A Simple and Accurate Interpretation Method of In Situ Stress Measurement Based on Rock Kaiser Effect and Its Application

Abstract

Many deep underground excavation practices show that the size and distribution of in situ stress are the main factors resulting in the deformation and instability of the surrounding rock structure. The in situ stress measured by the Kaiser effect of rock is used by engineers because of its economy and convenience. However, due to the lack of quantitative judgment basis in determining the Kaiser point position, there is a large artificial error in the practical application. In response to the problem, this study systematically investigates the characteristics of rock acoustic emission curve on the basis of the fractal theory and establishes an accurate and simple interpretation method for determining the Kaiser point position. The indoor rock acoustic emission test was carried out by drilling a rock sample at a mine site. By using the conventional tangent method, the cumulative ringing count rate-time-stress curve of rock acoustic emission is analyzed to preliminarily determine the time range of Kaiser point appearance. Considering that the fractal dimension of the rock Kaiser point is lower than the adjacent point, the minimum point of the fractal dimension of this time range can be determined from the fractal dimension-time-stress curve. Such determined point is the Kaiser point. The size of the in situ stress is calculated using an analytical method. Based on the value of the in situ stress, the distribution of the in situ stress in the mining area is further analyzed using the geological structure of the mine. The maximum principal stress is 19.38 MPa, with a direction of N (30°-40°) E, and the minimum principal stress is 8.02 MPa with a direction of N (50°-60°) W. The maximum and minimum principal stresses are approximately in the horizontal plane. The intermediate principal stress is 11.73 MPa in vertically downward. These results are basically consistent with the distribution statistical law of the measured in situ stress fields in the world. The results presented in the study could provide a reference for the later mining, stability evaluation, and support of the surrounding rock.

A novel in situ stress measurement method based on acoustic emission Kaiser effect: a theoretical and experimental study

“…Before the experiment, Vaseline was used as a coupling agent to paste four AE transducers on the upper and lower ends of the specimen [ 52 , 53 ], as shown in figure 8 . Then the sound emission signal channel function was checked, and the parameters for the AE collection and analysis system were set, the gain of the pre-amplifier was set to 6 dB, and the threshold of the AE transducer was set to 45 dB [ 52 , 54 ]. After confirming that the PCI-2 AE system was working properly, a uniform layer of grease was applied to the rock specimen's surface, the specimen was placed on the AG-I250 test bench, the AG-I250's loading head was adjusted so that it contacted the rock specimen's upper face, and the stress loading parameters were entered.…”

“…Before the experiment, Vaseline was used as a coupling agent to paste four AE transducers on the upper and lower ends of the specimen [52,53], as shown in figure 8. Then the sound emission signal channel function was checked, and the parameters for the AE collection and analysis system were set, the gain of the pre-amplifier was set to 6 dB, and the threshold of the AE transducer was set to 45 dB [52,54].…”

3D displacement discontinuity analysis of in-situ stress perturbation near a weak faul

“…Consideration of perturbed stresses and displacements near a fault is important in mining, geotechnical tunneling and petroleum engineering as well as in earth science when the behaviour of the rocks and soils is sensitive to local stresses. Precise field measurement of local in-situ stress state in a large area is either impractical or can be very costly (Zhao et al, 2018;Kuszewski et al, 2021). Alternative analytical and numerical analysis assuming relatively homogeneous and isotropic strata is typical (Li, 2015).…”

Local Stress Field Correction Method Based on a Genetic Algorithm and a BP Neural Network for In Situ Stress Field Inversion

“…In situ measurement is a direct method of obtaining the in situ stress field, and the main methods of measurement include stress relief, acoustic emission, overcoring, hydraulic fracturing test, and AE-based ground stress methods [6][7][8][9]. However, due to site and financial constraints, the scope and number of measurement points are limited, especially in complex and steep mountainous regions.…”