Pile expanding method based on high-voltage pulse discharge and application thereof

Abstract

This invention discloses a pile expansion method and its application based on high-voltage pulse discharge, belonging to the field of pile foundation construction technology. This invention expands the borehole diameter at the desired pile location to the required pile diameter using high-voltage pulse discharge. During this process, the soil compression modulus and Poisson's ratio are measured in real time. Based on the relationship between discharge parameters, soil characteristic parameters, and the preset borehole diameter, the optimal discharge parameters for high-voltage pulse discharge are set. Specifically, these parameters include the number of discharges, the electrode gap distance for a single pulse discharge, and the discharge energy. This achieves coupled calculation of discharge parameters, shock wave load, and soil deformation. It can determine the corresponding optimal discharge parameters based on soil characteristic parameters and the required pile diameter, and can efficiently and accurately achieve the required pile diameter by controlling the high-voltage pulse discharge parameters under different soil environments.

Description

Technical Field

[0001] This invention belongs to the field of pile foundation construction technology, and more specifically, relates to a pile expansion method based on high-voltage pulse discharge and its application. Background Technology

[0002] Pile foundations are essential infrastructure and reinforcement tools for important projects such as bridges, tunnels, mines, and large buildings, playing a vital role in foundation construction. Traditional pile foundations are cylindrical or enlarged-base pile foundations, which have limited friction with the soil layer. Simply increasing the number of piles to improve strength would reduce economic efficiency and increase construction difficulty.

[0003] High-voltage pulse discharge is an emerging technology with advantages such as simple operation, no pollution, repeatability, and controllable energy. The discharge can generate a powerful shock wave (also known as a "shock wave") to achieve the effect of diameter expansion. By filling the initial borehole with mortar, cement grout, or other liquid media, the cumulative effect of multiple high-voltage pulse discharges at different heights can expand the diameter of the pile foundation at different heights, thereby constructing a continuous spherical pile foundation. This can increase the end resistance and frictional resistance between the pile foundation and the soil layer, effectively improving the strength of the pile foundation material per unit volume.

[0004] However, the soil environment has a significant impact on the pile enlargement effect. Different soil types and soil layer heights result in significant differences in the pile enlargement effect. To achieve pile enlargement that is adaptable to different soil environments, existing technologies have studied the relationship between soil deformation and discharge frequency, discharge energy, and soil compaction characteristics to adaptively control high-voltage pulse discharge parameters. However, in practical applications, this method still struggles to accurately and effectively achieve the required pile hole diameter, severely restricting the field application of this technology. Therefore, how to control the high-voltage pulse discharge parameters to achieve pile enlargement that is adaptable to different soil environments and accurately achieve the required pile hole diameter has become an urgent technical problem to be solved. Summary of the Invention

[0005] In view of the above-mentioned defects or improvement needs of the existing technology, the present invention provides a pile expansion method and application based on high-voltage pulse discharge, which solves the technical problem that the existing technology cannot accurately achieve the required pile foundation hole diameter by controlling the high-voltage pulse discharge parameters in different soil environments.

[0006] To achieve the above objectives, in a first aspect, the present invention provides a pile expansion method based on high-voltage pulse discharge, comprising:

[0007] At the location of the pile to be expanded in the pile foundation hole, a high-voltage pulse discharge is performed using a discharge electrode to enlarge the hole diameter to the preset hole diameter size.

[0008] The pile foundation holes are filled with pile foundation material in a liquid state; the discharge parameters of the high-voltage pulse discharge are set based on their relationship with soil property parameters and preset hole size; the discharge parameters include: the number of discharges, the electrode gap distance and discharge energy of a single pulse discharge; the soil property parameters include: soil compression modulus and Poisson's ratio.

[0009] More preferably, the relationship between the discharge parameters, soil characteristic parameters, and preset pore size is as follows:

[0010]

[0011] Where R is the preset aperture size; r0 is the initial aperture size before pile expansion; n is the number of discharges; and the aperture change during the i-th pulse discharge is... μ is the Poisson's ratio of the soil surrounding the borehole; l i E represents the electrode gap distance during the i-th pulse discharge. s P represents the compressibility modulus of the soil at the location where the piles are to be enlarged; mi =k×E Bi δ ×s i -α k is an empirical coefficient; E Bi δ is the discharge energy of the i-th pulse discharge; δ is the energy exponent; s i α is the distance from the center of the discharge gap to the soil boundary before the i-th pulse discharge; α is the distance decay exponent.

