Water-rock interaction of weakly cemented mudstone is intense due to its complex pore structure and mineral compositions. As primary channels for water imbibition, pore structures determine water migration. In this paper, pore properties of weakly cemented mudstone are measured by scanning electron microscopy (SEM), nitrogen adsorption/desorption (NAD), and mercury intrusion porosimetry (MIP), respectively. Water imbibition tests under free and lateral restraints are performed on self-developed water absorption instruments. The results show that skeleton aggregates, pore zone, and fissure zone constitute the basic structure of the rock, together with pore scales in nanoscale, submicron-scale, and micron-scale, respectively. The porosities of each zone are inferred with the values of 13.5%, 7.3%, and 2.3% by comparison of different methods. The main pore type is mesopore. Based on water imbibition tests, water rises along the large fissure and pore zones initially. Pores in the skeleton aggregates absorb water from pore and fissure zones subsequently. However, water imbibition is limited under lateral restraints. Owing to lateral restraints, the ascending height and rate of the sample with lateral restraints are lower than those of the sample with free confinements. The results suggest that lateral restraints can restrain water migration and water-rock interaction for weakly cemented mudstones, and measures can be taken to control swelling deformation by strengthening lateral restraints.
Short-term and creep tests of fractured sandstone with different degrees of damage prepared using pre-peak and post-peak unloading tests on intact sandstone were carried out using a servo-controlled rock mechanics system. Based on our experimental results, the influence of confining pressure and damage on short-term mechanical behavior of fractured sandstone with different degrees of damage was first analyzed. The results show that the peak strength, residual strength, elastic modulus, and secant modulus of fractured sandstone increase linearly with increasing confining pressure, but decrease with increasing damage. The short-term failure modes depend on the damage and change from typical shear failure modes to multiple shear failure modes with increasing damage. Then, the influence of the differential stress, confining pressure, and the degree of damage on the creep mechanical behavior of fractured specimens was further investigated. The axial instantaneous strain and creep strain increase linearly with increasing differential stress, and the specimens exhibit significant time-dependent behavior under high stress. The steady creep rate increases with increasing stress, but it decreases with increasing confining pressure and damage. However, the long-term strength and creep failure strength of fractured specimens increase linearly with increasing confining pressure, but they decrease linearly with increasing damage. The creep failure modes of fractured specimens are also the main shear failure modes, which are similar to the short-term failure modes.
Coal is typically considered a special engineering rock mass because of its low strength, high internal fracture development, good permeability, and random distribution of microparticles and fractures. The results of cyclic loading and unloading tests indicate that the strain energy during the coal deformation process can be divided into three parts: plastic strain energy; fracture strain energy; and base-material strain energy. The energy composition ratio differs depending on coal strength. Lower proportions of fracture strain energy are associated with higher elastic energy indexes, and there is a negative correlation between fracture strain energy and other coal burst tendency indexes. The results were applied on the 4206 isolated island working face of coal mine A in Yan’an, Shanxi, China, yielding good benefits. The findings presented here provide a theoretical basis for understanding the principle of coal seam bursting and guidance for reducing burst risks.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.