Construction method for improving bearing capacity of soft ground soil layer

Abstract

The application provides a construction method for improving the bearing capacity of soft foundation soil, which comprises the following steps: selecting a soil position and taking out a sample soil for testing; measuring and setting out; aiming a drill of a mixer at the pile position and leveling a pile body of the mixer; sinking while feeding slurry under stirring; after the deep mixer is sunk to the depth of the pile foundation and stays at the bottom of the hole to stir and feed slurry, the stirring head is reversed and lifted from the pile end; the steps of sinking and stirring under slurry feeding and the steps of stirring and lifting under slurry feeding are repeated. The application improves the bearing capacity of the foundation by mixing the solidifying agent and the soil body into one through the deep stirring method, maximally utilizes the original soil, slightly disturbs the surrounding soil body, and solves the problems of the complex treatment mode and long construction period in the existing soft soil area.

Description

Technical Field

[0001] This invention relates to the field of construction engineering technology, and more specifically, to a construction method for improving the bearing capacity of soft foundation soil layers. Background Technology

[0002] In existing technologies, the soil conditions for foundation construction are diverse. my country has a vast territory, and deep mixing methods can be widely used in soft soil layers in the middle and lower reaches of rivers, in addition to the soft soil deposits in coastal areas. It has wide applications, serving as a method for reinforcing building foundations as well as for reinforcing the foundations of ports, stations, highways, and railways. It also features low cost, high efficiency, and good economic benefits. With the continuous improvement of materials and technology in deep cement-soil mixing and the increasing social benefits, existing methods for treating soft soil areas are complex and have long construction cycles. This embodiment provides a convenient and quick foundation treatment method for soft soil areas. Summary of the Invention

[0003] In view of this, the present invention proposes a construction method for improving the bearing capacity of soft soil layers, aiming to solve the problems of complex treatment methods and long construction cycles in existing soft soil areas.

[0004] This invention proposes a construction method for improving the bearing capacity of soft soil layers. The method includes the following steps: a cement-soil strength test step, selecting the soil layer location, taking soil samples, and conducting tests on the physical properties, water content, organic matter content, and cement-soil mix proportion strength of the soft soil to verify whether the properties of the soft soil and the strength of the cement-soil mixing piles meet the requirements; a measurement and layout step, performing measurement and layout at the coating location; a mixer positioning and straightening step, aligning the mixer's drilling rig with the pile location and leveling the mixer's pile driver body to ensure the verticality of the pile; and a grouting and mixing sinking step, preparing the mix according to the preset proportion. Cement slurry is prepared and poured into a storage tank. The storage grouting pump is connected to the mixing pile machine via a grouting hose. The grouting pump is started, and after the mixing drill bit produces slurry, the motor is started, causing the mixer to move along the guide frame to mix and cut the soil as it sinks. Slurry delivery begins simultaneously with the mixing and sinking. In the grouting, mixing, and lifting step, after the deep mixer has slurried to the pile foundation depth and stopped at the bottom of the hole for a preset time period, the mixing head is reversed and lifted from the pile end to mix and inject cement slurry until the preset pile top height is reached. The mixing step is repeated, and the grouting, mixing, sinking step and the grouting, mixing, and lifting step are repeated to complete the construction of one pile foundation.

[0005] Furthermore, the above-mentioned construction method for improving the bearing capacity of soft foundation soil layers, after the repeated mixing step, also includes the following steps: a cleaning step, after the construction of one pile foundation is completed, the mixer is turned off, and the cement clods on the mixer blades and the cement at the grouting nozzle are cleaned; if construction is stopped, the cement in the storage tank is cleaned, an appropriate amount of clean water is injected into the storage tank, the grout pump is turned on, and the residual cement slurry in the pipeline is cleaned until it is clean.

[0006] Furthermore, the above-mentioned construction method for improving the bearing capacity of soft foundation soil layers, after the cleaning step, also includes the following step: a mixer relocation step, in which the mixer is moved to the next pile foundation, and the mixer placement and straightening steps are repeated until the repeated mixing step is completed, so as to perform deep mixing on the current pile foundation.

[0007] Furthermore, the above-mentioned construction method for improving the bearing capacity of soft foundation soil layers also includes the following step before the measurement and setting-out step: a site leveling step, in which the selected soil layer location is leveled.