[0012] More preferably, the discharge electrode is connected to the capacitor-type energy storage device via a trigger switch. After the trigger switch is turned on, the energy of the energy storage capacitor in the capacitor-type energy storage device is applied to both ends of the discharge electrode to perform high-voltage pulse discharge.

[0013] More preferably, the discharge energy of the i-th pulse discharge is:

[0014]

[0015] Where C is the size of the energy storage capacitor; U Bi Let be the capacitor voltage at the breakdown moment during the i-th pulse discharge.

[0016] More preferably, the discharge electrode is placed at the location of the pile to be expanded in the pile foundation. The discharge electrode generates a shock wave through liquid breakdown, or metal wire electric explosion, or the simultaneous action of liquid breakdown and metal wire electric explosion, so as to perform high-voltage pulse discharge.

[0017] More preferably, the pile foundation material in the liquid state includes mortar, cement grout, or a mixture of the two.

[0018] Secondly, the present invention provides a pile-forming method based on high-voltage pulse discharge, comprising:

[0019] Drill holes in the soil to be used for pile foundations to form pile holes;

[0020] The pile foundation is filled with pile foundation material in a liquid state, and at different depths of the pile foundation hole, the hole diameter at different depths is enlarged to the preset hole diameter size at the corresponding depth using the pile expansion method provided in the first aspect of the present invention, thereby forming a spherical cavity and constructing a continuous spherical pile foundation.

[0021] More preferably, the pile foundation material in the liquid state includes mortar, cement grout, or a mixture of the two.

[0022] In summary, the above-described technical solutions conceived in this invention can achieve the following beneficial effects:

[0023] 1. This invention provides a pile expansion method based on high-voltage pulse discharge. The method expands the borehole diameter at the desired pile location to the required pile diameter using high-voltage pulse discharge. During this process, the soil compression modulus and Poisson's ratio are measured in real time. Based on the relationship between discharge parameters, soil characteristic parameters, and the preset borehole diameter, the optimal discharge parameters for high-voltage pulse discharge are set. These parameters include the number of discharges, the electrode gap distance for each pulse discharge, and the discharge energy. This achieves coupled calculation of discharge parameters, shock wave load, and soil deformation. The optimal discharge parameters can be determined according to soil characteristic parameters and the required pile diameter, enabling accurate achievement of the required pile diameter under different soil conditions by controlling the high-voltage pulse discharge parameters.

[0024] 2. The pile expansion method provided by this invention is a purely physical method that uses the shock wave generated by discharge to achieve the pile expansion effect. It has advantages such as high energy efficiency, controllability, safety and environmental protection, and high economic benefits (low cost).

[0025] 3. This invention provides a pile formation method based on high-voltage pulse discharge. By accumulating the effects of multiple high-voltage pulse discharges at different depths of the pile foundation hole, a continuous spherical pile foundation can be constructed, which greatly improves the end resistance and frictional resistance between the pile foundation and the soil layer, and effectively improves the strength of the pile foundation material per unit volume. In this process, based on the relationship between the obtained discharge parameters, soil characteristic parameters and the preset hole size, a coupled calculation of discharge parameters-shock wave load-soil deformation is performed to determine the optimal discharge parameters, thereby efficiently and accurately achieving the required pile foundation hole size.

[0026] 4. The high-voltage pulse discharge-based pile forming method provided by this invention significantly reduces construction costs and is less difficult to construct compared to pile forming methods that simply increase the number of piles to improve strength. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the propagation and aperture change of a single discharge shock wave provided in Embodiment 1 of the present invention;

[0028] Figure 2 This is a voltage waveform diagram of a discharge of the capacitor-type energy storage device provided in Embodiment 1 of the present invention.

[0029] Figure 3 This is a graph showing the aperture change versus the number of high-voltage pulse discharges provided in Embodiment 1 of the present invention.

