A device for measuring sediment at the bottom of bridge pile holes

Abstract

This invention relates to the field of engineering surveying technology and discloses a device for measuring sediment at the bottom of bridge pile holes, comprising a rheological impedance probe, a depth transmission component, and a main control terminal. The probe contains an inertial base, a miniature impedance acquisition circuit, and a suspended torsional piezoelectric transducer; a shear wave sensing rod with shear coupling texture is rigidly connected to the lower end of the transducer, extending through the probe. The device utilizes the rheological difference between the boundary slip of fluid mud and the mechanical interlocking of solid sediment to cause a sudden change in the mechanical load of the sensing rod, thereby inducing a step change in the electrical impedance signal. The main control terminal combines depth data and impedance change characteristics to automatically locate the top surface of the sediment and the hard bottom of the bearing layer. This invention achieves accurate and objective measurement of the thickness of sediment at the bottom of pile holes through electromechanical coupling impedance analysis, solving the problem of fuzzy interface identification in complex mud environments using traditional methods.

Description

Technical Field

[0001] This invention relates to the field of engineering surveying technology, specifically to a device for measuring sediment at the bottom of bridge pile holes. Background Technology

[0002] Currently, bored piles are widely used as a primary foundation type in bridge engineering foundation construction. The degree of sediment removal at the bottom of the borehole directly determines the ultimate bearing capacity and subsequent settlement of the pile foundation. If the thickness of the sediment remaining at the bottom of the borehole after pile completion exceeds the specified limit, a highly compressible and weak interlayer will form between the pile tip and the bearing stratum, significantly weakening the end-bearing capacity and even posing a safety hazard to the project. Therefore, accurate and objective on-site measurement of the sediment thickness at the bottom of the borehole before the concrete pouring process is an indispensable and crucial step in controlling the quality of concealed works.

[0003] To address the need for sediment thickness detection, current engineering applications primarily employ techniques such as the hammer test, resistivity method, and ultrasonic reflection method. The hammer test relies on operators lowering a standard weight using a handheld measuring rope, estimating sediment location by sensing changes in rope tension and the rebound upon contact with the bottom. The resistivity method utilizes the differences in porosity and conductivity between sediment and mud, inferring the interface by measuring the apparent resistivity profile using a lowered electrode system. The ultrasonic reflection method uses a probe to emit high-frequency longitudinal waves towards the bottom of the borehole, calculating the sediment layer thickness based on the time difference of reflection echoes at different acoustic impedance interfaces, combined with the sound velocity in the medium.

[0004] However, the aforementioned existing technologies exhibit limitations when dealing with complex wellbore environments. Firstly, in conditions where high-density wall-supporting mud and loose floating sludge coexist, their physical densities and electrochemical properties are quite similar, making it difficult for detection methods based on density or conductivity differences to capture a clear physical interface, often resulting in blurred interfaces or even misjudgments. Secondly, traditional acoustic or vibration detection probes often employ a structure where the excitation source is directly coupled to the casing, lacking effective mechanical isolation measures. This causes vibration energy to easily be converted into parasitic resonance in the casing or dissipated along the cable, resulting in a reduced signal-to-noise ratio and making the measurement data susceptible to fluctuations due to downhole environmental noise. Furthermore, the over-reliance on manual experience in interpretation lacks unified quantitative indicators, making it impossible to objectively evaluate the density or rheological state of the sediment, and failing to meet the stringent requirements of modern construction for the accuracy and traceability of detection data.

[0005] Therefore, the present invention provides a device for measuring sediment at the bottom of bridge pile holes to address the shortcomings of the prior art. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a device for measuring sediment at the bottom of bridge pile holes. This device solves the problems of insufficient accuracy and objectivity in existing technologies due to the similar physical properties of sediment and mud in high-density mud environments, resulting in blurred interface recognition, low signal-to-noise ratio, and reliance on human experience.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solution: a device for measuring sediment at the bottom of bridge pile holes, comprising a ground main control terminal, a depth transmission component, and a rheological impedance detection probe connected via a load-bearing communication cable; A torsional piezoelectric transducer is rigidly fixed under the inertial base inside the rheological impedance detection probe. The torsional piezoelectric transducer is connected to a shear wave sensing rod extending to the outside. A miniature impedance acquisition circuit and an auxiliary unlocking exciter are provided on the inertial base. The miniature impedance acquisition circuit is used to drive the torsional piezoelectric transducer and the auxiliary unlocking exciter. The ground main control terminal is used to determine the position of sediment based on impedance data and depth data, and to control the auxiliary unlocking exciter to generate vibration when the torsional piezoelectric transducer is in a mechanically locked state, thereby releasing the mechanically locked state through the vibration.

[0008] Preferably, the rheological impedance detection probe further includes a sealed housing, and the outer peripheral surface of the inertial base is rigidly fixedly connected to the inner wall surface of the sealed housing; An air vibration isolation gap is provided between the side of the torsional piezoelectric transducer and the inner wall of the sealed housing. A dynamic sealing assembly is provided between the shear wave sensing rod and the bottom opening of the sealed housing. The dynamic sealing assembly is used to block the entry of external liquid and allow the shear wave sensing rod to generate micro-amplitude torsional vibration relative to the sealed housing.

[0009] Preferably, the torsional piezoelectric transducer is composed of stacked piezoelectric ceramic rings that are tangentially polarized along the circumference, and the torsional piezoelectric transducer is used to generate reciprocating shear deformation around the central axis; The mass of the inertial base is greater than the sum of the masses of the torsional piezoelectric transducer and the shear wave sensing rod. The inertial base is used to provide a reference ground potential where the vibration displacement is zero when the shear wave sensing rod is in operation.

[0010] Preferably, the shear wave sensing rod has a shear coupling texture on its surface exposed outside the sealed housing, and the shear coupling texture is composed of a microstructure array of grooves or protrusions; The shear coupling texture is used to generate fluid boundary layer slip in the mud medium and to form a mechanical interlock with the sediment particles when in contact with the sediment medium.

[0011] Preferably, the auxiliary unlocking exciter is rigidly fixed to the upper surface of the inertial base, and the auxiliary unlocking exciter is an eccentric rotating mass motor or a linear resonant actuator; The miniature impedance acquisition circuit is used to apply a driving signal with gradually increasing voltage amplitude or duty cycle to the auxiliary unlocking exciter; During the operation of the auxiliary unlocking exciter, the micro impedance acquisition circuit intermittently drives the torsional piezoelectric transducer to detect impedance. When the detected impedance value deviates from the mechanical lock-up threshold range, the micro impedance acquisition circuit stops driving the auxiliary unlocking exciter.

[0012] Preferably, the miniature impedance acquisition circuit includes a direct digital frequency synthesizer and a power amplifier. The miniature impedance acquisition circuit is used to apply a sinusoidal sweep voltage signal to the torsional piezoelectric transducer and simultaneously acquire response current and terminal voltage data in the circuit, and calculate the complex impedance modulus using the response current and terminal voltage data.

[0013] Preferably, a hydrostatic pressure sensor is installed on the side wall of the sealed housing, the sensing end face of the hydrostatic pressure sensor is exposed outside the sealed housing, and the signal output terminal of the hydrostatic pressure sensor is electrically connected to the miniature impedance acquisition circuit.

[0014] Preferably, the rheological impedance detection probe is provided with a flow guide cover at the top, the flow guide cover has a streamlined conical structure and is sealed to the upper end face of the sealing housing; The load-bearing communication cable passes through the central axis of the flow guide and enters the sealed housing. The tensile bearing point of the load-bearing communication cable is located inside the flow guide.

[0015] Preferably, the depth transmission component includes a ground winch system and a depth encoder, wherein the ground winch system is used to drive the winding and unwinding of the load-bearing communication cable, and the depth encoder is used to generate a pulse signal corresponding to the probe depth; The ground control terminal is used to bind the probe depth with the impedance data received at the same time to generate a depth impedance data pair.

[0016] Preferably, the ground control terminal is used to calculate the normalized impedance depth change rate, which is a value obtained by dividing the degree of deviation of the impedance modulus at the current depth point relative to the impedance modulus of the mud baseline by the change per unit depth. When the normalized impedance depth change rate continuously exceeds the preset rheological threshold, the ground main control terminal determines that the shear wave sensing rod has contacted the top surface of the sediment layer.

