Geology and depth structures of the main Karatau strike-slip fault, Southern Kazakhstan

The Main Karatau fault is a classical crustal strike-slip zone. It originated as a continental rift structure in the Late Proterozoic and had been developed incessantly for almost 1 billion years as inherited structure. The fault was subjected to polyphase deformations associated with both dextral and sinistral shifts. The Main Karatau fault crosses the Earth’s crust, including the structures of granite-metamorphic layer and granulite-basitic layer and fades without crossing the Moho discontunious. The amplitude of displacement of the Syr-Daria and Chu-Sarysu blocks relative to each other along the Main Karatau fault is estimated at approximately 200 km.

An optimal method of distribution of the slip zone on thrust bearing surfaces

Research to achieve a reasonable distribution of the slip zone of the sliding pair for better improvement of the hydrodynamic pressure of the liquid film is an intractable topic. To solve this issue, this paper takes the thrust bearing as the research object, and proposes to use the position number of the grid nodes at the boundary line between the slip and no-slip zone in each radial zone of the inclined pad to be variables. The variables are then defined as chromosomes in an adaptive genetic algorithm (AGA) and used to optimize the bearing capacity of the tilting pad. The results show that the optimal method of the AGA, which has good stability and repeatability, remarkably improves the distribution of the slip zone on the surface of the inclined pad. Therefore, the bearing capacity of the liquid film is significantly improved. Particularly, by using the optimization, the boundary line between the slip/no-slip zone is a composite form of a part of an arc and a part of the whisker. When the liquid flow through the heterogeneous slip/on-slip surfaces is used by this composite splicing method, the liquid pressure is upgraded in two steps. This is more conducive to increasing the pressure on multiple areas on the surface of the tilting pad, thereby achieving higher bearing capacity.

Influence of Particle Shape on the Macroscopic and Mesolevel Mechanical Properties of Slip Zone Soil Based on 3D Scanning and 3D DEM

The macroscopic and mesolevel mechanical mechanisms of slip zone soil are a crucial subject for the research of landslide deformation evolution and slope control, but the effects of the shape and psephicity of coarse particles in a slip zone soil on the mechanical properties of the slip soil zone still need to be explored. Discrete element method (DEM) can effectively monitor and track the mesolevel mechanical parameters of geotechnical materials, such as displacement vector field, contact force chain, and particle coordination number. The rock blocks in the medium-sized shear test undergo a sophisticated process by 3D scanning technology, and a database of the blocks is established and accurately modeled by combining 3D DEM to simulate the indoor medium-sized shear test for numerical investigation in line with the test conditions. The numerical simulation results demonstrate that the psephicity and particle shape of the rock blocks significantly affect the dilatancy and mesolevel mechanical parameters of the slip zone soil specimens. In addition, the numerical models featured by poorer psephicity and more irregular particle shape display more evident dilatancy, larger particle coordination numbers, as well as better contact density inside the model. Some references for the study of the macroscopic and mesolevel mechanical mechanisms of slip zone soil are provided.

Study on Minimum Rollable Thickness in Asymmetrical Rolling

A new model for the asymmetrical rolling is proposed to calculate the minimum rollable thickness simply and fast by the slab method. The calculation formulas of the rolling pressure, the rolling force, the critical roll speed ratio and the critical front tension under different deformation zone configurations are proposed, and the deformation zone configuration - rolling parameters relationship diagram is given and analyzed. The results show that the minimum rollable thickness can be reached when the rolling parameters keep the deformation zone configuration as cross-shear zone + backward-slip zone (C+B) or all cross-shear zone (AC). The calculation formulas of the minimum rollable thickness and the required rolling parameters for different deformation zone configurations are proposed respectively. The calculated value is in good agreement with the experimental results.

Frictional properties and microstructural evolution of dry and wet calcite–dolomite gouges

Calcite and dolomite are the two most common minerals in carbonate-bearing faults and shear zones. Motivated by observations of exhumed seismogenic faults in the Italian Central Apennines, we used a rotary-shear apparatus to investigate the frictional and microstructural evolution of ca. 3 mm thick gouge layers consisting of 50 wt % calcite and 50 wt % dolomite. The gouges were sheared at a range of slip rates (30 µm s−1–1 m s−1), displacements (0.05–0.4 m), and a normal load of 17.5 MPa under both room-humidity and water-dampened conditions. The frictional behaviour and microstructural evolution of the gouges were strongly influenced by the presence of water. At room humidity, slip strengthening was observed up to slip rates of 0.01 m s−1, which was associated with gouge dilation and the development of a 500–900 µm wide slip zone cut by Y-, R-, and R1-shear bands. Above a slip rate of 0.1 m s−1, dynamic weakening accompanied the development of a localised < 100 µm thick principal slip zone preserving microstructural evidence for calcite recrystallisation and dolomite decarbonation, while the bulk gouges developed a well-defined foliation consisting of organised domains of heavily fractured calcite and dolomite. In water-dampened conditions, evidence of gouge fluidisation within a fine-grained principal slip zone was observed at a range of slip rates from 30 µm s−1 to 0.1 m s−1, suggesting that caution is needed when relating fluidisation textures to seismic slip in natural fault zones. Dynamic weakening in water-dampened conditions was observed at 1 m s−1, where the principal slip zone was characterised by patches of recrystallised calcite. However, local fragmentation and reworking of recrystallised calcite suggests a cyclic process involving formation and destruction of a heterogeneous slip zone. Our microstructural data show that development of well-defined gouge foliation under the tested experimental conditions is limited to high velocities (>0.1 m s−1) and room humidity, supporting the notion that some foliated gouges and cataclasites may form during seismic slip in natural carbonate-bearing faults.

Oxidative weathering deterioration of black shale and its bedding shear failure modeling

&lt;p&gt;This work investigated the oxidative weathering deterioration of black shale along a bedding slip zone and how it affects the bedding shear failure in the Xujiaping landslide, southern Sichuan Province in China. Many dissolved pits were found on the limestone, and part of the black shale in the slip zone is mud-like and clastic, showing local shear failure, which can be one of the main reasons of slope instabiliy. The microstructure of black shale under oxidative weathering condition was observed by scaning electron microscopy (SEM), characterized by dissolved pores, weathering crust (iron sulfate) of pyrite crystals, and the filling gypsum crystal in the bedding foliation. The deterioration mechanism was expanded: (i) rock-forming and carbonate minerals were especially prone to dissolution by sulfuric acid from black shale oxidation in the slip zone, and (ii) volume expansion due to the crystallization force of precipitated minerals caused further fracture expansion and deformation. Therefore, two theoretical models were developed that use stoichiometric calculations of pyrite and calcite to determine the dissolution rate and the rock structure after chemical weathering; and establish a rock structure model characterized by foliation weakening of gypsum crystallization. In order to analyze the landslide failure, discrete element method (DEM) is used to analyze the black shale shear failure mechanism of the two degradation models after oxidative weathering. It will be useful to better understand how these oxidative weathering deterioration contribute to bedding shear failure in natural hazards.&lt;/p&gt;