A Method for Quantitative Evaluation of Seismic Stability of Loess Slope Based on the Shaking Table Model Test

The large-scale shaking table model test, which can directly reproduce the process of slope instability and failure, is an important technical means for the prediction and evaluation of slope seismic stability. However, up to now, the systematic slope stability evaluation method based on the shaking table slope model test has not been established, which limits the application of the expensive shaking table model test in slope seismic design. Therefore, the slope stability evaluation method based on the model test needs to be developed and innovated. In this research, through three loess slope model tests with different rainfall, according to the change law of the peak value of transfer function spectrum, combined with the macrodestructive characteristics of the slope model, an accurate calculation method of the critical instability acceleration of the slope is proposed. Based on the behavior similarity theory, for the shaking table model test of slope whose soil cohesion cannot meet the similarity ratio, the reduction method of applying the critical instability acceleration obtained from the model test to prototype slope is proposed. Based on first-order natural frequency and damping ratio extracted from the TF spectrum curve, a calculation method for the stability factor Fs of loess slope based on the shaking table model test is proposed, and the stability factors of loess slope under the action of different seismic ground motion would be quantitatively calculated. The above methods provide another effective way for qualitative prediction and evaluation of seismic stability of loess slope.

Deformation Development Mechanism in a Loess Slope With Seepage Fissures Subjected to Rainfall and Traffic Load

Loess landslides induced by rainfall and traffic load are significant hazards during the construction and operation of highways in many loess-covered areas. Studies of the deformation and stability of loess slopes with seepage fissures are limited. In the study, a case study of the Yangpoyao loess slope with seepage fissures in China’s Loess Plateau was conducted to reveal the deformation development mechanism and assess the landslide hazards of such fissured loess slopes. First, the hydraulic-mechanical properties of the Q2 loess were investigated through experiments, and the mathematical expressions of the relationships between various mechanical parameters and water content were fitted, indicating that the mechanical parameters, such as cohesion, angle of internal friction, and deformation modulus, vary in a quasi-linear manner with the water content. Then, a new numerical method was proposed to simulate the mechanical behaviours of the loess considering its water sensitivity and transverse isotropy, where the water sensitivity was considered through the implementation of the mathematical expressions of the hydraulic-mechanical relationships, and the transverse isotropy was considered by the modified constitutive model that combined the logics of transversely elastic model and a ubiquitous-joint model. Finally, the deformation development mechanism of the fissured loess slope under rainfall and traffic load was revealed by using the proposed method. The roles of the rainfall and traffic load in the fissure propagation and deformation development process of the slope were explored, and some stabilisation measures are recommended for the prevention of its failure. The proposed method and findings arising therefrom may provide references for future studies of the stability and landslide hazard assessment of fissured loess slopes.

Study of PLSR-BP model for stability assessment of loess slope based on particle swarm optimization

The assessment of loess slope stability is a highly complex nonlinear problem. There are many factors that influence the stability of loess slopes. Some of them have the characteristic of uncertainty. Meanwhile, the relationship between different factors may be complicated. The existence of multiple correlation will affect the objectivity of stability analysis and prevent the model from making correct judgments. In this paper, the main factors affecting the stability of loess slopes are analyzed by means of the partial least-squares regression (PLSR). After that, two new synthesis variables with better interpretation to the dependent variables are extracted. By this way, the multicollinearity among variables is overcome preferably. Moreover, the BP neural network is further used to determine the nonlinear relationship between the new components and the slope safety factor. Then, a new improved BP model based on the partial least-squares regression, which is initialized by the particle swarm optimization (PSO) algorithm, is developed, i.e., the PLSR-BP model. The network with global convergence capability is simplified and more efficient. The test results of the model show satisfactory precision, which indicates that the model is feasible and effective for stability evaluation of loess slopes.