A method of coupling vibration energy in a subsurface medium

Abstract

The application provides a kind of underground medium vibration energy coupling method, including the delivery of vibration excitation device to underground target area, so that its epitaxial coupling structure is formed with underground medium mechanical embedded coupling state;According to the type of underground medium, the frequency range of vibration excitation signal is determined, the waveform type and coding sequence are determined according to the target vibration response characteristics, and the driving signal is generated accordingly;Control the corresponding periodic mechanical vibration generated by the vibration excitation unit, and transmit it to the epitaxial coupling structure through the force transmission unit, and input mechanical vibration energy to underground medium.The application can realize efficient transmission of vibration excitation energy from device to underground medium, and improve the coupling efficiency of underground vibration energy and the controllability of target area vibration response.

Description

Technical Field

[0001] This invention relates to the field of vibration excitation technology for underground engineering, and more specifically to a method for coupling vibration energy in underground media. Background Technology

[0002] In underground engineering exploration, geological modification, and resource development, effectively inputting controllable mechanical vibration energy into the underground medium is a key technical means to achieve stratum detection, soil and rock improvement, and resource extraction. Currently, conventional underground vibration excitation methods mainly employ surface excitation or borehole contact excitation. Surface excitation suffers severe attenuation of vibration energy during propagation due to absorption and scattering by the surface soil, resulting in weak vibration responses in deep target areas and difficulty in precise control. While borehole excitation can shorten the distance between the vibration source and the target area, existing excitation devices often have simple contact or support connections with the borehole wall, resulting in gaps or slippage at the coupling interface, low vibration energy transfer efficiency, and excitation parameters are often set empirically, failing to adaptively adjust according to the physical characteristics of the underground medium and the target response requirements. Furthermore, the waveform, frequency, and timing coding of excitation signals in existing technologies are relatively simple, making it difficult to simultaneously meet the dual requirements of detection resolution and anti-interference, thus limiting the accuracy and reliability of vibration excitation operations under complex geological conditions.

[0003] In implementing the embodiments of the present invention, the prior art has at least the following problems or defects: the coupling efficiency between the excitation device and the underground medium is low and the energy transfer loss is large; the excitation parameters cannot be adaptively optimized according to the medium type and target response characteristics; the waveform, frequency and encoding method of the vibration signal are simple and it is difficult to meet the requirements of high-resolution detection and strong anti-interference at the same time; the accuracy and controllability of deep vibration energy input are insufficient. Summary of the Invention

[0004] This invention provides a method for coupling vibration energy in underground media, comprising: The excitation device is transported to the underground target area; This enables the extensional coupling structure of the excitation device to form a mechanically embedded coupling state with the underground medium; The frequency range of the excitation signal is determined based on the type of underground medium. Based on the target vibration response characteristics, determine the waveform type and encoding sequence of the excitation signal; Based on the frequency range, the waveform type, and the encoding sequence, a corresponding driving signal is generated; According to the driving signal, the excitation unit is controlled to generate corresponding periodic mechanical vibrations; According to the periodic mechanical vibration, the vibration force is transmitted to the extended coupling structure through the force transmission unit; Mechanical vibration energy is input into the underground medium based on the vibration force transmitted to the extended coupling structure.

[0005] Furthermore, determining the frequency range of the excitation signal based on the type of underground medium includes: Collect media samples from the underground target area and obtain the density value of the media samples; The longitudinal wave velocity value of the medium sample was obtained by acoustic wave testing; Based on the density value and the longitudinal wave velocity value, the characteristic frequency value is calculated by dividing the longitudinal wave velocity value by twice the diameter of the excitation device housing, or by dividing the longitudinal wave velocity value by the characteristic wavelength. Set the calculated characteristic frequency value as the frequency value of the excitation signal.

[0006] Furthermore, determining the waveform type and encoding sequence of the excitation signal based on the target vibration response characteristics includes: The waveform type of the excitation signal is determined based on the detection resolution requirements in the target vibration response characteristics. Based on the anti-interference requirements in the target vibration response characteristics, a pseudo-random binary sequence is generated as the encoding sequence of the excitation signal; The excitation timing of the excitation signal is determined based on the encoded sequence.

[0007] Furthermore, the step of generating the corresponding driving signal based on the frequency range, waveform type, and encoding sequence includes: Based on the frequency range, set the fundamental frequency parameter of the driving signal; Based on the waveform type, set the waveform function of the driving signal; Based on the encoded sequence, set the timing on / off parameters of the driving signal; A continuous voltage drive signal is synthesized based on the fundamental frequency parameter, the waveform function, and the timing on / off parameter.

[0008] Furthermore, the step of controlling the excitation unit to generate corresponding periodic mechanical vibrations according to the driving signal includes: The voltage drive signal is output to the electrical input terminal of the excitation unit; The excitation unit generates mechanical vibration at a corresponding frequency according to the fundamental frequency parameter of the voltage drive signal; The excitation unit generates mechanical vibration corresponding to the waveform profile according to the waveform function of the voltage drive signal. The excitation unit generates corresponding coded discontinuous mechanical vibrations based on the timing on / off parameters of the voltage drive signal.

[0009] Furthermore, the delivery of the excitation device to the underground target area includes: Connect the excitation device to the end of the drill rod or feed rod; The drill rod or push rod is driven to move linearly along the borehole axis by a hydraulic propulsion mechanism. The drilling depth of the drill pipe or push rod is monitored in real time, and the push is stopped when the drilling depth reaches the preset target depth value; Lock the position of the drill rod or push rod to keep the excitation device within the underground target area.

[0010] Furthermore, the process of establishing a mechanically embedded coupling state between the extensional coupling structure of the excitation device and the underground medium includes: After the excitation device reaches the underground target area, the driving mechanism causes the extended coupling structure to rotate around the axis. During the rotation process, an axial thrust is applied to the excitation device, causing the spiral blades or embedded ribs of the extended coupling structure to gradually rotate into the surrounding underground medium. The screwing torque value is monitored in real time, and the screwing is stopped when the screwing torque value reaches the preset clamping torque threshold. Maintaining the axial thrust, a stable mechanically embedded contact state is formed between the extended coupling structure and the underground medium; wherein, the preset embedding torque threshold is calculated according to the following formula; ; in, The embedding torque threshold, The coefficient of friction between the surface of the extended coupling structure and the underground medium. The shear strength of the underground medium. This refers to the effective contact area between the extended coupling structure and the underground medium. The effective radius of the extended coupling structure.

[0011] Furthermore, the transmission of vibrational force to the extensional coupling structure via the force transmission unit based on periodic mechanical vibration includes: The periodic mechanical vibration displacement generated by the excitation unit is input to the first end face of the waveguide core rod; The waveguide core rod propagates the periodic mechanical vibration displacement along the rod's axial direction to the second end face; At the second end face, the periodic mechanical vibration displacement is converted into a periodic push-pull force, and the periodic push-pull force is transmitted to the force transmission interface of the extended coupling structure through the connecting sleeve.

