I. Overview of Geological Survey of Water Conservancy Engineering
(A) the significance of geological exploration work
In the construction of water conservancy projects, geological exploration can reasonably avoid some problems existing in water conservancy projects and make the project construction and natural environment in a state of balance. For example, during the construction of the Three Gorges Dam in China, many difficulties have been overcome, among which the typical ones are: excavation of high slope of permanent shiplock, deep-water cofferdam, large-scale concrete pouring and so on. The paper of water conservancy project investigates the rock and soil seriously and scientifically, effectively grasps the geological deformation, applies new materials and technologies in the construction, avoids cracks in concrete during the construction, and improves the overall construction quality of water conservancy project. To sum up, the geological investigation of water conservancy projects can reasonably analyze and evaluate geological problems, thus providing accurate and detailed information for the project construction and construction, determining the foundation and rocks of water conservancy projects, and ensuring to meet the construction requirements.
(2) The main contents of geological survey
Geological survey mainly includes: soil sampling, survey and mapping, indoor test, in-situ test, etc. These are the key points of geological survey. In the process of survey, the staff need to make qualitative and quantitative analysis of geological conditions and prepare geological survey reports. In the survey stage, the surveyors first need to complete geological mapping, which includes pit exploration, drilling and geophysical exploration. When investigating the geotechnical properties, they chose the best exploration method to complete the exploration work. The main purpose of indoor test and in-situ test is to determine the geological strength parameters, stress, permeability and other indicators, while the main purpose of on-site monitoring is to analyze the geotechnical load and its impact on the environment, so as to minimize the adverse impact on water conservancy project construction.
Two, the three stages of geological investigation of water conservancy projects
(1) control measuring point
In the construction of water conservancy projects, the quality of geological survey will directly affect the geological quality, and the surveyors should control drilling in strict accordance with the geotechnical engineering survey specifications. The determination of control survey points is mainly to complete preliminary exploration, and it is not necessary to control survey points during detailed exploration. In addition, the surveyors also need to evaluate the geology, determine the bearing capacity and stability of the geology at the construction site of the water conservancy project, analyze the deformation of the rock and soil, determine the strength and compression index of the rock and soil, and make an accurate evaluation of the stability of the foundation.
(2) Determine the bearing capacity of rock and soil
There are many methods to determine the bearing capacity of rock and soil. Firstly, the ultimate bearing capacity of foundation is determined according to Hansen formula.
The value of safety factor is related to the load nature, safety grade and shear strength index of the project. Usually, the safety factor is 3 or 2. Surveyors determine the foundation bearing capacity according to the shear strength of rock mass to ensure that the foundation bearing capacity meets the construction requirements. Secondly, according to the load test, the surveyors use the in-situ test to realize the graded loading, and the determination of the overall bearing capacity of the foundation should be completed on the basis of measuring the settlement. In addition, the surveyors analyzed the change characteristics of the foundation rock and soil through the analysis look-up table method, and determined the bearing capacity of the foundation through the in-situ test and theoretical formula.
(3) Determination of groundwater
During the survey, surveyors need to determine the groundwater level and elevation. The dry season and wet season of groundwater will have great influence on the project. Due to the limitation of construction period, geological surveyors can collect data from relevant departments in their work, fully grasp the groundwater information and change law, and adopt reasonable methods in foundation treatment. In addition, the surveyors also need to determine the foundation permeability coefficient, and the determination of data needs to be based on field test and indoor test methods, and the test site is scientific and accurate.
Thirdly, the control points of geotechnical engineering are analyzed.
Compared with general projects, water conservancy projects are not only complicated but also difficult. Especially under the complicated geological price adjustment of water level, it is very necessary to study and analyze the geological data of water level. If the research is not in place, geotechnical disasters may occur frequently in the process of water conservancy project construction, which will cause serious harm to the project, not only wasting funds, but also making it difficult to carry out follow-up work. Therefore, the key content of water conservancy engineering geological investigation is geotechnical engineering control.
Hydrogeological evaluation
Bad geology is found and treated to provide stable foundation and bearing capacity for engineering construction. The primary task of geological exploration is to evaluate hydrogeology in order to avoid major safety accidents in the future. Hydrogeological evaluation mainly includes: finding out the water quality, making detailed geological data, predicting various possible impacts on groundwater in water conservancy projects, and what factors will affect the surrounding groundwater. Geological survey institute should accurately analyze the rock mass in the process of engineering construction, determine the harm caused by rock mass, and verify its water abundance and groundwater permeability through experiments to avoid the settlement caused by human factors in the process of engineering construction.
(2) Geotechnical hydraulics
The main properties of rock and soil cover the physical and hydraulic properties of rock and soil, and the relationship between rock and soil and groundwater formation is also rock and soil hydraulics. Groundwater can exist in rocks and soil in many ways. Such as confined water, fissure water, karst water, etc. In geological survey, the expansion, contraction and disintegration of water bodies are the objects to be tested. In addition, the water resistance and weathering strength of the exposed wall are also needed.
(3) testing rocks and soil
In-situ testing and indoor testing are the main methods of geological exploration and testing. The indoor test is mainly aimed at cohesive soil, and the field test is mainly aimed at sedimentary soil. The content of testing needs to include strength, compactness and so on. There are many testing methods, such as cone dynamics and vane shear. Put the cone probe into the soil and analyze the foundation in layers. This method is relatively simple to operate and requires less equipment, but the accuracy of the research results is relatively low. Clean the casing, press the template into the soil, and carry out stress test on the geology. Different test methods are suitable for different soil properties, so the study of different geotechnical properties depends on the topography of the site and the accuracy of the test results.
Water conservancy project is a basic project, and China's water conservancy project construction faces many difficulties. It is very necessary to strengthen the discussion on geological investigation of water conservancy engineering and geotechnical engineering control. Through scientific investigation, the staff can put forward better control measures, provide more accurate data support for construction and promote the development of water conservancy projects in China.
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