Observations of the Kaiser Effect under multiaxial stress states: Implications for its use in determining in situ stress

1993 ◽  
Vol 20 (19) ◽  
pp. 2119-2122 ◽  
Author(s):  
David J. Holcomb
Keyword(s):  
In Situ Stress ◽  
Multiaxial Stress ◽  
Kaiser Effect ◽  
Stress States

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

Geofluids ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Kang Zhao ◽  
Shuijie Gu ◽  
Yajing Yan ◽  
Keping Zhou ◽  
Qiang Li ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Fractal Dimension ◽  
Principal Stress ◽  
In Situ Stress ◽  
Time Range ◽  
Kaiser Effect ◽  
Time Stress ◽  
Stress Curve ◽  
Interpretation Method

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.

scholarly journals Uncertainties in geomechanical models – exhaustive vs. feasible approach

2021 ◽  
Vol 1 ◽  
pp. 187-188
Author(s):  
Moritz Ziegler ◽  
Oliver Heidbach
Keyword(s):  
Standard Deviation ◽  
Stress State ◽  
Stress Tensor ◽  
In Situ Stress ◽  
Rock Properties ◽  
Geomechanical Model ◽  
Rock Property ◽  
Stress Changes ◽  
Stress States

Abstract. The stress state is a key component for the safety and stability of deep geological repositories for the storage of nuclear waste. For the stability assessment and prediction over the repository lifetime, the stress state is put in relation to the rock strength. This assessment requires knowledge of both the future stress changes and the current in situ stress state. Due to the limited number of in situ stress data records, 3D geomechanical models are used to obtain continuous stress field prediction. However, meaningful interpretation of the stress state model requires quantification of the associated uncertainties that result from the geological, stress and rock-property data. This would require thousands of simulations which in a high-resolution model is called an exhaustive approach. Here we present a feasible approach to reduce computation time significantly. The exhaustive approach quantifies uncertainties that are due to variabilities in stress data records. Therefore, all available data records within a model volume are used individually in separate simulations. Due to the inherent variability in the available data, each simulation represents one of many possible stress states supported by data. A combination of these simulations allows estimation of an individual probability density function for each component of the stress tensor represented by an average value and a standard deviation. If weighting of the data records can be performed, the standard deviation can usually be reduced and the significance of the model result is improved. Alternatively, a range of different stress states supported by the data can be provided with the benefit that no outliers are disregarded, but this comes at the cost of a loss in precision. Both approaches are only feasible since the number of stress data records is limited. However, it is indicated that large uncertainties are also introduced by variabilities in rock properties due to natural intra-lithological lateral variations that are not represented in the geomechanical model or due to measurement errors. Quantification of these uncertainties would result in an exhaustive approach with a high number of simulations, and we use an alternative, feasible approach. We use a generic model to quantify the stress state uncertainties from the model due to rock property variabilities. The main contributor is the Young's module, followed by the density and the Poisson ratio. They affect primarily the σxx and σyy components of the stress tensor, except for the density, which mainly affects the σzz component. Furthermore, a relative influence of the stress magnitudes, the tectonic stress regime and the absolute magnitude of rock properties is observed. We propose to use this information in a post-computation assignment of uncertainties to the individual components of the stress tensor. A range of lookup tables need to be generated that compile information on the effect of different variabilities in the rock properties on the components of the stress tensor in different tectonic settings. This allows feasible quantification of uncertainties in a geomechanical model and increases the significance of the model results significantly.

In situ stress states and lateral deformations of soil–bentonite cutoff walls during consolidation process

2020 ◽  
Vol 57 (1) ◽  
pp. 139-148
Author(s):  
Xing Tong ◽  
Yu-Chao Li ◽  
Han Ke ◽  
Ying Li ◽  
Qian Pan
Keyword(s):  
Earth Pressure ◽  
Lateral Wall ◽  
In Situ Stress ◽  
Depth Range ◽  
Consolidation Process ◽  
Pressure Distributions ◽  
Cutoff Walls ◽  
Horizontal Strain ◽  
Stress States

A long-term in situ test was performed on two soil–bentonite (SB) cutoff walls with different dimensions. The total stresses and pore pressures in the walls were monitored for 8 months, and the lateral wall deformations were monitored for 15 months. The monitoring results revealed that the primary consolidation of the presented SB cutoff walls took approximately 8 months. In the first 5 days, the stress states of the walls were nearly isotropic. The total stresses were less than the geostatic stress, and the lateral wall deformations were negligible. As the consolidation developed, the total horizontal stresses in the walls decreased and then remained unchanged at most depths after 1 month, while the stresses at the bottoms continued decreasing. The nonlinear profiles of the horizontal effective stresses in the cutoff walls were similar to the active earth pressure distributions behind the retaining walls moving in translation mode. The trench sidewall movements were found in translation mode within a specific depth range. Obvious dependencies of the horizontal effective stress and the horizontal strain on the wall height were observed. Comparison with the literature illustrates the influence of backfill properties on the consolidation behavior of the SB cutoff walls.

scholarly journals Time-sensitivity of the Kaiser effect of acoustic emission in limestone and its application to measurements of in-situ stress

2009 ◽  
Vol 6 (2) ◽  
pp. 176-180 ◽  
Author(s):  
Yan Jin ◽  
Zili Qi ◽  
Mian Chen ◽  
Guangqing Zhang ◽  
Guangqiang Xu
Keyword(s):  
Acoustic Emission ◽  
In Situ Stress ◽  
Kaiser Effect ◽  
Time Sensitivity

Regional in-situ stress states in Japan based on measurements

Rock Stress ◽  
2020 ◽  
pp. 335-341
Author(s):  
T. Yokoyama ◽  
K. Ogawa ◽  
T. Kanagawa ◽  
M. Tanaka ◽  
T. Ishida
Keyword(s):  
In Situ Stress ◽  
Stress States
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