Variable strength variable cross-section cement-soil slurry jet pile and drilling, stirring and jetting integrated construction method

Abstract

The application discloses a variable-strength variable-section cement-soil slurry jet pile and a drilling, stirring and jetting integrated construction method, and the variable-strength variable-section cement-soil slurry jet pile comprises a large-diameter section, a transition section and a small-diameter section, the large-diameter section and the small-diameter section are connected through the transition section, the large-diameter section is a variable-strength slurry jet pile, and the small-diameter section is a high-pressure splitting slurry jet pile. The transition section is an integrated pile formed through simultaneous construction of jetting and stirring and high-pressure splitting and stirring.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of road engineering and construction engineering foundation treatment, in particular to a drilling, stirring and jetting integrated pile construction equipment and construction method. BACKGROUND

[0002] Cement soil slurry jet pile is a commonly used foundation treatment method. The slurry jet pile technology forms a pile by drilling, jetting and stirring on site with a construction drill bit, has small engineering disturbance, rapid construction, relatively low cost, large foundation reinforcement depth, and is widely used in highway engineering and industrial and civil building foundation reinforcement engineering. However, in combination with a large number of engineering practices in recent years, some variable cross-section cement soil mixing piles are disclosed in the existing cement soil slurry jet pile. For example, a continuous variable diameter cement soil mixing pile forming method is disclosed in the patent with publication number CN102561332A. The variable diameter cement soil mixing pile proposed in this patent only proposes a construction variable cross-section pile transition section to relieve stress concentration, but does not strengthen the transition section. When the overlying load is large, there is still a high possibility of damage. And the same cement content is generally used for construction, the strength of the pile body does not change significantly, and the top of the pile is not strengthened, so the variable cross-section at a deeper place cannot effectively develop the bearing capacity.

[0003] In the patent with publication number CN102561332A, a continuous variable diameter cement soil mixing pile forming method is disclosed. This method uses hydraulic telescopic stirring blades to construct large diameter sections. The power of the construction machinery is higher when driving the large diameter blades, and higher power requirements are placed on the motor driving the pile machine to rotate, resulting in higher energy consumption, more complex equipment, and higher specifications for the pile machine, which limits the popularization and application. Moreover, the hydraulic telescopic blades may not be able to expand in hard clay strata, and the cement is difficult to fully mix with the soil without changing the cement jetting pressure, which can easily cause engineering quality problems. To ensure the cement dosage, increasing the cement dosage at the enlarged head position in a proportional manner will result in material waste, making it difficult to achieve the goal of reducing costs. SUMMARY

[0004] To solve the quality problems of conventional slurry jet pile forming and fully develop the bearing capacity of cement slurry jet pile, the present application provides a drilling, stirring and jetting integrated pile construction equipment and construction method, which effectively solves the quality problem of composite foundation mixing pile forming and reduces engineering costs.

[0005] The technical solution adopted by the present application is as follows:

[0006] In a first aspect, the present application provides a variable strength variable cross-section cement soil slurry jet pile, which includes a large diameter section, a transition section and a small diameter section. The large diameter section and the small diameter section are connected through the transition section. The large diameter section is a variable strength slurry jet pile, and the small diameter section is a high pressure splitting slurry jet pile. The transition section is an integrated pile formed by simultaneous construction of jetting and stirring and high pressure splitting stirring.

[0007] As a further technical solution, the transition section is a circular truncated cone pile body to avoid stress concentration when the small diameter transitions to the large diameter.

[0008] As a further technical solution, the outer ring of the variable strength slurry jet pile is high-strength cement soil, and the inner ring is low-strength cement soil.

[0009] As a further technical solution, the unconfined compressive strength of the high-strength cement soil is 7-10 MPa.

[0010] As a further technical solution, the unconfined compressive strength of the low-strength cement soil is 3-5 MPa.

