CN-122017977-A - Underground cavity detection and filling quality safety assessment method based on elastic wave exploration

Abstract

The invention belongs to the technical field of underground disease detection of traffic infrastructure, and particularly relates to an underground cavity detection and filling quality safety assessment method based on elastic wave exploration. The method comprises the following steps of 1, arranging elastic wave exploration measuring lines longitudinally and transversely along a target area, simultaneously extracting 3 characteristic values of reflection intensity, double-pass time and instantaneous spectrum bandwidth for each voxel to identify a cavity area, searching and dividing filling areas through a three-dimensional connected domain, determining target filling volumes of the filling areas, and 2, after filling the cavity areas with filling media, evaluating filling effects and formulating a differential inspection management scheme in combination with sedimentation monitoring. The method realizes the differential inspection management of the cavity refined partition identification, the quantitative evaluation of filling quality and the multi-source data fusion based on elastic wave exploration.

Inventors

• LI JINGBIN
• YANG HAIE
• SUN HAIDONG
• Sang Boyang
• Bai Zongyang

Assignees

• 聊城市交通发展有限公司

Dates

Publication Date

20260512

Application Date

20260317

Claims (10)

1. 1. The underground cavity detection and filling quality safety evaluation method based on elastic wave exploration is characterized by comprising the following steps of: Step 1, longitudinally and transversely laying elastic wave exploration test lines along a target area, receiving and collecting elastic wave reflection profile data below the target area through a source excitation and detector, carrying out three-dimensional offset imaging processing on the elastic wave reflection profile data to obtain a reflection intensity three-dimensional voxel model of an underground space of the target area, simultaneously extracting 3 characteristic values of reflection intensity, double-pass time and instantaneous spectrum bandwidth from each voxel in the reflection intensity three-dimensional voxel model, marking voxels with 3 characteristic values exceeding respective set abnormal thresholds as cavity candidate voxels, carrying out three-dimensional connected domain search on all the cavity candidate voxels, merging the cavity candidate voxels which are adjacent to each other in space into the same connected area, forming 1 independent filling partition by each connected area, and determining the target filling volume of each filling partition; step 2, after filling medium is injected into each cavity area identified in the step 1, retesting is carried out along the same elastic wave exploration test line in the step 1, reflection profile data after filling is obtained through source excitation and receiving of a detector, structural similarity is obtained through reflection waveform cross-correlation calculation of the reflection profile data after filling and the elastic wave reflection profile data obtained in the step 1 by measuring points, a filling effect scoring distribution diagram is generated, a section of the filling effect scoring distribution diagram, which is lower than a set qualified threshold value, is marked as an insufficient filling section, settlement monitoring points are distributed on the surface of a target area longitudinally, accumulated settlement of each settlement monitoring point is collected according to a set monitoring period, early warning information is generated when the accumulated settlement of any settlement monitoring point exceeds a preset settlement alarm value, filling is arranged for corresponding filling sections or inspection intervals are shortened according to the positions of the insufficient filling sections and the early warning information, and conventional inspection intervals are maintained for the filling sections, the filling effect scoring reaches the qualified threshold value and the accumulated settlement is within the settlement alarm value.
2. 2. The method according to claim 1, wherein in step 1, the reflection intensity represents impedance difference of a medium interface, the double-pass time represents cavity burial depth, the instantaneous spectrum bandwidth represents scattering characteristics of cavity boundary, and only part of voxels with characteristic values exceeding an abnormality threshold are marked as suspected voxels.
3. 3. The method according to claim 2, wherein in step 1, for the suspected voxels spatially adjacent to the connected region, whether to merge the suspected voxels into the adjacent filling region is determined according to whether the ratio of the adjacent area between the suspected voxels and the connected region to the surface area of the suspected voxels exceeds a set merge ratio threshold, the suspected voxels having a ratio exceeding the merge ratio threshold are merged into the adjacent filling region to participate in the calculation of the filling volume, the voxel volumes of all voxels contained in each filling region are summed to obtain a total estimated volume of the cavity, the total estimated volume of the cavity is multiplied by a filling coefficient to obtain a target filling volume, the filling coefficient is larger than 1, the volume estimation error generated by the three-dimensional offset imaging process and the voxel segmentation is compensated, and the filling priority order is determined according to the total estimated volume of the cavity and the depth of each filling region, and the filling region having a large depth and volume is filled with priority.
4. 4. The method of claim 1, wherein the filling medium injection process comprises drilling 1 air bag placing hole at the junction position of the current filling area and the adjacent filling area according to the filling priority order, folding the air bag body of the recyclable flexible air bag, sending the air bag body into the junction section of the inside of the cavity through the air bag placing hole, unfolding the air bag body of the recyclable flexible air bag, uniformly arranging 3 attaching pressure sensors on the outer surface of the air bag body along the circumferential direction, connecting the air bag body to an air pump control valve group on the ground through a high-pressure air pipe, starting the air pump control valve group to charge compressed air into the air bag body, enabling the air bag body to expand gradually inside the cavity until the outer surface of the air bag body is attached to the wall surface of the cavity, continuously reading real-time pressure values of the 3 attaching pressure sensors in the inflation process, and closing the air pump control valve group and locking the air pressure in the air bag when the real-time pressure values of the 3 attaching pressure sensors reach preset attaching pressures and fluctuation amplitudes are smaller than preset stable deviations in 10 seconds.