[0017] This invention provides a device for measuring sediment at the bottom of bridge pile holes. It has the following beneficial effects: 1. This invention employs a torsional piezoelectric transducer in conjunction with a shear wave sensing rod featuring shear coupling texture. Utilizing the rheological difference between fluid media, which cannot withstand shear stress, and solid sediment media, which possess shear modulus, the sensing rod undergoes boundary slippage in the mud, forming a mechanical interlock within the sediment. This mechanism converts the phase change of the medium into an electrical impedance step signal, thereby achieving highly sensitive identification of the mud-sludge interface and solving the problem of blurred interface identification in low-density-difference environments using traditional density methods or longitudinal wave reflection methods.

[0018] 2. This invention utilizes a large-mass inertial base and a suspended vibration isolation mounting structure. By setting the mass of the inertial base to be greater than the total mass of the excitation assembly and setting an air vibration isolation gap on the side of the transducer, the leakage of torsional vibration energy to the sealed housing and the load-bearing communication cable is effectively blocked. This structural design provides a stable mechanical fixed point for the vibration system, ensuring that the impedance change obtained by the miniature impedance acquisition circuit truly reflects the load characteristics of the external medium, eliminating the measurement noise caused by the parasitic resonance of the probe housing itself, and improving the signal-to-noise ratio of the system.

[0019] 3. This invention combines the synchronous acquisition and analysis logic of the depth transmission component and the main control terminal with an active protection mechanism. It locks the top surface of the sediment by calculating the normalized impedance depth change rate in real time, and locks the bottom of the hole by utilizing the mechanical load change characteristics when the shear wave sensing rod touches the bearing layer. During this process, in response to the risk of probe seizure that may be caused by deep high-viscosity media, the system uses impedance feedback to automatically trigger the auxiliary unlocking vibrator to generate vibration to break the thixotropic adhesion and achieve in-situ detachment. This method not only eliminates the subjective error of the traditional hammer test method that relies too much on human touch, but also solves the engineering pain points of traditional probes being easy to get stuck and difficult to retrieve, thus improving the objectivity of bridge pile foundation detection data and the safety of the operation process. Attached Figure Description

[0020] Figure 1 This is a three-dimensional schematic diagram of the overall appearance of the rheological impedance detection probe according to an embodiment of the present invention; Figure 2 This is a longitudinal internal structural cross-sectional view of the rheological impedance detection probe according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the overall system connection principle of the device according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the sediment determination method according to an embodiment of the present invention.

[0021] Among them, 100 is the rheological impedance detection probe; 101 is the sealed housing; 102 is the inertial base; 103 is the torsional piezoelectric transducer; 104 is the shear wave sensing rod; 105 is the miniature impedance acquisition circuit; 106 is the hydrostatic pressure sensor; 107 is the rigid connector; 108 is the dynamic sealing assembly; 109 is the flow guide; 110 is the shear coupling texture; 111 is the auxiliary unlocking exciter; 200 is the depth transmission assembly; 201 is the load-bearing communication cable; 202 is the depth encoder; 203 is the ground winch system; and 300 is the ground main control terminal. Detailed Implementation

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] See attached document Figure 1 and attached Figure 2 This invention provides a device for measuring sediment at the bottom of bridge pile holes. Its main structure includes a rheological impedance probe 100 located underground, a depth transmission component 200 for connecting to a surface system, and a ground-based main control terminal 300. The rheological impedance probe 100 is mechanically connected and electrically communicated with the depth transmission component 200 and the ground-based main control terminal 300 via a load-bearing communication cable 201.

[0024] The external protective structure of the rheological impedance probe 100 mainly consists of a sealed housing 101 and a flow guide shroud 109 located at the top. The sealed housing 101 is a high-pressure resistant hollow cylindrical rigid cylinder used to isolate the external mud environment and protect the internal precision components. The flow guide shroud 109 is fixedly connected to the top of the sealed housing 101, and the load-bearing communication cable 201 passes through the central axis of the flow guide shroud 109 and enters the interior of the sealed housing 101 through a watertight connector. The outer surface of the flow guide shroud 109 is designed with a streamlined conical structure to reduce the resistance of the mud fluid during probe lowering and to prevent the probe from snagging on well wall obstacles. A hydrostatic pressure sensor 106 is installed at a predetermined position on the side wall of the sealed housing 101. The sensing end face of the hydrostatic pressure sensor 106 is exposed to the external space of the sealed housing 101 to sense the hydrostatic pressure at the probe location in real time. The electrical lead end of the hydrostatic pressure sensor 106 is located inside the sealed housing 101.

[0025] The internal core support structure of the rheological impedance detection probe 100 includes an inertial base 102. The inertial base 102 is a high-density metal block, and its outer peripheral surface is rigidly fixed to the inner wall of the sealed housing 101 through an interference fit or mechanical fasteners. The inertial base 102 divides the internal space of the sealed housing 101 axially into an upper electrical compartment and a lower electromechanical transducer compartment. A miniature impedance acquisition circuit 105 and an auxiliary unlocking exciter 111 are installed on the upper surface of the inertial base 102. The miniature impedance acquisition circuit 105 is electrically connected to the load-bearing communication cable 201, the torsional piezoelectric transducer 103, the hydrostatic pressure sensor 106, and the auxiliary unlocking exciter 111 via cables.

[0026] The excitation and detection actuator of the rheological impedance detection probe 100 is arranged longitudinally along the central axis of the probe, and mainly includes a torsional piezoelectric transducer 103, a rigid connector 107, and a shear wave sensing rod 104. The upper end face of the torsional piezoelectric transducer 103 is mechanically fixed to the lower surface of the inertial base 102. A physical gap is maintained between the side of the torsional piezoelectric transducer 103 and the inner wall of the sealed housing 101 to form an air vibration isolation layer, ensuring that the torsional piezoelectric transducer 103 is in a cantilever working state. The lower output surface of the torsional piezoelectric transducer 103 is rigidly connected to the upper end of the shear wave sensing rod 104 coaxially through the rigid connector 107.

[0027] The shear wave sensing rod 104 is the actuator that directly contacts the external medium. The shear wave sensing rod 104 extends axially through the bottom opening of the sealing housing 101 and outwards. A dynamic sealing assembly 108 is provided between the shear wave sensing rod 104 and the bottom opening of the sealing housing 101. The dynamic sealing assembly 108 surrounds the circumference of the shear wave sensing rod 104, preventing external liquid from entering the interior of the sealing housing 101 while allowing the shear wave sensing rod 104 to generate small-amplitude, high-frequency torsional vibrations relative to the sealing housing 101. The surface of the shear wave sensing rod 104 exposed outside the sealing housing 101 is machined with a shear coupling texture 110, which consists of a set roughness microstructure or a micro-knurled mesh, used to enhance the mechanical shear coupling efficiency between the shear wave sensing rod 104 and the sediment medium.

[0028] See attached document Figure 1 and attached Figure 2 The rheological impedance detection probe 100 provided by the present invention includes a sealed housing 101, a flow guide 109, and an inertial base 102 located inside the sealed housing 101, which together constitute the pressure-resistant sealing and mechanical bearing system of the device.

[0029] The sealed housing 101 is the main supporting component of the rheological impedance probe 100, and has a hollow cylindrical structure. The sealed housing 101 is made of high-yield-strength stainless steel or titanium alloy, and its sidewall thickness is designed based on the hydrostatic pressure at the preset maximum operating depth to ensure that no plastic deformation or crushing failure occurs in the mud environment at depths of hundreds of meters. The inner surface of the sealed housing 101 is precision-machined to provide a standard mounting reference surface. The sealed housing 101 physically isolates the internal space of the rheological impedance probe 100 from the external mud-filled operating environment, providing a dry and standard atmospheric pressure operating environment for the internal miniature impedance acquisition circuit 105 and torsional piezoelectric transducer 103.

[0030] The inertial base 102 is located in the center of the inner cavity of the sealed housing 101 and is a high-density solid metal cylindrical block. The outer circumferential surface of the inertial base 102 and the inner circumferential surface of the sealed housing 101 are assembled by an interference fit or by radial locking with high-strength threaded fasteners, thereby achieving a rigid connection between the inertial base 102 and the sealed housing 101 and ensuring that they are considered as the same rigid body in terms of vibration transmission characteristics. The inertial base 102 serves as the main load-bearing structure in the axial direction. Its upper end face is used to install the miniature impedance acquisition circuit 105, and its lower end face is used to suspend and fix the torsional piezoelectric transducer 103.