[0012] Furthermore, the input of mechanical vibration energy into the underground medium based on the vibration force transmitted to the extended coupling structure includes: The extended coupling structure generates synchronous radial expansion displacement or axial expansion displacement according to the received periodic push-pull force. The embedded protrusions or helical blades on the surface of the extended coupling structure directly compress the displacement into the surrounding underground medium. The underground medium undergoes elastic deformation under compression and propagates vibration energy in the form of elastic waves in a direction away from the excitation device.

[0013] Furthermore, the pseudo-random binary sequence is an m-sequence, and its order n is determined according to the following formula: ; in, For characteristic frequencies, For target detection depth, For the longitudinal wave velocity of the underground medium, The quality factor of the underground medium. This is the floor function.

[0014] The embodiments of the present invention have at least the following beneficial effects: 1. By forming a mechanically embedded coupling state with the underground medium through an extended coupling structure, and by using helical blades or embedded ribs to screw into the surrounding medium and reach the preset embedded torque threshold, the interface gap and sliding problems existing in traditional contact excitation are effectively eliminated, the transmission efficiency of vibration energy is significantly improved, and the problems of poor coupling between the excitation device and the underground medium and large energy transmission loss in the existing technology are solved, ensuring that the deep target area can obtain stable and efficient vibration energy input.

[0015] 2. Based on the density and longitudinal wave velocity values ​​of the underground medium sample, the characteristic frequency value is calculated. Combined with the detection resolution and anti-interference requirements in the target vibration response characteristics, the waveform type is adaptively selected and a pseudo-random binary code sequence is generated. This achieves precise matching and dynamic control of the excitation signal frequency, waveform profile, and excitation timing. It solves the problems of existing technologies where the excitation parameters cannot be adaptively optimized according to the physical characteristics of the medium and operational requirements, and the vibration signal form is singular. It effectively balances the dual requirements of high-resolution detection and strong anti-interference.

[0016] 3. The waveguide core rod is used to propagate the periodic mechanical vibration displacement generated by the excitation unit along the axial direction and convert it into periodic push-pull force. This force is then transmitted to the extended coupling structure through the connecting sleeve, thereby causing the coupling structure to generate synchronous radial expansion displacement or axial contraction displacement. This directly compresses the surrounding underground medium to produce elastic deformation and propagates the vibration energy in the form of elastic waves. This forms a complete closed-loop control link from the generation of driving signals, the response of the excitation unit, the transmission of force by the force transmission unit, to the energy output of the coupling structure. This solves the problems of low accuracy and poor controllability of deep vibration energy input in existing technologies and realizes precise control and reliable excitation of the vibration response characteristics of underground target areas. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. The following drawings are not intentionally drawn to scale to actual size; their focus is on illustrating the main points of this disclosure.

[0018] Figure 1 A schematic diagram of the structure of the excitation device provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of an epitaxial coupling structure provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of an epitaxial coupling structure provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of the underground medium vibration energy coupling method provided in an embodiment of the present invention. Detailed Implementation

[0019] The technical solutions in the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are also within the scope of protection of this disclosure.

[0020] As indicated in this application and claims, unless the context clearly indicates otherwise, the words "a," "an," "an," and / or "the" are not specifically singular and may include plural forms. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of explicitly identified steps and elements, which do not constitute an exclusive list, and the method or apparatus may also include other steps or elements.

[0021] While this application makes various references to certain modules of the systems according to embodiments of this application, any number of different modules can be used and run on user terminals and / or servers. The modules described are merely illustrative, and different aspects of the systems and methods may use different modules.

[0022] Flowcharts are used in this application to illustrate the operations performed by the system according to embodiments of this application. It should be understood that the preceding or following operations are not necessarily performed in exact order. Instead, various steps can be processed in reverse order or simultaneously as needed. Furthermore, other operations can be added to these processes, or one or more steps can be removed from them.

[0023] The present invention will now be described in detail with reference to the accompanying drawings. Figure 1 A schematic diagram of the structure of the active vibration device for underground media used in this invention is shown.

[0024] The vibration excitation device mainly consists of a shell structure, a vibration excitation unit, a force transmission unit, an extended coupling structure, and a sealing and vibration isolation structure.

[0025] The shell structure is a cylindrical sealed compartment, such as Figure 1 As shown in the sealed chamber diagram, the interior forms a closed working space. The shell structure is made of high-strength stainless steel, with a wall thickness of 8 mm, an outer diameter of 150 mm, and a length of 600 mm. The upper end of the shell structure is connected to the drill pipe via a connection and vibration isolation structure, while the lower end is open for the force transmission unit to pass through. Multiple O-rings are installed on the outside of the shell structure to prevent groundwater and mud from entering the interior. The shell structure also serves to waterproof and moisture-proof, protecting the internal components.

[0026] The excitation unit is located within the internal working space of the shell structure. The excitation unit includes a vibrator, an inertial mass block, and control circuitry. The vibrator is an electromagnetic vibrator, model JZK-50, with a rated output force of 500 Newtons and a frequency range of 0 to 5000 Hz. The inertial mass block is a cylindrical steel block weighing 5 kg, fixed to the mover output end of the vibrator, used to increase the output amplitude of the excitation force. The control circuitry includes a power amplifier and a signal conditioning module, used to receive external drive signals and drive the vibrator to generate periodic mechanical vibrations.

[0027] The force transmission unit is used to transfer the vibration force generated by the excitation unit to the extended coupling structure. The force transmission unit includes a waveguide core rod and a force transmission shaft. The waveguide core rod is a slender cylindrical rod made of high-strength alloy steel, with a diameter of 20 mm and a length of 500 mm. The first end face of the waveguide core rod is rigidly connected to the inertial mass block, and the second end face passes through the end cap of the shell structure and connects to the force transmission shaft. The force transmission shaft is a stepped shaft; its large-diameter end contacts the second end face of the waveguide core rod, and its small-diameter end passes through the end cap of the shell and is fixedly connected to the extended coupling structure.

[0028] like Figure 2 As shown, the extended coupling structure can employ a helical waveguide blade structure. This helical waveguide blade is spirally arranged along the outer wall of the excitation device housing, forming a continuous single- or multi-headed helix. The helix angle is set to 15 degrees to ensure sufficient axial thrust and radial embedding force when spiraling into the underground medium. The blade is 30 mm high and 5 mm thick, with its outer edge 35 mm from the housing surface. Multiple embedding ridges, 2 mm high and 5 mm apart, are machined on the blade surface, evenly distributed along the blade's length to increase the microscopic engagement between the blade and the underground medium. The helical waveguide blade is made of high-strength alloy steel, with its inner end rigidly connected to the force transmission shaft via welding or threaded connection, and its outer end being a free end. When the force transmission shaft transmits periodic push-pull forces, the helical waveguide blade generates synchronous axial extension and radial expansion displacements, thereby creating compression and shearing effects on the surrounding underground medium. This structure is particularly suitable for applications requiring rotational embedding, such as loose soil, sand layers, or soft soil strata, achieving stable mechanical embedding coupling through spiraling action.

