maintained at 1.37–1.49 g / cm³.

[0015] According to some embodiments of this application, when drilling into the mixing drill bit, the drilling and lifting speed is no greater than 1 m / min, the rotation speed of the mixing drill bit is controlled at 50 to 60 r / min, and the grouting pressure is controlled at 0.5 to 0.8 MPa.

[0016] According to some embodiments of this application, when using the core drilling method for quality inspection, the number of piles inspected shall not be less than 1% of the total number of piles and not less than 3 piles.

[0017] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0018] The accompanying drawings are used to provide a further understanding of the technical solutions disclosed in this application and form part of the specification. They are used together with the embodiments disclosed in this application to explain the technical solutions of this application and do not constitute a limitation on the technical solutions disclosed in this application.

[0019] Figure 1 This is a schematic diagram of the construction method for cement mixing piles on coastal soft soil foundations according to an embodiment of this application; Figure 2 This is a schematic diagram of the structure of the mixing drill bit in the cement mixing pile construction method for coastal soft soil foundation in this application embodiment.

[0020] Reference numerals: 100-Drill bit body, 200-Blade assembly, 210-Blade. Detailed Implementation

[0021] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0022] In the description of this application, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0023] In the description of this application, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0024] In the description of this application, unless otherwise expressly defined, terms such as "setup," "installation," and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this application in conjunction with the specific content of the technical solution.

[0025] In the description of this application, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0026] Coastal areas are widely covered by typical soft strata such as silt and silty soil. These strata are characterized by high water content, low strength, and high compressibility, which bring serious problems such as large foundation settlement and poor structural stability to the construction of tunnels, roadbeds, and foundation pits, seriously affecting the quality of projects and construction safety.

[0027] When traditional pure cement mixing pile reinforcement technology is applied to this type of coastal soft soil stratum, there are many insurmountable defects: on the one hand, pure cement has poor compatibility with soft soil with high water content and high salinity, which easily leads to problems such as insufficient solidification reaction, insufficient pile integrity, low strength compliance rate or even failure to form, and cannot meet the design requirements for foundation bearing capacity and stability; on the other hand, the construction process relies entirely on manual experience for control, and there is a lack of precise monitoring methods for the entire process from slurry preparation to mixing and pile formation, resulting in low construction efficiency, large quality fluctuations, and difficulty in tracing the root cause of problems.

[0028] The existing technological system has significant shortcomings in addressing the above-mentioned pain points: First, there is a lack of systematic research on the improvement of pile quality in coastal soft soil by cement composite curing agents, and there is a lack of composite cementitious material ratio schemes that have been verified by engineering; Second, an intelligent construction management and control scheme for the complex characteristics of coastal soft soil strata has not yet been formed, and it is impossible to achieve integrated management of accurate pile location, real-time control of construction parameters and dynamic quality monitoring, which makes it difficult to meet the needs of refined construction under complex geological conditions.

[0029] To address this issue, this application proposes a method for constructing cement-mixing piles on coastal soft soil foundations. Soil data is obtained through on-site surveys of the coastal soft soil foundation, guiding the mixing scheme of cement-composite binders and thus making the mixing piles more suitable for the site environment. The pile locations are determined using a satellite positioning system, enabling full monitoring of the piling process. Post-pile completion sampling inspections ensure the quality of the mixed piles.

[0030] Reference Figure 1 The construction method for cement mixing piles on coastal soft soil foundations in this application includes the following steps: S100. Detect the underlying distribution and physical and mechanical properties of coastal soft soil foundations, analyze soil moisture content, organic matter content and salinity index, and provide a basis for pile composition ratio; S200. Based on the test results of the coastal soft soil foundation, the cement-composite cementitious material mix ratio scheme is determined, so as to make specific adjustments according to the specific situation, so that the mixing piles are more compatible with the existing foundation during the subsequent piling process, and the impact of environmental corrosion on the mixing piles is reduced. S300. During construction, the location of each pile is determined based on a satellite positioning system; the satellite positioning system can be the Beidou satellite positioning system or the GPS positioning system, or other types of satellite positioning systems that can accurately locate the pile positions. S400. Drill the mixing drill bit at the set pile position, and grouting is carried out simultaneously during the drilling process to ensure that the grout is mixed evenly; S500. After the piling is completed, record the piling time, pile length, verticality and cement content data, and upload these data to the back-end system for subsequent monitoring, analysis and adjustment. S600. After pile completion, the core drilling method is used for quality testing to check the integrity of the core sample and its unconfined compressive strength. The compressive strength is required to be not less than 1.0 MPa. S700. After core drilling is completed, the voids are filled with grout to avoid affecting the stability of the foundation.

