To study the mechanical properties of red clay under repeated dry and wet cycle test conditions, in this paper, the disturbed red clay in an engineering area in Liuzhou, Guangxi Province, was taken as the research object. By artificially controlling different dry and wet cycles in the laboratory, a direct shear test and triaxial consolidation drainage test were carried out on the red clay samples after different dry and wet cycles. The stress‐strain curve and change rule of corresponding c and φ values were obtained. The results showed that, in both the direct shear test and the triaxial test, the shear strength parameters of red clay decreased with an increase in the number of dry and wet cycles and the attenuation was most obvious during the first cycle. With an increase in the number of dry and wet cycles, the attenuation gradually decreased. The constitutive model of the deviatoric stress and strain curve of red clay under dry and wet cycles was a plastic‐hardening type. By analyzing the variation in parameters in the P‐H model, the relationship between c, φ, and the number of dry and wet cycles n was obtained. The results showed that the parameters had different degrees of attenuation with the action of dry and wet cycles. To explain the above rules, some samples under different drying‐wetting cycles were selected for environmental electron microscope scanning, and appropriate assumptions were made based on the microstructure.

In the process of tunnel construction, the bias of layered rock mass tunnels has always been a prominent problem that troubles the construction and safe operation of tunnels. In this paper, a comprehensive method that combines monitoring technology and discrete element (3DEC) numerical simulation is proposed to analyze the deformation characteristics of the surrounding rock in the layered rock tunnel and the deformation law of the bias tunnel. The results indicate that the tunnel surrounding rock deformation in the study area showed the characteristics of bias. Based on the bias mechanism, the surrounding rock deformation law, the construction deformation control, and the optimization measures of layered rock mass in the bias tunnel were studied by means of combining monitoring technology with discrete element (3DEC) numerical simulation. Based on the research results, appropriate methods for controlling the deformation of the surrounding rock of the tunnel with comprehensive consideration of the anchor rod length, anchor rod angle, and anchor rod layout spacing were proposed. The method proposed in this paper could visually reveal the deformation characteristics of the surrounding rock of layered rock tunnels and the deformation law of bias tunnels. It could also better solve the problem of deformation control in the tunnel construction process. This approach provides a novel idea for special layered rock mass tunnel bias evaluation and deformation control parameter optimization and serves as a valuable reference for analogous engineering cases through engineering case analysis.

This paper developed a study of risk assessment for landslide disaster from oil and gas pipeline construction by systematically analyzing the characteristics of landslide bodies during the construction phase. Typical cases of slope landslides caused by pipeline construction are introduced and combined with the landslide disaster that occurred at the China-Burma oil and gas pipeline, supporting the following conclusions: the concept of risk is introduced by proposing adoption of semi-quantitative risk assessment methods. Summarizing the causal factors for the landslide disasters, during the China-Burma pipeline construction, and establishing a landslide risk evaluation indicator system. By evaluating the risk level at three typical geological disaster-prone zones, we confirm that evaluation results coincide with actual situation. Therefore, the proposed semi-quantitative evaluation methods have reference value for risk management of pipeline construction at geological disaster points (segments).