Method and device for reducing side friction of cast-in-place pile by using lateral jet

Abstract

The application discloses a method and device for reducing side negative friction of a cast-in-place pile by utilizing lateral jet flow, and belongs to the technical field of friction reduction and control of geotechnical engineering. The method divides a jet flow control section in the length direction of the cast-in-place pile, takes the difference between the actual negative friction and the theoretical negative friction of the jet flow control section as the judgment value of the jet flow control, calculates the adjustment pressure value of the lateral jet flow by using the difference between the actual negative friction and the theoretical negative friction when the judgment value exceeds the judgment threshold, further obtains the adjustment jet flow speed, finally solves the jet flow trajectory equation to obtain the adjustment jet flow angle, and sprays in the corresponding jet flow control section according to the corresponding adjustment jet flow angle and adjustment jet flow speed to reduce the side negative friction of the cast-in-place pile. The application adopts the preset high-pressure water flow nozzle in the pile body to reduce the loss of the vertical bearing capacity of the pile body caused by the side negative friction of the pile, and avoids the problem that the negative friction increases again due to the post-construction settlement and coating falling of the traditional replacement cushion.

Description

Technical Field

[0001] This invention relates to the fields of pile foundation engineering, soft soil foundation treatment and geotechnical engineering friction reduction and control technology, and in particular to a method and device for reducing the side negative skin resistance of cast-in-place piles by using lateral jets. Background Technology

[0002] With the continuous advancement of global urbanization and the ongoing upgrading of major infrastructure construction, engineering projects have placed stringent requirements on the bearing capacity of deep foundations. Cast-in-place piles, as a type of deep foundation that requires no prefabrication and can be directly cast on-site, have become widely used in various engineering fields such as high-rise buildings, cross-river and cross-sea bridges, port terminals, and wind power foundations due to their outstanding advantages, including flexible adjustment of pile length and diameter, high single-pile bearing capacity, minimal construction disturbance, and adaptability to complex geological conditions.

[0003] The negative skin friction of piles in pile foundation construction is a significant issue. Currently, in pile foundation projects involving negative skin friction, most methods employed are pile coating and surrounding isolation piles to reduce its impact on the engineering piles. However, pile coating can adversely affect the surrounding water quality and should be used with caution in engineering projects; isolation piles cannot completely eliminate the impact of negative skin friction and increase the amount of construction work and prolong the construction period.

[0004] Therefore, developing a new type of pile foundation that can reduce negative skin friction has become an urgent need for the industry. The core objective of this new type of pile foundation is to reduce negative skin friction while simultaneously addressing changes in negative skin friction over long-term use, thus performing multiple reductions in negative skin friction, improving the bearing capacity of the pile foundation, enhancing economic efficiency, strengthening environmental protection, and ultimately overcoming the current problem of high pile foundation costs. Summary of the Invention

[0005] The technical problem this invention aims to solve is to address the shortcomings of the prior art by providing a method and apparatus for reducing the side negative skin friction of cast-in-place piles using lateral jetting. This method divides the length of the cast-in-place pile into jet control sections. The difference between the actual and theoretical negative skin friction of the control section is used as the judgment value for jet control. If the difference exceeds the judgment threshold, the adjustment pressure value of the lateral jet is calculated using the difference between the actual and theoretical negative skin friction, thereby obtaining the adjustment jet velocity. Finally, the jet trajectory equation is solved to obtain the adjustment jet angle. Jetting is then performed within the corresponding jet control section according to the corresponding adjustment jet angle and velocity to reduce the side negative skin friction of the cast-in-place pile.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] A method for reducing the negative skin friction of cast-in-place piles using lateral jetting includes the following:

[0008] The cast-in-place pile is divided into multiple jet control sections along its length; the jet trajectory equation is established within each jet control section.

[0009] The jet angle of the lateral jet within each jet control section is obtained by solving the jet trajectory equation;

[0010] Obtain the axial force at the beginning and end of each jet control section and calculate the measured negative frictional resistance corresponding to each jet control section;

[0011] Obtain the theoretical negative frictional resistance for each jet control section;

[0012] The measured negative skin friction and the theoretical negative skin friction of each jet control section are subtracted and the absolute value is calculated. If the result is greater than or equal to the negative skin friction difference threshold, the corresponding jet control section needs to use lateral jet to reduce the negative skin friction of the cast-in-place pile. If the result is less than the negative skin friction difference threshold, the corresponding jet control section does not need to use lateral jet to reduce the negative skin friction of the cast-in-place pile.