[0011] In a second aspect, based on the above-mentioned variable strength and variable cross-section cement soil slurry jet pile, the present application also provides a construction method, which uses a construction drill bit, the construction drill bit comprises a drill rod, a jet stirring blade is arranged on the upper part of the drill rod, a slurry jet pipeline is arranged in the jet stirring blade, and a jet port is arranged at the end of the jet stirring blade; a lower stirring blade is arranged at the lower part of the drill rod, a first group of jet holes is arranged above the connection position of the jet stirring blade and the drill rod, and a second group of jet holes is arranged on the drill rod section between the jet stirring blade and the stirring blade; the construction method is as follows:

[0012] The large-diameter section is constructed, the jet port of the jet stirring blade is opened, the jet stirring blade and the lower stirring blade are jet stirred and constructed, the outer ring of the pile body formed by the jet stirring blade is high-strength cement soil formed by slurry jetting to the soil, the inner ring is low-strength cement soil formed by mixing and stirring the cement return slurry and the soil, and a variable strength slurry jet pile with high strength on the outside and low strength on the inside is formed;

[0013] The transition section is constructed, the first group of jet holes, the second group of jet holes, and the jet port of the jet stirring blade are opened, and jet stirring construction and high-pressure splitting stirring construction are simultaneously performed;

[0014] The small-diameter section is constructed, the first group of jet holes and the second group of jet holes on the drill rod are opened, and high-pressure splitting stirring construction is performed in combination with the lower stirring blade.

[0015] As a further technical solution, all jet holes are also opened within the depth range set at the top of the pile, the lifting speed is 20 cm / min, and the top of the pile is capped.

[0016] As a further technical solution, the upper large-diameter section uses a cement content of 10%-20%, 20 MPa-25 MPa of jetting pressure is used in relatively hard cohesive soil layers, 10 MPa-15 MPa of jetting pressure is used in relatively loose silty soil layers, and the lifting speed is 30 cm / min-40 cm / min.

[0017] As a further technical solution, the lower small-diameter section adopts high-pressure splitting mixing process, adopts 15% cement content, adopts 15MPa-20MPa spraying pressure in relatively hard cohesive soil, adopts 10MPa-15MPa spraying pressure in relatively loose silty soil layer, and the lifting speed is 100cm / min-110cm / min.

[0018] As a further technical solution, the transition section selects the pressure according to the soil quality, adopts 15MPa-20MPa spraying pressure in relatively hard cohesive soil, adopts 10MPa-15MPa spraying pressure in relatively loose silty soil layer, and the lifting speed is linearly slowed down from 100-110cm / min to 30cm / min-40cm / min, and the length of the transition section is 0.5-1.0m.

[0019] As a further technical solution, the transition section selects the pressure according to the soil quality, adopts 15MPa-20MPa spraying pressure in relatively hard cohesive soil, adopts 10MPa-15MPa spraying pressure in relatively loose silty soil layer, and the lifting speed is linearly slowed down from 100cm / min-110cm / min to 3cm / min 0-40cm / min, and the length of the transition section is 0.5-1.0m.

[0020] The beneficial effects of the present application are as follows:

[0021] 1. The drilling, mixing and spraying integrated construction method proposed in the present application solves the problem of difficult mixing of the slurry spraying pile in relatively hard cohesive soil by the methods of spraying mixing and high-pressure splitting mixing.

[0022] 2. The variable strength and variable cross-section cement-soil slurry spraying pile is formed after fully analyzing the stress characteristics of the cement-soil slurry spraying pile, which includes a large-diameter section, a transition section and a small-diameter section, the large-diameter section and the small-diameter section are connected through the transition section, the large-diameter section is a variable strength slurry spraying pile, which can reduce the cement consumption and appropriately improve the construction efficiency while ensuring the formation of a large-diameter pile, and the further reinforced pile top ensures the quality of the pile top and increases the overall bearing capacity of the pile body, the construction efficiency of the high-pressure splitting slurry spraying pile of the small-diameter section is higher than that of the traditional slurry spraying pile, the transition section is an integrated pile formed by simultaneous construction of spraying mixing and high-pressure splitting mixing, and the circular truncated cone-shaped high-strength transition section avoids the premature damage caused by stress concentration at the variable cross-section.

