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To gain insights into the impact of lithological and geometric configurations
of Shendong strata on the propagation of damage within overlying rock
layers, a model simulating overlying rock movement and damage propagation
under varied lithological combinations was developed. The study involved
four physical and seventeen numerical simulations to assess geological
factors influencing strata be?havior post-mining. Key findings include:
Decreasing the thickness of the key stra?tum reduces the first weighting
interval, accelerates fracture initiation, enlarges the subsidence area, and
increases maximum subsidence; Raising the key stratum elevation diminishes
both subsidence and its range, while delaying fracture initi?ation; Reducing
mining thickness results in smaller pressure fluctuations, slightly extends
the first weighting interval, and decreases both subsidence and its range;
Enhancing key stratum hardness delays fracture occurrence, lowers the
fracture zone height, and decreases the plastic zone volume.- Book : 29(2 Part A)
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Abstract
The stability and confinement of the pedestal, the outermost region of the con-
fined plasma in a tokamak, are crucial for its efficient operation and performance.
This work describes ASDEX Upgrade experiments designed to analyse the pedestal
structure under varying conditions of normalized poloidal pressure (βpol) and plasma
shaping. The individual treatment of temperature, density, and pressure for ion and
electron pedestals is emphasized. We show that the ion temperature (Ti) increases
with βpol, whereas the electron temperature (Te) shows only a slight increase and the
electron density (ne) remains relatively unaffected. The changes in shape influence
ne, making its pedestal higher and wider, whereas Ti remains unchanged despite a
lower heating power required to keep the same βpol at high shaping.
The findings highlight the importance of distinguishing between different channels
when predicting and controlling the pedestal. The stabilising influence of the radial
electric field Er, and its correlation with different pedestal top positions, is explored.
The roles of ballooning modes and local magnetic shear are emphasized, and the
conditions for access to second stability in different pedestal regions are presented.
The global MHD stability sets the overall limit, but the radial composition of electron
density and electron and ion temperature can strongly vary. The results show that the
width of the electron pressure pedestal is determined by the equilibrium via the local
magnetic shear. The strongest correlation of the ion pressure pedestal top position
is found with the gradient of Er. We found that the second stability access requires
both a highly shaped boundary and a q profile modification due to higher pressure
gradients. The results contribute to understanding the mechanisms governing the
pedestal behaviour, offering insights for optimizing plasma performance and stability.- Book : ()
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