[0030] Figure 4 This is a schematic diagram of the structure of the continuous spherical pile foundation provided in Embodiment 2 of the present invention;

[0031] Where r0 is the initial radius of the borehole; ΔR total-n The total expansion diameter after n discharges; ΔR total-n-1 The total diameter expansion for n-1 discharges; ΔR i For the expansion of the diameter during the i-th high-voltage pulse discharge; ΔR n The diameter is expanded by n discharges; l is the electrode gap distance; P m This is an effective shock wave from a single discharge; U B Voltage at breakdown time; μ is Poisson's ratio of the soil surrounding the borehole; E s δ is the compressibility modulus of the soil surrounding the borehole; k is an empirical coefficient; δ is the energy index; C is the size of the energy storage capacitor; α is the distance decay index; and s is the distance from the center of the discharge gap to the boundary between the pile and the soil before a certain discharge. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0033] Example 1

[0034] A pile expansion method based on high-voltage pulse discharge includes:

[0035] At the location of the pile to be expanded in the pile foundation hole, a high-voltage pulse discharge is performed using a discharge electrode to enlarge the hole diameter to a preset size; the pile foundation hole is filled with pile foundation material in a liquid state.

[0036] Specifically, in this embodiment, the pile foundation cavity is first filled with pile foundation material in a liquid state. The pile foundation material in a liquid state can be mortar, cement grout, or a mixture of mortar and cement grout. Then, the discharge electrode is placed at the location of the pile to be expanded. The discharge electrode generates a shock wave through liquid breakdown, metal wire electro-explosion, or a combination of liquid breakdown and metal wire electro-explosion to perform high-voltage pulse discharge.

[0037] Furthermore, the discharge parameters of the aforementioned high-voltage pulse discharge are set based on their relationship with soil characteristic parameters and preset aperture size; the discharge parameters include: the number of discharges, the electrode gap distance and discharge energy of a single pulse discharge; the soil characteristic parameters include: the soil compression modulus and Poisson's ratio, which can be measured in real time.

[0038] It should be noted that there are multiple methods to obtain the relationship between discharge parameters, soil characteristic parameters, and preset pore size. For example, a relationship model between the three can be established through machine learning methods, or the relationship between the three can be derived by combining elasticity mechanics.

[0039] Preferably, in this embodiment, the relationship between the three is derived using elasticity mechanics. Specifically, as shown below... Figure 1 The diagram shown illustrates the propagation of the nth discharge shock wave and the change in borehole diameter in this example. The initial radius of the borehole is r0, and the diameter expansion after n-1 discharges is ΔR. total-n-1 The electrode gap distance remains constant at l. At this time, the distance between the center of the electrode gap and the distance between the soil and the mortar medium is r0 + ΔR. total-n-1 The attenuation distance of the shock wave generated by the high-voltage pulse discharge is r0 + ΔR. total-n-1 The effective shock wave intensity of the nth high-voltage pulse discharge is P. mn After the nth high-voltage pulse discharge, the diameter expansion of the spherical pile is ΔR. n .

[0040] Based on elasticity mechanics, and combining discharge parameters (electrode gap distance and effective shock wave peak value during discharge) with soil mechanical parameters (soil Poisson's ratio and compression modulus), the soil displacement when the shock wave generated by the discharge acts on the soil is derived. This yields the relationship between the aperture change of a single pulse discharge and the discharge parameters and soil characteristic parameters. Furthermore, the relationship between the discharge parameters, soil characteristic parameters, and the preset aperture size is obtained as follows:

[0041]

[0042] Where R is the preset aperture size; r0 is the initial aperture size before pile expansion; n is the number of discharges; and the aperture change during the i-th pulse discharge is... μ is the Poisson's ratio of the soil surrounding the borehole; l iE represents the electrode gap distance during the i-th pulse discharge. s The compression modulus of the soil at the location to be expanded is denoted as P; the effective shock wave peak value P of the i-th pulse discharge is denoted as P. mi =k×E Bi δ ×s i -α , refers to the actual strength at the point of application after the electric arc channel is generated and after attenuation by the liquid medium (the pile foundation material in a liquid state); k is an empirical coefficient; E Bi δ is the discharge energy of the i-th pulse discharge; δ is the energy exponent; s i The distance from the center of the discharge gap to the soil boundary before the i-th pulse discharge is the attenuation distance of the shock wave before it acts on the soil, s = R0 + ΔR total-i-1 , △R total-n-1 The aperture expansion after i-1 discharges, i.e., the total aperture change before the i-th discharge, is represented by ΔR. total-0 =0; α is the distance decay exponent.