[0031] The mass of the inertial base 102 is designed to be greater than the sum of the masses of the torsional piezoelectric transducer 103, the rigid connector 107, and the shear wave sensing rod 104. Based on Newton's second law and vibration mode theory, the large-mass inertial base 102 can provide a near-stationary mechanical fixed point, i.e., a reference ground potential where the vibration displacement is zero, when the torsional piezoelectric transducer 103 undergoes high-frequency torsional vibration. This mass distribution design effectively blocks the leakage and dissipation of torsional vibration energy to the upper part of the sealed housing 101 and the load-bearing communication cable 201, forcing the vibration energy to be mainly transmitted downward to the contact interface between the shear wave sensing rod 104 and the external medium. This ensures that the impedance change measured by the system mainly reflects the load characteristics of the external medium, rather than the parasitic resonance of the probe's own structure.

[0032] The flow guide shroud 109 is coaxially mounted on the top of the sealing housing 101, with its lower end face connected to the upper end face of the sealing housing 101 via a threaded seal. The outer contour of the flow guide shroud 109 adopts a hydrodynamically optimized frustum conical or parabolic design, with its maximum outer diameter not exceeding the outer diameter of the sealing housing 101, and a smooth surface transition. This streamlined structure effectively guides the mud fluid during the lowering of the rheological impedance detection probe 100, reducing fluid resistance and maintaining attitude stability. Simultaneously, during the lifting and recovery process, it prevents the protruding part at the top of the probe from snagging on the well wall grooves or reinforcing cage, serving as a guide and anti-jamming function. The load-bearing communication cable 201 passes through the central shaft hole of the flow guide shroud 109 and is mechanically fixed inside the flow guide shroud 109 by a cable locking mechanism, directly transmitting the tension of the load-bearing communication cable 201 to the flow guide shroud 109 and the sealing housing 101, preventing the tension from acting on the internal electrical connection points.

[0033] See attached document Figure 2 , Figure 2 The detailed structural layout of the core excitation and transmission components inside the rheological impedance detection probe 100 is shown. The device provided by this invention utilizes a torsional piezoelectric transducer 103 as an active excitation source and a rigid connector 107 as an energy transmission bridge to construct an efficient conversion and transmission link from electrical energy to mechanical torsional vibration energy.

[0034] The torsional piezoelectric transducer 103 is located in the lower electromechanical transducer compartment inside the sealed housing 101, and adopts a cylindrical longitudinal stacked structure. The torsional piezoelectric transducer 103 is composed of multiple circumferentially tangentially polarized piezoelectric ceramic rings and thin metal electrode sheets stacked alternately, and is encapsulated as a single unit by applying axial preload through a central prestressed bolt. This stacked structure allows the torsional piezoelectric transducer 103 to generate micro-amplitude torsional vibrations reciprocating around its central axis through the d15 piezoelectric shear effect when excited by an alternating voltage applied by a micro-impedance acquisition circuit 105. Compared to traditional longitudinal wave or bending wave transducers, the torsional vibration mode has a pure shear characteristic in the axial direction, which can maximize the excitation of the shear modulus response of the contact medium.

[0035] The torsional piezoelectric transducer 103 is installed using a strict suspended vibration isolation design. The upper surface of the torsional piezoelectric transducer 103 is rigidly fixed to the lower surface of the inertial base 102; this connection surface is the only mechanical fixing point for the torsional piezoelectric transducer 103. A predetermined annular air gap of a specific width is reserved between the cylindrical outer surface of the torsional piezoelectric transducer 103 and the inner wall of the sealing housing 101. This air gap physically completely isolates the direct contact between the torsional piezoelectric transducer 103 and the side wall of the sealing housing 101, forming an acoustic and mechanical isolation layer. This suspended installation method ensures that the torsional vibration energy generated by the torsional piezoelectric transducer 103 does not leak radially to the sealing housing 101, avoiding measurement noise introduced by housing resonance, thus ensuring that all vibration energy is guided downwards for output.

[0036] A rigid connector 107 is positioned below the torsional piezoelectric transducer 103 to transmit high-frequency torsional vibrations to external actuators. The rigid connector 107 is made of a high-modulus metal and has a stepped shaft-like structure. The upper end of the rigid connector 107 is a large-diameter flange, which is connected to the lower radiating surface of the torsional piezoelectric transducer 103 via high-strength adhesive or screws, ensuring acoustic impedance matching at the contact interface and gapless torque transmission. The lower end of the rigid connector 107 is a tapered journal section extending to the bottom opening of the sealing housing 101. As a mechanical waveguide, the rigid connector 107's geometry has been optimized through modal analysis, and its longitudinal resonant frequency is much higher than the operating frequency band, ensuring that the rigid connector 107 behaves as a purely rigid body within the operating frequency range, transmitting the angular displacement of the torsional piezoelectric transducer 103 to the subsequent shear wave sensing rod 104 without attenuation or phase shift.

[0037] See attached document Figure 1 and attached Figure 2 In the device provided by the present invention, the shear wave sensing rod 104 is the terminal execution component for the physical interaction between the probe and the bottom medium. Its design focuses on achieving effective radiation of shear waves and sensitive capture of the rheological properties of the medium.

[0038] The shear wave sensing rod 104 is made of a high-modulus, corrosion-resistant metallic material, such as martensitic precipitation-hardening stainless steel or titanium alloy, to ensure structural integrity under harsh mud corrosion environments and high-intensity mechanical penetration conditions. The shear wave sensing rod 104 has a slender cylindrical structure. Its upper end is coaxially fixed to the rigid connector 107 inside the sealed housing 101, and its lower end extends through the central through-hole at the bottom of the sealed housing 101 to the external space. The aspect ratio of the shear wave sensing rod 104, i.e., the ratio of its length to its diameter, is specifically designed to ensure that it, as an acoustic waveguide, has a pure torsional mode at the operating frequency, avoiding coupling mode interference from bending vibration or longitudinal vibration.

[0039] The dynamic sealing assembly 108 is disposed within the annular gap between the inner wall of the central through hole at the bottom of the sealing housing 101 and the outer cylindrical surface of the shear wave sensing rod 104. The dynamic sealing assembly 108 is mainly composed of a wear-resistant and high-pressure-resistant special rubber sealing ring or a polytetrafluoroethylene (PTFE) plug seal. The dynamic sealing assembly 108 is pressed and fixed, preventing external high-pressure mud fluid from intruding into the interior of the sealing housing 101 while allowing the shear wave sensing rod 104 to undergo small-amplitude high-frequency torsional vibration relative to the sealing housing 101. The contact interface friction damping of the dynamic sealing assembly 108 is controlled within a preset range to reduce the dissipation of vibration energy by the sealing structure itself and ensure that most of the excitation energy can be transmitted to the detection area of ​​the shear wave sensing rod 104 exposed to the outside.

[0040] The shear coupling texture 110 is machined on the cylindrical side surface of the shear wave sensing rod 104 exposed outside the sealing housing 101. The shear coupling texture 110 is not a random surface roughness, but rather an array of microstructures with regular geometric shapes, such as cross-knurled grids, axial microgrooves, or spiral protrusions. The groove depth and protrusion height of the shear coupling texture 110 are designed to match the characteristic particle size of the sediment particles being measured, typically ranging from hundreds of micrometers to several millimeters.

[0041] The presence of the shear coupling texture 110 alters the boundary conditions between the surface of the shear wave sensing rod 104 and the contact medium. When the shear wave sensing rod 104 is in a fluid medium such as bentonite slurry or groundwater, the fluid medium cannot withstand the shear stress, causing boundary layer slippage of fluid molecules on the surface of the shear coupling texture 110. This results in the mechanical load experienced by the shear wave sensing rod 104 being primarily weak viscous damping. When the shear wave sensing rod 104 contacts and penetrates the sediment layer, solid particles in the sediment become embedded in the groove structure of the shear coupling texture 110, forming a mechanical interlocking effect. This mechanical interlocking eliminates the relative slippage at the contact interface, forcing the torsional displacement of the shear wave sensing rod 104 to induce shear deformation in the surrounding sediment skeleton. This effectively couples the shear viscoelastic modulus of the sediment to the detection system, amplifying the difference in impedance response between the fluid and solid media.

[0042] See attached document Figure 1 and attached Figure 2 The rheological impedance probe 100 provided by the present invention integrates an electronic system for signal excitation and data acquisition, mainly including a miniature impedance acquisition circuit 105 and a hydrostatic pressure sensor 106 for auxiliary measurement.

