Slate with inherently transverse isotropy is abundant in metamorphic rock, in buildings, and in geotechnical engineering worldwide; the tensile and shear fracture behavior of layered slate is vital to know for engineering applications. In this paper, the Brazilian and semi-circular bend (SCB) tests of layered slate were performed. The fracture characteristics of the slate were investigated by numerical simulations developed by the hybrid finite and cohesive element method (FCEM). Results showed that the measured experimental tensile strength, and mode I fracture toughness of layered slate all showed a typical V-type trend as the bedding angle increased from 0° to 90°, and with divider type. The developed empirical relationship between tensile fracture toughness and tensile strength K_IC = 0.094σ_t + 0.036 fitted experimentally and strongly correlated. The mechanical response and fracture patterns predicted by FCEM agreed well with those of the laboratory experiments. Moreover, the shear fracture behavior and mode II fracture toughness of the layered slate were explored by systematic numerical simulations. Research results provide potential insights for further prediction and improvement of the complex fracture behavior of anisotropic rock masses for rock engineering.

This contribution focuses on understanding the bedding effect of coal rocks under the Brazilian splitting test. First, multiple Brazilian splitting tests were performed on coal rocks with various bedding angles to systematically investigate the influence of stratification. Subsequently, numerical models with stratified structures were constructed, and a continuous–discontinuous numerical analysis method based on the cohesive zone model (CZM) was employed to conduct the corresponding numerical investigations. Results indicate that the load–displacement curves of coal rock specimens with different bedding angles can be classified into four stages: initial compaction stage, elastic deformation stage, crack rapid coalescence stage, and final destruction stage. With increase in the bedding angle, the failure patterns of coal rock specimens can be categorized into three groups: 1) stretching damage along bedding planes; 2) mixed tension and shear failure along the bedding planes and the coal matrix; and 3) stretching failure passing through the coal matrix. Furthermore, the tensile strength and cumulative acoustic emission (AE) energy–displacement relations are significantly influenced by the bedding angle. The numerical model can effectively predict the mechanical responses and fracture behavior of coal rock specimens, providing empirical parameters for the simulation of similar rock engineering.

To investigate the internal force and deformation characteristics of the supporting structure of structural loess foundation pit, 15 field monitoring data of foundation pits in Shaanxi, Gansu and Ningxia, were collected. The lateral movement of the supporting structure, settlement of soil behind piles and axial force of supporting point were studied on the basis of induction and systemize. The results show that: (1) due to the influence of spatial effect, the pile lateral displacement, surface settlement at the corner of foundation pit were significantly smaller than the middle of foundation pit; (2) the pile maximum lateral displacement at the middle of foundation pit ranges from 0.8 %” ∼ 2.0 %” of excavation depth, the pile top lateral displacement ranges from 0.2 %” ∼ 0.6 %” of excavation depth, the lateral displacement at the corner of foundation pit decreased by 60% ∼ 70%; (3) the maximum surface settlement in the middle of the foundation pit can reach 0.35%<r∼1.2%o of the excavation depth, and the maximum settlement at the corner of foundation pit decreased by 60% ∼ 70%; (4) the position of largest axial force of supporting point occurs near the maximum lateral displacement, between 0.4 ∼ 0.8 of excavation depth, the maximum measured axial force of the supporting point reached 35% ∼ 80% of the designed axial force, indicated that many foundation pits were too conservative in the design process, the structural characteristics of loess in northwest area should be considered, and the design scheme of the foundation pit should be optimized to save the cost of foundation pit engineering to avoid unnecessary waste.