[0029] like Figure 3 As shown, the extended coupling structure can also employ a rib-type embedding structure, including multiple longitudinal ribs evenly distributed along the circumference of the shell and extending axially, as well as annular reinforcing ribs connecting adjacent longitudinal ribs. There are six longitudinal ribs, evenly distributed around the circumference of the shell. Each rib is 25 mm high, 10 mm wide, and has the same length as the effective length of the shell. The outer surface of the longitudinal ribs is machined with serrated embedding teeth, 3 mm high, 8 mm pitch, and an asymmetrical triangular shape with its steep slope facing the bottom of the device to enhance anti-slip capability. Two annular reinforcing ribs are located in the middle and lower part of the longitudinal ribs, each 8 mm wide and flush with the height of the longitudinal rib. The rib-type embedding structure is fixed to the outside of the shell by integral casting or welding, with its inner end integrated with the shell and its outer end being a free end. This structure is suitable for applications where rotation is not possible and only linear propulsion is required. For example, when the device is directly pressed into the underground medium via a hydraulic propulsion mechanism, the ribs and embedding teeth embed into the surrounding medium under axial thrust, forming friction enhancement and mechanical embedding coupling. This structure is particularly suitable for strata requiring greater embedding force, such as hard clay, dense sand, or fractured rock.

[0030] A sealing and vibration isolation structure is installed between the shell end cap and the force transmission unit, including a flexible sealing ring and a wave impedance isolation layer. The flexible sealing ring is made of polyurethane and is used to prevent mud from entering the shell. The wave impedance isolation layer is made of rubber and metal mesh composite and is used to prevent vibration energy from propagating along the shell, so that vibration energy is preferentially transmitted forward along the force transmission unit.

[0031] The supporting conveying and propulsion structure includes drill pipe, a hydraulic propulsion mechanism, and a rotary drive mechanism. The drill pipe is connected to the upper part of the shell structure and to the vibration isolation structure. The hydraulic propulsion mechanism uses an HSG series double-acting hydraulic cylinder with a rated thrust of 10 tons, used to push the excitation device along the borehole to the underground target area. The rotary drive mechanism is a BMR-200 hydraulic motor with a displacement of 200 ml / rpm and a maximum output torque of 1200 Nm, used to drive the drill pipe to rotate, thereby driving the extended coupling structure to rotate into the underground medium.

[0032] Specifically, such as Figure 4 As shown, S1: Transport the excitation device to the underground target area.

[0033] First, the vibration excitation device and vibration isolation structure are connected to the end of the drill rod via threads. The drill rod is a hollow steel pipe, each section is 3 meters long and has an outer diameter of 110 mm. The hydraulic propulsion mechanism drives the drill rod to move linearly downwards along the borehole axis. The borehole is a cylindrical channel with a diameter of 200 mm, pre-formed in the strata by a geological drilling rig. During propulsion, a wire-type displacement sensor installed on the top of the drill rod collects the advance depth in real time, with a sensor accuracy of 1 mm. When the advance depth reaches the preset target depth value, such as 20 meters underground, the programmable logic controller outputs a stop signal, the hydraulic reversing valve cuts off the oil circuit, and propulsion stops. Then, the locking device is activated. The locking device is a pneumatic clamp that uses compressed air to drive the clamping blocks to grip the drill rod, keeping the vibration excitation device within the target underground area. The target underground area refers to the specific stratum location where vibration energy injection is required, such as loose soil, water-bearing sand, or soft soil.

[0034] S11: Connect the excitation device to the end of the drill rod or feed rod.

[0035] The upper end cap of the excitation device has an internal thread interface, size M80×2, which matches the male thread at the lower end of the drill pipe. Before connection, apply molybdenum disulfide grease to the thread surface to reduce friction. Slowly screw the drill pipe into the excitation device interface until the end faces fit tightly. Apply a pre-tightening torque of 500 Nm using a torque wrench to ensure a reliable connection. The push rod is a solid steel rod without rotation function, used for linear pushing conditions where rotation is not required, and the connection method is the same.

[0036] S12: Drives the drill rod or push rod to move linearly along the borehole axis via a hydraulic propulsion mechanism.

[0037] The hydraulic propulsion mechanism includes a hydraulic power unit, hydraulic cylinders, and a control system. The hydraulic power unit supplies hydraulic oil at a rated pressure of 16 MPa and a flow rate of 40 liters per minute. The piston rod extension speed of the hydraulic cylinder is adjusted via a throttle valve, typically 0.1 meters per second. The drill rod moves linearly downwards along the borehole axis under the push of the hydraulic cylinder. A guide frame lined with a nylon sleeve is installed at the borehole opening to prevent drill rod deflection. The operator controls the advance and reverse movement via a joystick on the control panel, or the drill rod can be automatically propelled at a set speed.

[0038] S13: Monitor the drilling depth of the drill pipe or push rod in real time, and stop pushing when the drilling depth reaches the preset target depth value.

[0039] An absolute rotary encoder is used to measure the drilling depth. The encoder is mounted on the guide wheel of the hydraulic cylinder. The movement of the drill pipe rotates the guide wheel, and the encoder generates pulse signals, each pulse corresponding to a 1 mm displacement. These pulse signals are input to the high-speed counter module of a Siemens S7-1200 programmable logic controller (PLC). The operator presets a target depth value, such as 15.5 meters, via a touchscreen. When the counter accumulates to the preset number of pulses, the PLC outputs a digital signal to drive a relay to disconnect the solenoid coil of the hydraulic directional valve, cutting off the hydraulic circuit and stopping the hydraulic cylinder. Simultaneously, a buzzer sounds an alarm.

[0040] S14: Lock the position of the drill rod or push rod to keep the excitation device within the target area underground.

[0041] The locking device employs a pneumatic gripper. Compressed air drives the gripper's piston, causing two arc-shaped clamps to grip the drill pipe surface. The clamps are lined with a rubber layer to increase friction. The clamping force is controlled by adjusting the air pressure, typically 5 kN, sufficient to overcome the combined weight of the drill pipe and the exciter. After locking, the pressure in the hydraulic propulsion mechanism is released, and the exciter hovers at the target depth using the friction of the gripper. The locked state is fed back to the control system via a pressure switch.

[0042] S2: To enable the extended coupling structure of the excitation device to form a mechanically embedded coupling state with the underground medium.

[0043] After the excitation device reaches the target depth underground, the ground-based rotary drive mechanism applies rotational torque to the excitation device through the drill pipe. The rotary drive mechanism is a hydraulic motor, model BMR-200, with a displacement of 200 ml / rpm and a maximum output torque of 1200 Nm. Simultaneously, the hydraulic propulsion mechanism maintains a constant axial thrust, typically 2 tons. Under the action of rotation and thrust, the helical waveguide blades of the extended coupling structure gradually spiral into the surrounding underground medium. The carbide teeth at the blade tip break up local soil, and the blade's inclined surface squeezes the soil to both sides, forming a tight embedded interface. A torque sensor monitors the spiraling torque in real time. When the torque rises from the initial value of 50 Nm to the preset threshold of 300 Nm, it indicates that the blade has been fully embedded and has obtained sufficient friction, at which point rotation stops. Finally, the axial thrust is maintained constant to ensure a stable embedded state. The mechanical embedded coupling state refers to a thread-like engagement between the extended coupling structure and the underground medium, with no relative slippage, thus enabling efficient transmission of vibrational energy.

[0044] S21: After the excitation device reaches the underground target area, the driving mechanism causes the extended coupling structure to rotate around the axis.