[0008] Furthermore, the above-mentioned construction method for improving the bearing capacity of soft foundation soil layers also includes the following steps: a pile foundation depth confirmation step, which determines the pile foundation depth based on the water content of the sample soil determined in the cement-soil strength test step, and determines the cement slurry mix ratio based on the organic matter content of the sample soil.

[0009] Furthermore, the above-mentioned construction method for improving the bearing capacity of soft foundation soil layers, in determining the pile foundation depth based on the moisture content of the sample soil determined in the cement-soil strength test step, includes: setting a first preset moisture content ω1, a second preset moisture content ω2, and a third preset moisture content ω3, where ω1 < ω2 < ω3; setting a first preset impact depth D1, a second preset impact depth D2, a third preset impact depth D3, and a fourth preset impact depth D4, where D1 < D2 < D3 < D4; and determining each preset impact depth as the depth during pile foundation construction based on the relationship between the moisture content Δω of the sample soil and each of the preset moisture contents.

[0010] Furthermore, in the above-mentioned construction method for improving the bearing capacity of soft foundation soil layers, when determining the preset impact depth as the depth for pile foundation construction based on the relationship between the water content Δω of the sample soil and each preset water content: when Δω < ω1, the first preset impact depth D1 is selected as the depth for pile foundation construction; when ω1 ≤ Δω < ω2, the second preset impact depth D2 is selected as the depth for pile foundation construction; when ω2 ≤ Δω < ω3, the third preset impact depth D3 is selected as the depth for pile foundation construction; when Δω ≥ ω3, the fourth preset impact depth D4 is selected as the depth for pile foundation construction.

[0011] Furthermore, in the above-mentioned construction method for improving the bearing capacity of soft foundation soil layers, after selecting the i-th preset impact depth Di as the depth during the pile foundation construction, i=1, 2, 3, 4, the number of times the shotcrete mixing sinking step and the shotcrete mixing lifting step are repeated in the repeated mixing step is determined according to the i-th preset impact depth Di.

[0012] Furthermore, in the above-mentioned construction method for improving the bearing capacity of soft foundation soil layers, the step of determining the number of repetitions of the shotcrete mixing and sinking step and the shotcrete mixing and lifting step in the repeated mixing step according to the i-th preset impact depth Di includes: setting a first preset number of repetitions f1, a second preset number of repetitions f, a third preset number of repetitions f3, a fourth preset number of repetitions f4, and a fifth preset number of repetitions f5, where f1 < f2 < f3 < f4 < f5; setting a first preset reference value for impact depth S1, a second preset reference value for impact depth S2, a third preset reference value for impact depth S3, and a fourth preset reference value for impact depth S4, where 0 < S1 < S2 < S3 < S4, and S1, S2, S3, and S4 are all positive integers; and determining the number of repetitions of the shotcrete mixing and sinking step and the shotcrete mixing and lifting step in the repeated mixing step based on the relationship between the selected i-th preset impact depth Di and each of the preset impact depth reference values.

[0013] Furthermore, in the above-mentioned construction method for improving the bearing capacity of soft foundation soil layers, when determining the number of repetitions of the shotcrete mixing and sinking step and the shotcrete mixing and lifting step in the repeated mixing step based on the relationship between the selected i-th preset impact depth Di and each of the preset impact depth reference values: when Di < S1, the first preset repetition number f1 is selected as the number of repetitions of the shotcrete mixing and sinking step and the shotcrete mixing and lifting step in the repeated mixing step; when S1 ≤ Di < S2, the second preset repetition number f2 is selected as the number of repetitions of the shotcrete mixing and sinking step in the repeated mixing step. The number of times the settling step and the shotcrete mixing and lifting step are repeated; when S2≤Di<S3, the third preset number of repetitions f3 is selected as the number of times the shotcrete mixing and settling step and the shotcrete mixing and lifting step are repeated in the repeated mixing step; when S3≤Di<S4, the fourth preset number of repetitions f4 is selected as the number of times the shotcrete mixing and settling step and the shotcrete mixing and lifting step are repeated in the repeated mixing step; when Di≥S4, the fifth preset number of repetitions f5 is selected as the number of times the shotcrete mixing and settling step and the shotcrete mixing and lifting step are repeated in the repeated mixing step.