[0043] The miniature impedance acquisition circuit 105 is the core of the downhole probe's electronic control system, and its physical carrier is a multilayer printed circuit board assembly. The miniature impedance acquisition circuit 105 is rigidly fixed to the upper surface of the inertial base 102 by screws or shock-absorbing supports. This mounting position utilizes the large mass of the inertial base 102 to effectively isolate the mechanical vibration generated during the operation of the torsional piezoelectric transducer 103, preventing solder joint fatigue or poor contact of electronic components due to long-term high-frequency vibration. The miniature impedance acquisition circuit 105 integrates a direct digital frequency synthesizer, a power amplifier, a high-precision current and voltage sampling unit, and a communication modulation and demodulation unit. The miniature impedance acquisition circuit 105 passes through a pre-drilled hole in the inertial base 102 via internal wires and is welded to the electrode plates of the torsional piezoelectric transducer 103. It is used to apply a frequency-controllable sinusoidal sweep voltage signal to the torsional piezoelectric transducer 103 and synchronously acquire the response current and terminal voltage data in the circuit in real time. In addition, the miniature impedance acquisition circuit 105 is also used to drive the auxiliary unlocking vibrator 111. When the probe encounters sediment adsorption or well wall jamming during the lifting process, the auxiliary unlocking vibrator 111 generates high-energy vibration to break the adhesion force of the contact surface, thereby achieving auxiliary unlocking and safe recovery of the probe.

[0044] The hydrostatic pressure sensor 106 is installed in a pre-set mounting hole on the side wall of the sealed housing 101. The hydrostatic pressure sensor 106 employs a rigid sealing mounting structure, either threaded in or flanged. The hydrostatic pressure sensor 106 has a clearly directional configuration; its sensing end, i.e., the end with the metal isolation diaphragm or ceramic pressure-sensing diaphragm, extends through the wall thickness of the sealed housing 101 towards the outside of the probe, remaining flush with or slightly concave with the outer cylindrical surface of the sealed housing 101, to directly contact the external well fluid medium and withstand the hydrostatic pressure. A high-pressure resistant O-ring or combination gasket is provided at the threaded connection of the hydrostatic pressure sensor 106 to prevent external high-pressure fluid from seeping into the probe along the thread gap.

[0045] The electrical leads of the hydrostatic pressure sensor 106 are located inside the cavity of the sealed housing 101 and are connected to the analog signal input port of the miniature impedance acquisition circuit 105 via a signal shielded cable. The hydrostatic pressure sensor 106 converts the sensed external fluid static pressure into an analog voltage signal or a digital signal and transmits it to the miniature impedance acquisition circuit 105. The miniature impedance acquisition circuit 105 packages and encodes the raw voltage and current data of the torsional piezoelectric transducer 103 and the pressure data of the hydrostatic pressure sensor 106, and transmits them to the ground receiving system via the load-bearing communication cable 201 on top, thereby realizing real-time calibration of the probe at the downhole depth and synchronous measurement of the rheological impedance characteristics of the medium at different depths.

[0046] See attached document Figure 3The bridge pile hole bottom sediment measuring device provided by the present invention adopts a cable-type logging system architecture. A long-distance mechanical connection and two-way electrical communication link are established between the rheological impedance detection probe 100 located downhole and the ground main control terminal 300 located on the ground operation platform through a load-bearing communication cable 201.

[0047] The load-bearing communication cable 201 is a composite special cable integrating a mechanical load-bearing unit and an electrical transmission unit. The lower end of the load-bearing communication cable 201 is fixed within the guide shroud 109 on top of the rheological impedance detection probe 100 via a mechanical locking mechanism, bearing the entire weight of the rheological impedance detection probe 100 and the lifting tension within the pile hole mud. The electrical core wires inside the load-bearing communication cable 201 are electrically interconnected with the miniature impedance acquisition circuit 105 inside the rheological impedance detection probe 100. The upper end of the load-bearing communication cable 201 extends to the ground, connecting to the data communication interface and power supply module of the ground main control terminal 300.

[0048] The ground control terminal 300 is the energy supply center and data processing hub of the entire measuring device, typically consisting of a portable industrial computer or a dedicated measuring and control instrument. The ground control terminal 300 supplies a stable DC operating voltage to the downhole rheological impedance detection probe 100 via the power line core of the load-bearing communication cable 201, driving the miniature impedance acquisition circuit 105 and the torsional piezoelectric transducer 103. Simultaneously, the ground control terminal 300 transmits configuration parameters such as the scanning frequency range, step size, and sampling trigger commands downwards via the communication line core of the load-bearing communication cable 201.

[0049] In the data uplink transmission path, the complex impedance response data of the torsional piezoelectric transducer 103 collected by the rheological impedance detection probe 100 and the pressure data measured by the hydrostatic pressure sensor 106 are digitized, encoded, and modulated by the micro impedance acquisition circuit 105, and then transmitted in real time to the ground main control terminal 300 via the load-bearing communication cable 201. The ground main control terminal 300 demodulates and analyzes the received data stream to reconstruct the impedance spectrum data and depth pressure data that change over time, providing raw data support for subsequent sediment interface identification and thickness calculation.

[0050] See attached document Figure 3 The depth transmission component 200 provided by this invention mainly includes a ground winch system 203 and a depth encoder 202. These two components work in conjunction with the ground main control terminal 300 to construct a precision deployment control and depth measurement subsystem for the rheological impedance detection probe 100. The depth transmission component 200 is not only responsible for the physical winding and tension maintenance of the load-bearing communication cable 201, but also for generating a high-precision depth reference signal to achieve precise spatial anchoring of downhole measurement data.

[0051] The ground winch system 203 is fixedly installed on a stable working plane at the wellhead of the bridge pile hole. Its mechanical structure mainly includes a high-power variable frequency drive motor, a precision reduction gearbox, a cable storage drum, and a cable guide mechanism. The ground winch system 203 drives the cable storage drum to rotate clockwise or counterclockwise, realizing the controlled lowering and retrieval of the load-bearing communication cable 201. The ground winch system 203 integrates an industrial-grade variable frequency speed controller, which receives digital control commands from the ground main control terminal 300 through an electrical interface to steplessly adjust the vertical lifting speed of the rheological impedance detection probe 100. When performing sediment interface detection tasks, the ground winch system 203 can stably maintain the lowering speed of the rheological impedance detection probe 100 within a low constant speed range, ensuring that the probe obtains a sufficiently dense number of sampling points in the vertical direction, preventing the sampling interval from exceeding the physical thickness of the sediment layer due to excessively fast lowering speed, thereby avoiding missed detection of thin sediment interfaces.

[0052] The depth encoder 202 is the core metering sensor for achieving synchronous alignment of depth and impedance data. The depth encoder 202 is mechanically coupled to the guide pulley shaft at the cable outlet of the surface winch system 203, or directly connected to the main shaft of the cable storage drum. The depth encoder 202 indirectly measures the effective release length of the load-bearing communication cable 201 by sensing the rotation angle of the guide pulley or drum. When the load-bearing communication cable 201 drives the rheological impedance probe 100 to generate vertical displacement within the wellbore, the depth encoder 202 converts the mechanical displacement into a corresponding number of electrical pulse signals in real time. The depth encoder 202 uses a high-resolution incremental photoelectric encoder or absolute magnetic encoder, with a linear measurement resolution better than millimeters, enabling precise capture of minute positional changes of the rheological impedance probe 100 in a mud environment.

[0053] The ground control terminal 300 is internally configured with dedicated data synchronization and acquisition logic to process position signals from the depth encoder 202 and physical quantity signals from the rheological impedance probe 100. The pulse signal output by the depth encoder 202 is transmitted to the ground control terminal 300 via a high-speed counting interface. The ground control terminal 300 calculates the current absolute depth value of the rheological impedance probe 100 in real time based on the accumulated pulse count and a preset pulse equivalent coefficient. Simultaneously, the ground control terminal 300 continuously receives the complex impedance data stream uploaded by the downhole rheological impedance probe 100 via a serial communication interface. Upon receiving each valid impedance data frame, the ground control terminal 300 immediately reads the current depth calculation value and binds this depth value as a position tag to the impedance data, generating a one-to-one depth-impedance data pair. This synchronization mechanism, based on hardware interrupts or high-priority threads, ensures that each set of rheological impedance data accurately corresponds to its physical depth position within the borehole, eliminating spatial positioning errors caused by signal transmission delays or software processing lags.

[0054] The detection principle of this invention is based on the modulation mechanism of acoustic shear wave propagation behavior by the rheological properties of the medium. To achieve high-sensitivity identification of the interface between fluid slurry and solid sediment, this invention specifically selects torsional shear waves as the detection carrier. In physical acoustics, the propagation of sound waves depends on the medium's ability to recover from deformation. For fluid media, such as water or bentonite slurry, they primarily possess a bulk modulus, which supports the propagation of longitudinal waves, but lack a shear-resistant framework in their microstructure, and their shear modulus approaches zero at low frequencies. Therefore, when the shear wave sensing rod 104 undergoes torsional vibration in the fluid, it cannot excite propagable elastic shear waves within the medium, and the energy cannot radiate outward in wave form, only manifesting as viscous boundary layer loss and additional mass effects attached to the surface of the sensing rod. This physical characteristic results in a low mechanical impedance load on the probe in the slurry.