[0043] In this embodiment, the discharge electrode is connected to the capacitor-type energy storage device via a trigger switch. After the trigger switch is turned on, the energy of the energy storage capacitor in the capacitor-type energy storage device is applied to both ends of the discharge electrode to perform high-voltage pulse discharge. It should be noted that, in addition to capacitor-type energy storage devices, the present invention can also use inductive energy storage devices, battery energy storage devices, etc. This embodiment uses a capacitor-type energy storage device as an example for explanation.

[0044] Specifically, the discharge energy of the i-th pulse discharge when using a capacitor-type energy storage device is:

[0045]

[0046] Where C is the size of the energy storage capacitor; U Bi Let be the capacitor voltage at the breakdown moment during the i-th pulse discharge.

[0047] Correspondingly, the discharge energy of a pulsed discharge is the residual energy of the capacitor at the moment of breakdown, determined by the discharge waveform. The voltage waveform of a capacitor-type energy storage device during a certain discharge is given by the capacitor voltage at the moment of discharge as U. B like Figure 2 As shown.

[0048] Table 1 shows the calculated data of borehole diameter change under a high-voltage pulse discharge provided in this example. During this diameter expansion process, the energy storage capacitor C = 4.5 μF, the empirical coefficient k = 3075, the energy index δ = 0.82, the distance attenuation index α = 1.32, the Poisson's ratio of the soil around the borehole μ = 0.45, the single discharge gap distance l = 30 mm, and the compression modulus E of the soil around the borehole. s=10MPa, initial borehole radius r0 = 300mm, and remains constant; capacitor voltage U at breakdown time B 1. The distance *s* from the center of the discharge gap to the boundary between the pile and the soil before a certain discharge; 2. The effective shock wave *P* of a single discharge. m The aperture change ΔR of a single pulse discharge i The total aperture change ΔR after n discharges total-n The value varies during each high-voltage pulse discharge. As the high-voltage pulse discharge progresses, the aperture change ΔR during a single pulse discharge. i The value of P continuously decreases, and the effective shock wave P of a single discharge... m Decrease, △R i The decrease in the value of / s indicates that the high-voltage pulse discharge diameter expansion efficiency decreases with the increase of the number of discharges. Correspondingly, as Figure 3 The figure shows a curve of aperture change versus number of high-voltage pulse discharges provided in this embodiment; it can be seen from the figure that as the high-voltage pulse discharge proceeds, the aperture change ΔR of a single pulse discharge increases. i The value keeps decreasing.

[0049] Table 1

[0050]

[0051] Based on the above analysis, and taking into account construction costs, construction efficiency, and pile foundation stability, and based on the relationship between the aperture change of a single pulse discharge and the discharge parameters and soil characteristic parameters, the discharge parameters, namely the number of discharges, the electrode gap distance of a single pulse discharge, and the discharge energy, can be adjusted to achieve the optimal discharge parameters.

[0052] Specifically, in one optional implementation, the electrode gap distance and discharge energy (corresponding to the capacitor voltage at the breakdown moment during pulse discharge in this embodiment) of a single pulse discharge can be fixed, and a high-voltage pulse discharge can be performed under this discharge condition. At this time, the specific number of discharges to reach the preset aperture can be determined.

[0053] However, based on the relationship between the aperture change of a single pulse discharge and the discharge parameters and soil characteristic parameters, it can be seen that the aperture expansion efficiency of high-pressure pulse discharge decreases with the increase of the number of discharges. Therefore, in one specific implementation, the electrode gap distance and discharge energy of a single pulse discharge (corresponding to the capacitor voltage at the breakdown moment during pulse discharge in this embodiment) can be fixed first. When the number of discharges is greater than the preset number of discharges (10 in this embodiment), it is determined whether the aperture at the location to be expanded has been expanded to the preset aperture size. If not, the electrode gap distance or discharge energy is increased before high-pressure pulse discharge is performed again; otherwise, the above process is repeated until the aperture at the location to be expanded is expanded to the preset aperture size.

[0054] Furthermore, the aforementioned preset number of discharges can be determined using the aperture change of a single pulse discharge as an indicator. In one specific implementation, the electrode gap distance and discharge energy of a single pulse discharge (corresponding to the capacitor voltage at the breakdown moment during pulse discharge in this implementation) can be fixed first. When the absolute value of the difference between the aperture changes of two adjacent pulse discharges is less than a preset threshold (5 mm in this implementation), it is determined whether the aperture at the location to be expanded has been expanded to the preset aperture size. If not, the electrode gap distance or discharge energy is increased before high-voltage pulse discharge is performed. Otherwise, the above process is repeated until the aperture at the location to be expanded is expanded to the preset aperture size.