[0014] The present invention provides a construction method for improving the bearing capacity of soft soil layers in foundations. As a construction method for replacing soft soil in the bearing layer of a foundation, it improves the bearing capacity of the foundation by mixing the solidifying agent and the soil together through deep mixing. This method maximizes the use of the original soil, minimizes disturbance to the surrounding soil, and solves the problems of complex treatment methods and long construction cycles in existing soft soil areas. It is flexible in use, and suitable solidifying agents can be selected for mixing according to different soil types and design requirements. During construction, there is less vibration, noise, and pollution, which can be carried out in urban areas and areas with dense surrounding buildings. After reinforcement, the density of the soil remains basically unchanged, and it will not cause significant settlement to the underlying soft soil layer. Attached Figure Description

[0015] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0016] Figure 1 This is a schematic flowchart of a construction method for improving the bearing capacity of soft foundation soil layers provided in an embodiment of the present invention.

[0017] Figure 2 A flowchart illustrating a construction method for improving the bearing capacity of soft foundation soil layers, provided in an embodiment of the present invention.

[0018] Figure 3 This is a schematic diagram of the construction method for improving the bearing capacity of soft foundation soil layers provided in an embodiment of the present invention;

[0019] Figure 4 This is a schematic diagram of the construction method for improving the bearing capacity of soft foundation soil layers provided in an embodiment of the present invention.

[0020] Figure 5 This is another schematic diagram of the construction method for improving the bearing capacity of soft foundation soil layers provided in an embodiment of the present invention;

[0021] Figure 6 Another flowchart of a construction method for improving the bearing capacity of soft foundation soil layers provided in an embodiment of the present invention. Detailed Implementation

[0022] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the disclosure to those skilled in the art. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0023] See Figures 1 to 2 The figure illustrates a preferred flow of a construction method for improving the bearing capacity of soft foundation soil layers provided by an embodiment of the present invention. As shown, the construction method includes the following steps:

[0024] Step S1 of the cement-soil strength test involves selecting the soil layer location, taking out soil samples, and conducting tests on the physical properties, water content, organic matter content, and cement-soil mix proportion strength of the soft soil to verify whether the properties of the soft soil and the strength of the cement-soil mixing piles meet the requirements.

[0025] Specifically, before construction, the geological conditions of each construction site should be thoroughly understood, representative soil layers should be selected, and a certain number of soil samples should be drilled to conduct necessary tests on the physical properties, water content, organic matter content, and cement-soil mix ratio strength of the soft soil. This is to verify whether the properties of the soft soil and the designed strength of the cement-soil mixing piles can meet the requirements. All test results should be submitted to the client and supervising engineer in the form of a written report for review and verification in a timely manner. If the results do not conform to the original geological drilling data and design requirements, the designer should be informed.

[0026] Measurement and layout step S2: Measurement and layout are carried out at the coating location.

[0027] Specifically, the guide points and leveling points handed over by the design unit shall be reviewed by the client and supervising engineer before construction, and used only after confirmation that they are correct. Surveyors shall conduct surveying and setting out work related to the location of the mixing piles, the original ground elevation, and the borehole elevation according to the construction design drawings. Surveying and setting out records and pile layout diagrams shall be submitted to the client and supervising engineer for review and random checks, and a surveying and setting out inspection report shall be filled out and signed by the client and supervising engineer after review and confirmation that they are correct.

[0028] Step S3: Position and straighten the mixer, align the mixer's drilling rig with the pile position, and level the mixer's pile driver body to ensure the verticality of the pile.

[0029] Specifically, after assembling the mixer, professional personnel should inspect the connections of all parts of the main unit, as well as the installation and trial adjustment of the hydraulic, electrical, and shotcrete systems, and the sealing of the pipelines to ensure they are normal. Necessary adjustments and tightening should be made, and operation can only commence after any abnormalities have been eliminated. After the ash hopper is filled with material, the inlet should be sealed. When installing the drilling rig, align it with the pile position and level the rig body to ensure the verticality of the pile.

[0030] In step S4 of the shotcrete mixing and sinking process, cement slurry is prepared according to the preset mix ratio and poured into the storage tank. The storage grouting pump is connected to the mixing pile machine through the grouting hose. The grouting pump is started. After the grout is discharged from the mixing drill bit, the motor is started so that the mixer can mix and cut the soil along the guide frame and sink. Grouting is started at the same time as the mixing and sinking.