[0045] The rotary joint mechanism includes a hydraulic motor, a reducer, and a rotary seal. The rotary motion output from the hydraulic motor is reduced in speed and torque by a planetary gear reducer with a reduction ratio of 10:1, resulting in an output speed of 5 revolutions per minute. The rotary motion is transmitted to the drill pipe via a spline sleeve, and then to the vibratory device housing, thereby driving the extended coupling structure to rotate clockwise around the central axis of the device. The rotary seal is a mechanical seal to prevent mud from entering the rotary joint.

[0046] S22: During rotation, an axial thrust is applied to the excitation device, causing the spiral blades or embedded ribs of the extended coupling structure to gradually rotate into the surrounding underground medium.

[0047] The axial thrust is provided by a hydraulic propulsion mechanism, with the pressure set via a proportional relief valve; a typical value is 2 MPa, corresponding to a thrust of 2 tons. Thrust is applied while the rotor rotates, causing the helical blades to screw into the underground medium like a screw. The helix angle of the helical blades is 15 degrees, the pitch is 50 mm, and the insertion depth is approximately 50 mm per rotation. The embedding ribs are longitudinally arranged strip-shaped protrusions, suitable for pressing in non-rotating conditions. During the screwing process, the carbide teeth at the blade tip break up local soil, while the back of the blade compacts the soil, forming a dense embedding layer.

[0048] S23: Monitor the screwing torque value in real time. When the screwing torque value reaches the preset clamping torque threshold, stop screwing.

[0049] The torque value is indirectly measured using pressure sensors installed at the inlet and outlet of the hydraulic motor. The relationship between torque and differential pressure is as follows: ,in Torque; The pressure difference between the motor inlet and outlet is expressed in Pascals. The value represents the motor displacement, expressed in cubic meters per revolution. The pressure sensor is a diffused silicon type, with a range of 0 to 25 MPa and an accuracy of 0.5 class.

[0050] The preset embedment torque threshold is calculated according to the following formula; ; in, The embedding torque threshold, The friction coefficient between the surface of the extended coupled structure and the underground medium was determined through indoor direct shear tests. The shear strength of the underground medium can be obtained through in-situ vane shear tests or indoor triaxial tests. This refers to the effective contact area between the extended coupling structure and the underground medium, such as the effective contact area between the helical blade or rib and the medium. The effective radius of the extended coupling structure can be taken as the average distance from the outer edge of the blade to the axis of the device.

[0051] Furthermore, the embedment torque threshold can be pre-calibrated according to the type of underground medium: 200 Nm for soft soil and 400 Nm for hard clay. When the torque reaches the threshold, the programmable logic controller sends a signal to close the hydraulic motor's oil supply valve, stopping the rotation.

[0052] S24: Maintain axial thrust to ensure a stable mechanically embedded contact between the extended coupling structure and the underground medium.

[0053] After the rotation stops, the hydraulic propulsion mechanism does not depressurize, but continues to provide axial thrust. This thrust firmly presses the blades or ribs of the extended coupling structure against the sidewall of the underground medium, making them difficult to loosen even during vibration. The characteristic of the mechanically embedded contact state is that there is no relative sliding between the extended coupling structure and the underground medium, and vibration energy can be directly transferred through the contact surface. By monitoring the displacement of the excitation device before and after vibration, if the displacement change is less than 1 mm, the embedding is considered stable.

[0054] S3: Determine the frequency range of the excitation signal based on the type of underground medium.

[0055] The types of underground media include loose soil, fill layers, sand layers, soft soil layers, and aquifers. Different media exhibit different propagation characteristics of elastic waves, requiring matching with different excitation frequencies. The excitation signal is an electrical signal used to drive the excitation unit to generate mechanical vibration; its frequency range determines the attenuation characteristics and detection resolution of the vibration wave underground. The method for determining the frequency range is as follows: first, collect media samples from the target underground area; obtain the density and P-wave velocity of the media through laboratory testing; then calculate the characteristic frequency value; and use this characteristic frequency value or its vicinity as the frequency value of the excitation signal. In practice, a borehole sampler is used to extract undisturbed soil cores. The sampler is a thin-walled soil sampler with an inner diameter of 100 mm. The soil core is then cut into cylindrical samples with a height-to-diameter ratio of 2:1.

[0056] S31: Collect media samples from the underground target area and obtain the density value of the media samples.

[0057] Medium samples were collected using a double-tube, single-acting core tube, with an inner tube diameter of 75 mm and a length of 1 m. After core collection, the cores were immediately wrapped and sealed with plastic wrap to prevent moisture evaporation. Density was determined in the laboratory using the ring cutter method. The ring cutter was made of stainless steel, with an inner diameter of 61.8 mm, a height of 20 mm, and a volume of 60 cubic centimeters. Vaseline was applied to the inner wall of the ring cutter, and the cutting edge was pressed into the soil core. Excess soil was removed using a trimming knife until the soil sample was flush with the top and bottom edges of the ring cutter. The total mass of the ring cutter and soil sample was weighed, and the mass of the soil sample was obtained by subtracting the mass of the ring cutter. Dividing this by the volume of the ring cutter yielded the wet density ρ. Typical values: loose soil 1.4 to 1.6 g / cm³, dense sand 1.8 to 2.0 g / cm³.

[0058] S32: Obtain the longitudinal wave velocity value of the medium sample through acoustic wave testing.

[0059] The ZBL-U520 non-metallic ultrasonic testing instrument was used for testing. The sample was placed on the test stage, with the transmitting and receiving probes in close contact with the two end faces of the sample, respectively, using Vaseline as the coupling agent. The instrument's transmitting voltage was set to 500 volts, and the sampling period to 0.1 microseconds. The time difference t between the ultrasonic wave and its reception was measured in microseconds. The sample length L was measured using vernier calipers with an accuracy of 0.02 mm. Longitudinal wave velocity... For example, if a clay sample with a length of 100 mm is measured at a time t = 50 microseconds, then... =2000 m / s. Typical range: 500 to 1500 m / s for loose soil, 1500 to 2500 m / s for dense sand.

[0060] S33: Calculate the characteristic frequency value based on the density value and the longitudinal wave velocity value. The calculation method is to divide the longitudinal wave velocity value by twice the diameter of the excitation device shell, or divide the longitudinal wave velocity value by the characteristic wavelength.

[0061] The characteristic frequency is the theoretical frequency at which the excitation device achieves optimal energy coupling with the underground medium. The first calculation method is applicable to cases where the diameter of the excitation device shell is used as the characteristic dimension, and the formula is as follows:

[0062] In the formula, The characteristic frequency value is expressed in Hertz. is the longitudinal wave velocity value, in meters per second; D is the diameter of the excitation device housing, in meters. For example, =1500 meters per second, D=0.15 meters, then =1500 / (2×0.15)=5000 Hz. The second calculation method is applicable to operating conditions where the characteristic wavelength λ is the dimension, and the formula is as follows:

[0063] In the formula, The characteristic wavelength, measured in meters, is typically taken as the maximum lateral dimension of the epitaxial coupling structure, such as the outer diameter of a helical blade. A typical value is 0.2 meters. =1500 / 0.2=7500 Hz. The appropriate formula should be selected based on the actual structure during calculation. Typical values ​​for the shell diameter D are 0.1 m to 0.3 m.