[0055] Example 2

[0056] A pile-forming method based on high-voltage pulse discharge, such as Figure 4 As shown, it includes:

[0057] Drill holes in the soil to be used for pile foundations to form pile holes;

[0058] The pile foundation is constructed by filling the pile foundation cavity with pile foundation material in a liquid state, and then using the pile expansion method provided in Embodiment 1 of the present invention at different depths of the pile foundation cavity to enlarge the hole diameter to the preset hole diameter size at the corresponding depth, forming a spherical cavity, thereby constructing a continuous spherical pile foundation. In this embodiment, the pile foundation material in a liquid state includes: mortar, cement grout, or a mixture of the two.

[0059] This invention constructs a continuous spherical pile foundation by accumulating multiple high-voltage pulse discharges at different depths of the pile foundation hole. This enhances the end resistance and frictional resistance between the pile foundation and the soil layer, effectively increasing the strength of the pile foundation material per unit volume. Furthermore, during this process, based on the relationship between the obtained discharge parameters, soil characteristic parameters, and the preset hole diameter, a coupled calculation of discharge parameters, shock wave load, and soil deformation is performed to determine the optimal discharge parameters, thereby efficiently and accurately achieving the required pile foundation hole diameter.

[0060] The relevant technical solutions are the same as in Embodiment 1, and will not be repeated here.

[0061] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for pile enlarging based on high-voltage pulse discharge, characterized in that, include: At the location of the pile to be expanded in the pile foundation hole, a high-voltage pulse discharge is performed using a discharge electrode to enlarge the hole diameter to the preset hole diameter size. The pile foundation holes are filled with pile foundation material in a liquid state; the discharge parameters of the high-voltage pulse discharge are set based on their relationship with soil property parameters and preset hole size; the discharge parameters include: the number of discharges, the electrode gap distance and discharge energy of a single pulse discharge; the soil property parameters are obtained through real-time measurement, including: soil compression modulus and Poisson's ratio. The relationship between the discharge parameters, the soil characteristic parameters, and the preset pore size is as follows: in, The preset aperture size; This refers to the initial borehole diameter before pile expansion; n For the number of discharges; the first i aperture change of the secondary pulse discharge ; The Poisson's ratio of the soil surrounding the borehole; For the first i Electrode gap distance of the next pulse discharge; The compression modulus of the soil at the location where the piles are to be expanded; the first i The effective shock wave peak value of the secondary pulse discharge ; This is an empirical coefficient; For the first i The discharge energy of the next pulse discharge; Energy index; For the first i The distance from the center of the discharge gap before the next pulse discharge to the soil boundary; This is the distance decay index.

2. The pile enlargement method according to claim 1, characterized in that, The discharge electrode is connected to the capacitor-type energy storage device via a trigger switch. When the trigger switch is turned on, the energy of the energy storage capacitor in the capacitor-type energy storage device is applied to both ends of the discharge electrode to perform high-voltage pulse discharge.

3. The pile enlargement method according to claim 2, characterized in that, No. i The discharge energy of the next pulse discharge is: in, The size of the energy storage capacitor; For the first i The capacitor voltage at the moment of breakdown during the next pulse discharge.

4. The pile enlargement method according to claim 1, characterized in that, The discharge electrode is placed at the location of the pile to be expanded in the pile foundation. The discharge electrode generates a shock wave through liquid breakdown, metal wire electric explosion, or both liquid breakdown and metal wire electric explosion to perform high-voltage pulse discharge.

5. The pile enlargement method according to claim 1, characterized in that, The pile foundation materials in the liquid state include: mortar, cement grout, or a mixture of the two.

6. A pile-forming method based on high-voltage pulse discharge, characterized in that, include: Drill holes in the soil to be used for pile foundations to form pile holes; The pile foundation is filled with pile foundation material in a liquid state, and at different depths of the pile foundation hole, the hole diameter at different depths is enlarged to the preset hole diameter size at the corresponding depth using the pile expansion method described in any one of claims 1-5, thereby forming a spherical cavity and constructing a continuous spherical pile foundation.

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