How to prevent pavement collapse?

Technical application of vehicle-mounted array radar in early warning and pre-detection of road collapse disaster

(Dalian Zhong Rui Science and Technology Development Co., Ltd.)

Application of Vehicle Array Radar

Early warning detection of road collapse

Abstract: In recent years, road collapse disasters have occurred in many cities, resulting in huge loss of life and property and serious social impact. In order to meet the needs of early warning and detection of urban road collapse disasters, a vehicle-mounted array radar system with independent intellectual property rights is developed, which can visually detect and accurately locate road diseases. The radar system has been successfully applied to the early warning and detection of road collapse disasters in many cities, forming a set of technical methods for road collapse disaster detection.

Keywords: road diseases; Disease early warning and detection; Vehicle-mounted array radar

I. Introduction

In recent years, urban road collapse disasters broke out frequently all over the country, and large-scale, high-frequency vicious collapse accidents occurred one after another, resulting in huge loss of life and property and serious social impact, which directly threatened urban public safety. Disaster control is urgent. At present, urban road collapse disasters have occurred all over the country, from first-tier cities such as Beijing, Shanghai, Guangzhou and Shenzhen to second-tier cities such as Harbin, Changchun, Dalian, Taiyuan, Xi 'an, Wuhan, Changsha, Fuzhou and Xiamen, as well as remote western cities such as Lanzhou, Yinchuan and Urumqi, and even Zhangjiakou, Handan, Xuancheng, Jingzhou, Xiangtan and Loudi.

Investigation shows that urban road collapse is mostly directly related to underground pipelines, which is a typical secondary disaster of underground pipelines. According to statistics, most underground caves collapse in the range of 0~3m below the surface [1]. Various inducements lead to the damage of underground pipelines or directly loosen the soil around the pipelines, and soil loss occurs under the action of various running water factors, resulting in cavities around the pipelines, which gradually develop and expand, eventually leading to road surface collapse and disasters. The reasons for these cave collapses include [2] and [3]: aging and leakage of underground pipelines, false backfilling of pipeline construction, infiltration and erosion of surface water, decline of groundwater level, subway construction disturbance, aging and collapse of underground civil air defense facilities, collapsible loess collapse, cave collapse and so on.

Scientific research and investigation and analysis of collapse disasters show that only by using advanced high-tech geophysical prospecting equipment to regularly survey and detect urban roads, find hidden holes in the ground in advance, give early warning and take measures to eliminate risks, can we nip in the bud and avoid collapse accidents.

Second, the vehicle-mounted array radar system

To carry out the detection of hidden cavities under urban roads, the common engineering geophysical methods such as high-density electrical method, shallow seismic method and transient electromagnetic method have poor application effect, high cost and slow speed, so it is difficult to be widely used in cities. Ground penetrating radar (GPR) has the characteristics of high efficiency, anti-interference, high precision and convenient field operation, and is the first choice technology for general survey and detection of urban road collapse disasters. Engineering practice at home and abroad shows that ground penetrating radar (GPR) has become the only practical and feasible technical means to detect hidden diseases under roads, and it is suitable for detecting many road diseases such as cavities, cavities, loose soil and rich water [4][5].

Due to the large number of cities in China, the urban area is generally large, and the underground geological conditions and underground structures are complex, the conventional single (double) channel ground penetrating radar and manual detection methods have certain limitations in detection efficiency and reliability of detection results, and the detection efficiency is low and the workload is heavy, which cannot meet the needs of long-distance and large-area road detection in cities. Therefore, a fast and efficient vehicle-mounted multi-channel array radar system is urgently needed.

In order to meet the above requirements, we have developed a vehicle-mounted array radar system (as shown in figure 1), which is based on multi-channel ultra-wideband ground penetrating radar technology and large antenna array technology, and is specially used for the general survey and detection of large-scale and long-distance highway and urban road collapse disasters.

Figure 1 Vehicle-mounted early warning radar system for road diseases and disasters

The antenna array includes five 400MHz antennas, two 200MHz antennas and 1 100MHz antennas (as shown in Figure 2), which gives consideration to the detection depth and resolution of the radar. The detection width of the radar system is 3.75m, the detection depth is 0~ 10m, the driving speed is 10 ~ 20 km/h, and the detection accuracy can reach centimeter level, so it can be used for carpet and full coverage survey of urban roads. The radar system carries out multi-channel synchronous joint scanning measurement of underground disease bodies, and obtains the spatial information and disease characteristics of the disease bodies to the maximum extent, which greatly improves the quality and efficiency of radar detection and identification. At the same time, the correlation between multi-channel data makes the interpretation of radar images more accurate and reliable.

