Special research on the deformation monitoring industry: deformation monitoring the beginning of the east wind.

(Report producer/author: Changjiang Securities, Yu Haining, Huang Tianyou)

High-precision positioning is an important dependence of deformation monitoring

Precision and intelligence are the development direction of the next stage of deformation monitoring.

The deformation can be monitored and the safety of life and property can be guaranteed.Changes in the shape of objects are common in nature and daily life, such as the uplift or collapse of the surface, the collapse of a dam, the collapse of a bridge, and the tilt of a bridge. This kind of change is often accumulated by small shape variables, which trigger a macro displacement at a certain moment through quantitative change, resulting in huge disasters and losses. Taking landslide as an example, the rock and soil on the slope are affected by natural (such as rivers, earthquakes, etc.) and human factors for a long time. Under the action of gravity, it is possible to slide down along the weak layer. my country is a country with more serious geological disasters. According to the disclosure of the Ministry of Natural Resources, there will be 4772 geological disasters across the country in 2021, resulting in 80 deaths, 11 missing, and direct economic losses of 3.2 billion. At present, geological disasters and hidden dangers of engineering construction can not be completely eliminated, but the occurrence and loss of disasters can be reduced by means of monitoring and prediction.

Deformation monitoring has gradually changed from "passive" to "active.Deformation monitoring in China started late, but it is developing rapidly, and the development of technology and methods promotes the monitoring from passive governance to active prevention. The industry can be divided into three stages of development: simple observation stage means a single, simple use of tools, relying on manual inspection and measurement, it is difficult to find abnormal conditions in time; The instrument monitoring stage adopts a combination of manual inspection and instrument measurement, and uses various instruments to greatly improve the monitoring accuracy. The monitoring system stage highly integrates various instruments and technologies to promote the development of monitoring to intelligence.

As the core means of the transformation from "ex post" to "ex ante", the importance of deformation monitoring has become increasingly prominent.Deformation monitoring uses measurement and special instruments and methods to carry out continuous observation of the deformation phenomenon of the deformation body, analysis of its deformation form and prediction of the development trend. Its task is to determine the space state and time state of the shape, size and position of the deformed body under the action of various loads and external forces, and to find its change characteristics according to the comparative data analysis of the measurement results before and after, so as to judge and predict the deformation, and take timely and effective protective measures to reduce the occurrence of disasters. There are a large number of hidden danger points in our country and the types are complicated. The development and popularization of the monitoring system still needs time. Precision and intelligence will become the theme of the next stage of development.

The significance of deformation monitoring lies in data analysis and prediction and early warning, and precision and intelligent systems are expected to be fully popularized.With the frequent occurrence of geological disasters and the large-scale construction of infrastructure in China in recent years, more and more scenes need to be monitored. Specifically, the object scenarios involve geological disasters, bridges, reservoirs, dams, highways, etc., and different scenarios are applied with different sensor devices, such as GNSS receivers, inclinometers, displacement meters, crack meters, monitoring radars, etc. The technologies involved include high-precision positioning technology, sensor technology, communication technology, etc. Using the deformation monitoring system with high precision and accurate time to make accurate prediction and early warning before the disaster occurs plays an important role in disaster reduction.

The national government has achieved initial results in promoting the prevention and control of geological disasters.China's geological disasters are widely distributed and harmful. By the end of 2020, more than 330000 hidden danger points of geological disasters have been found in China. It is urgent to change from paying attention to post disaster relief to paying attention to pre disaster prevention. According to the Ministry of Natural Resources, a total of 4772 geological disasters occurred nationwide in 2021, causing 91 casualties (missing) and direct economic losses of 3.2 billion yuan. Compared with the average of the same period in the previous five years, the number of geological disasters and the number of deaths and disappearances caused by geological disasters in 2021 decreased by 30.3 per cent and 63.2 per cent, respectively, and direct economic losses were flat; compared with the same period last year, they decreased by 39.1 per cent, 34.5 per cent and 36.3 per cent, respectively. In 2022, the Ministry of Natural Resources will continue to promote the combination of geological disaster group special monitoring and early warning experimental surface, and plans to build 20040 geological disaster early warning experimental sites. Generally speaking, there are still a large number of hidden dangers of geological disasters in China, and the monitoring coverage of hidden danger points is low, so deformation monitoring is still the focus of geological disaster prevention and control.

High-precision positioning technology is the key to the development of deformation monitoring

The core of deformation monitoring is to monitor displacement, and high-precision positioning equipment and technology are its core components.In 2020, the industry's high-precision applications are developing rapidly, and the sales scale of infrastructure construction, high-precision devices and products in the power, precision agriculture, deformation monitoring and other market segments show an accelerated growth trend, of which the total sales volume of various precision application terminals (including measurement receivers) in the domestic market is close to 1.5 million units. At present, the common GNSS positioning equipment (receivers) on the market can be divided into three categories according to the accuracy: 1~10 meter level, decimeter to centimeter level and millimeter level. The positioning accuracy difference of the three types of equipment is mainly determined by the internal GNSS receiver chip. Among them, the real-time positioning equipment, after the receiver processor decodes the satellite information, there are many different algorithm modes (single point positioning, SBAS, RTD, RTK, etc.) in navigation processing, and different algorithms lead to different positioning accuracy, while measurement receivers often save the decoded satellite signals for post-analysis and calculation, so as to obtain higher-precision positioning results.