[0064] S34: Set the calculated characteristic frequency value as the frequency value of the excitation signal.

[0065] characteristic frequency value The frequency value is directly used as the excitation signal, meaning the excitation unit vibrates at a single frequency. If frequency sweep or broadband excitation is required, the frequency range is set to include... The interval, for example In the control software, the frequency parameter is written into the register of the digital signal synthesizer. For fixed-frequency excitation, the frequency value is fixed at... For frequency sweep excitation, the starting frequency is set to 0.8. The termination frequency is set to 1.2. The sweep rate is set to 5 Hz per second. The typical frequency range is 100 Hz to 10000 Hz.

[0066] S4: Determine the waveform type and encoding sequence of the excitation signal based on the target vibration response characteristics.

[0067] Target vibration response characteristics refer to the engineering target parameters that the user hopes to achieve through vibration excitation, mainly including detection depth and resolution. Detection depth requires the elastic wave to propagate to the target stratum, and resolution requires the ability to distinguish adjacent subsurface anomalies. Waveform types include sine waves, square waves, and pulse waves. Sine waves have concentrated energy, square waves contain abundant higher harmonics, and pulse waves have a wide spectrum but dispersed energy. Encoded sequences are used to modulate the excitation signal to improve the signal-to-noise ratio; for example, pseudo-random binary sequences or Barker code sequences. During implementation, the operator inputs the detection depth through a human-machine interface. and resolution Requirements. The control system automatically selects based on preset rules: when >50 meters and When the distance is >2 meters, select sine wave and continuous mode with no coding; when... ≤50 meters and For distances ≤1 meter, pulse waves and Barker code sequences are selected. The code sequence length is typically 7, 11, or 13 bits.

[0068] S41: Based on the detection resolution requirements in the target vibration response characteristics, select one waveform type from sine wave, square wave and pulse wave as the waveform type of the excitation signal.

[0069] The detection resolution requirement refers to the smallest identifiable underground target size, measured in meters. When the resolution requirement is low, such as greater than 2 meters, a sine wave is chosen because it has a pure spectrum, concentrated energy, and a large penetration depth. When the resolution requirement is moderate, such as 1 to 2 meters, a square wave is chosen because its steep rising edge generates high-frequency components, which helps improve resolution. When the resolution requirement is high, such as less than 1 meter, a pulse wave is chosen because its extremely narrow width corresponds to a wide spectrum, enabling the resolution to distinguish fine structures. For example, when detecting a 0.5-meter diameter cavity 5 meters underground, with a resolution requirement of 0.5 meters, a pulse wave is selected. The waveform type is determined by modifying the waveform lookup table of the drive signal synthesizer; the lookup table stores the waveform amplitude values ​​of 256 points.

[0070] S42: Based on the anti-interference requirements in the target vibration response characteristics, generate a pseudo-random binary sequence as the encoding sequence of the excitation signal.

[0071] Interference immunity requirements refer to the signal-to-noise ratio (SNR) requirements when mechanical noise, electromagnetic interference, or other vibration sources are present in the field. Pseudo-random binary sequences exhibit white noise characteristics and have a sharp autocorrelation function; correlation processing at the receiver can enhance the useful signal. Commonly used pseudo-random binary sequences are m-sequences, generated using linear feedback shift registers. For example, a 4-stage shift register can be used, with a feedback polynomial of x... 4+x+1, with an initial state of 1111, can generate an m-sequence of length 15: 111100010011010. The generation algorithm can be written in ST language in a programmable logic controller or by calling the pseudo-random sequence generation module in LabVIEW. The length of the encoded sequence is determined by the detection depth and symbol width, typically ranging from 7 to 255 bits.

[0072] In practical applications, the length of the encoded sequence (i.e., the order of the m-sequence) should be dynamically determined based on the attenuation characteristics of the underground medium and the detection requirements. This invention provides a quantization calculation method: The pseudo-random binary sequence is an m-sequence, and its order n is determined according to the following formula: ; in, For characteristic frequencies, For target detection depth, For the longitudinal wave velocity of the underground medium, The quality factor of the underground medium. This is the floor function.

[0073] The quality factor can be obtained through cross-well seismic tomography, vertical seismic profiles (VSP), or laboratory ultrasonic attenuation testing. Specifically, ,in, This is the amplitude attenuation coefficient.

[0074] S43: Determine the excitation timing of the excitation signal based on the encoding sequence.

[0075] Excitation timing refers to the sequential start-up and shutdown arrangement of the excitation unit. Each bit in the encoded sequence corresponds to a symbol time window, and the window length is set to... A typical value is 10 milliseconds. If this bit is binary 1, then in the corresponding... The excitation signal within the window is valid; if it is 0, then... The excitation signal amplitude is zero within the window. For example, the excitation timing of the sequence [1,0,1] is: oscillation for the first 10 milliseconds, cessation for the middle 10 milliseconds, and oscillation for the last 10 milliseconds. Timing control is achieved through the gating function of the digital signal synthesizer; a high level of the gating signal enables the output, and a low level disables the output. In practice, the encoded sequence is converted into a Boolean array, and array elements are read sequentially at fixed time steps to control the switching of the output channel.

[0076] S5: Generate the corresponding driving signal based on the frequency range, waveform type, and encoding sequence.

[0077] The drive signal is an analog voltage signal used to drive the excitation unit. The generation process employs direct digital frequency synthesis (DDS). First, the start frequency, stop frequency, and step frequency of the digital frequency synthesizer are set according to the frequency range; the corresponding waveform table is loaded according to the waveform type; and the gating timing is generated according to the encoding sequence. Then, the digital frequency synthesizer calculates the output amplitude point-by-point at a fixed sampling rate (e.g., 1 MHz) to obtain the digital drive signal. Finally, it is converted into an analog voltage drive signal through a digital-to-analog converter and a power amplifier. Specifically, the AD9854 DDS chip is used, which integrates a high-speed phase accumulator and a sine / cosine lookup table. The microcontroller writes the frequency tuning word and waveform control word to the chip via the SPI bus. The formula for calculating the frequency tuning word is: , in, For output frequency, The typical system clock frequency is 200 MHz. Gating of the coded sequence is implemented by an external AND gate circuit, and the output of the direct digital frequency synthesizer is sent to the power amplifier after passing through the AND gate.

[0078] S51: Set the base frequency parameter of the drive signal according to the frequency range.

[0079] The fundamental frequency parameters include the starting frequency, the ending frequency, and the rate of frequency change. For fixed-frequency excitation, the starting frequency equals the ending frequency, and the rate of frequency change is zero. For swept-frequency excitation, the starting frequency... Set as the lower limit of the frequency range, and terminate at the specified frequency. Set as the upper limit of the frequency range, sweep rate Set to the number of Hertz that changes per second, typically 10 Hertz per second. The frequency tuning word of the digital frequency synthesizer is updated linearly over time. This is achieved by setting a timer interrupt in the microcontroller, which occurs every [time / period]. Calculate the current frequency based on time: , And update the frequency tuning word. The typical value is 10 milliseconds.

[0080] S52: Set the waveform function of the drive signal according to the waveform type.

