Hydraulic engineering geological survey?

Geological survey of water conservancy projects is very important. The data obtained by survey technology will directly affect the progress and quality of later project construction. Every detail is very critical. Zhongda Consulting would like to briefly introduce to you the geological survey of water conservancy projects.

1 Engineering geological surveying and cataloging Engineering geological surveying and cataloging is the first comprehensive basic work carried out in geological survey. The main methods include: route mapping method, geological point surveying method, measured profile method, etc. Generally speaking, for an engineering area, we should first study and clarify the regional crustal stability and seismic activity conditions, and then make full use of the existing area survey results to conduct special engineering geological surveying and carry out research on other special engineering geological issues. . The application of 3S technologies such as Global Positioning System (GPS), Remote Sensing (RS), and Geographic Information System (GIS) reflects the development of engineering geological surveying and cataloging. 2 Engineering Geological Exploration Engineering geological exploration is based on engineering geological surveying and mapping to further identify engineering problems below the surface and obtain deep geological data. There are mainly three methods: mountain exploration, drilling, and geophysical prospecting, which are explained below. . 2.1 Mountain exploration Mountain exploration refers to the exploration methods that use manual or mechanical methods to strip soil, or excavate exploration pits, exploration trenches, exploration wells or adits to reveal the shallow geological conditions on the surface. It can directly conduct testing, sampling and observation of geological phenomena. The tools and technical requirements used are relatively simple, so they are often used in shallow surface geological surveys. This is also a disadvantage of mountain exploration, that is, its exploration depth is limited. 2.2 Drilling In recent years, the improvement of drilling methods, techniques and construction levels has accelerated the development of geological survey levels in water conservancy and hydropower projects, which is mainly reflected in the following aspects: 2.2.1 The development of drilling equipment such as drill bits and drilling rigs. For example: Since the 1980s, various new drilling rigs with fast rotation speed, large torque and stable performance have been developed. In addition, when drilling relatively complete hard rock, diamond drill bits basically replace steel particles or carbide drill bits, greatly improving the drilling speed and core recovery rate. 2.2.2 The development of drilling sampling technology for special layers such as sand and gravel layers, weak interlayers, and fracture zones. The sand and gravel layer is stuck and difficult to drill, as well as drilling in special layers such as weak interlayers. The core recovery rate is low and sampling difficulties have always been technical problems in drilling water conservancy and hydropower projects. In recent years, the new technology of SM vegetable gum and MY-1A vegetable gum flushing fluid diamond drilling into the sand and gravel layer has been widely used, which has better solved the problems of drilling and sampling in the sand and gravel layer. When drilling in weak interlayers and fractured zones, due to core grinding, the core recovery rate is always very low and it is difficult to obtain undisturbed soil samples. The casing drilling technology developed in recent years, or the use of special core drilling tools, and other protection systems to ensure that the core is protected from erosion and extrusion, have better solved this technical problem. 2.2.3 The development of other drilling processes. For example, the new rope core drilling technology achieves the purpose of collecting rock cores without lifting the drill. Its application in water conservancy and hydropower projects has proven that this technology greatly reduces the workload of lifting the drill back and forth during the coring process. It has better solved the problems that often occur during drilling in special formations such as weak layers, such as hole collapse and low core quality. 2. 3 Geophysical Prospecting (Geophysical Prospecting) is referred to as geophysical prospecting. It uses observation instruments to measure the geophysical field of the exploration area, and infers and discovers local geological bodies that may exist underground through the processing and geological interpretation of measurement field data. , the science of the location, burial depth, size and properties of geological structures. Engineering geophysical exploration methods mainly include gravity field exploration, magnetic field exploration, DC electric field exploration, etc. based on potential field theory, as well as seismic wave exploration, electromagnetic wave exploration, etc. based on wave theory. 2.3.1 Exploration of gravity and magnetic potential fields. Gravity and magnetic potential field exploration is the oldest type of geophysical prospecting. Compared with seismic exploration, its accuracy and reliability are poor. At present, due to the development and application of some high-precision gravimeters and magnetometers, the accuracy of gravity and magnetic potential field exploration has been greatly improved. At the same time, the application of neural network technology in gravity and magnetic potential field exploration, as well as the research and application of magnetic vector tomography theory, have enabled gravity and magnetic potential field exploration to gain widespread development and application in the last century. The use of micro-G gravimeters enables microgravity measurements to be used to explore the changing shapes of caverns and slope geological bodies and monitor their stability.

Magnetic prospecting is mainly used in regional and deep geological structure research, mineral exploration, archaeology and other fields, and is rarely used in engineering geological surveys. 2.3.2 Seismic exploration. Artificially excited source seismic wave exploration is widely used in engineering geological exploration, and there are many types of artificially excited sources. At present, seismic exploration is developing rapidly in the field of water conservancy and hydropower engineering. For example, elastic waves and longitudinal waves are used to qualitatively evaluate the rock mass quality of large-scale water conservancy and hydropower projects such as the Three Gorges, and have achieved significant engineering and economic benefits; the negative velocity method and the horizontal seismic profile method developed by China Railway Southwest Research Institute, The TSP long-distance advance prediction method developed by Switzerland's Amberg Surveying Technology Company, and the true reflection tomography (TRT) advance prediction technology developed by the American NSA Engineering Company have better solved the problem of using reflection wave seismic survey for tunnel advance prediction. problem. In recent years, seismic CT has developed into a series of methods. Its imaging methods have developed to the point where it can use various wave combinations such as direct waves, reflected waves, refracted waves, surface waves, etc., and can use various wave combinations such as boreholes, tunnels, slopes, and mountains. Two-dimensional and three-dimensional geological imaging are carried out under the observation conditions, which promotes the development of geological survey from qualitative to quantitative. 2.3.3 Electromagnetic exploration. It includes various methods such as electromagnetic detection of natural field sources (MT method) and continuous electromagnetic wave exploration of artificial field sources (EM method). In recent years, electromagnetic exploration has been increasingly used in water conservancy and hydropower projects. For example, technologies such as controlled source audio magnetotellurics, artificial and natural field sources, multiple field sources, and two-dimensional and three-dimensional resistivity imaging are used to infer the structural characteristics of the surrounding rock media of deep and long tunnels in water conservancy and hydropower projects. , hidden faults, fracture zones and abnormal areas and other factors that may affect the project, and achieved significant economic benefits. Geological radar (frequency range 1 ~ 100MHz) is currently the geophysical prospecting method with the highest resolution. Geological radar has a high ability to identify fault zones, especially water-bearing zones and fracture zone strata. 2.3.4 Electrical exploration. It mainly includes resistivity method, charging method and natural electric field method, induced polarization method, and electromagnetic induction method. It can be divided into two branches: stable current field theory and alternating flow theory. The resistivity method is widely used in geological surveys of water conservancy and hydropower projects. The high-density electrical survey developed in recent years belongs to the category of resistivity method, but it introduces the data collection method of seismic survey, which can realize the rapid and automatic collection of data. Its measurement results can be processed in real time and displayed on the geoelectric section or Profiles, developed from traditional one-dimensional exploration to two-dimensional exploration. At present, on the basis of single source and single point measurement, it has developed into multi-source, multi-point and multi-line measurement, thus developing three-dimensional observation technology.

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