Engineering geological exploration is an investigation to study the geological factors affecting buildings. Hydrological conditions, some natural geological phenomena, geotechnical mechanical properties and geological structures are the main factors of geological exploration. The following is my engineering geological exploration paper, welcome to read.

1 application status of geotechnical engineering geological investigation technology

1. 1 Technical Problems in Geological Survey

Geotechnical engineering geological investigation is the key to ensure the implementation of geotechnical engineering.

At present, there are still some problems in the application of geological exploration technology. In the process of investigation, geological surveyors need to divide the interface according to the various properties of rock and soil in order to treat it differently. However, in practical work, interface division lacks pertinence. It is easy to ignore the comprehensiveness when sampling rock and soil, especially some undisturbed rock and soil samples, which leads to the lack of comprehensiveness in the indoor test of rock and soil and the narrow contact surface of the obtained parameters.

Some geotechnical surveyors' own survey ability is not high, which leads to their limited field work and data collation and analysis ability, and can not effectively meet the actual needs of survey work. In addition, in the survey work, the lack of combination with the building structure often leads to a strong one-sidedness of the survey work.

1.2 causes of technical problems in geological exploration

First of all, in the process of geological survey, the survey basis is insufficient, and the survey report lacks the analysis of relevant information of construction projects, which leads to the layout of survey points in the survey work can not be targeted, so that the survey results can not meet the requirements of construction projects. Moreover, the maximum load within the scope of the project was not comprehensively considered, which led to the inadequate investigation work. Especially in the process of engineering pile foundation construction, if there is a special geotechnical structure in a certain area, it is necessary to replace the water pile in the process of pile foundation construction, which requires revising the structural design of the building, resulting in a lot of waste of manpower, material resources and financial resources.

Secondly, the investigation work lacks rationality. In the survey process, there are great differences in the survey spacing and survey point layout of different buildings. However, in the specific operation process of the survey work, due to the failure to operate according to the requirements of the specification, the phenomenon of insufficient hole depth and out-of-range survey points often occurs. In geological exploration, because of not considering the survey grade, it is often found that the foundation conditions are good when geological exploration is carried out according to ordinary standards, but in the later shear wave velocity test, it is often found that there is a special structure of rock stratum in the drilling depth. Finally, at present, the level of geological exploration is relatively backward, and the static sounding method is mostly used in gravel soil layer, which leads to the lack of coherence in the sounding process and the lack of comprehensiveness in the drilling process because of ignoring the core recovery rate.

2 Geotechnical engineering geological survey technology

2. 1 Geological Survey and Mapping

Geotechnical engineering geological mapping refers to mapping the landform, changes and geological conditions of geotechnical engineering. The specific contents include: within a certain width range inside and outside the boundary of geotechnical engineering investigation, investigate whether there are adverse geological phenomena such as landslides, soil caves and collapses, as well as the exposed parts, scope and distribution of rocks and weak geological bodies, and mark these investigation contents on the drawings according to a certain proportion; Hydrometeorological investigation of the climate where the rock and soil is located, and the damage degree of surrounding living and production buildings to the rock and soil, etc. Analyze the characteristics and weathering degree of rocks, the relationship between landforms and geotechnical layers, and preliminarily divide geomorphic units; Investigate the groundwater situation in the geotechnical position, including the type, water level and flow rate of groundwater, and mark it on the mapping map according to a certain proportion. In addition to marking the above-mentioned survey contents on the drawings, the field photos or sketches of the survey should be taken as the basic data for compiling the geological exploration report.

2.2 Drilling Technology

In geotechnical engineering geological investigation, it is necessary to master the first-hand information through geotechnical drilling, which requires high technology, and it is necessary to effectively master some practical methods in the drilling process to ensure that the drilling technology level can be better played.

