The burial depth is the bottom boundary ((H_{text{b}})) of brittle zone when OCR reached the threshold value and is determined by: H_{text{b}} approx frac{{H_{hbox{max} } }}{{{text{OCR}}_{text{threshold}} }} (6).
As can be seen, the bottom boundary of BZ of the Silurian shale varies with its maximum burial depth.
In this study plain strain numerical analysis is performed using Plaxis dynamic program where prescribed displacement is applied at the bottom boundary of the soil to simulate the applied seismic load.
A unit gradient boundary (UG) is considered at the bottom boundary of the monolithic cover.
When the seismic wave is applied to the bottom boundary of the model as a shear stress wave loading, the wave propagates upwards perpendicular to the bottom static boundary while horizontal displacements occur in the ground as the amplitude of the wave decays with distance.
Firstly, the over-consolidation ratio (OCR) of shale was employed to determine the bottom boundary of the brittle zone (BZ), and the specific technical procedure is as follows: 1. Determination of pre-consolidation pressure ((p_{text{c}})) with a uniaxial strain test 2.
For example, the TBDZ of Longmaxi shale of wells Jiaoye1, Heye1 and Jianshen1 is 4464, 4428 and 4545 m, respectively, and the bottom boundary of BZ is 2195, 2485 and 2763 m, respectively.
If there is no knick point of the free-face of the slope, the bottom boundary of A is the end of the hollow in cross-section.
If there is no free-face of the slope, i.e. the distance of contour lines of downslope is the same with or more than the distance of contour lines of A, the bottom boundary of A is the same level of the bottom contour line of a hollow in a cross-section.
The bottom boundaries of A R and A L are at the same level of the bottom boundary of A. The top boundaries of A R and A L are the edges of the lateral concavity which induced convergence of subsurface water flow.
