Effect of porewater pressure on the mechanical properties of red sandstone with different unloading rates

Author:

Ren Jian-Xi1,Chen Xu1,Chen Xing-Zhou1,Yun Meng-Chen1,Cao Xi-TaiLang1,Liu Tian-Tian1

Affiliation:

1. School of Architecture and Civil Engineering, Xi'an University of Science and Technology, Xi'an 710054, China

Abstract

The red sandstone in the Luohe Formation in Shaanxi Province, China, contains a rich aquifer system. The excavation of coal mines and tunnels through the Luohe Formation affects the mechanical properties of the rocks in the surrounding environment, creating the need to determine the effect of the porewater pressure and unloading rate on the mechanical properties of the red sandstone. Using the constant axial pressure unloading method, triaxial unloading tests were performed under different unloading rates (0.1, 0.3 and 0.6 MPa s−1 and porewater pressure conditions (0, 1.0, 1.5 and 2.0 MPa). Based on the results, an unloading statistical damage model of red sandstone was established under the impacts of unloading rate and porewater pressure. During the loading stage, as the porewater pressure increased, the slope of the stress–strain curve and elastic modulus gradually decreased. During the unloading stage, lateral deformation larger than the axial deformation was observed owing to the influence of porewater pressure. The porewater pressure effect became significant as the unloading rate decreased. An increase in porewater pressure or a decrease in the unloading rate increased the confining strain flexibility. Unloading failure of rock samples was dominated by tensile shear failure, thus indicating that a faster unloading rate or larger porewater pressure causes more tensile cracks and severe fracture in the rock samples.

Publisher

Geological Society of London

Subject

Earth and Planetary Sciences (miscellaneous),Geology,Geotechnical Engineering and Engineering Geology

Reference41 articles.

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