The study on microscopic mechanical properties of mineral is of great significance to reveal the damage mechanism of rock and can provide important basis for nondestructive testing of building materials and assisted rock breaking technology. As the main test method for rock and mineral microscopic mechanical properties, nanoindentation test has several parameters such as loading time, indentation depth, and loading rate, which have great influence on the test results. Three schemes are designed as follows: (1) The loading and unloading rates remain unchanged, and the holding time is 0 s, 5 s, 10 s, 20 s, 50 s, and 100 s, respectively. (2) Ten cycles of loading and unloading tests are used to calculate micromechanical indexes at different indentation depth. (3) The maximum load and holding time remain unchanged, and the loading rate is 5 mN/s, 10 mN/s, 20 mN/s, 30 mN/s, 40 mN/s, and 50 mN/s, respectively. The results show that (1) with the increase of holding time, the elastic modulus and hardness of feldspar decrease sharply between 0 s and 5 s, decrease slightly between 5 s and 10 s, and stabilize after 10 s. The creep displacement of feldspar is positively correlated with holding time. The holding time does not change the development path of creep displacement. (2) With the increase of indentation depth, the elastic modulus and hardness of feldspar decrease gradually and become stable when the indentation depth is more than 350 nm. (3) The elastic modulus and hardness of quartz increase with loading rate. The maximum indentation depth and residual indentation depth decrease with the increase of loading rate. The creep displacement increases with loading rate, while the creep compliance decreases with the increase of loading rate. With the increase of holding time, the creep rate decreases and tends to be stable. The results provide theoretical basis for obtaining more accurate rock nanoindentation mechanical properties and revealing rock damage mechanism.

In most concrete-related computer tomography (CT) experiments, detailed information on the damage and fracture process is obtained using nonreal-time approaches, with the CT method constantly regarded as a qualitative method. This study develops a quasi real-time method with the use of experimental instruments. The average CT number is used to analyse the damage and fracture process in concrete specimens and the theory that underlies concrete damage and fracture is improved. Various characteristics of the fracture form in different loading cases are investigated at the macro and micro levels. This study provides a convenient and fast method for qualitatively and quantitatively analysing concrete. qin yuAn. PhD, the Institute of Water Resources and Hydro-electric Engineering of Xi'an University (China). His research interests: the mechanical property of concrete and concrete technology. chai Junrui. Professor at the Institute of Water Resources and Hydro-electric Engineering of Xi'an University of Technology (China) and College of Civil and Hydropower Engineering of China Three Gorges University (China). His research interests: the mechanical property of concrete and non-linear seepage problem for dam engineering. ding WeihuA. Associate Professor at the Civil Engineering and Architecture of Xi'an University of Technology (China). His research interests: the CT experiment of concrete material and the problems of engineering geological. dang fAning. Professor at the Civil Engineering and Architecture of Xi'an University of Technology (China). His research interests: the mechanical property of concrete and seepage problem for dam engineering. lei mAn. Master in the Civil Engineering and Architecture of Xi'an University of Technology (China). Her research interests include the CT experiment of concrete material and meso-damage process for concrete material. Xu ZengguAng. Lecturer of the Institute of Water Resources and Hydro-electric Engineering of Xi'an University (China). His research interests: the environmental and non-linear seepage problem for civil engineering.

In order to study the mechanical properties of granite at the micro- and nanoscale, the load-displacement curve, residual indentation information, and component information of the quartz, feldspar, and mica in granite were obtained using a nanoindentation test, a scanning electron microscope (SEM), and X-ray diffraction (XRD). The elastic modulus and the hardness of each component of the granite were obtained through statistical analysis. Treating rock as a composite material, the relation between the macro- and microscopic mechanical properties of rock was established through the theory of micromechanical homogenization. The transition from micromechanical parameters to macromechanical parameters was realized. The equivalent elastic modulus and Poisson’s ratio of the granite were obtained by the Self-consistent method, the Dilute method, and the Mori-Tanaka method. Compared with the elastic modulus and the Poisson ratio of granites measured by a uniaxial compression test and the available data, the applicability of the three methods were analyzed. The results show that the elastic modulus and hardness of the quartz in the granite is the largest, the feldspar is the second, the mica is the smallest. The main mineral contents in granite were analyzed using the semiquantitative method by XRD and the rock slice identification test. The elastic modulus and the Poisson ratio of granite calculated by three linear homogenization methods are consistent with those of the uniaxial compression test. After comparing the calculation results of the three methods, it is found that the Mori-Tanaka method is more suitable for studying the mechanical properties of rock materials. This method has an important theoretical significance and practical value for studying the quantitative relationship between macro- and micromechanical indexes of brittle materials. The research results provide a new method and an important reference for studying the macro-, micro-, and nanomechanical properties of rock.

e stability analysis of loess slopes with a rising groundwater level is a problem that integrates unsaturated and transient seepage, stress analysis, and stability prediction. For this purpose, a sequentially coupled method of seepage-softening-stability was used. First, seepage analysis of a loess slope with a rising groundwater level was conducted according to unsaturated and transient seepage analysis theory. Second, the spatial distribution of the deformation and strength parameters of the soil, both of which were based on the calculated results of the seepage analysis, were adjusted according to the water-induced structural deterioration equation. ird, the vector sum analysis method of loess slope stability, which was based on the temporal-spatial distribution laws of effective unit weight, elastic modulus, Poisson's ratio, cohesion, internal friction angle, and seepage force, was performed by the body force method. To verify the proposed method, the limit equilibrium method of loess slope stability was conducted by the surface force method. Finally, the progressive failure process of a loess slope with a rising groundwater level on the White Deer Plain was presented as an example. A comparison analysis of the calculated results of the two methods revealed that the proposed method was reasonable and reliable.