[0031] Specifically, cement slurry is prepared according to a preset mix ratio and poured into a storage tank. The grouting pump is connected to the mixing pile machine via a grout delivery hose. The grouting pump is started, and after the mixing drill bit produces slurry, the motor is started, causing the mixer to move along the guide frame, mixing and cutting the soil as it sinks. The sinking speed can be controlled by the motor's current monitoring meter, and the operating current should not exceed the rated value. Grout delivery begins simultaneously with the mixing and sinking process. The preset mix ratio can be determined based on actual conditions.

[0032] In step S5, after the deep mixer is lowered to the depth of the pile foundation and stops at the bottom of the hole for a preset time period of mixing and spraying, the mixing head is reversed and lifted from the pile end to mix and spray cement slurry until the preset pile top height is reached.

[0033] Specifically, after the deep mixing machine is driven to the pile foundation depth, it sinks to the preset pile bottom depth and remains at the bottom of the hole for a preset time period of mixing and spraying grout. Then, the mixing head is reversed from the pile end and lifted at a uniform speed to mix and spray cement grout until the preset pile top height is reached. The pile foundation depth, preset pile bottom depth, and preset pile top height can be determined based on actual conditions; the preset time period can be 30 seconds or other time periods, and this embodiment does not impose any limitations on them.

[0034] Repeat the mixing step S6, the shotcrete mixing and sinking step, and the shotcrete mixing and lifting step to complete the construction of one pile foundation.

[0035] Specifically, the grouting and mixing process is repeated to sink the pile to the preset pile bottom depth, and then the grouting and mixing process is repeated to raise the pile to the designed pile top height, achieving one repetition. The number of repetitions can be determined according to the actual situation, and no limit is made on it in this embodiment.

[0036] See Figure 3 This is another flowchart illustrating a construction method for improving the bearing capacity of soft foundation soil layers provided by an embodiment of the present invention. As shown in the figure, the construction method includes the following steps:

[0037] Step S1 of the cement-soil strength test involves selecting the soil layer location, taking out soil samples, and conducting tests on the physical properties, water content, organic matter content, and cement-soil mix proportion strength of the soft soil to verify whether the properties of the soft soil and the strength of the cement-soil mixing piles meet the requirements.

[0038] Measurement and layout step S2: Measurement and layout are carried out at the coating location.

[0039] Step S3: Position and straighten the mixer, align the mixer's drilling rig with the pile position, and level the mixer's pile driver body to ensure the verticality of the pile.

[0040] In step S4 of the shotcrete mixing and sinking process, cement slurry is prepared according to the preset mix ratio and poured into the storage tank. The storage grouting pump is connected to the mixing pile machine through the grouting hose. The grouting pump is started. After the grout is discharged from the mixing drill bit, the motor is started so that the mixer can mix and cut the soil along the guide frame and sink. Grouting is started at the same time as the mixing and sinking.

[0041] In step S5, after the deep mixer is lowered to the depth of the pile foundation and stops at the bottom of the hole for a preset time period of mixing and spraying, the mixing head is reversed and lifted from the pile end to mix and spray cement slurry until the preset pile top height is reached.

[0042] Repeat the mixing step S6, the shotcrete mixing and sinking step, and the shotcrete mixing and lifting step to complete the construction of one pile foundation.

[0043] In step S7, after the construction of one pile foundation is completed, turn off the mixer and clean the cement clods on the mixer blades and the cement in the grouting nozzle. If construction is stopped, clean the cement in the storage tank, inject an appropriate amount of clean water into the storage tank, turn on the grout pump, and clean the residual cement slurry in the pipeline until it is clean.

[0044] Specifically, after the construction of one pile is completed, the mixer is turned off, and the cement clods on the mixer blades and the cement in the grouting nozzle are cleaned. If it is necessary to stop construction, the cement in the storage tank must be cleaned out. An appropriate amount of clean water can be injected into the storage tank, the grout pump can be turned on, and all residual cement slurry in the pipelines can be cleaned until it is clean.

[0045] See Figure 4 This is another flowchart illustrating a construction method for improving the bearing capacity of soft foundation soil layers provided in an embodiment of the present invention. As shown in the figure, the construction method includes the following steps:

[0046] Step S1 of the cement-soil strength test involves selecting the soil layer location, taking out soil samples, and conducting tests on the physical properties, water content, organic matter content, and cement-soil mix proportion strength of the soft soil to verify whether the properties of the soft soil and the strength of the cement-soil mixing piles meet the requirements.