1) Selection of drilling technology. In different geological environments, the drilling technology chosen will be different. When drilling holes in strata above groundwater, the dry drilling method with spoon drilling should be adopted. This drilling method is simple and convenient, but it will bring great interference to the soil layer when drilling, so it is not suitable when the drilling depth is high. According to the depth of various geotechnical engineering investigations, core rotary mud wall protection drilling method can be used for drilling. In general geological exploration, drilling methods such as double-tube single-action single-body drilling and impact drilling are often selected for work.

2) Control of drilling depth. When measuring the layered depth of rock and soil layer, the error must be strictly controlled to ensure that the measurement error is less than 5cm. In the process of drilling with core rotary mud wall protection method, in order to better control the layering accuracy, it is necessary to strictly control the footage of discontinuous coring drilling, generally within 2 m.

3) Control the coring speed of different types of rocks and soils. When the geotechnical properties are different, it is necessary to control the coring speed according to the different properties. For soil layer, the coring rate needs to reach 100%, and when drilling weathered rock residual soil, the coring rate needs to reach 85%. However, the heart rate of half rock and half soil is controlled at 90%, that of broken rock is controlled at 65%, that of soft rock is controlled at 65%, and that of intact rock is controlled at 80%.

4) During drilling, it is necessary to fill in drilling records according to drilling times, which can be used as the necessary basis for the application of drilling technology.

2.3 sampling and testing technology

First, sampling technology. Sampling should be carried out according to the engineering foundation conditions. Generally, the upper positions of moderately weathered and slightly weathered rocks are collected, because these weathering zones have transitional characteristics and the upper positions are representative, and the experimental values of ultra-weathered zones in other positions are too scattered.

The collected samples should be sealed with wax in time, and the rock samples should be covered with tape to prevent water loss, and classified and properly kept. Each sample should be marked, and the depth of the hole section should be recorded, and then sent to the civil engineering test site for analysis and test of soil samples and rock samples. Secondly, in-situ testing, that is, in the natural state of ensuring that the detected object is not disturbed and destroyed, the indicators are determined by various testing methods. In-situ testing is an important part of geotechnical engineering geological investigation, and obtaining geotechnical engineering design parameters is also an important means of geotechnical engineering construction quality inspection. There are many methods for in-situ testing, including load, static penetration test and standard penetration test.

The detection method depends on the engineering conditions and requirements, and the commonly used detection method is standard penetration test. According to Code for Design of Building Foundation, standard penetration test is an automatic drop hammer test method. According to the foundation conditions, this method should take 1~ 1.5m as the main drilling unit depth. If the geology is loose soil, the drilling depth should be determined according to the actual situation. The unit depth of primary drilling in weathered residual soil and fully weathered zone is 1.5m, and that in strongly weathered zone is 2 ~ 2.5m.. Finally, the geological survey report is compiled. It should be compiled in strict accordance with the requirements of relevant regulations. Before compilation, all kinds of survey data should be summarized and sorted out, and an outline should be drawn up in combination with the actual situation, including the basic contents of survey, geological conditions, engineering analysis and evaluation, relevant conclusions and suggestions, etc.

3 Conclusion

Geotechnical engineering geological investigation is a comprehensive work, which is not only complicated, but also has strong variability. At present, there are still some shortcomings in the application of geotechnical engineering geological survey technology. Therefore, it is necessary to analyze the causes of these problems, improve the technical content of geological survey through comprehensive application of various survey techniques, and comprehensively and objectively judge and evaluate the geological environment, so as to ensure the provision of scientific geotechnical engineering geological survey data for the construction of construction projects and ensure the smooth progress of construction.

refer to

[1] Liu Zhan province. Discussion on Railway Engineering Geological Exploration in Karst Area [J]. Western Exploration Project, 20 10( 7): 15.

[2] Liu Qun. Discussion on some problems in the code for engineering geological investigation of dikes [J]. People's Yangtze River, 2015 (1):14.

[3] Zhang. Analysis on quality control factors of geotechnical engineering geological investigation [J]. Heilongjiang Science Department, 2014 (10):15.

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