[0013] Furthermore, the jet trajectory equation is shown in the following formula:

[0014]

[0015] In the formula, It is the jet trajectory equation; It is the scouring radius of the jet; is the jet angle; g is the gravitational acceleration; k is the jet velocity coefficient; v is the jet velocity.

[0016] Furthermore, by solving the jet trajectory equation, the specific details of the lateral jet angle within each jet control section are as follows:

[0017] The initial jet velocity v1 within each jet control section is calculated using the following formula.

[0018]

[0019] In the formula, Q is the jet flow rate; d is the diameter of the jet nozzle;

[0020] Based on the initial jet velocity within each jet control segment Design scour radius The jet angle of the lateral jet within each jet control section is obtained by iteratively solving the jet trajectory equation, along with the distance L between adjacent nozzles, so that the scouring range of the lateral jet within each jet control section covers its jet control section without overlapping with the scouring range of adjacent lateral jets.

[0021] Furthermore, the calculation formula for the measured negative friction resistance is as follows:

[0022]

[0023] In the formula, It is the measured negative friction resistance; and These are the axial forces at the beginning and end of the jet control section, respectively. It refers to the spacing of the jet control sections; and These are the head position information and tail position information of the jet control section, respectively.

[0024] Furthermore, the formula for calculating the theoretical negative friction resistance is as follows:

[0025]

[0026] In the formula, K is the lateral earth pressure coefficient of the cast-in-place pile; δ is the friction angle of the cast-in-place pile-soil interface. is the effective unit weight of the soil lateral to the cast-in-place pile; z is the vertical depth of the calculation point from the soil surface.

[0027] Furthermore, the specific details regarding the use of lateral jets to reduce the negative skin friction of the cast-in-place piles in the jet control section are as follows:

[0028] The adjustment pressure value of the lateral jet is obtained by the absolute value of the difference between the measured negative friction resistance and the theoretical negative friction resistance.

[0029] The adjusted jet velocity of the lateral jet is calculated based on the adjusted pressure value;

[0030] The adjustment angle of the lateral jet is obtained by iteratively solving the jet trajectory equation based on the adjusted jet velocity, the designed scouring radius, and the distance L between adjacent nozzles.

[0031] The lateral jet within the controlled jet section is sprayed according to the adjusted jet angle and jet velocity to reduce the negative skin friction of the cast-in-place pile.

[0032] Furthermore, the formula for calculating the pressure value is as follows:

[0033]

[0034] In the formula, It is the adjustment pressure value of the jet control section; It is the critical initiation shear stress of the soil layer outside the jet control section of the cast-in-place pile body; It is the absolute value of the difference between the measured negative frictional resistance and the theoretical negative frictional resistance in the jet control section; It is the theoretical negative frictional resistance of the jet control section; T is the set flushing time.

[0035] Furthermore, the formula for calculating the jet velocity is adjusted as follows:

[0036]

[0037] In the formula, It involves adjusting the jet velocity in the jet control section; It is the fluid density of the lateral jet.

[0038] A device for reducing the negative skin friction of cast-in-place piles using lateral jetting includes an annular water pipe installed on each jetting control section of the cast-in-place pile. High-pressure water gun nozzles are mounted on the rotating shafts on both sides of the annular water pipe via nozzle connecting plates. A nozzle tail extension plate is provided at the tail of each high-pressure water gun nozzle. Inner wall elastic metal plates are provided on the inner walls of the cast-in-place piles on both sides of the annular water pipe. When the device sprays water according to the method for reducing the negative skin friction of cast-in-place piles using lateral jetting as described in any of claims 1-8, the high-pressure water gun nozzles, initially positioned, are pushed outwards by the high-pressure water flow until the nozzle tail extension plate jams the inner wall elastic metal plate.

[0039] Furthermore, the cast-in-place pile includes a concrete body, main reinforcement bars set in the concrete body, and stirrups wrapped around the outer periphery of the main reinforcement bars; the ring-shaped water pipe is connected to the main reinforcement bars through a water pipe connecting piece; a steel bar axial force gauge is installed on the main reinforcement bars at the beginning and end of each jet control section and connected to the steel bar axial force gauge wire.

