We study the creep properties of clastic soil in residual state. The intact samples are taken from a reactivated slow-moving landslide in the Three Gorges Reservoir Region, China. Firstly, the patterns of the landslide movement are analysed based on recent monitoring data, which indicate that the soil within the shear zone is undergoing two deformation processes: a creep phase, characterised by different creep rates, and a dormant phase. We then study the creep behaviour of the soil samples through a series of ring shear creep tests under various shear stress conditions. The creep response depends strongly on the ratio of the shear stress to the residual strength, and the normal effective stress, whereas the creep rate decreases due to strength regain. The long-term strength of the clastic soil is close to the residual strength. Therefore, the residual strength obtained from conventional shear test, which is less time consuming than creep test, can be used in long-term stability analyses of creeping landslides. 相似文献
The Tirek gold deposit hosted in the Archean shield is one of the richest sources of mined gold for Algeria. The deposit is controlled by the East Ouzzal shear zone (EOSZ), a transcurrent N–S lithospheric fault. The EOSZ is a late Pan-African dextral-ductile shear zone separating two contrasting Precambrian domains: the Archean In Ouzzal block to the west (Orthogenesis with subordinate metasediments reworked and granulitized during the ca. 2 Ga Eburnean event) and a middle Proterozoic block to the east involved in the ca. 600 Ma Pan-African event. The auriferous quartz veins are mainly oriented in two directions, N–S veins hosted in mylonitic rocks and NE–SW veins hosted in gabbroic or gneissic bands. The NE–SW veins contain the richest ore. Gold ore is found in a system of veins and lenticular quartz veinlets arranged in anastomosing networks. The hydrothermal alteration associated with these veins is characteristically a carbonate-sericite-albite-pyrite assemblage. Gold is the main metal of economic importance; it is disseminated in the quartz as grains or fibers along microcracks and as microscopic grains in the host rocks. Microthermometric results and Raman laser data from fluid inclusions demonstrate that the ore-forming fluids contained H2O-CO2±CH4 and were low salinity. Homogenization temperatures are commonly 250–310 °C. In the Tirek deposit, the role of the shear zone that hosts the mineralization was to drain the hydrothermal fluid. Interactions between the fluid and the mafic host rocks and CO2 also contributed to the formation of the hydrothermal gold deposit at Tirek. 相似文献
Shale gas has currently attracted much attention during oil and gas exploration and development. Fractures in shale have an important influence on the enrichment and preservation of shale gas. This work studied the developmental period and formation mechanism of tectonic fractures in the Longmaxi Formation shale in the Dingshan area of ??southeastern Sichuan Basin based on extensive observations of outcrops and cores, rock acoustic emission (Kaiser) experiments, homogenization temperature of fracture fill inclusions, apatite fission track, thermal burial history. The research shows that the fracture types of the Longmaxi Formation include tectonic fractures, diagenetic fractures and horizontal slip fractures. The main types are tectonic high-angle shear and horizontal slip fractures, with small openings, large spacing, low densities, and high degrees of filling. Six dominant directions of the fractures after correction by plane included NWW, nearly SN, NNW, NEE, nearly EW and NW. The analysis of field fracture stage and fracture system of the borehole suggests that the fractures in the Longmaxi Formation could be paired with two sets of plane X-shaped conjugate shear fractures, i.e., profile X-shaped conjugate shear fractures and extension fractures. The combination of qualitative geological analysis and quantitative experimental testing techniques indicates that the tectonic fractures in the Longmaxi Formation have undergone three periods of tectonic movement, namely mid-late Yanshanian movement (82–71.1 Ma), late Yanshanian and middle Himalaya movements (71.1–22.3 Ma), and the late Himalayan movement (22.3–0 Ma). The middle-late period of the Yanshanian movement and end of the Yanshanian movement-middle period of the Himalayan movement were the main fracture-forming periods. The fractures were mostly filled with minerals, such as calcite and siliceous. The homogenization temperature of fracture fill inclusions was high, and the paleo-stress value was large; the tectonic movement from the late to present period was mainly a slight transformation and superposition of existing fractures and tectonic systems. Based on the principle of tectonic analysis and theory of geomechanics, we clarified the mechanism of the fractures in the Longmaxi Formation, and established the genetic model of the Longmaxi Formation. The research on the qualitative and quantitative techniques of the fracture-phase study could be effectively used to analyze the causes of the marine shale gas fractures in the Sichuan Basin. The research findings and results provide important references and technical support for further exploration and development of marine shale gas in South China. 相似文献
Acta Geotechnica - One-dimensional compression tests on quartz sands treated by microbially induced carbonate precipitation (MICP) were carried out to evaluate the effects of gradation and calcium... 相似文献
Acta Geotechnica - Microbially induced carbonate precipitation (MICP) has been actively investigated as a promising method to improve soil properties. A burning issue impeding its wide application... 相似文献
Rainfall-induced slope instabilities are ubiquitous in nature, but simulation of this type of hazards with centrifuge modelling still poses difficulties. In this paper, we introduce a rainfall device for initiating slope failure in a medium-sized centrifuge. This rainfall system is simple, robust and affordable. An array of perforated hoses is placed close above the model slope surface to generate the raindrops. The rainfall intensity depends on the centrifuge acceleration and the flow rate of the water supply, which is controlled by the size and number of the tiny pinholes in the hose walls. The rainfall intensities that are tested range from 2.5–30 mm/h, covering the intensity range of moderate, heavy and torrential rainfall events. Our model test with rainfall-induced slope failure shows that this system is capable of generating relatively uniform rainfall of wide intensities and leads to various patterns of slope failure.