[0023] 3. The present application is expected to reduce the engineering reinforcement cost by more than 30%, improve the construction efficiency by more than one time, greatly reduce the maintenance and repair costs caused by the quality problems of foundation treatment after construction, and ensure the safe operation of the overlying structures. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1It is a construction drill bit of a construction drill stirring and jetting integrated pile;

[0025] Figure 2 It is a construction drill bit of a construction drill stirring and jetting integrated pile;

[0026] Figure 3 It is a schematic diagram of the variable strength variable cross-section cement soil jet pile proposed by the present application;

[0027] Figure 4 It is a schematic diagram of the cross-section of the large-diameter section;

[0028] In the figure: 1. Upper jetting hole, 2. Upper jetting stirring blade, 3. Stirring and jetting port, 4. Lower jetting hole, 5. Lower stirring blade, 6. Outer high-strength cement soil, 7. Inner low-strength cement soil, 8. Capping section, 9. Large-diameter section, 10. Transition section, 11. Small-diameter section. Specific implementation method

[0029] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present application. Unless otherwise indicated, all technical and scientific terms used in the present application have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs.

[0030] It should be noted that the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the present application explicitly indicates otherwise, the singular form is also intended to include the plural form, and furthermore, it should be understood that when the terms "comprise" and / or "include" are used in the present specification, they indicate the presence of a feature, step, operation, device, component and / or combination thereof;

[0031] As described in the background section, the variable cross-section cement soil mixing pile disclosed in the prior art is constructed by a large-diameter (more than 50 cm) stirring blade, which results in higher power of the construction machinery when driving the large-diameter blade, and higher requirements for the motor power driving the pile machine to rotate, resulting in higher energy consumption, more complex equipment and higher requirements for the pile machine specifications, which limits the popularization and application. In order to ensure the cement dosage, the cement dosage is increased proportionally at the enlarged head position, while the main stress concentration position of the variable cross-section pile is the top of the pile and the transition section of the variable cross-section, and there is no need to increase the cement dosage proportionally at the large-diameter variable cross-section. The cement is difficult to fully mix with the soil, which easily causes a lot of engineering waste; the cement content of the pile formed by increasing the cement content for jetting and stirring construction is too high, and the strength is too large, which cannot fully play its strength, resulting in material waste; the cement slurry jet pile mainly relies on the side friction resistance for bearing, and the pile diameter of the existing mixing pile is mostly 50 cm, the pile-soil contact area is small, and the side friction resistance cannot be fully utilized.

[0032] AsFigure 3 As shown in the schematic diagram of the variable cross-section pile disclosed in the embodiment, the upper part is a large-diameter variable strength jet grouting pile, the lower part is a small-diameter high-pressure split jet grouting pile, and the middle part is a transition section; the transition section is an integrated pile formed by simultaneous jet mixing and high-pressure split mixing construction; the transition section is a circular truncated cone pile body constructed to avoid stress concentration when the small-diameter gradually transitions to the large-diameter. The variable strength variable cross-section cement-soil jet grouting pile proposed in the present application is the result of a full analysis of the stress characteristics of the cement-soil jet grouting pile; first, the difficult mixing of the jet grouting pile in hard clay and the poor pile quality problem are solved by the drill-mix-jet integrated construction method. On this basis, since the bearing ratio of the lower pile body is small, the lifting speed of the lower small-diameter pile body is accelerated, the cement consumption is saved, and the construction efficiency is improved; when the construction reaches the variable cross-section, a circular truncated cone transition section is provided to avoid premature damage caused by stress concentration at the variable cross-section; the construction speed of 30-40 cm / min is between the high-pressure rotary jet grouting pile and the jet grouting pile, and the variable strength pile formed by the jet mixing blade can reduce the cement consumption and appropriately accelerate the lifting speed while ensuring the formation of a large-diameter pile. By opening all the jet grouting holes at the top of the pile and reducing the lifting speed, the top of the pile is further reinforced to ensure the quality of the pile top and increase the overall bearing capacity of the pile body. The variable strength variable cross-section cement-soil jet grouting pile has reliable pile quality, and is expected to reduce the engineering reinforcement cost by more than 30% and improve the construction efficiency by more than one time.

[0033] As a further technical solution, the outer ring of the variable strength jet grouting pile is high-strength cement soil, and the inner ring is low-strength cement soil. The unconfined compressive strength of the high-strength cement soil is 7-10 MPa. The unconfined compressive strength of the low-strength cement soil is 3-5 MPa.