5. 5. The method of claim 4, wherein the blocking effectiveness verification is specifically that after the air pressure in the bag is locked, the current air pressure value in the bag is recorded as a locking pressure reference value, a preset pressure maintaining observation period is kept for detecting whether an air leakage channel exists between the bag body and the wall surface of the cavity, after the pressure maintaining observation period is finished, the air pressure value in the bag is read again, the pressure drop of the air pressure value in the bag relative to the locking pressure reference value is calculated, if the pressure drop is smaller than a preset allowable pressure drop threshold value, blocking effectiveness is judged, if the pressure drop reaches or exceeds the allowable pressure drop threshold value, the air pump control valve group is restarted to carry out pressure compensation, after the pressure compensation is finished, the air pressure value in the bag is recorded again as a new locking pressure reference value, and pressure maintaining observation is repeatedly carried out until the blocking effectiveness is judged.
6. 6. The method according to claim 1, wherein the filling medium injection process comprises drilling a filling hole and an exhaust hole at the top of the current filling partition, the exhaust hole being located at one end of the current filling partition far from the filling hole and being used as an observation channel for exhausting air in the filling partition during filling and overflowing slurry when filling is terminated, inserting a filling pipeline into the current filling partition through the filling hole, sequentially installing a pressure transmitter and an electromagnetic flowmeter at an orifice section of the filling pipeline, installing a displacement sensor at the orifice surface of the filling hole, and installing a conductivity probe at a position close to the back of the recyclable flexible air bag through an air bag placing hole or an additionally drilled monitoring hole of the adjacent filling partition, for detecting whether the foam concrete slurry bypasses or penetrates the recyclable flexible air bag into the adjacent filling partition.
7. 7. The method of claim 6, wherein the grouting pump is a variable frequency screw pump, the variable frequency screw pump is used as a grouting power source to inject foam concrete into a current filling area through a filling pipeline, the sliding mode controller operates cycle by cycle in fixed control periods, the instantaneous injection flow value acquired by the electromagnetic flowmeter is read in each control period and added with the injected volume accumulated in each previous control period to obtain a current accumulated injection volume, the actual rotation speed value of the variable frequency screw pump is read, the actual rotation speed value is converted into a pump discharge volume estimated value according to the single-rotation displacement of the variable frequency screw pump, the pump discharge volume estimated value is compared with the current accumulated injection volume, the current accumulated injection volume is corrected by the pump discharge volume estimated value if the deviation exceeds a preset integral verification deviation threshold, and the current accumulated injection volume is directly used for next control calculation if the deviation of the two is within the integral verification deviation threshold.
8. 8. The method of claim 7 wherein the slip-form controller calculates a volume deviation between the corrected current accumulated injection volume and the target fill volume during each control period, calculates a change in volume deviation of the current control period relative to a change in volume deviation of a previous control period to obtain a volume deviation change rate, uses a weighted combination of the volume deviation and the volume deviation change rate as a slip-form variable, indicates that the injection process is still in a phase approaching the target fill volume when the slip-form variable is greater than zero, and indicates that the current accumulated injection volume has reached the target fill volume when the slip-form variable is equal to or less than zero.
9. 9. The method of claim 8, wherein when the sliding mode variable is greater than zero, the sliding mode controller enters an approaching stage, if the current injection pressure value acquired by the pressure transmitter is lower than a pressure safety upper limit and the current road rebound displacement value acquired by the displacement sensor is lower than a channeling conductivity threshold, the sliding mode controller outputs a forward pump speed increment command according to a constant-speed approaching mode to drive the variable-frequency screw pump to maintain or increase injection flow, if the current injection pressure value reaches the pressure safety upper limit or the current road rebound displacement value reaches the displacement safety upper limit, the pump speed increment command is switched to a negative value, the forward approaching is resumed after the current injection pressure value and the current road rebound displacement value fall below the respective upper safety limits, if the current conductivity value reaches or exceeds the channeling conductivity threshold, the sliding mode controller outputs a stopping pump command, the sliding mode control is continued from the accumulated injection volume when the sliding mode variable is equal to zero or less than zero after the recoverable flexible air bag is subjected to pressure boost or replaced, the sliding mode controller is stopped, the filling pump is stopped, the flexible air bag is completely stopped, the pressure pump is stopped, the air bag is completely filled up after the foam air bag is completely filled, and the pressure of the air bag is completely removed, and the pressure of the air is completely recovered after the pressure of the air bag is completely filled, and the pressure of the air bag is completely filled by the variable-frequency converter is completely closed, and the pressure of the air bag is completely closed, and the air is completely filled by the pressure pump is completely and the air pump is completely filled.
10. 10. The method according to claim 1, wherein in the step 2, the cross-correlation calculation is specifically that normalized cross-correlation coefficients are calculated for the elastic wave reflection waveforms of the same measuring point before and after filling in a set time window, the higher the cross-correlation coefficient is, the better the wave impedance matching degree between the filling body and surrounding medium is, the higher the corresponding filling effect score is, and the section corresponding to the measuring point with the cross-correlation coefficient lower than the set qualification threshold is judged as the underfilling section.