[0081] The waveform function describes how the voltage amplitude changes over time. For a sine wave, the waveform function is: , Where A is the amplitude and f is the frequency. This is the initial phase. For a square wave, the waveform function is a periodic step signal with the amplitude switching between +A and -A, and a duty cycle of 50%. For a pulse wave, the waveform function is a single narrow pulse or a periodic pulse sequence, with a pulse width of... Much smaller than the period T, typical value =0.1 microseconds. In a direct digital frequency synthesizer, waveform functions are implemented using waveform lookup tables: the sine wave lookup table stores the amplitude sequence of a sine function within one cycle; the square wave lookup table stores +A in the first half of the cycle and -A in the second half; the pulse wave lookup table stores +A only within a very short time window, and 0 for the rest. Users can switch between lookup tables using a selector switch.

[0082] S53: Set the timing on / off parameters of the drive signal according to the encoding sequence.

[0083] Timing on / off parameters include symbol period And the output enable signal within each symbol. The encoded sequence is converted into a set of binary numbers, each binary number corresponding to a... Time window. Within the window, if the binary number is 1, the output is enabled; if it is 0, the output is disabled. The enable signal is generated by an independent timer: the timer presses... A periodic interrupt occurs when the interrupt service routine reads the next encoded bit and sets or clears the level of a general-purpose input / output (GPIO) pin. This pin is connected to the control terminal of an analog switch, which is connected in series between the direct digital frequency synthesizer and the power amplifier. For example, using a DG419 analog switch, the switch is on when the control pin is high and off when it is low.

[0084] S54: Synthesize a continuous voltage drive signal based on the fundamental frequency parameters, waveform function, and timing on / off parameters.

[0085] The synthesis process is divided into two stages: First, a direct digital frequency synthesizer generates a continuous basic waveform signal based on the fundamental frequency parameters and waveform function. Then, it is chopper-modulated by an AND gate or analog switch according to timing parameters to obtain the encoded continuous signal. The basic waveform signal is a voltage sequence with an amplitude of ±1 volt, which is output after digital-to-analog conversion. This signal is then ANDed with a gating signal; a high level gating signal outputs the original signal, and a low level gating signal outputs 0 volts. Finally, the signal is sent to a power amplifier, amplified to ±50 volts to drive the excitation unit. The entire synthesis process is controlled in a closed loop by an FPGA or microcontroller to ensure strict synchronization of frequency, waveform, and timing.

[0086] S6: Based on the driving signal, control the excitation unit to generate corresponding periodic mechanical vibration.

[0087] The excitation unit is an actuator that converts electrical energy into mechanical vibration; in this embodiment, an electromagnetic exciter is used. The electromagnetic exciter consists of an excitation coil, an iron core, and a mover. The drive signal is a voltage signal applied to both ends of the excitation coil. When the drive signal changes, the coil current changes accordingly, generating a changing magnetic field force that drives the mover to reciprocate, thus producing periodic mechanical vibration. The frequency, waveform profile, and coded discontinuities of the mechanical vibration are entirely determined by the drive signal. In implementation, the voltage drive signal output from the power amplifier is directly connected to the input terminals of the exciter. The mover output terminal of the exciter is fixedly connected to an inertial mass block, which is a cylindrical steel block weighing 5 kg, used to increase the excitation force.

[0088] Periodic mechanical vibrations can be fixed-frequency continuous vibrations, swept-frequency continuous vibrations, or coded-modulated pulse vibrations.

[0089] Fixed-frequency continuous vibration refers to the excitation unit continuously outputting at a single fixed frequency, suitable for exploration scenarios requiring a stable single frequency, such as resonance detection. Sweep-frequency continuous vibration refers to the frequency continuously changing within a certain range, such as linearly increasing from 100 Hz to 1000 Hz, suitable for scenarios requiring wideband excitation, such as analyzing formation frequency response. Encoded modulation pulse vibration refers to on / off modulation of vibration according to a coded sequence, with each pulse having a narrow width, suitable for high-resolution shallow exploration or interference-resistant exploration. The three modes are selected through an external control system, and the corresponding drive signal generation methods are described in S5. During implementation, users select the mode through the software interface according to engineering requirements; for example, coded modulation pulse vibration is selected for tunnel advance prediction, and sweep-frequency continuous vibration is selected for foundation detection.

[0090] S61: Outputs the voltage drive signal to the electrical input terminal of the excitation unit.

[0091] The voltage drive signal is transmitted via a two-core shielded cable, with the shield grounded at one end to suppress electromagnetic interference. One end of the cable connects to the output terminal of the power amplifier, and the other end connects to the junction box of the exciter unit. The junction box contains transient voltage suppression diodes to absorb overvoltage spikes and protect the exciter coil. The typical impedance of the exciter unit's input terminal is 8 ohms. The voltage amplitude of the drive signal is user-defined, typically ±50 volts. Before output, the signal waveform is monitored using an oscilloscope to confirm it matches expectations.

[0092] S62: The excitation unit generates mechanical vibration at a corresponding frequency based on the fundamental frequency parameter of the voltage drive signal.

[0093] The mechanical vibration frequency of the electromagnetic exciter is strictly equal to the fundamental frequency of the drive signal. When the drive signal frequency is f, the coil current changes at the same frequency, and the generated electromagnetic force also changes at frequency f, driving the mover to vibrate at frequency f. For example, if the drive signal frequency is 500 Hz, the exciter will output a mechanical vibration of 500 Hz. The accuracy of the frequency depends on the frequency tuning word precision of the direct digital frequency synthesizer, with an error of less than 0.01 Hz. The vibration frequency is verified by measuring and attaching an accelerometer to the housing.

[0094] S63: The excitation unit generates mechanical vibration corresponding to the waveform profile based on the waveform function of the voltage drive signal.

[0095] Waveform profile refers to the shape of vibration displacement, velocity, or acceleration over time. For a sinusoidal drive signal, the exciter outputs a sinusoidal displacement, meaning the mover position changes sinusoidally. For a square wave drive signal, the mover position rapidly switches from one end to the other and remains there for a period of time, forming a trapezoidal waveform profile. Due to mechanical inertia, the actual displacement cannot achieve an ideal square wave, but the acceleration waveform approximates a square wave. For a pulse wave drive signal, the mover generates an instantaneous impact, and the displacement is a spike pulse. The waveform profile is verified by measuring the mover displacement using a laser displacement gauge and compared with the shape of the drive signal. Electromagnetic exciters have a fast electromagnetic force response speed and a bandwidth of up to 10 kHz, thus they can reproduce the waveform profile relatively well.

[0096] S64: The excitation unit generates corresponding coded discontinuous mechanical vibrations based on the timing on / off parameters of the voltage drive signal.

[0097] Encoded discontinuity refers to the complete cessation of mechanical vibration within the time window corresponding to the 0th bit of the encoded sequence. When the drive signal is gated off and the voltage is zero, the electromagnetic exciter coil current is zero, the electromagnetic force is zero, and the mover returns to its center position and stops vibrating under the spring's restoring force. Due to the inertia of the mechanical system, the vibration requires a certain amount of time to stop, typically with the amplitude decaying to below 5% within 1 millisecond. The length of the time window for encoded discontinuity... It should be much longer than the vibration decay time, typically 10 milliseconds. In this way, during the time period when the encoded sequence is 0, the excitation device does not output vibration energy, thus realizing the encoded modulation of vibration energy.