[0055] Conversely, the sediment layer is composed of a large number of solid particles, with contact friction and interlocking forces between them, forming a solid skeleton with a certain shear strength, exhibiting a non-zero complex shear modulus. When the shear wave sensing rod 104 contacts and couples to the sediment layer, torsional vibration can effectively drive the surrounding sediment skeleton to produce shear deformation, causing the vibration energy to propagate and dissipate into the depth of the sediment medium in the form of a shear wave. At this time, the mechanical load applied by the external medium to the sensing rod undergoes a step-like abrupt change, that is, from the pure viscous damping characteristics of the fluid to the elastic and radiation damping characteristics of the solid.

[0056] To convert the aforementioned changes in the mechanical load of the external medium into a measurable electrical signal, this invention utilizes the electromechanical coupling effect of the torsional piezoelectric transducer 103. As a bidirectional energy conversion device, the torsional piezoelectric transducer 103 is equivalent to a parallel network containing static and dynamic branches in the circuit system. The static branches primarily reflect the dielectric properties of the device, while the dynamic branches directly map the motion state of the mechanical vibration system. When the mechanical load impedance of the external medium changes, it directly affects the resonant frequency, quality factor, and amplitude of the vibration system, thereby modulating the electrical impedance spectrum at the input terminal in reverse through the piezoelectric effect.

[0057] Based on the Mason equivalent circuit model or analog circuit theory, a specific mapping relationship exists between the input electrical impedance of the rheological impedance detection probe 100 and the mechanical load impedance of the external medium. By measuring the voltage-to-current ratio at the probe input, the total electrical impedance containing medium information can be obtained. This quantitative relationship of electromechanical coupling can be expressed by the following core formula: ; in, This represents the total input electrical impedance measured at the electrode terminals of the miniature impedance acquisition circuit. The static electrical impedance of a torsional piezoelectric transducer under mechanical clamping is mainly determined by the dielectric constant and geometric capacitance of the material. This represents the electromechanical conversion coefficient of a torsional piezoelectric transducer, reflecting the conversion efficiency between electrical energy and mechanical energy. The equivalent mechanical impedance of the probe vibration system itself includes the mass, stiffness, and internal losses of the inertial base, transducer, and sensing rod. This represents the acoustic load impedance applied by the external medium to the surface of the shear wave sensing rod. This term is directly related to the density of the measured medium and the shear wave velocity.

[0058] As can be seen from the above relationships, when the probe moves from mud into sediment, the load term increases, leading to a decrease in the equivalent admittance of the dynamic branch. Ultimately, this causes the spectral shape of the total input electrical impedance to shift and attenuate near the resonance point. The system achieves precise capture of the sediment interface by monitoring this characteristic change.

[0059] See attached document Figure 1 - Appendix Figure 4This embodiment further elucidates the physical identification mechanism of the mud-sludge interface. The interface identification method proposed in this invention does not rely on a single difference in medium density or acoustic reflection time difference, but is based on the load modulation effect of the medium rheological properties on the torsional vibration system. In the actual working environment of bridge pile holes, the mud filling the well is usually a bentonite suspension or polymer wall-protecting fluid, which is physically a non-Newtonian fluid or a viscous fluid. Although the mud has a high volume density, in terms of microstructure, the mud lacks a continuous solid skeleton and cannot withstand shear stress. When the shear wave sensing rod 104 of the rheological impedance probe 100 undergoes high-frequency torsional vibration in the mud, due to the microscale discontinuity between the shear coupling texture 110 on the surface of the shear wave sensing rod 104 and the fluid molecules, the fluid medium will generate boundary layer slip at the contact interface. This slip effect causes the shear wave sensing rod 104 to be unable to effectively drive the far-field fluid medium to participate in the vibration, so that the mechanical impedance applied by the external medium to the vibration system is mainly manifested as low-amplitude viscous friction damping, while the added mass effect and elastic stiffness effect are extremely weak.

[0060] Conversely, the sediment layer deposited at the bottom of the pile hole is mainly composed of sand, rock fragments, and clay particles, belonging to a typical viscoelastic solid or particle aggregate. The particles within the sediment layer have close physical contact, frictional interlocking, and van der Waals forces, forming a mechanical framework with a certain shear modulus. When the rheological impedance probe 100 contacts the surface of the sediment layer, the shear coupling texture 110 on the surface of the shear wave sensing rod 104 is embedded into the gaps between the sediment particles through mechanical interlocking, eliminating relative slippage at the contact interface. At this time, the torsional displacement of the shear wave sensing rod 104 is forcibly transmitted to the surrounding sediment framework, forcing the sediment medium to undergo shear deformation. Because the sediment medium has the ability to resist shear deformation, the reaction force it exerts on the shear wave sensing rod 104 includes not only huge frictional dissipation damping but also elastic restoring force introduced by the shear stiffness of the medium. This means that the nature of the external mechanical load impedance has undergone a fundamental change, namely, a sudden change from a purely viscous, low-impedance state in a mud environment to a high-impedance complex load state in a sediment environment.

[0061] This abrupt change in mechanical load characteristics is directly mapped onto the electrical impedance spectrum measured by the micro impedance acquisition circuit 105 through electromechanical coupling, forming a characteristic abrupt change that can be identified by the algorithm. In the mud environment, due to the small mechanical load, the vibration of the torsional piezoelectric transducer 103 is in an underdamped state, and its electrical conductivity spectrum shows a sharp resonance peak with high amplitude and narrow bandwidth, indicating that the mechanical quality factor of the system is high. Once the shear wave sensing rod 104 contacts the sediment interface, the increased mechanical damping causes the vibration energy to be rapidly dissipated, and the additional stiffness or additional mass of the medium will change the equivalent parameters of the vibration system. In the electrical impedance spectrum, this change is manifested as a sharp decrease in the resonance peak amplitude, a significant broadening of the resonance bandwidth, and a shift in the resonance frequency point. The system monitors the rate of change of the electrical impedance characteristic parameters with depth in real time. When the rate of change exceeds the preset rheological threshold, it is determined that the rheological impedance detection probe 100 has entered the solid phase from the liquid phase, thereby locking the precise depth of the sediment interface.

[0062] To quantitatively describe the impedance abrupt change characteristics in the interface recognition process described above, this invention introduces a normalized impedance change rate index as a judgment criterion. This index is calculated based on the spatial gradient of the complex impedance modulus, and its core judgment logic can be expressed by the following formula: ; in, This represents the normalized impedance depth change rate, used to quantify the sensitivity of a rheological impedance probe to changes in electrical impedance during vertical penetration. It represents the average value of the reference electrical impedance modulus measured in a mud environment, serving as a reference background value under no-load or light-load conditions. This represents the modulus value of the input electrical impedance of the torsional piezoelectric transducer, measured in real time at the current depth point; This represents the probe depth value synchronously acquired by the depth encoder. The calculated normalized impedance depth change rate... When the threshold value set by the system is exceeded continuously, the system can confirm that the shear wave sensing rod has contacted the top surface of the sediment layer.

[0063] See attached document Figure 4 The present invention provides a method for measuring sediment at the bottom of bridge pile holes. The method relies on the ground main control terminal 300 to coordinate the control of the downhole rheological impedance detection probe 100 and the depth transmission component 200. The entire measurement process includes five consecutive and logically related standardized steps.

[0064] Step S1 is system initialization and zero-point calibration. Before the rheological impedance detection probe 100 is inserted into the pile hole, the ground main control terminal 300 sends an initialization command to the miniature impedance acquisition circuit 105 to execute a circuit self-test program to confirm the stability of the electronic system. Subsequently, in an air environment or a known clean water environment, the torsional piezoelectric transducer 103 is driven to perform a full-band frequency sweep excitation. The system acquires and records the electrical impedance spectrum data at this time, setting it as the system's inherent background impedance or zero-point reference. This step aims to eliminate the background interference of the circuit's own temperature drift, the discrete errors of electronic components, and the distributed parameters of the load-bearing communication cable 201 on subsequent precision measurements, and to establish the calculation origin of subsequent impedance changes.

