Cemented sand-gravel (CSG) is an innovative material for dam construction with a wide range of applications. Nevertheless, a comprehensive understanding of the dynamic properties of CSG is lacking. A series of cyclic triaxial dynamic shear tests were carried out on CSG materials to investigate their complex dynamic mechanical properties, leading to the establishment of a dynamic constitutive model considering damage. The findings indicate that both the application of confining pressure and the addition of cementitious material have a noticeable influence on the morphology of the hysteresis curve. Further research scrutiny reveals that augmenting confining pressure and gel content leads to an increase in the dynamic shear modulus and a decrease in damping ratio. Furthermore, a constitutive dynamic damage constitutive model was constructed by linking a damage element to the generalized Kelvin model and defining the damage variable D based on energy interaction principles. The theoretical formulas for dynamic shear modulus and damping ratio were adjusted accordingly. In addition, the stiffness matrix of the dynamic damage constitutive model was derived, which demonstrated its strong fitting effects in dynamic triaxial shear tests on CSG. Finally, the dynamic response and damage distribution in the dam body under dynamic loading were analyzed using a selected CSG dam in China.

This study evaluated lime-lignin composite stabilisers for clay enhancement. Results showed their synergistic effect significantly improved shear strength (S), cohesion (c), friction angle (phi), and maximum dynamic shear modulus (Gmax) of clay. Microstructural analysis revealed lime-induced granular crystals and lignin-generated cementitious products, enhancing soil structure. After 1 and 7 days curing, the clay stabilised with 6% lime and 2% lignin exhibited the highest S, c, phi and Gmax. After 14 days curing, the clay stabilised with 4% lime and 4% lignin exhibited the highest S, c, phi, and Gmax. A novel relative structural characterization method based on c and phi was proposed, alongside a modified Hardin's model integrating relative structural to predict Gmax. The study demonstrates that 6% lime + 2% lignin and 4% lime + 4% lignin ratios effectively enhance embankment clay properties, offering sustainable solutions for industrial byproduct utilization and soil stabilisation in geotechnical engineering.

This study investigated the small-strain dynamic properties of expanded polystyrene (EPS) lightweight soil (ELS), a low-density geosynthetic material used to stabilize slopes and alleviate the subgrade settlement of soft soil. Resonant column tests were conducted to evaluate the effects of EPS's granule content (20-60%), confining pressures (50 kPa, 100 kPa, and 200 kPa), and curing ages (3 days, 7 days, and 28 days) on the dynamic shear modulus (G) of ELS within a small strain range (10-6-10-4). The results indicate that ELS exhibits a high dynamic shear modulus under small strains, which increases with higher confining pressure and longer curing age but decreases with an increasing EPS granule content and dynamic shear strain, leading to mechanical property deterioration and structural degradation. The maximum shear modulus (Gmax) ranges from 64 MPa to 280 MPa, with a 60% reduction in Gmax observed as the EPS granule content increases and increases by 11% and 55% with higher confining pressure and longer curing ages, respectively. A damage model incorporating the EPS granule content (aE) and confining pressure (P) was established, effectively describing the attenuation behavior of G in ELS under small strains with higher accuracy than the Hardin-Drnevich model. This study also developed an engineering testing experiment that integrates materials science, soil mechanics, and environmental protection principles, enhancing students' interdisciplinary knowledge, innovation, and practical skills with implications for engineering construction, environmental protection, and experimental education.

In biopolymer-soil stabilization, biopolymers function in the soil either as viscous fluids or rigid gels. However, the influence of these hydrogel states on soil liquefaction resistance and their underlying mechanisms remain insufficiently understood. This study examines the seismic response of sand treated with biopolymers under small-to-medium strain cyclic loading, with a focus on the efficacy of Cr3+-crosslinked xanthan gum (CrXG) in mitigating liquefaction. Liquefaction resistance and dynamic properties of CrXG-treated soil were compared against thermogelation and non-gelling viscous biopolymer treatments using cyclic direct simple shear and resonant column tests. CrXG treatment at 1 % content improved liquefaction resistance (CRR10) from 0.088 to 0.687 by preventing shear strain accumulation and pore pressure buildup, with enhancing dynamic shear stiffness and delaying stiffness degradation and damping ratio changes to higher strain levels. In contrast, soils treated with non-gelling viscous XG exhibited limited reinforcement under large strain cyclic loading, showing earlier liquefaction and lower CRR10 compared than untreated sand, alongside reduced dynamic shear modulus and rapid stiffness degradation. Comparisons across varying earthquake moment magnitudes revealed that CrXGtreated soil achieved liquefaction resistance comparable to other soil stabilization methods and demonstrated greater improvement efficiency than thermogelation biopolymers requiring thermal treatment. These findings highlight the potential of CrXG as a sustainable and practical solution for improving liquefiable soil stability under seismic loading.