[0034] When the variable cross-section is constructed, all the jet holes and jet openings within a range of 50 cm of the transition section are simultaneously opened, and jet mixing construction and high-pressure split mixing construction are simultaneously performed to ensure the construction quality of the transition section; when the variable diameter jet grouting pile is constructed, jet mixing rods are used for jet mixing construction when the upper pile body is constructed, and four jet holes on the drill rod are used for jet grouting pile construction when the lower small-diameter pile body is constructed.

[0035] As shown in Figure 4 , it is a cross-sectional view of the large-diameter variable strength jet grouting pile in Figure 3 , the outer side of the pile body is high-strength cement soil formed by jetting slurry into the soil, and the inner side is low-strength cement soil formed by mixing cement slurry with the soil, forming a jet grouting composite pile with high strength on the outside and low strength on the inside.

[0036] The pile body construction disclosed in the embodiment uses a drill bit as shown in Figure 1 , Figure 2As shown, including upper jetting hole 1, upper jetting stirring blade 2, stirring jetting port 3, lower jetting hole 4, lower stirring blade 5. The jetting hole of upper jetting stirring blade 2 is located at the end of stirring blade, for jetting high-pressure slurry to construct large-diameter pile, at the same time, the upper and lower stirring blades are used for stirring cement slurry and soil uniformly; the upper and lower jetting holes are used for the construction of high-pressure splitting slurry jetting pile; the upper jetting hole 1 is above the position where the jetting stirring blade is connected with the drill rod, and the lower jetting hole 4 is arranged on the drill rod section between the jetting stirring blade and the stirring blade. The above-mentioned upper jetting hole 1 includes two, and the two upper jetting holes 1 are oppositely arranged; the above-mentioned lower jetting hole 4 includes two, and the two lower jetting holes 4 are oppositely arranged.

[0037] The lower stirring blade in the above construction project assists in stirring construction with the rotation of the drill bit;

[0038] 1) Pile machine positioning, the position of the pile machine is determined according to the construction requirements on site.

[0039] 2) Before formal construction, soil layer detection and on-site pile test are carried out in typical stratum, and the selection of construction pile type is carried out according to different soil layer properties and bearing capacity requirements.

[0040] 3) Construction: in the lifting process, the jetting stirring process is used to construct the upper large-diameter pile body, the cement content of 10-20% is used, the jetting pressure of 20Mpa-25MPa is used in the relatively hard cohesive soil layer, the jetting pressure of 10Mpa-15MPa is used in the relatively loose silty soil layer, and the lifting speed of 20cm / min is used; the high-pressure splitting stirring process is used to construct the lower small-diameter pile body, the cement content of 15% is used, the jetting pressure of 15Mpa-20MPa is used in the relatively hard cohesive soil, the jetting pressure of 10Mpa-15MPa is used in the relatively loose silty soil layer, and the lifting speed of 100cm / min-110cm / min is used. All jetting ports in the range of 50cm of the variable-diameter connecting section are opened, and jetting stirring construction and high-pressure splitting stirring construction are carried out at the same time, so as to ensure the construction quality of the connecting section, all jetting holes in the range of 50cm depth of the pile top are also opened, the lifting speed is reduced to 20cm / min, and the pile top sealing treatment is carried out.

[0041] The present application greatly reduces the maintenance and repair costs caused by foundation treatment quality problems after construction, and ensures the safe operation of the overlying structure.

[0042] The variable strength variable section cement soil slurry jet pile in the embodiment is formed after fully analyzing stress characteristics of the cement soil slurry jet pile, and includes a large diameter section, a transition section and a small diameter section, the large diameter section and the small diameter section are connected through the transition section; the large diameter section is a variable strength slurry jet pile, which can reduce the cement consumption and appropriately improve the construction efficiency on the basis of forming a large diameter pile; the further reinforced pile top guarantees the quality of the pile top and increases the overall bearing capacity of the pile body; the construction efficiency of the small diameter section high pressure splitting slurry jet pile is higher than that of the traditional slurry jet pile; the transition section is an integrated pile formed by simultaneous construction of jet mixing and high pressure splitting mixing, and the circular truncated cone shaped high strength transition section avoids early damage caused by stress concentration at the variable section.

