Shallow soils are highly vulnerable to the combined impacts of various factors, including vehicle loading, precipitation, and groundwater. The slope soil at the roadside is inevitably subjected to long-term cyclic loading from traffic. Previous studies have demonstrated that ecological engineering measures can effectively mitigate soil deformation and reduce pore water pressure development, thereby preventing soil erosion and landslides. This study aims to investigate the influence of root distribution patterns on the elastic deformation and pore water pressure development trends in root reinforced soil by simulating cyclic traffic loading through dynamic triaxial tests. The study findings demonstrate that the presence of roots significantly enhances the soil's resistance to deformation. When the vertical root accounts for 25% (while the horizontal root accounts for 75%), experimental results indicate that the soil reinforced by roots exhibits minimal deformation and slower pore water development. Moreover, a parameter D is introduced to enhance the existing pore water pressure models with the increased coefficients of determination, thereby improving the applicability in root-reinforced soils. These findings provide valuable insights for enhancing strength and liquefaction resistance in root reinforced soils while providing guiding research for the mechanical effects of root reinforcement of soil for ecological restoration of highway slopes.

Measuring pore-water pressure (PWP) in frozen soils poses significant challenges in geotechnical testing experiments, and understanding PWP is crucial for unraveling the mechanism of frost heave generation in cold regions. This paper aims to clarify the development pattern of PWP in frozen soil through laboratory tests, specifically focusing on excess PWP generated under dynamic loading. Seven sets of triaxial tests were conducted to investigate the variations in excess PWP and deformation influenced by temperature, dynamic stress amplitude, and dry density. The results reveal that excess PWP in warm saturated frozen soil undergoes two stages: pore pressure increase and dissipation. The change of external factors mainly affects the peak value of excess PWP and the change rate of excess PWP. Unlike unfrozen soil, excess PWP has a small dissipation rate after the peak and may remain dynamically stable in the later stage of loading. In addition, two empirical models of excess PWP applicable to saturated frozen soils were proposed based on the developmental patterns of excess PWP in frozen soils, and the feasibility was validated using the results obtained from laboratory tests. The model is of great significance for predicting the development of excess PWP in frozen soil under dynamic load.

Under traffic load, earthquake load, and wave load, saturated sand foundation is prone to liquefaction, and foundation reinforcement is the key measure to improve its stability and liquefaction resistance. Traditional foundation treatment methods have many problems, such as high cost, long construction period, and environmental pollution. As a new solidification method, enzyme-induced calcium carbonate precipitation (EICP) technology has the advantages of economy, environmental protection, and durability. Through a triaxial consolidated undrained shear test under cyclic loading, the impacts of confining pressure (sigma 3), cementation number (Pc), cyclic stress ratio (CSR), initial dry density (rho d), and vibration frequency (f) on the development law of pore water pressure of EICP-solidified sand are analyzed and then a pore water pressure model suitable for EICP-solidified sand is established. The result shows that as sigma 3 and CSR increase, the rise rate of pore water pressure of solidified sand gradually accelerates, and with a lower vibration number required for liquefaction, the anti-liquefaction ability of solidified sand gradually weakens. However, as Pc, rho d, and f rise, the increase rate of pore water pressure of solidified sand gradually lowers, the vibration number required for liquefaction increases correspondingly, and its liquefaction resistance gradually increases. The test results are highly consistent with the predictive results, which show that the three-parameter unified pore water pressure model is suitable for describing the development law of A-type and B-type pore water pressure of EICP-solidified sand at the same time. The study results provide essential reference value and scientific significance in guidance for preventing sand foundations from liquefying.

The generation mechanism of pore pressure plays an essential role in understanding the liquefaction behavior of sand under cyclic loading. Extensive undrained simple shear tests were undertaken to study the pore pressure and shear strain development characteristics of calcareous sand reinforced by fibers. The results show that the deformation patterns of the tested calcareous sand gradually shift from brittle to ductile failure as fiber content increases. The mechanism of pore pressure generation in calcareous sand subjected to cyclic loading is quite distinct from that of siliceous sand, exhibiting more pronounced accumulation in the initial stage of cyclic loading. Fiber reinforced calcareous sand exhibits reverse shear contraction behavior when liquefaction is imminent. A remarkable finding is the establishment of a unique correlation between pore pressure ratio and shear strain, irrespective of the fiber reinforcement. Consequently, a shear strain-based pore pressure generation model of reinforced calcareous sand is then developed to predict the pore pressure built-up trend under varying fiber content and length conditions. This model is also applicable to various testing conditions and soil types.

Accurate prediction of excess pore water pressure (EPWP) generation in saturated sandy soils remains one of the most challenging issues in sandy site responses to strong earthquakes and extreme marine environments. This paper presents experimental results of undrained and drained multidirectional cyclic hollow cylinder (MCHC) tests on saturated coral sandy soils under various cyclic loadings. The results show that threshold generalized shear strain gamma ga,th, below which EPWP and volumetric strain can be neglected, is an inherent property depending only on the soil type and initial state. Furthermore, there exists a virtually unique form of relationships between the generalized shear strain amplitude (gamma ga) and the cumulative dissipated energy per unit volume of soil (Wc) at different relative density (Dr), irrespective of drainage conditions and cyclic loading conditions. These findings highlight the fundamental mechanism for cyclic deformation behavior and the uniqueness of correlations among rup (peak EPWP ratio), epsilon vp (peak volumetric strain), and gamma ga of saturated sandy soil at the similar Dr, regardless of cyclic loading conditions. Based on these findings, a novel unified model of gamma ga-based cyclic shear-volume coupling and EPWP generation is established, which is independent of cyclic loading conditions over a wide loading frequency range. Then the applicability of the proposed model is validated by the experimental data of the same tested coral sandy soil and siliceous Ottawa sand, as well as the data of siliceous fine sands in previous work. It is found that the proposed model surpasses the existing strain- and stress-based models in accurately predicting EPWP generation under complex cyclic loadings, which can offer new insights into the mechanisms of the EPWP generation in saturated sandy soils.

Cement mortar-expanded precast (CMEP) piles comprise a new class of expansion pile technology. To reveal their vertical bearing properties, full-scale research on the bearing performance of expanded piles under different pile top pressure modes and pre-bored conditions has been carried out. Test results have shown that pile top pressure mode had little effect on the bearing performance of expanded precast piles, but significantly affected internal load transfer mechanism. When internal precast pile was under pressure alone, the axial force of inner precast pile was relatively high. When the full of pile top was loaded, precast pile axial force was reduced by about 20-50%. Furthermore, different pre-bored conditions could cause different pile end support conditions, significantly impacting the performance of expanded pile bearing. The ultimate bearing capacity of expansion piles with super core (SC) pile, equal core (EC) pile and less core (LC) pile were 1200, 880 and 906 kN, respectively. However, all three expanded pile types had about 12% higher bearing capacity than conventional strong composite piles. The failure modes of all test piles under ultimate load were overall subsidence, indicating that the shear capacity of the interface between inner precast pile and outer cement mortar was greater than shear action between outer cement mortar and surrounding soil. When the strength of outer grouting material was greater than 15 MPa, the interface damage of inner precast pile and outer material may not be considered.