[0047] Measurement and layout step S2: Measurement and layout are carried out at the coating location.

[0048] Step S3: Position and straighten the mixer, align the mixer's drilling rig with the pile position, and level the mixer's pile driver body to ensure the verticality of the pile.

[0049] In step S4 of the shotcrete mixing and sinking process, cement slurry is prepared according to the preset mix ratio and poured into the storage tank. The storage grouting pump is connected to the mixing pile machine through the grouting hose. The grouting pump is started. After the grout is discharged from the mixing drill bit, the motor is started so that the mixer can mix and cut the soil along the guide frame and sink. Grouting is started at the same time as the mixing and sinking.

[0050] In step S5, after the deep mixer is lowered to the depth of the pile foundation and stops at the bottom of the hole for a preset time period of mixing and spraying, the mixing head is reversed and lifted from the pile end to mix and spray cement slurry until the preset pile top height is reached.

[0051] Repeat the mixing step S6, the shotcrete mixing and sinking step, and the shotcrete mixing and lifting step to complete the construction of one pile foundation.

[0052] In step S7, after the construction of one pile foundation is completed, turn off the mixer and clean the cement clods on the mixer blades and the cement in the grouting nozzle. If construction is stopped, clean the cement in the storage tank, inject an appropriate amount of clean water into the storage tank, turn on the grout pump, and clean the residual cement slurry in the pipeline until it is clean.

[0053] In step S8, the mixer is moved to the next pile foundation. The mixer placement and straightening steps are repeated until the mixing steps are repeated to perform deep mixing on the current pile foundation.

[0054] Specifically, the mixer is moved to the next pile, and the above steps are repeated until the construction of the next pile is completed.

[0055] See Figure 5 This is another flowchart illustrating a construction method for improving the bearing capacity of soft foundation soil layers provided in an embodiment of the present invention. As shown in the figure, the construction method includes the following steps:

[0056] Step S1 of the cement-soil strength test involves selecting the soil layer location, taking out soil samples, and conducting tests on the physical properties, water content, organic matter content, and cement-soil mix proportion strength of the soft soil to verify whether the properties of the soft soil and the strength of the cement-soil mixing piles meet the requirements.

[0057] Site leveling step S9 involves leveling the selected soil layer.

[0058] Measurement and layout step S2: Measurement and layout are carried out at the coating location.

[0059] Step S3: Position and straighten the mixer, align the mixer's drilling rig with the pile position, and level the mixer's pile driver body to ensure the verticality of the pile.

[0060] In step S4 of the shotcrete mixing and sinking process, cement slurry is prepared according to the preset mix ratio and poured into the storage tank. The storage grouting pump is connected to the mixing pile machine through the grouting hose. The grouting pump is started. After the grout is discharged from the mixing drill bit, the motor is started so that the mixer can mix and cut the soil along the guide frame and sink. Grouting is started at the same time as the mixing and sinking.

[0061] In step S5, after the deep mixer is lowered to the depth of the pile foundation and stops at the bottom of the hole for a preset time period of mixing and spraying, the mixing head is reversed and lifted from the pile end to mix and spray cement slurry until the preset pile top height is reached.

[0062] Repeat the mixing step S6, the shotcrete mixing and sinking step, and the shotcrete mixing and lifting step to complete the construction of one pile foundation.

[0063] In step S7, after the construction of one pile foundation is completed, turn off the mixer and clean the cement clods on the mixer blades and the cement in the grouting nozzle. If construction is stopped, clean the cement in the storage tank, inject an appropriate amount of clean water into the storage tank, turn on the grout pump, and clean the residual cement slurry in the pipeline until it is clean.

[0064] In step S8, the mixer is moved to the next pile foundation. The mixer placement and straightening steps are repeated until the mixing steps are repeated to perform deep mixing on the current pile foundation.

[0065] In other words, the process flow of this construction method for improving the bearing capacity of soft foundation soil layers is as follows: site leveling - surveying and setting out - pile driver positioning - shotcrete mixing and sinking - shotcrete mixing and lifting - repeated shotcrete mixing and sinking - repeated shotcrete mixing and lifting - completion. Alternatively, the process flow of this construction method for improving the bearing capacity of soft foundation soil layers is as follows: site leveling, surveying and setting out and verification - deep mixing machine positioning (bidirectional verticality control) - shotcrete mixing and sinking (preparation of cement slurry, slurry delivery) - shotcrete mixing and lifting - repeated shotcrete mixing and sinking - repeated shotcrete mixing and lifting of the orifice - shutting down the mixer and cleaning the blades - pile driver relocation - construction of the next pile - completion of all construction.