The application field is gradually broadening, and geological disaster monitoring has become the starting point.The combination of GNSS positioning technology and modern communication technology and computer technology has promoted the monitoring to all-weather, real-time, high-precision, continuous and automatic, and has been widely used in the field of deformation monitoring, such as settlement monitoring, water resources safety monitoring, highway monitoring and so on. Among them, geological disaster monitoring mainly uses high-precision positioning to obtain real-time three-dimensional coordinate changes of the monitored object to achieve early warning and forecasting. In recent years, it has been highly valued and promoted by the national competent authorities, showing a high-speed development trend and becoming the main force of the industry. With the global network of Beidou 3, the improvement of the core performance of navigation satellites will help build a more accurate positioning and more comprehensive monitoring system.

Deformation monitoring will develop in the direction of high precision, automation and intelligence, and high precision positioning technology will play a key role.At present, the commonly used high-precision positioning equipment has two ways of dynamic and static relative positioning, and the accuracy can reach centimeter level and millimeter level respectively. In the actual monitoring scene, because the deformation is usually in a small order of magnitude, the monitoring system generally adopts a GNSS measurement receiver. Considering the measurement error and monitoring requirements, the positioning accuracy determines the availability and reliability of the monitoring system, so the goal and primary task of the development of related technologies is to continuously improve the accuracy of deformation monitoring and the performance of monitoring instruments, which makes high-precision positioning technology gradually become The catalyst for technological innovation in the industry.

The United States, Japan deformation monitoring development model for reference

The deformation of geological disasters and buildings is a global problem. Countries around the world have explored their own development paths and experiences in the process of development. China has a vast territory and complex geological conditions. Land subsidence and collapse are easy to occur in plain and hilly areas, and slope deformation and failure are easy to occur in mountainous areas. Monitoring should be promoted by appropriate means according to the spatial and temporal distribution. The United States is vast and sparsely populated, and geological disasters occur frequently. It attaches great importance to the prevention and control of geological disasters, which provides an opportunity for the organic combination of engineering and policy systems; Japan is densely populated and is one of the countries with the most natural disasters, and has established a legal disaster prevention and mitigation management system. In addition, the United States and Japan are in the world's leading level in infrastructure construction, and have established a relatively complete monitoring system for high-rise buildings, bridges and other engineering buildings. Its development model has reference significance for my country.

The United States attaches great importance to the prediction and prevention of geological disasters, especially the monitoring of key areas. It has established a nationwide disaster network, including monitoring, forecasting, disaster relief, communication, etc., and various service systems can automatically respond to disasters. The United States Geological Hazards Survey USGS was established in 1879. It has continuously expanded and strengthened the monitoring network of geological disasters such as earthquakes, landslides and volcanoes, ensured the reliability of monitoring stations, and realized real-time monitoring of key monitoring stations. The United States has a long coastline and is located in the Pacific Rim volcanic belt. According to Smithsonian Institution statistics, the United States has the largest number of Holocene volcanoes in the world, reaching 161. Since 1960, the number of active volcanoes has reached 40, second only to Indonesia. At present, USGS has established 21 landslide monitoring stations and 5 volcano observation stations. The latter has established an active volcano monitoring network composed of more than 300 GPS continuous operation reference stations, which can continuously monitor potential active volcanoes all over the country with high precision. In addition, its data collection and distribution capabilities provide a data portal for the public.

Japan is located on the edge of the plate, with narrow and steep terrain and poor geological conditions. In the process of long-term struggle with disasters, Japan has established a world-leading comprehensive response system for disaster prevention, mitigation, disaster resistance and disaster relief. Japan has a complete set of disaster prevention and relief laws, with more than 200 relevant laws and regulations, which helps to build a national prevention and control system from the institutional level; it has a strong economic foundation and strong scientific and technological strength, and has special national budget support for relevant plans, such as disaster scientific research, disaster monitoring, etc. Japan has a large population and little land, and has a high population and building density. Although the geographical environment is harsh, its high-rise buildings are still in the forefront of the world. Japan's frequent strong seismic activity and seasonal strong winds and typhoons, for such extreme events, infrastructure (such as long-span bridges), high-rise buildings and other building structure monitoring has become the focus. The large-scale construction of conventional monitoring system is gradually playing a useful role in real-time structural monitoring, maintenance and management.

Industrialization promotes the rapid development of my country's social economy and engineering technology, but it also causes geological disasters such as landslides, mudslides, ground subsidence, ground fissures, and ground subsidence; with the rapid economic development and rapid population growth, bridges, high-rise buildings, roads and railways And other building facilities are also increasing rapidly, which are prone to deformation risks such as displacement, tilt, and cracks. The above problems are easy to cause huge loss of life and property safety, and bring greater challenges to our country's safety monitoring.

Compared with developed countries, China's deformation monitoring started late, and the geological disasters and engineering construction level of the United States and Japan are similar to those of China, and its development experience is worth learning. According to the actual situation, for geological disasters, China still needs to strengthen government promotion and standardization, expand and strengthen deformation monitoring, especially to strengthen monitoring of key distribution areas, so as to form a monitoring network system with wide coverage, high control degree and high measurement accuracy. For infrastructure such as bridges, strengthening scientific and technological empowerment according to structural changes is expected to provide early warning of health status through deformation monitoring.