[0065] Step S2 involves baseline scanning in a mud environment. The ground winch system 203 drives the drum to rotate, releasing the load-bearing communication cable 201 and lowering the rheological impedance probe 100 below the mud surface in the pile hole. The probe moves downwards at a preset constant speed. During this period, the shear wave sensing rod 104 continuously undergoes high-frequency torsional vibration driven by the micro-impedance acquisition circuit 105. Since the mud medium primarily exhibits viscous fluid characteristics, the shear coupling texture 110 on the surface of the shear wave sensing rod 104 slips against the mud, resulting in a low mechanical load and maintaining the impedance data in a stable state with low damping and high resonance amplitude. The ground main control terminal 300 records the impedance data sequence and corresponding depth data during this descent phase in real time. Statistical analysis is used to generate a dynamic baseline threshold in the mud environment, providing a comparative reference for subsequent identification of sediment interfaces.

[0066] Step S3 involves locking the sediment interface. As the rheological impedance probe 100 continues to descend, the shear wave sensing rod 104 contacts the sediment layer at the bottom of the borehole. The shear coupling texture 110 physically embeds into the sediment particle skeleton, causing a qualitative change in the mechanical coupling state of the contact interface. At this moment, the mechanical load impedance of the external medium on the probe undergoes a step-like abrupt change. The micro-impedance acquisition circuit 105 detects a sharp drop in the amplitude of the input electrical impedance, along with a phase deflection. The rheological threshold determination algorithm running inside the ground control terminal 300 processes the received data in real time. Once the calculated impedance change rate characteristic meets the preset conditions, the system immediately determines the current depth as the depth of the top surface of the sediment layer and records this depth value as the starting coordinate for calculating the sediment thickness.

[0067] Step S4 involves penetration detection and hard-bottom identification. After locking onto the top surface of the sediment, the ground winch system 203 continues to release the cable, using the weight of the rheological impedance spectroscopy probe 100 or additional counterweights to drive the shear wave sensing rod 104 into the sediment layer. As the penetration depth increases, the shear modulus and confining pressure of the medium surrounding the shear wave sensing rod 104 gradually increase, and the impedance spectrum characteristics show a gradual evolution trend. When the tip of the shear wave sensing rod 104 touches the hard bottom of the undisturbed soil or rock bearing layer at the bottom of the pile hole, due to the high mechanical impedance of the bearing layer, the probe vibration system exhibits near-mechanical locking characteristics, and the electrical impedance reaches its limit value. The system identifies this characteristic signal and records the corresponding depth as the bearing layer depth, serving as the termination coordinate for calculating the sediment thickness.

[0068] Step S5 involves data processing and property inversion. After the exploration mission is completed, the ground control terminal 300 comprehensively processes the depth impedance data collected throughout the process. The system directly determines the physical thickness of the sediment at the bottom of the pile hole by calculating the difference between the depth of the bearing layer and the top surface depth of the sediment layer. Furthermore, the system analyzes the slope characteristics of the impedance spectrum as a function of depth during the penetration process in step S4. Based on the rate and magnitude of impedance change, the system inverts the density and rheological properties of the sediment layer, distinguishing between a loose floating mud state and a hardened sediment state, ultimately generating a logging report containing sediment thickness values ​​and a description of sediment characteristics.

[0069] See attached document Figure 4 , Figure 4 This is a schematic flowchart of a sediment measurement method according to an embodiment of the present invention. Before performing any specific downhole exploration task, step S1, system initialization and zero-point calibration, must be performed first. This step aims to establish the electrical and acoustic reference planes of the entire measurement system and eliminate systematic errors introduced by ambient temperature, aging and drift of electronic components, and distributed parameters of transmission lines. The zero-point calibration process is mainly carried out in air or clean water with known physical properties. At this time, the rheological impedance probe 100 has not yet come into contact with any complex non-Newtonian fluid or sediment layer, and the external mechanical load it experiences is at its theoretical minimum or standard value.

[0070] Specifically, the operator first suspends the rheological impedance probe 100 above the wellhead, keeping the shear wave sensing rod 104 in a completely suspended, free state, ensuring that the surface of the sensing rod does not physically contact the well wall, casing, or any other solid obstacle. Alternatively, as an alternative implementation, the rheological impedance probe 100 is completely immersed in a calibration container filled with clean water, in which case the surrounding medium of the shear wave sensing rod 104 is a pure Newtonian fluid. The ground main control terminal 300 sends an initialization command to the downhole miniature impedance acquisition circuit 105 via the load-bearing communication cable 201. After receiving the command, the miniature impedance acquisition circuit 105 first performs a self-check of its power supply voltage, chip temperature, and signal channel noise floor to confirm that the circuit is in the linear operating range.

[0071] Subsequently, the miniature impedance acquisition circuit 105 initiates a frequency scanning program, applying a sinusoidal excitation voltage signal with constant amplitude and continuously varying frequency to the torsional piezoelectric transducer 103. The scanning frequency range covers the fundamental torsional resonant frequency of the torsional piezoelectric transducer 103 and its nearby sideband frequencies. During this process, the torsional piezoelectric transducer 103 converts electrical energy into mechanical torsional vibration energy, driving the shear wave sensing rod 104 to vibrate in air or water. Due to the low acoustic impedance of air or the low viscous damping of water, the vibration system is in a near-free vibration state, resulting in low energy dissipation. The high-speed sampling unit of the miniature impedance acquisition circuit 105 simultaneously acquires the instantaneous voltage signal across the torsional piezoelectric transducer 103 and the instantaneous current signal flowing through the transducer, and calculates the complex impedance value at each frequency point using discrete Fourier transform.

[0072] The ground control terminal 300 receives the aforementioned frequency sweep data and extracts the complex impedance characteristic value at the resonant frequency point, defining it as the initial calibration impedance of the system. This impedance value essentially includes the static capacitance impedance of the torsional piezoelectric transducer 103, the internal loss impedance of the mechanical system, and the equivalent impedance of the load-bearing communication cable 201. To accurately extract the impedance change caused by sediment in subsequent steps, the system calculates and stores the calibrated reference impedance vector according to the following core formula: ; in, This represents the initial calibration impedance of the system under standard conditions. This value will be stored in the system memory as a subtrahend or normalization denominator for subsequent measurement data. This indicates the effective excitation voltage applied by the miniature impedance acquisition circuit 105 to the two ends of the electrodes of the torsional piezoelectric transducer 103 during the frequency sweep process. This represents the effective response current flowing through the torsional piezoelectric transducer 103 at the corresponding frequency; This represents the line compensation coefficient determined by the length and temperature characteristics of the load-bearing communication cable 201. This coefficient is used to compensate for signal attenuation and phase shift errors caused by long-distance cable transmission. Through the execution of step S1, the system establishes a vibration zero potential, that is, establishes the system response baseline under the absence of effective external shear load, ensuring that any impedance deviation detected in subsequent steps S2 to S5 truly reflects the changes in the rheological properties of the downhole mud or sediment medium.

[0073] See attached document Figure 4 After system initialization, the process proceeds to step S2, the baseline scanning stage under mud conditions. The main task of this step is to establish a dynamic background impedance benchmark under this specific mud environment as the rheological impedance probe 100 traverses the mud-filled borehole fluid column region, providing a reference for accurate subsequent determination of the sediment interface. The ground control terminal 300 sends a lowering command to the ground winch system 203, driving the drum to rotate and release the load-bearing communication cable 201, allowing the rheological impedance probe 100 to move from the wellhead towards the bottom of the borehole at a constant vertical speed. During this process, the depth encoder 202 continuously monitors the lowering depth to ensure strict synchronization of depth and impedance data on the time axis.

[0074] When the rheological impedance probe 100 is fully submerged below the mud surface, the miniature impedance acquisition circuit 105 controls the torsional piezoelectric transducer 103 to maintain a constant frequency or narrow-band sweep frequency continuous excitation state, driving the shear wave sensing rod 104 to generate high-frequency torsional vibration. Since the mud in the pile hole is usually a mixture of bentonite, polymer, and water, its physical state is that of a thixotropic viscous fluid or suspension, lacking a continuous solid framework capable of transmitting elastic shear waves. Although the surface of the shear wave sensing rod 104 is processed with shear coupling textures 110 to enhance mechanical coupling, the fluid medium cannot withstand shear stress, and the fluid molecules and fine particles in the mud cannot form an effective mechanical interlock with the shear coupling textures 110 at the contact interface. Therefore, when the shear wave sensing rod 104 performs reciprocating torsional motion, the mud layer adjacent to the rod surface will experience relative flow, i.e., the so-called interface slip phenomenon occurs.