[0066] See Figure 6 This is another flowchart illustrating a construction method for improving the bearing capacity of soft foundation soil layers provided in an embodiment of the present invention. As shown in the figure, the construction method includes the following steps:

[0067] Step S1 of the cement-soil strength test involves selecting the soil layer location, taking out soil samples, and conducting tests on the physical properties, water content, organic matter content, and cement-soil mix proportion strength of the soft soil to verify whether the properties of the soft soil and the strength of the cement-soil mixing piles meet the requirements.

[0068] In step S10, the pile foundation depth is determined based on the water content of the sample soil determined in the cement-soil strength test step, and the cement grout mix ratio is determined based on the organic matter content of the sample soil.

[0069] Specifically, determining the pile foundation depth based on the water content of the sample soil determined in the cement-soil strength test step includes:

[0070] Set a first preset moisture content ω1, a second preset moisture content ω2, and a third preset moisture content ω3, where ω1 < ω2 < ω3;

[0071] Set a first preset impact depth D1, a second preset impact depth D2, a third preset impact depth D3 and a fourth preset impact depth D4, and D1 < D2 < D3 < D4;

[0072] Based on the relationship between the water content Δω of the sample soil and each of the preset water contents, the preset impact depth is determined as the depth during pile foundation construction.

[0073] Specifically, when determining the preset impact depth as the depth for pile foundation construction based on the relationship between the water content Δω of the sample soil and each preset water content:

[0074] When Δω<ω1, the first preset impact depth D1 is selected as the depth during the construction of the pile foundation;

[0075] When ω1≤Δω<ω2, the second preset impact depth D2 is selected as the depth during the construction of the pile foundation;

[0076] When ω2≤Δω<ω3, the third preset impact depth D3 is selected as the depth during the construction of the pile foundation;

[0077] When Δi≥ω3, the fourth preset impact depth D4 is selected as the depth during the construction of the pile foundation.

[0078] Preferably, after selecting the i-th preset impact depth Di as the depth during pile foundation construction, i = 1, 2, 3, 4, the number of repetitions of the shotcrete mixing sinking step and the shotcrete mixing lifting step are determined according to the i-th preset impact depth Di.

[0079] Specifically, determining the number of repetitions of the jet grouting and sinking step and the jet grouting and lifting step in the repeated stirring step based on the i-th preset impact depth Di includes:

[0080] Set a first preset number of repetitions f1, a second preset number of repetitions f, a third preset number of repetitions f3, a fourth preset number of repetitions f4, and a fifth preset number of repetitions f5, where f1 < f2 < f3 < f4 < f5;

[0081] Set a first impact depth preset reference value S1, a second impact depth preset reference value S2, a third impact depth preset reference value S3, and a fourth impact depth preset reference value S4, and 0 < S1 < S2 < S3 < S4, where S1, S2, S3, and S4 are all positive integers.

[0082] Based on the relationship between the selected i-th preset impact depth Di and each of the preset impact depth reference values, the number of times the sprayed agitation sinking step and the sprayed agitation lifting step are repeated in the repeated agitation step is determined.

[0083] In this embodiment, when determining the number of repetitions of the jet grouting and sinking step and the jet grouting and lifting step in the repeated stirring step based on the relationship between the selected i-th preset impact depth Di and each of the preset impact depth reference values:

[0084] When Di < S1, the first preset repetition number f1 is selected as the number of times the sprayed mixing sinking step and the sprayed mixing lifting step are repeated in the repeated mixing step.

[0085] When S1≤Di<S2, the second preset repetition number f2 is selected as the number of times the sprayed mixing sinking step and the sprayed mixing lifting step are repeated in the repeated mixing step;

[0086] When S2≤Di<S3, the third preset repetition number f3 is selected as the number of times the sprayed mixing sinking step and the sprayed mixing lifting step are repeated in the repeated mixing step;

[0087] When S3≤Di<S4, the fourth preset repetition number f4 is selected as the number of times the sprayed mixing sinking step and the sprayed mixing lifting step are repeated in the repeated mixing step.

