Abstract
Stress field or in-situ stress, beside rock mass strength, determines stability or instability of underground openings. It plays key role of every rock engineering project, and has been subject of many researches. There are many theoretical models of the stress field of the Earth's crust which have more or less limited domain of applicability. However, those models usually express horizontal stresses as ratio with vertical stress component. On the other side, it is well known that deformation modulus of the rock mass is dependent on the lateral stress it is subjected to. This dependence is, herein, coupled with practical findings of the stress field behavior and incorporated into the stress filed model. As the result new formulation for the stress filed components is obtained.
Highlights
Stress filed of the rock mass is defined through the three compressional stress components
In triaxial compression it can be seen that elastic modulus changes with the lateral stress, and this change is smaller for higher strength rocks (Figure 2) and significant for the weaker rocks (Figure 3)
Having in mind that measurements have confirmed that at the depths around 3000 m lithostatic stress state is present, horizontal stress magnitude can be estimated as the starting point of this model
Summary
Stress filed of the rock mass (in the Earth's crust) is defined through the three compressional stress components. The Swiss geologist Albert Heim (1849–1937) postulated that the rock under conditions of constant, persistent loads at depth will compensate for internal differential stresses (differences in principal stresses) by creep processes, given sufficient (geological) time (Zang and Stephansson, 2009) Many measurements confirmed that lithostatic stress state exists below the depth of 3000 m, while horizontal stresses may be up to 3.5 times higher than vertical at the depths to 300 m, Teraghi and Richart (1952) came to the conclusion that in undisturbed sedimentary rock masses biaxial stress field exists: H h. It is proven that elastic modulus of the rock is dependent and changes according to the lateral stress it is subjected to Those fundamental findings are incorporated into the stressfield model that tends to provide the objective engineering tool for stress estimation
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