[0075] This interfacial slippage phenomenon results in a low acoustic radiation impedance exerted by the mud medium on the vibration system. The external mechanical load mainly manifests as weak viscous damping caused only by fluid viscosity, with almost no elastic load caused by medium stiffness. Under the mapping of electromechanical coupling, the electrical impedance signal detected by the miniature impedance acquisition circuit 105 exhibits characteristics of high amplitude, high phase angle, and high mechanical quality factor. Although the hydrostatic pressure and density of the mud may change with increasing depth, this linear change caused by depth is orders of magnitude smaller compared to the impedance abrupt change when contacting sediment solids later. The system defines the impedance data continuously acquired during this stage of the mud journey as the mud baseline impedance and uses statistical algorithms to calculate its dynamic mean and fluctuation range in real time.

[0076] To mathematically define the baseline state in a mud environment and eliminate random noise interference, the system employs a sliding window averaging algorithm to update the baseline impedance value in real time. The physical definition formulas upon which this calculation process is based are as follows: ; in, This represents the average baseline impedance modulus of the mud at the current depth window. This value is dynamically updated as the depth increases, and represents the standard response of the probe in a pure fluid environment. This indicates the number of sampling points included in the moving average window. This value is automatically matched by the system based on the drop-down speed and sampling rate to ensure that the statistical sample is representative. Indicates the first [number] within the sliding window A discrete depth sampling point; Indicates the discrete depth sampling points The measured input electrical impedance modulus of the torsional piezoelectric transducer 103 was obtained through real-time calculation. The system can automatically adapt to background load changes in mud of different concentrations and well depths, and construct a dynamic baseline that varies with depth. This ensures that the identification of sediment interfaces in subsequent steps is based on relative changes rather than absolute fixed values, thereby improving the adaptability and accuracy of the detection device in complex mud environments.

[0077] See attached document Figure 4After completing the baseline scan in the mud environment, the detection process enters the crucial step S3, the sediment interface locking stage. The core task of this step is to accurately identify the interface location transitioning from the liquid mud zone to the solid sediment zone by utilizing the abrupt change characteristics of physical contact mechanics. As the ground winch system 203 continues to release the load-bearing communication cable 201, the rheological impedance probe 100 approaches the bottom of the hole at a constant low speed. When the tip of the shear wave sensing rod 104 contacts the surface of the sediment layer deposited at the bottom of the pile hole, the physical interaction mechanism undergoes a fundamental change. The shear coupling texture 110 distributed on the surface of the shear wave sensing rod 104, with its microscopic morphology designed as a rough structure capable of embedding into the particulate medium, penetrates and mechanically interlocks with the solid particle skeleton of the sediment surface layer at the moment of contact. This mechanical interlocking effect eliminates the fluid boundary layer slip phenomenon present in step S2, forcing the torsional vibration energy of the shear wave sensing rod 104 to propagate to the sediment medium with a certain shear modulus.

[0078] Due to the increased viscoelastic damping and shear stiffness of the sediment medium compared to the mud medium, the torsional shear mechanical load on the shear wave sensing rod 104 increases dramatically. This step-like increase in mechanical load is instantaneously transmitted to the torsional piezoelectric transducer 103 through the rigid connector 107, resulting in strong suppression of the transducer's vibration modes. The miniature impedance acquisition circuit 105 detects a drastic fluctuation in the input electrical impedance characteristics at the two ends of the torsional piezoelectric transducer 103 with a millisecond-level time resolution. Specifically, the impedance modulus amplitude at the resonant frequency drops rapidly from the high reference value in the mud environment, accompanied by a decrease in the resonant quality factor.

[0079] Upon receiving real-time impedance and depth data, the ground control terminal 300 immediately initiates the rheological threshold determination algorithm. To accurately extract the interface location from the dynamic signal and eliminate false signals caused by large suspended particles or probe oscillation, the system employs a normalized impedance gradient criterion for logical operations. This criterion quantifies the degree of change in the medium's rheological properties by calculating the impedance attenuation rate per unit depth change. Its core determination formula is as follows: ; Among them, symbols The determination index represents the sediment interface, reflecting the detector's sensitivity to phase transitions in the medium; symbol This represents the average baseline impedance modulus of the mud obtained and stored in step S2, representing the background reference in the liquid phase environment; symbol Represents the absolute value of the measured electrical impedance modulus at the current sampling time; symbol This represents the probe depth value fed back by the depth encoder 202 at the current sampling time; symbol This represents the probe depth value at the previous sampling time.

[0080] The system compares the real-time calculated judgment index with a preset rheological threshold constant. This rheological threshold constant is an empirical value pre-calibrated based on the typical density difference between sediment and mud and the geometric sensitivity of the shear wave sensing rod 104. When the judgment index is greater than the rheological threshold constant for three consecutive sampling periods, the logical judgment condition is met, confirming effective contact. The system then locks the depth value corresponding to the current moment, marks it as the depth of the top surface of the sediment, and records it in the logging data file as the starting geometric boundary for subsequent sediment thickness calculations. This locking process is entirely based on the objective physical response of the medium's rheological mechanics, avoiding the subjective errors of traditional hammer logging methods that rely on manual judgment.

[0081] See attached document Figure 4 After successfully determining the depth of the top surface of the sediment layer, the detection process immediately proceeds to step S4, the penetration detection and hard bottom identification stage. This step aims to detect the vertical structural characteristics of the sediment layer through physical penetration and accurately locate the mechanical interface between the sediment layer and the bearing layer at the bottom of the pile hole. The ground main control terminal 300 controls the ground winch system 203 to continue releasing the load-bearing communication cable 201. Utilizing the gravity of the rheological impedance detection probe 100 itself or the gravity of the pre-assembled weight, the shear wave sensing rod 104 is driven to overcome the frictional resistance between sediment particles and gradually penetrate deeper from the top surface of the sediment layer. During this penetration process, the micro impedance acquisition circuit 105 maintains continuous excitation of the torsional piezoelectric transducer 103 and records the evolution trajectory of the electrical impedance spectrum with depth in real time at a high sampling rate.

[0082] As the penetration depth of the shear wave sensing rod 104 increases, the physical environment surrounding the probe changes significantly. Unlike step S3, where only the tip of the sensing rod contacts the sediment surface, during the penetration stage, the cylindrical side of the shear wave sensing rod 104 is completely enveloped by the sediment medium. The contact area between the shear coupling texture 110 and the sediment particles is maximized. Simultaneously, with increasing depth, the confining pressure inside the sediment layer gradually increases, leading to a nonlinear enhancement of the shear constraint force exerted by the medium on the probe. This enhancement of physical constraint manifests in the electrical impedance spectrum as a continuous decrease in the impedance modulus and a further broadening of the resonant band. By monitoring this gradual impedance change in real time, the system can qualitatively analyze the compaction degree inside the sediment layer and identify the presence of interlayers or density inhomogeneities.

[0083] When the tip of the shear wave sensing rod 104 touches the undisturbed soil layer or bedrock bearing layer at the bottom of the pile hole, the mechanical properties of the contact interface undergo a second abrupt change because the shear modulus of the bearing layer is much higher than that of the overlying sediment layer. The near-rigid mechanical properties of the bearing layer forcefully fix the tip of the shear wave sensing rod 104, significantly suppressing torsional vibration, and the system enters a near-mechanically locked state. At this time, the vibration amplitude of the torsional piezoelectric transducer 103 is compressed to a lower level, and the input electrical impedance characteristics no longer change with time or small depth fluctuations, but stabilize near a specific limit value, which corresponds to the stimulated response when the system is fully confined.

[0084] To accurately determine this mechanical lock-up state and pinpoint the bearing layer depth, the ground control terminal 300 employs a hard bottom identification algorithm based on impedance saturation. This algorithm calculates in real-time the approximation between the current measured impedance and the theoretical mechanical lock-up impedance, only identifying the probe as having reached the bottom when the impedance characteristics meet specific saturation convergence conditions. The core calculation formula for this hard bottom identification logic is as follows: ; in, This represents the hard bottom mechanical lock-up determination index, and its value range is usually normalized to between 0 and 1. The closer the value is to 1, the closer the current state is to the theoretical absolute hard bottom. This represents the electrical impedance modulus value measured in real time at the current penetration depth point; This represents the limiting impedance modulus constant of the pre-calibrated rheological impedance probe 100 when its front end is rigidly clamped. This constant reflects the boundary of the system's electrical response under infinite mechanical load. When the system calculates... When the confidence threshold is exceeded continuously, the ground main control terminal 300 immediately sends a stop command to the ground winch system 203 and records the depth reading fed back by the depth encoder 202 at this time as the bearing layer depth, thereby completing the accurate calibration of the physical bottom boundary of the sediment layer.