[0031] Thus, through preliminary surveys, material proportioning experiments, precise positioning during construction, and post-construction data uploading and pile quality testing, comprehensive monitoring and precise control of each process are achieved throughout the pile driving process, thereby ensuring pile quality and efficiency and completing the cement mixing pile construction process for coastal soft soil foundations.

[0032] Furthermore, when determining the cement-composite cementitious material mix design, the variable control method was used to compare different mix designs and explore the influence of total admixture, material ratio, and water-cement ratio on the pile formation effect. Finally, the optimal mix design suitable for coastal soft soil foundation was determined, thereby obtaining the cement-composite cementitious material mix design most suitable for the coastal soft soil foundation environment to be constructed.

[0033] Furthermore, to ensure the feasibility of the mix design, indoor simulated pile driving tests were conducted first, followed by on-site pile testing to verify the mix design. The mix design of cement-composite cementitious materials was verified through these two experimental processes to avoid rework due to unsatisfactory results.

[0034] Furthermore, the drill bit of the mixing drill used for drilling into soil is a core component in the drilling process. In this embodiment, reference is made to... Figure 2 The mixing drill bit comprises a drill bit body 100 and multiple blade sets 200. Each blade set 200 includes at least two blades 210 symmetrically arranged around the center of the drill bit body 100, and the blade sets 200 are equidistantly distributed along the length of the drill bit body 100. The end of the drill bit body 100 is tapered to facilitate drilling into the soil. During the rotational drilling process of the drill bit body 100, the multiple blades 210 simultaneously agitate the surrounding soil, ensuring thorough mixing between the soil and the injected grout. The more blades 210 there are and the more times they agitate, the higher the degree of mixing between the soil and the grout, resulting in a denser pile structure during subsequent pile formation.

[0035] The number of blade group 200, and the number of blades 210 in blade group 200, can be increased or decreased according to the actual situation to adapt to different piling environments.

[0036] Furthermore, the two adjacent blade groups 200 are staggered to ensure that the drill bit body 100 is subjected to uniform force and to avoid vibration or displacement caused by uneven force.

[0037] Furthermore, in order to make the grout mixing more thorough, so as to make the pile body density higher after pile formation and reduce crack generation, the blade 210 mixes the grout at the same location more than 82.5 times during grout mixing.

[0038] Furthermore, the satellite positioning system monitors the piling location in real time to ensure that the piling location matches the intended pile position. If the piling location does not match the intended pile position, the satellite positioning system will issue an alarm to the user. Thus, by accurately monitoring the piling location through the satellite positioning system, it ensures that the pile position is consistent with the design.

[0039] Specifically, during grouting, a grout mixer is used to ensure uniform mixing of the grout and to control the grout density to be maintained at 1.37–1.49 g / cm³.

[0040] Specifically, when drilling into the mixing drill bit, the drilling and lifting speed should not exceed 1m / min, the rotation speed of the mixing drill bit should be controlled at 50 to 60 r / min, and the grouting pressure should be controlled at 0.5 to 0.8MPa.

[0041] Furthermore, when using the core drilling method for quality testing, the number of piles tested shall not be less than 1% of the total number of piles and not less than 3 piles, to ensure that the number of samples tested is sufficient, thereby verifying the quality of the pile body.

[0042] The technical effects of this cement mixing pile construction method for coastal soft soil foundation are illustrated below with examples: In a tunnel engineering project involving shallow overburden reinforcement in a marine area, the moisture content of the silt layer was found to be ≥60%, organic matter content 2%–5%, and salt content 0.3%–1%, necessitating optimization of the curing agent mix ratio. Through test piles, a scheme with a total admixture dosage of 23%, a cement:curing agent ratio of 4:6, and a water-cement ratio of 0.55 was determined. The core sample compressive strength of the test piles was 2.4~2.8MPa, meeting the design requirements. An SP-10A60 twin-shaft mixing pile machine was used, with the drill bit blades modified to 10 blades. A CJ-F8 intelligent monitoring system and a ZDT820 Beidou positioning system were installed, calibrating the pile position deviation to ≤0.2m. A "two-mixing, two-jetting" process was employed, controlling the drilling / lifting speed at 0.8m / min, the rotation speed at 55 rpm, and the grouting pressure at 0.6MPa. The intelligent system monitored the grout density in real time (1.37g / cm³) and the pile verticality at 0.2°. Five piles were extracted for core drilling after pile completion. The core samples were intact, with an average 28-day compressive strength of 2.6 MPa, achieving a 100% pass rate. This successfully solved the problem of pile completion for offshore mixing piles, eliminated the risk of grout leakage when the tunnel boring machine traverses shallow overburden, reduced construction costs by 31%, and shortened the construction period by 40%.