[0098] S7: Based on periodic mechanical vibration, the vibration force is transmitted to the extended coupling structure through the force transmission unit.

[0099] The force transmission unit is a mechanical component connecting the excitation unit and the extended coupling structure. Its function is to efficiently transmit mechanical vibration force while reducing energy loss. In this embodiment, the force transmission unit includes a waveguide core rod, an inertial mass block, and a connecting sleeve. The waveguide core rod is a slender rod of high-strength alloy steel, 20 mm in diameter and 500 mm in length. Its acoustic impedance is matched with the output end of the excitation unit to reduce reflection. The periodic mechanical vibration generated by the excitation unit first acts on the inertial mass block, which inputs the vibration displacement through the first end face of the waveguide core rod. The waveguide core rod propagates axially to the second end face in the form of an elastic wave. At the second end face, the displacement is converted into a push-pull force, which is transmitted to the force transmission interface of the extended coupling structure via the connecting sleeve. The sealing and vibration isolation structure prevents vibration energy from leaking along the shell.

[0100] S71: Input the periodic mechanical vibration displacement generated by the excitation unit to the first end face of the waveguide core rod.

[0101] The output end of the excitation unit's mover is connected to the inertial mass block via a thread, and the inertial mass block is in turn connected to the first end face of the waveguide core rod via an interference fit. The first end face is a precision-ground plane with a roughness Ra of less than 0.4 micrometers to ensure tight contact. The typical amplitude of the periodic mechanical vibration displacement is 0.5 millimeters. When the mover vibrates, the inertial mass block directly transmits the vibration displacement to the end face of the waveguide core rod, and the mass points on the end face move with the same displacement law.

[0102] S72: The waveguide core rod propagates the periodic mechanical vibration displacement along the axial direction of the rod to the second end face.

[0103] As an elastic waveguide, the waveguide core propagates axially as a longitudinal wave. The propagation speed depends on the Young's modulus and density of the material. For a steel waveguide core, the longitudinal wave velocity is approximately 5000 meters per second. With a core length of 500 millimeters, the propagation time is only 0.1 milliseconds, much shorter than the vibration period, thus it can be considered a quasi-static transmission, meaning the displacement of the second end face is almost synchronous with that of the first end face. During propagation, the energy attenuates slightly due to internal material damping, approximately 0.5 dB per meter. The waveguide core is externally wrapped with a damping rubber layer to suppress transverse vibration modes.

[0104] S73: At the second end face, the periodic mechanical vibration displacement is converted into periodic push-pull force, and the periodic push-pull force is transmitted to the force transmission interface of the extended coupling structure through the connecting sleeve.

[0105] The second end face contacts the force transmission shaft, which is a stepped shaft. Vibration displacement causes the second end face to periodically expand and contract, generating a pushing and pulling force on the force transmission shaft: when the end face extends outward, it exerts a pushing force on the force transmission shaft, and when it retracts inward, it exerts a pulling force. The magnitude of the pushing and pulling forces... ,in The axial stiffness of the force transmission shaft is expressed in Newtons per meter. Displacement amplitude, in meters. Typical value: Stiffness =1×10 7 per meter of cattle =0.5 mm, then F = 5000 N. The connecting sleeve is a threaded sleeve that fixes the force transmission shaft to the extended coupling structure, and the push and pull forces are transmitted to the extended coupling structure without loss. A bellows seal is provided between the connecting sleeve and the housing to prevent external impurities from entering.

[0106] S8: Based on the vibration force transmitted to the extended coupling structure, mechanical vibration energy is input into the underground medium.

[0107] The extended coupling structure generates synchronous mechanical displacement under periodic push-pull forces. Since the extended coupling structure has formed a mechanically embedded coupling with the underground medium, its displacement directly compresses the surrounding underground medium. Under this compression, the underground medium undergoes elastic deformation, which propagates as elastic waves away from the excitation device, thus achieving vibrational energy input. The propagation direction of the elastic waves is mainly radially outward, with some axial. The energy input efficiency depends on the quality of the embedded coupling; the tighter the embedding, the more energy is transferred. This process is repeated continuously, allowing the underground medium to receive continuous mechanical vibrational energy, forming a stable elastic wave field.

[0108] S81: The extended coupling structure generates synchronous radial expansion displacement or axial expansion displacement based on the received periodic push-pull force.

[0109] The extended coupling structure is in the form of a helical blade. When a thrust or pull force is applied axially, the helical blade, due to its helical geometry, not only undergoes axial expansion and contraction but also radial expansion. The axial thrust or pull force causes the blade to compress or stretch axially, while the outer edge of the blade expands or contracts radially due to the helix angle. The magnitude of the displacement is proportional to the thrust or pull force, and the proportionality coefficient is determined by the geometric stiffness of the blade and the elastic modulus of the material. For example, when the axial thrust is 5000 N, the axial displacement is 0.2 mm, and the radial expansion is 0.1 mm. These displacements are sufficient to effectively compress the surrounding medium at the vibration frequency.

[0110] S82: The embedded protrusions or helical blades on the surface of the extended coupling structure will directly compress the surrounding underground medium.

[0111] The embedded protrusions are serrated structures on the blade surface, 2 mm high and 5 mm apart. When the blade expands radially, the embedded protrusions apply radial pressure to the surrounding underground medium; when the blade contracts axially, the embedded protrusions apply axial shear force to the medium. Because the embedded protrusions are embedded inside the medium, the displacement is forcibly transmitted to the medium particles, causing the medium particles to undergo the same displacement. This direct contact transmission method avoids sliding friction losses, and the energy transfer efficiency can reach over 90%. During the compression process, the medium is repeatedly compressed and released hundreds to thousands of times per second, generating stress waves inside the medium.

[0112] S83: Under compression, the underground medium undergoes elastic deformation and propagates vibration energy in the form of elastic waves in a direction away from the excitation device.

[0113] Elastic deformation refers to the change in volume and shape of an underground medium under stress, a change that can be recovered after the stress is removed. For soil, elastic deformation mainly manifests as the compression and displacement between particles. Elastic wave propagation follows the wave equation, and the longitudinal wave velocity... This has been measured in S32. Vibrational energy propagates in the form of waves, and the propagation distance depends on the damping characteristics of the medium. In loose soil, high-frequency components attenuate rapidly, and an elastic wave with a center frequency of 500 Hz can propagate for tens of meters; in dense rock, it can propagate for hundreds of meters. During energy propagation, receiving sensors such as geophones are placed on the surface or in adjacent boreholes to record the elastic wave signal for inversion of underground structures.

[0114] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0115] This application uses specific terms to describe embodiments of the application. Terms such as "first / second embodiment," "an embodiment," and / or "some embodiments" refer to a particular feature, structure, or characteristic associated with at least one embodiment of the application. Therefore, it should be emphasized and noted that references to "an embodiment," "one embodiment," or "an alternative embodiment" in different locations throughout this specification do not necessarily refer to the same embodiment. Furthermore, certain features, structures, or characteristics in one or more embodiments of the application can be appropriately combined.

