Research On Geostress Measurement And Back Analysis Method Of The Three-Pressure Cell

Geostress is the fundamental stress which causes the rock deformation and damage, which is the necessary precondition of the rock stability analysis and the design of the underground rock excavation engineering. Most deep rock in mine is broken, soft and low mechanical strength, so it is difficult to measure stress accurately. Therefore, making accurate test for geostress of loose and soft rock, and doing inversion analysis of roadway area and the entire mine or mining area based on test data, which will have an important significance for planning of mining or mine area, overall layout of roadway and mining area, and the design of roadway supporting. In response to this idea, the article divide into two parts, which are stress measurement method in soft rock and back analysis of the stress field according to measured stress. The specific contents are as follows:In the first part, the article summarized the commonly used method, research status, and useful conditions, which concluded that there was no effective method for stress measurement in the soft rock. So it presented an effective method—stress measurement method by the three-pressure cell, which could use in soft rock. The study of this method included the principles of stress measurement, measurement procedures, geotechnical three-pressure cell, and the install poles and so on. Manufacturing of the geotechnical three-pressure cells was the most important content, which analyzed some factors which included principles of pressure sensing devices commonly using in geotechnical engineering, the measuring site conditions and so on. The design of the three-pressure cell was based on the principles of resistance strain pressure monitoring system. The design included the appearance design, the internal pressure control system, display circuit design, and complete temperature compensation technology and so on.In the second part, it summarized some commonly used back analysis methods of initial stress field. By comparing the advantages and disadvantages of each method, the article putted forwards the research ideas. It made further research on the back analysis of multivariate regression model. And it presented an improved algorithm, according to large deviations between the samples stress field and the actual stress field. It compared the results by an example through the use of conventional algorithms and improved algorithm, the latter's regression values closed to the measured values, and achieved higher accuracy.Finally, the article summarized the main work of the text, and discussed the future research.