[0040] The present invention has the following beneficial effects:

[0041] (1) The method in this invention divides the jet control section along the length of the cast-in-place pile. The difference between the actual negative skin friction and the theoretical negative skin friction of the jet control section is used as the judgment value of the jet control. After the judgment threshold is exceeded, the adjustment pressure value of the lateral jet is calculated by using the difference between the actual negative skin friction and the theoretical negative skin friction, and then the adjustment jet velocity is obtained. Finally, the jet trajectory equation is solved to obtain the adjustment jet angle. According to the corresponding adjustment jet angle and adjustment jet velocity, the jet is sprayed in the corresponding jet control section to reduce the side negative skin friction of the cast-in-place pile.

[0042] (2) The present invention uses a high-pressure water jet nozzle pre-installed inside the pile body. Compared with the traditional methods of controlling negative skin friction of the pile side, such as replacement cushion layer and pile body coating, the high-pressure water jet nozzle can directly act on the soil around the pile, which greatly saves construction materials and construction procedures. Under the same negative skin friction reduction effect, the precise flushing of the soil around the pile by the hydraulic jet can effectively weaken the bond between the soil around the pile and the pile body, reduce the loss of the vertical bearing capacity of the pile body due to the negative skin friction of the pile side, and avoid the problem of the negative skin friction increasing again due to the later settlement of the traditional replacement cushion layer and the peeling off of the coating. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the device for reducing negative skin friction of cast-in-place piles using lateral jetting in this embodiment.

[0044] Figure 2 yes Figure 1 The aa-direction sectional view in the middle.

[0045] Figure 3 yes Figure 1 The bb-direction section view.

[0046] Among them, 1-main reinforcement; 2-water pipe; 3-stirrup; 4-ring water pipe; 5-high-pressure water gun nozzle; 6-inner wall elastic metal sheet; 7-nozzle tail extension piece; 8-nozzle connecting piece; 9-rotating shaft; 10-reinforcing bar axial force gauge; 11-water pipe connecting piece; 12-concrete; 13-reinforcing bar axial force gauge wire. Detailed Implementation

[0047] The present invention will now be described in further detail with reference to the accompanying drawings and specific preferred embodiments.

[0048] In the description of this invention, it should be understood that the terms "left side," "right side," "upper part," "lower part," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention 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. "First," "second," etc., do not indicate the importance of the components, and therefore should not be construed as a limitation of this invention. The specific dimensions used in this embodiment are only for illustrating the technical solution and do not limit the scope of protection of this invention.

[0049] like Figures 1 to 3 As shown, a device for reducing negative skin friction of cast-in-place piles using lateral jetting includes annular water pipes 4 installed on each jetting control section of the cast-in-place pile. High-pressure water gun nozzles 5 are installed on the rotating shafts 9 on both sides of the annular water pipes 4 via nozzle connecting pieces 8. A nozzle tail extension piece 7 is provided at the tail of the high-pressure water gun nozzle 5. An inner wall elastic metal sheet 6 is provided on the inner wall of the cast-in-place pile on both sides of the annular water pipes 4. The cast-in-place pile includes a concrete body 12, main reinforcement 1 set in the concrete body 12, and stirrups 3 wrapped around the outer periphery of the main reinforcement 1. The annular water pipes 4 are connected to the main reinforcement via water pipe connecting pieces 11. All annular water pipes 4 are connected to a water pump via water supply pipes 2. A steel bar axial force gauge 10 is installed on the main reinforcement 1 at the beginning and end of each jetting control section and connected to a steel bar axial force gauge wire 13.

[0050] When the device sprays water according to the method of reducing the negative skin friction of the cast-in-place pile by using lateral jetting, the high-pressure water gun nozzle 5 in the initial state is pushed outward under the action of high-pressure water flow until the extension plate 7 at the tail of the nozzle gets stuck in the elastic metal plate 6 on the inner wall.

[0051] The method for reducing negative skin friction of cast-in-place piles using lateral jetting in this embodiment includes the following:

[0052] The cast-in-place pile is divided into multiple jet control sections along its length; the jet trajectory equation is established within each jet control section.

[0053] The jet trajectory equation is shown below.

[0054]

[0055] In the formula, L is the jet trajectory equation; It is the scouring radius of the jet; is the jet angle; g is the gravitational acceleration; k is the jet velocity coefficient; v is the jet velocity.

