Micropiles are a new type of retaining structure widely used in slope engineering due to their small footprint, low vibration and noise emissions, and simple construction process. This study aims to investigate the dynamic response and failure mechanisms of micropiles used in retaining accumulation landslides under seismic loading through shaking table tests and numerical simulation. The failure process, observed phenomena, and bending moments of micropiles in the test were discussed, and the shear force distribution of micropiles was thoroughly analyzed based on numerical simulation. The findings reveal that the natural frequency of the entire landslide system exhibits a gradual decrease and tends to stabilize under sustained earthquake excitation. The bending moment of micropiles follows an “S” shape, with a larger magnitude at the top and a smaller one at the bottom. Additionally, the shear force distribution exhibits a “W-shaped” pattern. Damage to micropiles mainly includes the flexural shear combination failure at the load-bearing section (which occurs within 1.4–3.6 times the pile diameter above the sliding surface) and the shear failure near the sliding surface. This study provides significant insights into the strengthening mechanisms of micropiles under seismic action and offers valuable guidance for the design of slope support.

The permeability coefficient of saturated clay plays a crucial role in practical engineering applications. In this paper, based on the fractal geometry theory and combined with the relationship between the flowing water volume and non-flowing water volume in saturated clay, the theoretical formulas for the effective pore specific surface area and the effective void ratio of saturated clay are established. Based on the capillary seepage channel model of saturated clay, combined with Poiseuille’s law and the concept of equivalent hydraulic radius, the theoretical formula for the permeability coefficient of saturated clay is established. Finally, the physical parameters of the remolded clay samples are measured and substituted into the modified Kozeny–Carman equation and the equivalent capillary seepage equation of saturated clay before and after the modification. Through the comparative analysis of the above theoretical values and the measured values of indoor seepage tests, it is found that the saturated clay seepage equation established in this paper is more suitable for dense saturated clay with relatively small pores. It has the characteristics of higher calculation accuracy and easier acquisition of basic parameters. The research results provide important references for practical engineering and the study of saturated clay seepage theory, and have broad prospects for practical engineering applications.

Based on the characteristics and distribution patterns of collapsed holes in cast-in-place bored pile foundations in the typical coastal area of Guangdong Petrochemical Company, the deformation and collapse behavior of pile walls in the project zone were systematically monitored and measured using a specialized pore diameter detection system for cast-in-place bored pile quality assessment. A collapse rate parameter is proposed and established as an evaluation index for pile wall stability and collapse. Using the basic principles of Quantification Theory I and considering the collapse characteristics of pile walls in a cast-in-place bored pile project in Guangdong, the influencing factors and mechanisms of pile wall collapse are comprehensively analyzed and evaluated. A quantitative theoretical evaluation model for the influencing factors of pile wall collapse is then established. Focusing on the construction technology of cast-in-place bored piles, the proposed quantitative theoretical evaluation model is applied to quantitatively analyze and assess the factors contributing to pile wall collapse in the project area. The relationships between pile wall collapse rate in the Guangdong Petrochemical Company cast-in-place bored pile project and influencing factors such as stratum structure, soil properties, sand layer thickness, drilling depth, and drilling methods are systematically determined. The primary collapse factors and secondary influencing factors in the pile wall collapse of the cast-in-place bored pile engineering zone are identified, providing a theoretical basis for determining optimal prevention and control measures against pile wall collapse during the drilling process of cast-in-place bored piles.