[0088] When Di≥S4, the fifth preset repetition number f5 is selected as the number of times the sprayed mixing sinking step and the sprayed mixing lifting step are repeated in the repeated mixing step.

[0089] Measurement and layout step S2: Measurement and layout are performed at the coating location;

[0090] Step S3: Position and straighten the mixer, align the mixer's drilling rig with the pile position, and level the mixer's pile driver body to ensure the verticality of the pile.

[0091] In step S4 of the shotcrete mixing and sinking process, cement slurry is prepared according to the preset mix ratio and poured into the storage tank. The storage grouting pump is connected to the mixing pile machine through the grouting hose. The grouting pump is started. After the grout is discharged from the mixing drill bit, the motor is started so that the mixer can mix and cut the soil along the guide frame and sink. Grouting is started at the same time as the mixing and sinking.

[0092] In step S5, after the deep mixer is lowered to the depth of the pile foundation and stops at the bottom of the hole for a preset time period of mixing and spraying, the mixing head is reversed and lifted from the pile end to mix and spray cement slurry until the preset pile top height is reached.

[0093] Repeat the mixing step S6, the shotcrete mixing and sinking step, and the shotcrete mixing and lifting step to complete the construction of one pile foundation.

[0094] In step S7, after the construction of one pile foundation is completed, turn off the mixer and clean the cement clods on the mixer blades and the cement in the grouting nozzle. If construction is stopped, clean the cement in the storage tank, inject an appropriate amount of clean water into the storage tank, turn on the grout pump, and clean the residual cement slurry in the pipeline until it is clean.

[0095] In step S8, the mixer is moved to the next pile foundation. The mixer placement and straightening steps are repeated until the mixing steps are repeated to perform deep mixing on the current pile foundation.

[0096] In this embodiment, deep mixing is a method for reinforcing saturated cohesive soil foundations. It utilizes materials such as cement or lime as a hardening agent, and through specialized mixing machinery, forcibly mixes the soft soil and the hardening agent (slurry or powder) deep within the foundation. A series of physicochemical reactions between the hardening agent and the soft soil cause the soft soil to harden into a solidified body with integrity, water stability, and a certain strength, thereby improving the foundation strength.

[0097] In this embodiment, the pile foundation can be reinforced using block, column, or grid-like reinforcement methods.

[0098] In summary, the construction method for improving the bearing capacity of soft soil layers provided in this embodiment, as a construction method for replacing the weak soil bearing layer of the foundation, improves the bearing capacity of the foundation by mixing the solidifying agent and the soil together through deep mixing. It maximizes the use of the original soil, minimizes disturbance to the surrounding soil, and solves the problems of complex treatment methods and long construction cycles in existing soft soil areas. It is flexible in use, and suitable solidifying agents can be selected for mixing according to different soil types and design requirements. During construction, there is less vibration, noise, and pollution, which can be carried out in urban areas and areas with dense surrounding buildings. After reinforcement, the density of the soil remains basically unchanged, and it will not cause significant settlement to the weak underlying layer.