[0056] The jet angle of the lateral jet within each jet control section is obtained by solving the jet trajectory equation, as detailed below:

[0057] The initial jet velocity within each jet control section is calculated using the following formula. ,

[0058]

[0059] In the formula, Q is the jet flow rate; d is the diameter of the jet nozzle;

[0060] Based on the initial jet velocity within each jet control segment Design scour radius ,Pick , ( Given the pile diameter and the distance L between adjacent nozzles, the jet angle of the lateral jet within each jet control section is obtained by iteratively solving the jet trajectory equation, so that the scouring range of the lateral jet within each jet control section covers its jet control section without overlapping with the scouring range of adjacent lateral jets.

[0061] Obtain the axial force at the beginning and end of each jet control section and calculate the measured negative frictional resistance corresponding to each jet control section;

[0062] The formula for calculating the measured negative skin friction is as follows:

[0063]

[0064] In the formula, It is the measured negative friction resistance; and These are the axial forces at the beginning and end of the jet control section, respectively. It refers to the spacing of the jet control sections; and These are the head position information and tail position information of the jet control section, respectively.

[0065] Obtain the theoretical negative frictional resistance for each jet control section;

[0066] The formula for calculating theoretical negative skin friction is as follows:

[0067]

[0068] In the formula, K is the lateral earth pressure coefficient of the cast-in-place pile; δ is the friction angle of the cast-in-place pile-soil interface. is the effective unit weight of the soil lateral to the cast-in-place pile; z is the vertical depth of the calculation point from the soil surface.

[0069] The measured negative skin friction and theoretical negative skin friction of each jet control section are subtracted and the absolute value is calculated. If the result is greater than or equal to the negative skin friction difference threshold, the corresponding jet control section needs to use lateral jet to reduce the negative skin friction of the cast-in-place pile side.

[0070] The details are as follows:

[0071] The adjustment pressure value of the lateral jet is obtained by the absolute value of the difference between the measured negative friction resistance and the theoretical negative friction resistance.

[0072] The formula for calculating the adjustment pressure value is as follows:

[0073]

[0074] In the formula, It is the adjustment pressure value of the jet control section; It is the critical initiation shear stress of the soil layer outside the jet control section of the cast-in-place pile body; It is the absolute value of the difference between the measured negative frictional resistance and the theoretical negative frictional resistance in the jet control section; It is the theoretical negative frictional resistance of the jet control section; T is the set flushing time.

[0075] The adjusted jet velocity of the lateral jet is calculated based on the adjusted pressure value;

[0076] The formula for adjusting the jet velocity is as follows:

[0077]

[0078] In the formula, It involves adjusting the jet velocity in the jet control section; It is the fluid density of the lateral jet.

[0079] The adjustment angle of the lateral jet is obtained by iteratively solving the jet trajectory equation based on the adjusted jet velocity, the designed scouring radius, and the distance L between adjacent nozzles.

[0080] The lateral jet within the controlled jet section is sprayed according to the adjusted jet angle and jet velocity to reduce the negative skin friction of the cast-in-place pile.

[0081] If the result is less than the threshold value of negative skin friction difference, there is no need to use lateral jetting to reduce the negative skin friction of the cast-in-place pile side.

[0082] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various equivalent transformations can be made to the technical solutions of the present invention, and these equivalent transformations all fall within the protection scope of the present invention.

Claims

1. A method for reducing the negative skin friction of cast-in-place piles using lateral jetting, characterized in that, Includes the following: The cast-in-place pile is divided into multiple jet control sections along its length; the jet trajectory equation is established within each jet control section. The jet angle of the lateral jet within each jet control section is obtained by solving the jet trajectory equation; Obtain the axial force at the beginning and end of each jet control section and calculate the measured negative frictional resistance corresponding to each jet control section; Obtain the theoretical negative frictional resistance for each jet control section; The measured negative skin friction and the theoretical negative skin friction of each jet control section are subtracted and the absolute value is calculated. If the result is greater than or equal to the negative skin friction difference threshold, the corresponding jet control section needs to use lateral jet to reduce the negative skin friction of the cast-in-place pile. If the result is less than the negative skin friction difference threshold, the corresponding jet control section does not need to use lateral jet to reduce the negative skin friction of the cast-in-place pile.

2. The method for reducing the negative skin friction of a cast-in-place pile using lateral jetting according to claim 1, characterized in that: The jet trajectory equation is shown below. ； In the formula, L is the jet trajectory equation; It is the scouring radius of the jet; is the jet angle; g is the gravitational acceleration; k is the jet velocity coefficient; v is the jet velocity.

