In order to understand the hydrological process of expansive soil slopes, simulated rainfall experiments were conducted to study the effects of slope gradient and initial soil moisture content on runoff and infiltration for expansive soil slopes located in south China. The field program consisted of four neighboring slopes (70%, 47%, 32%, and 21%) instrumented by a runoff collection system and moisture content sensors (EC-5). Results from the monitored tests indicate that there was delay in the response of surface runoff. The runoff initiation time decreased with initial soil water content and increasing slope gradient. After the generation of runoff, the cumulative runoff per unit area and the runoff rate increased linearly and logarithmically with time, respectively. The greater the initial soil moisture content was, the smaller the influence of slope gradient on runoff. A rainfall may contribute from 39% to about 100% of its total rainfall as infiltration, indicating that infiltration remained an important component of the rainwater falling on the slope, despite the high initial soil water content. The larger the initial sealing degree of slope surface was the smaller the cumulative infiltration per unit area of the slope. However, the soil moisture reaction was more obvious. The influence of inclination is no longer discernible at high initial moisture levels. The greater the initial soil moisture content and the smaller the slope gradient, the weaker was the change of soil water content caused by simulated rainfall. The influence of initial soil moisture content and slope gradient on the processes of flow and changes of soil water content identified in this study may be helpful in the surface water control for expansive soil slopes.

In this paper, four full-scale concrete columns with high-strength spiral stirrups (HSSS) are constructed and tested under low-cycle repeated loading. The specimens consisted of two castin-place columns and two precast concrete columns encased by a partly square steel pipe and bolt bars.The structural analysis of the HSSS columns of precast concrete conducted here is novel, and past experimental data for this are not available.To assess the seismic behavior and failure mechanisms of the new connections, quasi-static tests were carried out on columns prefabricated with them and cast-in-place specimens.The responses of all columns were compared, and the results showed that the failure modes of all columns are the large eccentric damage, and the destruction of all specimens occur at the column foot. The anti-seismic property of the precast HSSS concrete columns was comparable to that of the HSSS cast-in-place columns. A comparison of such performance parameters as energy dissipation and coefficient of ductility revealed that the precast HSSS concrete columns are suitable for use in earthquake zones.

The feasibility of reusing granular weathered (GW) soil as foundation fill is closely related to the strength and stability. Initial moisture content and compaction energy were identified as the main factors affecting the strength and deformation behavior of GW soil. GW soil samples were prepared with different initial moisture contents ranging from 7 ~ 15% and compacted under varying compaction energies ranging from 50 ~ 125%, respectively. The results indicate that the permeability coefficient decreases sharply with increasing compaction energy and then gradually stabilizes at higher compaction energy levels, suggesting that compaction energy is the dominant factor governing soil permeability. Higher initial moisture content leads to larger strains due to the presence of thicker adsorbed water films, whereas higher compaction energy enhances interparticle bonding, reduces the void ratio, and increases soil stiffness. In particular, the void ratio is affected by both initial moisture content and compaction energy, highlighting the necessity of incorporating compaction energy into predictive permeability models. Furthermore, a compaction-energy-based permeability prediction model was developed, with the predicted results showing strong agreement with the experimental data. These findings provide practical guidance for optimizing the compaction of GW soil to enhance foundation stability and reduce the risks associated with rainfall infiltration, and seepage failure.