[0085] See attached document Figure 4 After completing the penetration test and determining the bearing layer depth, the system enters step S5, the data processing and property inversion stage. This step is automatically executed by the processor inside the ground main control terminal 300. Its purpose is to convert the discrete depth coordinates and continuous impedance spectrum data obtained in the previous steps into quantitative indicators with engineering guidance significance, namely the physical thickness and density state of the sediment layer. The ground main control terminal 300 first retrieves the sediment top surface depth data locked in step S3 and the bearing layer depth data locked in step S4. These two sets of data constitute the upper and lower geometric boundaries of the sediment layer in the vertical space.

[0086] The system performs interpolation calculations to determine the physical thickness of the sediment at the bottom of the pile hole. Since the rheological impedance probe 100 is designed to ensure that the end of the shear wave sensing rod 104 is the unique positioning reference point, and the depth encoder 202 maintains continuous linear counting throughout the lowering process, an accurate thickness value can be obtained through direct subtraction of geometric coordinates. The system calculates the effective thickness of the sediment layer according to the following formula: ; in, This represents the calculated physical thickness of the sediment layer, which will be directly compared with the allowable sediment thickness standard in building construction specifications. This indicates the depth of the bearing layer identified in step S4, i.e., the depth coordinates when the shear wave sensing rod 104 touches the hard bottom and mechanically locks; This indicates the depth of the top surface of the sediment identified in step S3, which is the depth coordinate when the shear wave sensing rod 104 first contacts the sediment and triggers a sudden change in the rheological threshold.

[0087] Based on the obtained thickness data, the ground-based main control terminal 300 further performs rheological property inversion on the electrical impedance spectrum data recorded within this depth range. Because sediment media of different densities have varying degrees of resistance to the penetration process of the shear wave sensing rod 104, their impedance increases at different rates with depth, i.e., their impedance slopes differ. Loose sludge or flocculated sediment exhibits low viscous resistance, with impedance increasing slowly with depth; while compacted or dense sandy sediment exhibits high shear stiffness, with impedance rising sharply with depth. To quantify this characteristic, the system calculates the average impedance gradient within this range, using it as a density index to determine the physical properties of the sediment.

[0088] The system uses the least squares method to perform linear fitting on the depth and impedance data during the penetration process, or directly uses the endpoint slope method to calculate the compactness index. The calculation logic is as follows: ; in, This represents the density index of the sediment layer. The physical dimension of this value corresponds to the impedance increment per unit penetration depth. Indicates the depth of the bearing layer The limiting impedance modulus measured at the point; Indicates the depth at the top surface of the sediment The contact impedance modulus measured at the location. The ground main control terminal 300 will calculate the... Compare with a pre-set geotechnical engineering classification database. If If the sediment content is less than the preset loose threshold, the system determines that the sediment is high-moisture floating mud, indicating incomplete hole cleaning; if If the density exceeds a preset threshold, the system determines the sediment to be either solidified precipitate or a high-density sand layer. Ultimately, the system generates a value including the physical thickness of the sediment layer. A comprehensive test report, including numerical values, sediment characteristics description, and complete impedance logging curves, is provided for engineers to evaluate the quality of pile foundation drilling.

Claims

1. A device for measuring sediment at the bottom of bridge pile holes, characterized in that, It includes a ground control terminal (300), a depth transmission component (200), and a rheological impedance detection probe (100) connected via a load-bearing communication cable (201). A torsional piezoelectric transducer (103) is rigidly fixed under the inertial base (102) inside the rheological impedance detection probe (100). The torsional piezoelectric transducer (103) is connected to a shear wave sensing rod (104) extending to the outside. The inertial base (102) is provided with a miniature impedance acquisition circuit (105) and an auxiliary unlocking exciter (111). The miniature impedance acquisition circuit (105) is used to drive the torsional piezoelectric transducer (103) and the auxiliary unlocking exciter (111). The ground main control terminal (300) is used to determine the position of sediment based on impedance data and depth data, and to control the auxiliary unlocking exciter (111) to generate vibration when the torsional piezoelectric transducer (103) is in a mechanically locked state, thereby releasing the mechanically locked state through the vibration.

2. The device for measuring sediment at the bottom of bridge pile holes according to claim 1, characterized in that, The rheological impedance detection probe (100) also includes a sealed housing (101), and the outer peripheral surface of the inertial base (102) is rigidly fixedly connected to the inner wall surface of the sealed housing (101); An air vibration isolation gap is provided between the side of the torsional piezoelectric transducer (103) and the inner wall of the sealed housing (101). A dynamic sealing assembly (108) is provided between the shear wave sensing rod (104) and the bottom opening of the sealed housing (101). The dynamic sealing assembly (108) is used to block the entry of external liquid and allow the shear wave sensing rod (104) to generate a small-amplitude torsional vibration relative to the sealed housing (101).

3. The device for measuring sediment at the bottom of bridge pile holes according to claim 1, characterized in that, The torsional piezoelectric transducer (103) is composed of stacked piezoelectric ceramic rings that are tangentially polarized along the circumference, and the torsional piezoelectric transducer (103) is used to generate reciprocating shear deformation around the central axis; The mass of the inertial base (102) is greater than the sum of the masses of the torsional piezoelectric transducer (103) and the shear wave sensing rod (104). The inertial base (102) is used to provide a reference ground potential with zero vibration displacement when the shear wave sensing rod (104) is in operation.

4. The device for measuring sediment at the bottom of bridge pile holes according to claim 2, characterized in that, The shear wave sensing rod (104) exposed outside the sealed housing (101) has a shear coupling texture (110) on its surface, which is composed of a microstructure array of grooves or protrusions. The shear coupling texture (110) is used to generate fluid boundary layer slip in the mud medium and to form a mechanical interlock with the sediment particles when in contact with the sediment medium.

5. The device for measuring sediment at the bottom of bridge pile holes according to claim 1, characterized in that, The auxiliary unlocking exciter (111) is rigidly fixed to the upper surface of the inertial base (102), and the auxiliary unlocking exciter (111) is an eccentric rotating mass motor or a linear resonant actuator. The miniature impedance acquisition circuit (105) is used to apply a driving signal with gradually increasing voltage amplitude or duty cycle to the auxiliary unlocking exciter (111); During the operation of the auxiliary unlocking exciter (111), the micro impedance acquisition circuit (105) intermittently drives the torsional piezoelectric transducer (103) to detect impedance. When the impedance value is detected to be outside the mechanical lock-up threshold range, the micro impedance acquisition circuit (105) stops driving the auxiliary unlocking exciter (111).

6. The device for measuring sediment at the bottom of bridge pile holes according to claim 1, characterized in that, The miniature impedance acquisition circuit (105) includes a direct digital frequency synthesizer and a power amplifier. The miniature impedance acquisition circuit (105) is used to apply a sinusoidal sweep voltage signal to the torsional piezoelectric transducer (103) and simultaneously acquire the response current and terminal voltage data in the circuit, and calculate the complex impedance modulus using the response current and terminal voltage data.

7. The device for measuring sediment at the bottom of bridge pile holes according to claim 2, characterized in that, A hydrostatic pressure sensor (106) is installed on the side wall of the sealed housing (101). The sensing end face of the hydrostatic pressure sensor (106) is exposed outside the sealed housing (101). The signal output terminal of the hydrostatic pressure sensor (106) is electrically connected to the miniature impedance acquisition circuit (105).

8. The device for measuring sediment at the bottom of bridge pile holes according to claim 2, characterized in that, The rheological impedance detection probe (100) is provided with a flow guide (109) on the top. The flow guide (109) has a streamlined cone structure and is sealed to the upper end face of the sealing shell (101). The load-bearing communication cable (201) passes through the central axis of the flow guide (109) and enters the interior of the sealed housing (101). The tensile bearing point of the load-bearing communication cable (201) is located inside the flow guide (109).

9. The device for measuring sediment at the bottom of bridge pile holes according to claim 1, characterized in that, The depth transmission component (200) includes a ground winch system (203) and a depth encoder (202). The ground winch system (203) is used to drive the load-bearing communication cable (201) to be wound up and down, and the depth encoder (202) is used to generate a pulse signal corresponding to the probe depth. The ground control terminal (300) is used to bind the probe depth with the impedance data received at the same time to generate a depth impedance data pair.

10. A device for measuring sediment at the bottom of bridge pile holes according to claim 9, characterized in that, The ground control terminal (300) is used to calculate the normalized impedance depth change rate, which is a value obtained by dividing the degree of deviation of the impedance modulus at the current depth point relative to the impedance modulus of the mud baseline by the change per unit depth. When the normalized impedance depth change rate continuously exceeds the preset rheological threshold, the ground main control terminal (300) determines that the shear wave sensing rod (104) has contacted the top surface of the sediment layer.

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