[0099] It should be noted that in the description of this invention, the terms "upper", "lower", "left", "right", "inner", "outer", etc., which indicate directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0100] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0101] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A construction method for improving the bearing capacity of soft foundation soil layers, characterized in that, Includes the following steps: The cement-soil strength test procedure involves selecting the soil layer location, taking out soil samples, and conducting tests on the physical properties, water content, organic matter content, and cement-soil mix proportion strength of the soft soil to verify whether the properties of the soft soil and the strength of the cement-soil mixing piles meet the requirements. The surveying and setting-out procedure involves surveying and setting out the locations of soil layers. The steps for positioning and straightening the mixer are as follows: Align the mixer's drilling rig with the pile position and level the mixer's pile driver body to ensure the verticality of the pile. In the shotcrete mixing and sinking step, cement slurry is prepared according to the preset mix ratio and poured into the storage tank. The storage grouting pump is connected to the mixing pile machine through the grouting hose. The grouting pump is started. After the mixing drill bit produces slurry, the motor is started so that the mixer can mix and cut the soil along the guide frame and sink. Grouting is started at the same time as mixing and sinking. In the shotcrete mixing and lifting step, after the deep mixer is shotcrete down to the depth of the pile foundation and stays at the bottom of the hole for a preset time period of mixing and spraying, the mixing head is reversed and lifted from the pile end to mix and spray cement slurry until the preset pile top height is reached. Repeat the mixing step, repeat the shotcrete mixing and sinking step and the shotcrete mixing and lifting step to complete the construction of one pile foundation; Following the repeated stirring step, the following steps are also included: Cleaning steps: After the construction of one pile foundation is completed, turn off the mixer and clean the cement and soil clods on the mixer blades and the cement in the grouting nozzle; if construction is stopped, clean the cement in the storage tank, inject an appropriate amount of clean water into the storage tank, turn on the grout pump, and clean the residual cement slurry in the pipeline until it is clean. Following the cleaning step, the following steps are also included: The mixer relocation step involves moving the mixer to the next pile foundation and repeating the mixer placement and straightening steps until the repeated mixing step is completed, so as to perform deep mixing on the current pile foundation. Before the measurement and layout step, the following steps are also included: The site leveling step involves leveling the selected soil layer. It also includes the following steps: The pile foundation depth confirmation step determines the pile foundation depth based on the water content of the sample soil determined in the cement-soil strength test step, and determines the cement grout mix ratio based on the organic matter content of the sample soil. Determining the pile foundation depth based on the water content of the sample soil determined in the cement-soil strength test procedure includes: Set a first preset moisture content ω1, a second preset moisture content ω2, and a third preset moisture content ω3, where ω1 < ω2 < ω3; Set a first preset impact depth D1, a second preset impact depth D2, a third preset impact depth D3 and a fourth preset impact depth D4, and D1 < D2 < D3 < D4; Based on the relationship between the water content Δω of the sample soil and each of the preset water contents, each preset impact depth is determined as the depth during pile foundation construction. When determining the preset impact depth as the depth for pile foundation construction based on the relationship between the water content Δω of the sample soil and each preset water content: When Δω<ω1, the first preset impact depth D1 is selected as the depth during the construction of the pile foundation; When ω1≤Δω<ω2, the second preset impact depth D2 is selected as the depth during the construction of the pile foundation; When ω2≤Δω<ω3, the third preset impact depth D3 is selected as the depth during the construction of the pile foundation; When Δi≥ω3, the fourth preset impact depth D4 is selected as the depth during the construction of the pile foundation; After selecting the i-th preset impact depth Di as the depth during the pile foundation construction, i=1, 2, 3, 4, the number of times the shotcrete mixing sinking step and the shotcrete mixing lifting step are repeated in the repeated mixing step is determined according to the i-th preset impact depth Di. The step of determining the number of repetitions of the jet grouting and sinking step and the jet grouting and lifting step in the repeated stirring step based on the i-th preset impact depth Di includes: Set a first preset number of repetitions f1, a second preset number of repetitions f2, a third preset number of repetitions f3, a fourth preset number of repetitions f4, and a fifth preset number of repetitions f5, where f1 < f2 < f3 < f4 < f5; Set a first impact depth preset reference value S1, a second impact depth preset reference value S2, a third impact depth preset reference value S3, and a fourth impact depth preset reference value S4, and 0 < S1 < S2 < S3 < S4, where S1, S2, S3, and S4 are all positive integers. Based on the relationship between the selected i-th preset impact depth Di and each of the preset impact depth reference values, the number of times the sprayed slurry mixing sinking step and the sprayed slurry mixing lifting step are repeated in the repeated mixing step is determined. When determining the number of repetitions of the jet grouting and sinking step and the jet grouting and lifting step in the repeated stirring step based on the relationship between the selected i-th preset impact depth Di and each of the preset impact depth reference values: When Di < S1, the first preset repetition number f1 is selected as the number of times the sprayed mixing sinking step and the sprayed mixing lifting step are repeated in the repeated mixing step. When S1≤Di<S2, the second preset repetition number f2 is selected as the number of times the sprayed mixing sinking step and the sprayed mixing lifting step are repeated in the repeated mixing step; When S2≤Di<S3, the third preset repetition number f3 is selected as the number of times the sprayed mixing sinking step and the sprayed mixing lifting step are repeated in the repeated mixing step; When S3≤Di<S4, the fourth preset repetition number f4 is selected as the number of times the sprayed mixing sinking step and the sprayed mixing lifting step are repeated in the repeated mixing step. When Di≥S4, the fifth preset repetition number f5 is selected as the number of times the sprayed mixing sinking step and the sprayed mixing lifting step are repeated in the repeated mixing step.

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