[0043] In some alternative embodiments, the functions / operations mentioned in the block diagrams may not occur in the order shown in the operation diagrams. For example, depending on the functions / operations involved, two consecutively shown blocks may actually be executed substantially simultaneously, or the blocks may sometimes be executed in reverse order. Furthermore, the embodiments presented and described in the flowcharts of this application are provided by way of example to provide a more comprehensive understanding of the technology. The disclosed methods are not limited to the operations and logic flows presented herein. Alternative embodiments are contemplated in which the order of various operations is changed and sub-operations described as part of a larger operation are executed independently.

[0044] The embodiments of this application have been described in detail above with reference to the accompanying drawings. However, this application is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of this application. Furthermore, unless otherwise specified, the embodiments and features described in the embodiments of this application can be combined with each other.

Claims

1. A method for constructing cement mixing piles on coastal soft soil foundations, characterized in that, include: The underlying distribution and physical and mechanical properties of coastal soft soil foundations were detected, and the soil moisture content, organic matter content and salinity index were analyzed to provide a basis for the composition ratio of piles. The cement-composite cementitious material mix design was determined based on the test results of the coastal soft soil foundation. During construction, the location of each pile is determined based on a satellite positioning system; Drill the mixing drill bit at the designated pile location, and grouting is carried out simultaneously during the drilling process to ensure that the grout is mixed evenly. After the piling is completed, the piling time, pile length, verticality and cement content data are recorded and uploaded to the back-end system for subsequent monitoring, analysis and adjustment. After pile completion, core drilling is used for quality testing to check the integrity of the core sample and its unconfined compressive strength. The compressive strength is required to be no less than 1.0 MPa. After core drilling is completed, the voids are filled with grout to avoid affecting the stability of the foundation.

2. The method for constructing cement mixing piles on coastal soft soil foundations according to claim 1, characterized in that: When determining the cement-composite cementitious material mix design, the variable control method was used to compare different mix designs and explore the effects of total admixture, material ratio, and water-cement ratio on the pile formation effect. Finally, the optimal mix design suitable for coastal soft soil foundation was determined.

3. The method for constructing cement mixing piles on coastal soft soil foundations according to claim 2, characterized in that: In determining the mix proportion scheme, an indoor simulated pile driving test was conducted first, followed by on-site pile driving verification.

4. The method for constructing cement mixing piles on coastal soft soil foundations according to claim 1, characterized in that: The mixing drill bit includes a drill bit body and multiple blade groups. Each blade group includes at least two blades symmetrically arranged around the center of the drill bit body. Each blade group is equidistantly distributed along the length direction of the drill bit body.

5. The method for constructing cement mixing piles on coastal soft soil foundations according to claim 4, characterized in that: Adjacent blade groups are staggered.

6. The method for constructing cement mixing piles on coastal soft soil foundations according to claim 4, characterized in that: When stirring the slurry, the blades stir the slurry at the same location more than 82.5 times.

7. The method for constructing cement mixing piles on coastal soft soil foundations according to claim 1, characterized in that: The satellite positioning system monitors the piling location in real time to ensure that the piling location is consistent with the pile position. If the piling location is inconsistent with the pile position, the satellite positioning system issues an alarm to the user.

8. The method for constructing cement mixing piles on coastal soft soil foundations according to claim 1, characterized in that: During grouting, a grout mixer is used to ensure uniform mixing of the grout and to control the grout density to be maintained at 1.37–1.49 g / cm³.

9. The method for constructing cement mixing piles on coastal soft soil foundations according to claim 1, characterized in that: When drilling into the mixing drill bit, the drilling and lifting speed shall not exceed 1m / min, the rotation speed of the mixing drill bit shall be controlled at 50 to 60 r / min, and the grouting pressure shall be controlled at 0.5 to 0.8 MPa.

10. The method for constructing cement mixing piles on coastal soft soil foundations according to claim 1, characterized in that: When using the core drilling method for quality inspection, the number of piles to be inspected shall not be less than 1% of the total number of piles and not less than 3 piles.

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