[0043] Finally, it should be noted that the relationship terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations.

[0044] The above only describes the preferred embodiments of the present application and is not used to limit the present application. The present application can have various modifications and changes for those skilled in the art. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A construction method for variable strength and variable cross-section cement-soil grouting piles, characterized in that, The variable-strength, variable-section cement-soil grouting pile includes a large-diameter section, a transition section, and a small-diameter section, with the large-diameter section and the small-diameter section connected by a transition section; the large-diameter section is a variable-strength grouting pile, and the small-diameter section is a high-pressure fracturing grouting pile; the transition section is an integral pile formed by simultaneous jet mixing and high-pressure fracturing mixing. The variable strength and variable cross-section cement-soil grouting pile is manufactured by the following construction method: a construction drill bit is used, including a drill rod, a jet mixing blade is set on the upper part of the drill rod, a grout jetting pipe is set inside the jet mixing blade, and a jetting port is set at the end of the jet mixing blade; a lower mixing blade is set on the lower part of the drill rod, a first set of grouting holes is set above the connection position between the jet mixing blade and the drill rod, and a second set of grouting holes is set on the drill rod section between the jet mixing blade and the mixing blade; When constructing large-diameter sections, the nozzles of the jet mixing blades are opened, and the jet mixing blades and the lower mixing blades carry out jet mixing construction. The outer ring of the pile formed by the jet mixing blades is high-strength cement soil formed by grout being sprayed onto the soil, and the inner ring is low-strength cement soil formed by cement grout returning and mixing with the soil, forming a variable-strength grout jet pile with high strength on the outside and low strength on the inside. During the construction transition section, the first set of grouting holes, the second set of grouting holes, and the nozzles of the jet mixing blades are opened to carry out jet mixing and high-pressure fracturing mixing construction simultaneously. When constructing small-diameter sections, open the first and second sets of grouting holes on the drill rod, and combine them with the lower mixing blades to carry out high-pressure splitting and mixing construction.

2. The construction method for a variable strength, variable cross-section cement-soil grouting pile as described in claim 1, characterized in that, The transition section is a frustum-shaped pile constructed to avoid stress concentration when transitioning from a small diameter to a large diameter.

3. The construction method for variable strength and variable cross-section cement-soil grouting piles as described in claim 1, characterized in that, The outer ring of the variable strength grouting pile is high-strength cement-soil, and the inner ring is low-strength cement-soil.

4. The construction method for variable strength and variable cross-section cement-soil grouting piles as described in claim 3, characterized in that, The unconfined compressive strength of the high-strength cement-soil is 7 MPa - 10 MPa.

5. The construction method for variable strength and variable cross-section cement-soil grouting piles as described in claim 3, characterized in that, The unconfined compressive strength of the low-strength cement-soil is 3 MPa - 5 MPa.

6. The construction method as described in claim 1, characterized in that: Within the depth range set at the top of the pile, the first and second sets of grouting holes on the drill rod are also opened to seal the top of the pile.

7. The construction method as described in claim 1, characterized in that: The large-diameter section uses 10%-20% cement content, and the grouting pressure is 20MPa-25MPa in harder cohesive soil layers and 10MPa-15MPa in looser silty soil layers, with a lifting speed of 30-40cm / min.

8. The construction method as described in claim 1, characterized in that: The lower small-diameter section adopts a high-pressure splitting and mixing process with a cement content of 15%. The grouting pressure is 15MPa-20MPa in harder cohesive soil and 10MPa-15MPa in looser silty soil. The lifting speed is 100-110cm / min.

9. The construction method as described in claim 1, characterized in that: The pressure for the transition section is selected according to the soil type. A grouting pressure of 15MPa-20MPa is used in harder cohesive soil, and a grouting pressure of 10MPa-15MPa is used in looser silty soil. The lifting speed is linearly reduced from 100-110cm / min to 30-40cm / min. The length of the transition section is 0.5 m-1.0 m.

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