Fig. 2 Schematic diagram of antenna array arrangement

The vehicle-mounted radar system integrates 8-channel ground penetrating radar antenna array, 3G antenna, laser line scanning industrial camera, RTK precise positioning system, control center, infrared high-definition camera system, DMI range finder and so on. (as shown in Figure 3), and synchronously collect array radar data, latitude and longitude coordinate information, live video scenes and high-definition road images, and integrate them into the system database to form a multi-information comprehensive collection platform, which can quickly and efficiently visually detect and accurately locate road diseases and disasters. Thanks to this pioneering detection technology platform and brand-new general survey and detection operation mode, geophysical engineers can obtain every underground cavity anomaly through multi-channel radar on an integrated and unified interface, determine its precise coordinate position, observe the site environment and road conditions, and quickly draw reliable conclusions through comprehensive analysis and judgment of various information.

Fig. 3 composition of vehicle-mounted radar system

The self-developed vehicle-borne road disease disaster early warning radar system obtained the product technology and software copyright granted by China National Intellectual Property Administration [6][7], forming a complete enterprise intellectual property system. 20 15, the system passed the appraisal of scientific and technological achievements of the Ministry of Housing and Urban-Rural Development.

Third, technical methods.

The technical method of detecting road collapse diseases by vehicle-mounted array radar is divided into five steps: general survey detection, screening of suspected points, rechecking of suspected points, pipeline countersigning and verification.

(1) general inspection

Vehicle-mounted radar system carries out general survey and detection on the designated operation area, and synchronously collects and stores various sensor data under the trigger of DMI.

(2) Screening of suspicious points

When screening suspected points, the platform software reads the database and displays multi-channel radar data, image data and maps synchronously. The steps of multi-channel radar data processing usually include zero adjustment, frequency domain filtering, gain adjustment, background removal and so on. According to the echo characteristics of the disease, the suspected disease spots are screened out, and the scale of the suspected disease spots is analyzed by combining the correlation of radar data of each channel. According to the latitude and longitude coordinates of the suspected point and the surrounding images, the specific position of the suspected point on the road is determined. When determining the suspected point, we should also refer to the image to eliminate interference, such as road bumps, steel plates, underground walkways, tunnels, overpasses and so on.

(3) Doubt review

Using conventional single-channel ground penetrating radar to check abnormal points. During recheck, the antenna with multiple center frequencies is used to detect the abnormal area with multiple survey lines. Through the radar image and the surrounding manhole cover, the pipeline distribution around the suspected point is determined, and the misjudgment caused by underground pipe trench and well chamber is eliminated. After reviewing the suspected points, determine the location, scale and buried depth of the abnormal area.

(4) pipeline countersignature

There are many underground pipelines in the city, which are managed by different professional departments, involving water supply, drainage, electricity, gas, heating, communication and information, radio and television, public security and transportation and other pipeline ownership units. In order to avoid damaging the pipeline during calibration, the countersigning procedure should be completed before construction. The municipal department organizes all pipeline ownership units to countersign pipelines at abnormal points of various diseases to verify the distribution of pipelines around suspected points.

(5) verification

Verified by drilling or excavation method.

Fourth, the case.

Vehicle-mounted array radar system has been successfully applied in Shenyang, Dalian, Xiamen, Guangzhou, Shenzhen, Nanjing, Zhenjiang, Changchun, Shijiazhuang and other cities.

4. 1 General Survey and Detection of Road Collapse Disaster in Siming District of Xiamen City

2065438+From May to September, 2005, Siming District of Xiamen City used the vehicle-mounted array radar system to survey and detect the main roads in its jurisdiction, and the mileage of the survey line was about 200 kilometers. Through the detection, many hollow disaster points were found, which effectively warned the road collapse disaster and avoided the collapse accident after engineering treatment.

Figure 4 shows a big hole detected in Xidi Road, Xiamen. After drilling verification, excavation and backfilling were carried out, and the danger was eliminated in time.

Figure 4 Xidi Road Cave in Xiamen

4.2 General Survey and Detection of Road Collapse Disaster in Tianhe District of Guangzhou City

From April, 2065438 to April, 2005, the vehicle-mounted array radar system conducted a general survey of road collapse disasters in Tianhe District, Guangzhou, and found many sunken disaster points. Figure 5 shows a big hole detected in Yun Ke Road, Tianhe District. The affected area is 30 square meters, the bottom is 3.2 meters deep, and the ceiling is only 0.3 meters away from the ground, which will collapse at any time. After drilling, drilling and electronic endoscope were used to check and evaluate the disease point, the relevant departments carried out grouting at this position to avoid accidents.

