Numerical simulation of direct shear tests on mechanical properties of talus deposits based on self-adaptive PCNN digital image processing

The macro mechanical properties of materials with characteristics of large scale and complicated structural composition can be analyzed through its reconstructed meso-structures.In this work,the meso-structures of talus deposits that widely exist in the hydro-power engineering in the southwest of China were first reconstructed by small particles according to the in-situ photographs based on the self-adaptive PCNN digital image processing,and then numerical direct shear tests were carried out for studying the mechanical properties of talus deposits.Results indicate that the reconstructed meso-structures of talus deposits are more consistent with the actual situation because the self-adaptive PCNN digital image processing has a higher discrimination in the details of soil-rock segmentation.The existence and random distribution of rock blocks make the initial shear stiffness,the peak strength and the residual strength higher than those of the "pure soil" with particle size less than 1.25 cm apparently,but reduce the displacements required for the talus deposits reaching its peak shear strength.The increase of rock proportion causes a significant improvement in the internal friction angle of talus deposit,which to a certain degree leads to the characteristics of shear stress-displacement curves having a changing trend from the plastic strain softening deformation to the nonlinear strain hardening deformation,while an unconspicuous increase in cohesion.The uncertainty and heterogeneity of rock distributions cause the differences of rock proportion within shear zone,leading to a relatively strong fluctuation in peak strengths during the shear process,while movement features of rock blocks,such as translation,rotation and crossing,expand the scope of shear zone,increase the required shear force,and also directly lead to the misjudgment that the lower shear strength is obtained from the samples with high rock proportion.That,however,just explains the reason why the shear strength gained from a small amount of indoor test data is not consistent with engineering practice.

Meso-structure and fracture mechanism of mudstone at high temperature

The meso-structure mineral composition and fracture mechanism of uniaxial compressed mudstone samples at high temperature were analyzed by XRD and scanning electron microscopy. The effect of tem- perature on mudstone composition and fracture mechanism were studied from a meso-structural per- spective, and the relationship between meso-structure and macro-mechanical characteristics at high temperature was revealed. The findings demonstrated that the fluctuation in diffraction intensity of kao- linite in the mudstone caused the fluctuation in its mechanical properties. The overall structure under- went a phase change around 600℃, which led to the sudden change in the mechanical properties of mudstone samples. When the temperature reached 600 ℃, the crystalline state worsened and kaolinite disappeared; however, some illite was produced, indicating that the chemical reaction of the structure and sudden drop of bearing capacity of the mudstone. Mudst0ne fracturing at high temperature involves mainly intergranular and transgranular fractures, which are typical in micro-brittle tensile failure. Con- sidering the macro-fracture characteristics of mudstone, the results suggested that macro-fracture under external force corresoonds to the meso-fracture.

Construction of a 3D meso-structure and analysis of mechanical properties for deposit body medium

For deposit body medium, the internal structural properties may be the controlling factors for the strength of the material and the mechanical response. Based on the results of soil-rock meso-statistics using digital imaging, a simulated annealing algorithm is adopted to expand the meso-structural features of deposit bodies in 3D. The construction of the 3D meso-structure of a deposit body is achieved, and then the particle flow analysis program PFC3 D is used to simulate the mechanical properties of the deposit body. It is shown that with a combination of the simulated annealing algorithm and the statistical feature functions, the randomness and heterogeneity of the rock distribution in the 3D inner structure of deposit body medium can be realized, and the reconstructed structural features of the deposit medium can match the features of the digital images well. The spatial utilizations and the compacting effects of the body-centered cubic, hexagonal close and face-centered packing models are high, so these structures can be applied in the simulations of the deposit structures. However, the shear features of the deposit medium vary depending on the different model constructive modes. Rocks, which are the backbone of the deposit, are the factors that determine the shear strength and deformation modulus of the deposit body. The modeling method proposed is useful for the construction of 3D meso-scope models from 2D meso-scope statistics and can be used for studying the mechanical properties of mixed media, such as deposit bodies.

Synthesis and Crystal Structure of a New Cu^II Complex of N,N'-Bis(quinolin-2-ylmethyl)-1, 4-diazacycloheptane

A new CuII complex with a diazamesocyclic ligand based on 1,4-diazacycloheptane (DACH) and functionalized with two additional quinoline donor groups, namely N,N-bis(quinolin-8- ylmethyl)-1,4-diazacycloheptane L, has been synthesized and characterized. X-ray diffraction analysis at room temperature indicates that the title complex [CuLCl](ClO4) 1 (C25H26Cl2N4O4Cu, Mr = 580.94) crystallizes in triclinic, space group P1 with a = 9.589(3), b = 10.857(4), c = 12.724(5) ? a = 98.168(7), b = 106.945(7), g = 101.248(7), V = 1214.6(8) 3, Z = 2, Dc = 1.588 g/cm3, F(000) = 598 and m(MoKa) = 1.161 mm-1. The final R = 0.0479 and wR = 0.0985 with 4267 independent reflections. In the mononuclear CuII complex, the CuII center is pentacoordinated to four nitrogen donors of the ligand and one axial chloride anion, taking a coordination sphere in the midst of the ideal square- pyramid and trigonal bipyramid.

含有硫酸根离子的新型阴离子交换剂的制备

通过新制备的硫酸钛表面活性剂胶粒的内消旋结构（TS）消除亚硒酸根离子和其它粒子的特性，比较了TS与硫酸锆表面活性剂胶粒内消旋结构（ZS）。TS是通过投加硫酸钛到表面活性剂（C16TMABr）溶液中合成的。在以HCl或NH3溶液控制pH条件下，H2SeO3、H3AsO4、HsPO4和K2CrO4用作阴离子交换反应中的阴离子源。lgTS投加到60mL含氧酸阴离子的溶液中，以303K搅动24h，