Offshore wind power construction is currently experiencing rapid growth worldwide, with China leading in the number of offshore wind turbines. Approximately 60 % to 70 % of these turbines are situated in the offshore area of the South Yellow Sea, Jiangsu Province. Despite its frequent exposure to waves and earthquakes, this region lacks comprehensive studies on the dynamic characteristics of local marine soils, which hinders the development of marine engineering design. This study addresses this gap by conducting a series of tests on marine silty sand using a combination of resonant column and dynamic triaxial tests. The investigation examined various dynamic parameters at both small and large strain scales, taking into account the soil ' s relative density, dynamic loading frequency, and cyclic stress ratio (CSR). The experimental results revealed that the attenuation of dynamic shear modulus aligns well with the classic H -D model. Moreover, the damping ratio exhibited an increase with cyclic loading until reaching a peak value at dynamic shear strains between 0.5 % and 0.8 %, followed by a rapid decrease due to liquefaction. Additionally, the failure behavior of the marine silty sand was found to be more sensitive to relative density than dynamic loading frequency under undrained shearing condition. The critical CSR for soil with a relative density of 73 % was approximately 0.18. Whereas for soil with a relative density of 53 %, it was about 0.12. The experimental findings provide valuable insights and parameters for the design of offshore engineering in this area.

Expansive soil is known for its ability to undergo significant volume changes in response to changes in moisture levels. Several investigations have been conducted to explore the stabilisation of expansive soils, encompassing a variety of reinforcement techniques and stabilisation approaches. Analysing dynamic properties such as shear modulus and damping ratio in expansive soil is imperative as they provide vital insights into the soil's response to dynamic loads. The use of lime and fibre treatment for stabilising expansive soil offers a comprehensive solution that addresses both chemical and physical stabilisation. This approach enhances soil properties and reduces the risk of damage to structures. To understand the complex behaviour of soil systems under varying conditions, cyclic triaxial tests on expansive soil were conducted using fibre-lime treatment. The variations in dynamic shear modulus and damping ratio with respect to shear strain amplitude, as well as the dynamic shear stress-strain curves, were studied across various confining pressures. The paper also presents the small strain shear modulus and modulus reduction curves. Besides, for a comprehensive understanding of the microstructural reactions of the fibre-lime-treated soil, specimens subjected to cyclic loading were examined using SEM analysis. A comparative analysis, examining the dynamic properties of soil under varying lime percentages, with and without 0.5% polypropylene (PP) fibre, as well as comparing scenarios with different lime contents between 0 and 0.5% PP fibre conditions has been presented. The experimental findings suggests that the fibre-lime treatment led to an enhancement in the dynamic shear modulus and damping ratio, with the increase of confining pressure. From the SEM analysis of the fibre-lime-treated soil, the microstructure displays a fabric-like pattern with cementitious gel connecting soil particle clusters. The images also show clay particles bonding together, forming a compact structure.

In this paper, a database consisting of the dynamic shear modulus ratio and damping ratio test data of clay obtained from 406 groups of triaxial tests is constructed with the starting area of Xiong'an New Area as the research background. The aim is to study the nonlinear dynamic properties of clay in this area under cyclic loading. The study found that the effective confining pressure and plasticity index have certain influences on the dynamic shear modulus ratio and damping ratio of clay in this area. Through data analysis, it was found that there was a certain correlation between effective confining pressure and plasticity index and dynamic shear modulus ratio and damping ratio, with fitting degree values greater than 0.1263 for both. However, other physical indices such as the void ratio, natural density, water content and specific gravity have only a small effect on the dynamic shear modulus ratio and the damping ratio, with fitting degree values of less than 0.1 for all of them. This indicates that it is important to consider the influence of effective confining pressure and plasticity index when studying the nonlinear dynamic properties of clays in this area. Based on the above, prediction models for the dynamic shear modulus ratio and damping ratio in this area were constructed separately. The results showed that the model that considered the combined effect of effective confining pressure and plasticity index performed best. The predicted dynamic shear modulus ratio and damping ratio closely matched the actual curves, with approximately 88% of the data falling within +/- 1.3 times the measured dynamic shear modulus ratio and approximately 85.1% of the data falling within +/- 1.3 times the measured damping ratio. In contrast, the prediction models that considered only a single influence deviated from the actual values, particularly the model that considered only the plasticity index, which predicted the dynamic shear modulus ratio and the damping ratio within a small distribution range close to the average of the test values. When compared with existing prediction models, it was found that the predicted dynamic shear modulus ratio in this paper was slightly higher, which was due to the overall hardness of the clay in this area, leading to a slightly higher determination of the dynamic shear modulus ratio by the prediction model. Finally, for the dynamic shear modulus ratio and damping ratio of the engineering site in the starting area of Xiong'an New Area, we confirm that the prediction formulas established in this paper have high reliability and provide the applicable range of the prediction model.