Description

Underground cavity detection and filling quality safety assessment method based on elastic wave exploration Technical Field The invention belongs to the technical field of underground disease detection of traffic infrastructure, relates to an intelligent sensing system, and particularly relates to an underground cavity detection and filling quality safety assessment method based on elastic wave exploration. Background With the continuous expansion of the construction and operation scale of traffic infrastructure, highway subgrade, urban roads and underground cavities below bridge and culvert foundations have become serious hidden hazards threatening traffic safety operation. The underground cavities comprise soil loss caused by groundwater erosion, loose areas formed by uncompacted backfill in construction period, surrounding soil hollowing caused by leakage of existing pipelines, corrosion effect of soluble rock areas and the like, and the cavities can cause pavement collapse, roadbed settlement and even cause serious traffic safety accidents under the repeated effect of traffic load. Therefore, the method for accurately detecting the underground cavity below the traffic infrastructure and scientifically evaluating the filling quality after filling treatment is a key technical problem to be solved in traffic engineering construction and maintenance management. In the current traffic engineering practice, geophysical nondestructive detection means such as elastic wave exploration, high-density electrical method and the like are generally adopted to detect a target area below a roadbed and a pavement. In the aspect of elastic wave exploration, the existing method is characterized in that an elastic wave pulse is excited and a reflected signal from an underground medium interface is received by arranging a seismic source and a detector array on a road surface, so that elastic wave reflection profile data is formed to identify an abnormal area below a roadbed. However, the existing elastic wave exploration method still has the following defects when being applied to underground cavity identification of traffic infrastructure, on one hand, detection results are usually only presented in a two-dimensional section diagram mode, traffic engineering technicians rely on experience to manually judge abnormal reflection areas in reflected wave sections to determine the approximate position and range of the cavity, the mode relying on manual experience judgment has larger subjectivity, different judges can have obvious differences on interpretation results of the same group of detection data, a systematic method for carrying out joint analysis on multidimensional elastic wave attributes such as reflection intensity, double-pass time and frequency spectrum characteristics is lacked, and three-dimensional geometric forms and volumes of the cavity are difficult to accurately quantify, on the other hand, the prior art lacks a three-dimensional connected domain automatic searching and partitioning method based on an elastic wave voxel model, cavity candidate voxels which are spatially connected cannot be automatically integrated into independent filling and filling areas, when a cavity roadbed backfill scheme is prepared, constructors can only roughly estimate the total amount of filling materials which need to be filled according to limited section information, accurate calculation of the distribution of the three-dimensional space of the cavity is lacked, the fact that the actual filling amount and the real volume are not matched with the real volume is high, and the situation of filling materials and the residual materials are wasted and the pavement and the residual filling situation are caused. In the aspect of filling quality safety evaluation, the existing elastic wave exploration technology also has obvious short plates, and the precision and reliability of the quality inspection and detection of the filling treatment of the roadbed cavity of the traffic engineering are restricted. In the prior art, the safety inspection of the filling effect of the road base cavity generally adopts a mode of re-laying the measuring line to carry out the elastic wave retest after the filling is completed, but the analysis of retest data still stays at the level of manually comparing the section difference before and after the filling, and a method for carrying out quantitative similarity calculation on the elastic wave reflection waveforms of the same measuring point before and after the filling is lacked. This qualitative comparison has significant subjectivity and inaccuracy. Although the change of the reflected waveform can reflect the improvement condition of wave impedance matching between the filling medium and the surrounding roadbed soil layer to a certain extent, the accurate filling effect safety score cannot be given only by visual comparison, and the specific position and range of the underfilling section cannot be autom