Water plays an important role in the mechanical properties of roadway surrounding rocks and poses a great threat to their stability. To study the damage and failure characteristics, and the fracture development laws of surrounding rock, a uniaxial compression test for prefabricated fractures in water-bearing surrounding rock was carried out. Results indicate that water-bearing prefabricated fracture specimens are in better development condition after failure. In water-bearing specimens, the propagation direction is more complex. There are more secondary fissures, and the fracture strength is significantly lower than in dry specimens. When immersed in water, the interior structure of surrounding rock is weakened and softened; thus, the intensity is reduced, and the development and propagation of fractures is promoted. For larger angles of the prefabricated fractures, the compression failure of surrounding rock changes into shear failure. As the angles approach 90°, the shear failure again prevails. Therefore, the strength of the surrounding rock firstly decreases and then increases. A new ultimate stress strength model is developed for fractures caused by shear slip failure in water-bearing surrounding rock. The model results are consistent with the experimental results, and the validity of the model is verified. These results are helpful for deeply understanding the failure process of water-bearing surrounding rock with prefabricated fractures. The proposed model could be used for the evaluation of water-bearing surrounding rock stability in coal mines, as well as dynamic risk monitoring. 相似文献
The use of biopolymer to improve the performance of microbially induced carbonate precipitation (MICP)-treated sands is a novel and eco-friendly concept. This work found an anionic biopolymer, γ-polyglutamate (γ-PGA), could significantly improve the performance of MICP-treated sands. Comparing the control with absence of γ-PGA, the concentration of 0.1–9 g/L γ-PGA increased the compressive strength of MICP-treated sands by 1.54–3.96 times and significantly reduced the brittleness. The MICP process analysis and microstructural detection demonstrated that γ-PGA in the specimens provided many nucleation sites and templates for calcite generation, partially kept the bacterial urease activity by replacement of the bacteria as nucleation sites, thereby improving the calcite generation. The γ-PGA also cemented sand grains with calcite through the hydrogen bond-type intermolecular interactions. Both the calcite generation and the hydrogen bond-type intermolecular interactions by γ-PGA played vital roles in enhancing MICP for soil improvement. Additionally, γ-PGA, as a viscoelastic admixture between the crystals and sand grains, effectively dissipated the energy of stress and thus reduced the brittleness of MICP-treated sands. This is the first report on the application of anionic biopolymer to MICP technology. It provides a novel concept in promoting the efficiency and sustainability of MICP.
Journal of Oceanology and Limnology - With the development of industrialization and aquaculture in Jiangsu and Shandong Provinces along the South Yellow Sea coast, China, eutrophication has greatly... 相似文献
Engineering research has shown that the surrounding rock of deep roadways experienced many times of post-peak cyclic loading and unloading. So studying on rock mechanical characteristics of post-peak loading and unloading is helpful to control the deep surrounding rocks. The test using RMT-150B rock mechanics testing system, to experiment on the mechanical properties of sandstone of post-peak cyclic loading and unloading. The results show that: the stress–strain curves of post-peak cyclic loading and unloading have significant plastic hysteretic loops. The area of plastic hysteretic loops gloss back. The enveloping outer enclosure of cycle loading curve is the similar as the stress–strain curves of strain softening stage when the samples failure, which shows that post-peak failure of rocks have significant memory. With the increase of cycles, the cumulative deterioration parameters are gradually increased, and the ultimate bearing capacity, elastic of loading section of samples and cumulative deterioration parameters conform with the exponential attenuation function with constant term. With the increase of surrounding pressure, the total energy, dissipated energy and elastic energy of samples are gradually increased. With the increase of cycles, the total energy, dissipated energy and elastic energy of samples all are gradually decreasing, the rate of reduction decreases gradually. The samples exist in vertical splitting and transverse shear combination failure under the post-peak uniaxial cycles, or exist in shear failure under the post-peak triaxial cycles. The shear plane exists slip traces. 相似文献