[0116] Furthermore, those skilled in the art will understand that aspects of this application can be described and illustrated through several patentable types or situations, including any new and useful combination of processes, machines, products, or substances, or any new and useful improvements thereof. Accordingly, aspects of this application can be implemented entirely by hardware, entirely by software (including firmware, resident software, microcode, etc.), or by a combination of hardware and software. All of the above hardware or software may be referred to as a “data block,” “module,” “engine,” “unit,” “component,” or “system.” Furthermore, aspects of this application may manifest as a computer product located on one or more computer-readable media, the product including computer-readable program code.

[0117] Unless otherwise defined, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in a common dictionary shall be interpreted as having a meaning consistent with their meaning in the context of the relevant art, and not as having an idealized or highly formalized meaning, unless expressly defined herein.

[0118] The foregoing description is illustrative of the invention and should not be construed as limiting it. Although several exemplary embodiments of the invention have been described, those skilled in the art will readily understand that many modifications can be made to the exemplary embodiments without departing from the novel teachings and advantages of the invention. Therefore, all such modifications are intended to be included within the scope of the invention as defined in the claims. It should be understood that the foregoing description is illustrative of the invention and should not be construed as limiting it to the specific embodiments disclosed, and modifications to the disclosed embodiments and other embodiments are intended to be included within the scope of the appended claims. The invention is defined by the claims and their equivalents.

Claims

1. A method for coupling vibration energy in underground media, characterized in that, include: The excitation device is transported to the underground target area; This enables the extensional coupling structure of the excitation device to form a mechanically embedded coupling state with the underground medium; The frequency range of the excitation signal is determined based on the type of underground medium. Based on the target vibration response characteristics, determine the waveform type and encoding sequence of the excitation signal; Based on the frequency range, the waveform type, and the encoding sequence, a corresponding driving signal is generated; According to the driving signal, the excitation unit is controlled to generate corresponding periodic mechanical vibrations; According to the periodic mechanical vibration, the vibration force is transmitted to the extended coupling structure through the force transmission unit; Mechanical vibration energy is input into the underground medium based on the vibration force transmitted to the extended coupling structure.

2. The method according to claim 1, characterized in that, Determining the frequency range of the excitation signal based on the type of underground medium includes: Collect media samples from the underground target area and obtain the density value of the media samples; The longitudinal wave velocity value of the medium sample was obtained by acoustic wave testing; Based on the density value and the longitudinal wave velocity value, the characteristic frequency value is calculated by dividing the longitudinal wave velocity value by twice the diameter of the excitation device housing, or by dividing the longitudinal wave velocity value by the characteristic wavelength. Set the calculated characteristic frequency value as the frequency value of the excitation signal.

3. The method according to claim 1, characterized in that, The process of determining the waveform type and encoding sequence of the excitation signal based on the target vibration response characteristics includes: The waveform type of the excitation signal is determined based on the detection resolution requirements in the target vibration response characteristics. Based on the anti-interference requirements in the target vibration response characteristics, a pseudo-random binary sequence is generated as the encoding sequence of the excitation signal; The excitation timing of the excitation signal is determined based on the encoded sequence.

4. The method according to claim 1, characterized in that, The step of generating the corresponding driving signal based on the frequency range, the waveform type, and the encoding sequence includes: Based on the frequency range, the fundamental frequency parameters of the driving signal are set, including the starting frequency value, the ending frequency value, and the frequency change rate; According to the waveform type, the waveform function of the driving signal is set. The waveform function is used to describe the change law of voltage amplitude with time, and the corresponding waveform lookup table is selected according to the sine wave, square wave or pulse wave. Based on the encoded sequence, the timing on / off parameters of the driving signal are set, and the timing on / off parameters include the symbol period and the output enable signal within each symbol; Based on the fundamental frequency parameters, the waveform function, and the timing on / off parameters, a digital drive signal is generated using direct digital frequency synthesis technology. The digital drive signal is then sequentially converted from digital to analog and amplified to synthesize a continuous voltage drive signal.

5. The method according to claim 4, characterized in that, The process of controlling the excitation unit to generate corresponding periodic mechanical vibrations according to the driving signal includes: The voltage drive signal is output to the electrical input terminal of the excitation unit; The excitation unit generates mechanical vibration at a corresponding frequency according to the fundamental frequency parameter of the voltage drive signal; The excitation unit generates mechanical vibration corresponding to the waveform profile according to the waveform function of the voltage drive signal. The excitation unit generates corresponding coded discontinuous mechanical vibrations based on the timing on / off parameters of the voltage drive signal.

6. The method according to claim 1, characterized in that, The process of delivering the excitation device to the underground target area includes: Connect the excitation device to the end of the drill rod or feed rod; The drill rod or push rod is driven to move linearly along the borehole axis by a hydraulic propulsion mechanism. The drilling depth of the drill pipe or push rod is monitored in real time, and the push is stopped when the drilling depth reaches the preset target depth value; Lock the position of the drill rod or push rod to keep the excitation device within the underground target area.

7. The method according to claim 1, characterized in that, The process of establishing a mechanically embedded coupling state between the extensional coupling structure of the excitation device and the underground medium includes: After the excitation device reaches the underground target area, the driving mechanism causes the extended coupling structure to rotate around the axis. During the rotation process, an axial thrust is applied to the excitation device, causing the spiral blades or embedded ribs of the extended coupling structure to gradually rotate into the surrounding underground medium. The screwing torque value is monitored in real time, and the screwing is stopped when the screwing torque value reaches the preset clamping torque threshold. Maintaining the axial thrust, a stable mechanically embedded contact state is formed between the extended coupling structure and the underground medium; wherein, the preset embedding torque threshold is calculated according to the following formula; ； in, The embedding torque threshold, The coefficient of friction between the surface of the extended coupling structure and the underground medium. The shear strength of the underground medium. This refers to the effective contact area between the extended coupling structure and the underground medium. The effective radius of the extended coupling structure.

8. The method according to claim 1, characterized in that, The method of transmitting vibrational force to the extended coupling structure through a force transmission unit based on periodic mechanical vibration includes: The periodic mechanical vibration displacement generated by the excitation unit is input to the first end face of the waveguide core rod; The waveguide core rod propagates the periodic mechanical vibration displacement along the rod's axial direction to the second end face; At the second end face, the periodic mechanical vibration displacement is converted into a periodic push-pull force, and the periodic push-pull force is transmitted to the force transmission interface of the extended coupling structure through the connecting sleeve.

9. The method according to claim 1, characterized in that, The input of mechanical vibration energy into the underground medium based on the vibration force transmitted to the extended coupling structure includes: The extended coupling structure generates synchronous radial expansion displacement or axial expansion displacement according to the received periodic push-pull force. The embedded protrusions or helical blades on the surface of the extended coupling structure directly compress the displacement into the surrounding underground medium. The underground medium undergoes elastic deformation under compression and propagates vibration energy in the form of elastic waves in a direction away from the excitation device.

10. The method according to claim 3, characterized in that, The pseudo-random binary sequence is an m-sequence, and its order n is determined according to the following formula: ； in, For characteristic frequencies, For target detection depth, For the longitudinal wave velocity of the underground medium, The quality factor of the underground medium. This is the floor function.

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