3. The method for reducing the negative skin friction of a cast-in-place pile using lateral jetting according to claim 2, characterized in that: The specific details of the lateral jet angle within each jet control section, obtained by solving the jet trajectory equation, are as follows: The initial jet velocity within each jet control section is calculated using the following formula. , ； In the formula, Q is the jet flow rate; d is the diameter of the jet nozzle; Based on the initial jet velocity v1 in each jet control section, the designed scouring radius... The jet angle of the lateral jet within each jet control section is obtained by iteratively solving the jet trajectory equation, along with the distance L between adjacent nozzles, so that the scouring range of the lateral jet within each jet control section covers its jet control section without overlapping with the scouring range of adjacent lateral jets.

4. The method for reducing the negative skin friction of a cast-in-place pile using lateral jetting according to claim 1, characterized in that: The formula for calculating the measured negative friction resistance is as follows: ； In the formula, It is the measured negative friction resistance; and These are the axial forces at the beginning and end of the jet control section, respectively. It refers to the spacing of the jet control sections; and These are the head position information and tail position information of the jet control section, respectively.

5. The method for reducing the negative skin friction of a cast-in-place pile using lateral jetting according to claim 1, characterized in that: The formula for calculating the theoretical negative friction resistance is as follows: ； In the formula, K is the lateral earth pressure coefficient of the cast-in-place pile; δ is the friction angle of the cast-in-place pile-soil interface; γ' is the effective unit weight of the soil on the side of the cast-in-place pile; and z is the vertical depth of the calculation point from the soil surface.

6. The method for reducing the negative skin friction of a cast-in-place pile using lateral jetting according to claim 3, characterized in that: The specific details of using lateral jets to reduce the negative skin friction of the cast-in-place piles in the jet control section are as follows: The adjustment pressure value of the lateral jet is obtained by the absolute value of the difference between the measured negative friction resistance and the theoretical negative friction resistance. The adjusted jet velocity of the lateral jet is calculated based on the adjusted pressure value; The adjustment angle of the lateral jet is obtained by iteratively solving the jet trajectory equation based on the adjusted jet velocity, the designed scouring radius, and the distance L between adjacent nozzles. The lateral jet within the controlled jet section is sprayed according to the adjusted jet angle and jet velocity to reduce the negative skin friction of the cast-in-place pile.

7. The device for regulating temperature and reducing negative skin friction of cast-in-place piles according to claim 6, characterized in that: The formula for calculating the adjustment pressure value is as follows: ； In the formula, It is the adjustment pressure value of the jet control section; It is the critical initiation shear stress of the soil layer outside the jet control section of the cast-in-place pile body; It is the absolute value of the difference between the measured negative frictional resistance and the theoretical negative frictional resistance in the jet control section; It is the theoretical negative frictional resistance of the jet control section; T is the set flushing time.

8. The device for regulating temperature and reducing negative skin friction of cast-in-place piles according to claim 6, characterized in that: The formula for adjusting the jet velocity is as follows: ； In the formula, It involves adjusting the jet velocity in the jet control section; It is the fluid density of the lateral jet.

9. An apparatus for carrying out the method of reducing negative skin friction of cast-in-place piles using lateral jetting as described in any one of claims 1-8, characterized in that: The device includes an annular water pipe installed on each jet control section of the cast-in-place pile. High-pressure water gun nozzles are installed on the rotating shafts on both sides of the annular water pipe via nozzle connecting plates. A nozzle tail extension plate is provided at the tail of the high-pressure water gun nozzle. An inner wall elastic metal plate is provided on the inner wall of the cast-in-place pile on both sides of the annular water pipe. When the device sprays water according to the method of reducing the negative friction of the cast-in-place pile by using lateral jet as described in any of claims 1-8, the high-pressure water gun nozzle in the initial state is pushed outward under the action of high-pressure water flow until the nozzle tail extension plate jams the inner wall elastic metal plate.

10. The device for reducing negative skin friction of cast-in-place piles using lateral jetting according to claim 9, characterized in that: The cast-in-place pile includes a concrete body, main reinforcement bars set in the concrete body, and stirrups wrapped around the outer perimeter of the main reinforcement bars; the ring-shaped water pipe is connected to the main reinforcement bars through a water pipe connecting piece; a steel bar axial force gauge is installed on the main reinforcement bars at the beginning and end of each jet control section and connected to the steel bar axial force gauge wire.

Images