Figure 5 Yun Ke Road is empty.

4.3 General Survey and Detection of Road Collapse Disaster along Changchun Metro

Due to the stratum disturbance caused by subway construction, many road collapse accidents occurred along Changchun subway. From March, 2065438 to March, 2006, the vehicle-mounted array radar system conducted a general survey of road collapse disasters along the subway 1 Line and Line 2 (renmin street, Jilin Road and Jiefang Road) under construction in Changchun, and many suspected diseases were found in the general survey. The Road Lighting Department of Changchun Municipal Facilities Maintenance and Management Center called all pipeline ownership units to countersign pipelines at abnormal points of various diseases to verify the distribution of pipelines around suspected points (Figure 6). Through the verification of drilling or excavation (Figure 7), many cavities and loose road disease points are identified, and the distribution of disease points is shown in Figure 8.

Figure 6 Pipeline countersignature drawing

Fig. 7 Drilling site

Distribution map of road diseases in Changchun city.

Case 1:

The disaster site is located in the slow lane from east to outside at the intersection of Jilin Road and He Lin Road. The investigation of radar vehicles found that there were significant abnormal cavity reactions in radar scanning images. After on-site re-examination, borehole verification and borehole endoscope video recording (Figure 9), it is confirmed that the disaster site is a typical underground hidden cave disaster, with a length of 2.5 meters in the north-south direction, a width of 2 meters in the east-west direction and a depth of 0.42 meters. After exploration, there is a concrete drainage pipe at 1.7 meters below the disaster point, and the pipe body is connected to the drainage well next to the disaster point. After opening the manhole cover, it is found that there is a phenomenon of flowing soil around the connection part of the pipe body, and it is judged that the water body of the nearby road surface collecting well invades the disaster site and washes the soil, which is lost through the nearby drainage well and forms a cavity. Relevant departments immediately excavated and backfilled the cavities in the disaster area and renovated the drainage wells.

Fig. 9 Video screenshot of drilling endoscope

Case 2:

Figure 10 shows the water-rich hole discovered by the slow lane radar system on the east side of Jiefang Road. During the general survey, it was found that there were obvious abnormal cavity reactions and water body reactions in radar scanning images. After on-site re-examination, borehole inspection and borehole endoscope video recording, it is confirmed that this place is a serious underground hidden cave disaster, which is 4 meters long in the east-west direction, 2 meters wide in the north-south direction and 0.35 meters deep. After investigation, there is a tap water pipeline 2 meters below the disaster site, and the pipe body is seriously leaking, which washes the soil at the disaster site and flows into the fork-road water collection well. The water erosion loss is large and the water flow is clear. Drilling shows that the soil at the disaster site has been completely washed away, leaving only gravel, forming a water-filled cavity. There is a great risk of collapse when it is washed away by leaked tap water for a long time. Relevant departments immediately repaired the tap water pipeline in the disaster area and backfilled the cavity in time.

Figure 10 Changchun Jiefang Road Air

Verb (abbreviation of verb) conclusion

Vehicle-mounted array radar is the first choice for early warning and detection of urban road collapse disaster. In engineering practice, making reasonable operation procedures and methods and giving full play to its technical advantages and efficiency can accurately and reliably detect and discover underground hidden caves, give early warning in time, and effectively prevent and reduce road collapse disasters and accidents.

refer to

Yang Caixia. Preliminary study on the causes of urban pavement collapse. Shanxi architecture, 2013,39 (15):113-14

[2] Song Jiachang, Ye, Liu. Causes and countermeasures of urban road collapse in Beijing. Urban roads and bridges and flood control, 20 1 1, 8:250-252.

[3] Zhou Zhenggang. Cause analysis and preventive measures of urban road collapse. Road and Bridge Engineering, 2015,5 (11).

[4] Ryoji Hirata, AkioMatstyama. Introduction and case study of vehicles using ground penetrating radar to detect underground structures, Asia-Pacific conference on near-surface geophysics, July17-19,2013, Beijing, China.

Zeng Zhaofa, Wang, Liu Minghui. Technical method of detecting urban subway holes by ground penetrating radar. Geophysical and geochemical exploration, 20 10/0,34 (5): 617-621.

Vehicle-mounted road disaster and disease early warning radar system (VGPR-20) of Dalian Zhong Rui Science and Technology Development Co., Ltd., patent publication number CN302973058S, publication date: 20 14- 10-22.

[7] Dalian Zhong Rui Science and Technology Development Co., Ltd., a vehicle-borne road disaster disease early warning radar system, patent publication number? :CN203870250U。 Opening date: 20 14- 10-08.