There has been a growing interest in controlled low strength material CLSM due to its engineering features, such as self-leveling and early strength development, as well as it potential for utilizing industrial waste. Still, the dynamic properties on CLSM are rarely studied. This study evaluates the feasibility of red mud as a partial aggregate replacement in foamed-lightweight CLSM, incorporating high-carbon fly ash and preformed foam. We varied both the red mud contents RMc and foam volume ratio FVR within the mixtures and examined their impact on unconfined compressive strength and dynamic properties including shear modulus G and damping ratio D. The results reveal that the red mud enhances foam stability, leading to more uniform pore structures and increased porosity, which reduces bulk densities. Despite higher porosity, red mud serves as a strong alkaline activator, enhancing geopolymer reactions of high-carbon fly ash and thereby increasing both compressive strength and initial shear modulus G0. Interestingly, increasing FVR had minimal impact on the D, while higher RMcnotably increased D, highlighting its distinct role in energy dissipation. The red mud-incorporated foamed CLSM exhibits strain-dependent normalized shear modulus G/G0 comparable to that of gravel, while its D is 40-100 % higher than gravel or gravelly soil at shear strain of 1.10-5, which corresponds to typical traffic-induced vibration levels. Moreover, theoretical volumetric-gravimetric relationships are introduced to account for the combined effects of FVR and RMcon CLSM behavior. These findings demonstrate that the red mud included foamed CLSM can be utilized as advanced structural backfill material capable of effectively mitigating the vibrations induced by traffic, low-amplitude seismic events, and mechanical sources.

Seismic safety of high concrete face rockfill dams (CFRD) on thick layered deposit is crucial. This study develops a seismic performance assessment procedure for high CFRD on thick layered deposit considering multiple engineering demand parameters (EDPs), and evaluates the effectiveness of gravel column and berm reinforcement for a typical CFRD. Solid-fluid coupled seismic response analysis of high CFRD on thick layered deposit is conducted using an advanced elasto-plastic constitutive model for soil, revealing the unique seismic response of the system, including the buildup of excess pore pressure within the thick deposit. Based on the high-fidelity simulations, appropriate intensity measure (IM) and EDPs are identified, and corresponding damage states (DS) are determined. Fragility curves are then developed using multiple stripe analysis, so that the probability of damage under different input motion intensities can be quantified for different DS. Using the proposed procedure, the reinforcement effects of berms and gravel columns are evaluated. Results show that berms can contribute significantly to reducing the probability of damage for the system, while the effect of gravel columns is unsatisfactory due to the limited achievable installation depth compared to the thickness of the deposit and low replacement ratio.

To evaluate the beneficial effect of rubber bearings on the seismic performance of underground station structures, three-dimensional finite element models of seismic soil-structural systems are established for a single-layer double span subway station. The seismic mitigation effect is investigated by employing the pushover analysis method. The obtained results indicated that the installation of rubber bearings can effectively alleviate stress concentration and damage degree of the central column, especially at its end area. Compared with the conventional column, the elastic and elastoplastic deformation capacity of the column fitted with rubber bearings both improved significantly. It was also found that the load bearing and deformation performance decrease with the increase of the axial pressure ratio. Furthermore, the lateral force distribution mechanism of the structural system fitted with the rubber bearings is significantly different from the original structure; the deformation and internal forces of central column of the seismic mitigation structure decreased substantially, but side walls' deformation and internal forces increased slightly. The proportion of shear force taken by the central column has decreased, while the side walls have taken larger share, i.e., the rubber bearings facilitated the transfer of seismic forces from the middle column to the side wall.

Three-dimensional numerical models are developed to investigate the anti-liquefaction of ordinary (OSCs) and geosynthetic-encased (GESCs) stone columns in sandy soil under sinusoidal loading using the fluid-solid coupling method. The validated models capture and compare the vertical and radial deformation, excess pore water pressure (EPWP), and vertical effective stress of OSC, GESC, and sandy soil. Furthermore, ten essential factors are selected to conduct the parametric study. Numerical results reveal that GESC is more suitable for improving sandy soil and resisting dynamic load considering the deformation and EPWP. The bulging deformation is no longer the primary reason for failure. The partial encasement (e.g., 1-2D, D = column diameter) and short floating and end-bearing GESCs (e.g., 1-2.5D) are not recommended for reinforcing the sandy soil. GESC is more sensitive to low-frequency and high-amplitude loads, with shear and bending, whereas displays a block movement under higher frequency and lower amplitude loading. The change in loading amplitude is more disadvantageous to GESC than loading frequency. GESC with a large diameter cannot effectively resist the dynamic loads.

This study investigates the influence of wood pellet fly ash blended binder (WABB) on the mechanical properties of typical weathered granite soils (WS) under a field and laboratory tests. WABB, composed of 50 % wood pellet fly ash (WA), 30 % ground granulated blast furnace slag (GGBS), and 20% cement by dry mass, was applied at dosages of 200-400 kg/m3 to four soil columns were constructed at a field site deposited with WS. After 28 days, field tests, including coring, standard penetration tests (SPT), and permeability tests, revealed enhanced soil cementation and reduced permeability, indicating a denser soil matrix. Unconfined compressive tests (UCT) and free-free resonant column (FFRC) tests on field cores at 28 and 56 days, compared with laboratory specimens and previously published data, demonstrated strength gains 1.2-2.1 times higher due to field-induced stress. The presence of clay minerals influenced the WABB's interaction and microstructure development. Correlations between seismic waves, small-strain moduli, and strength were developed to monitor in-situ static and dynamic stiffness gain of WABB-stabilized weathered granite soils.

Stone columns are a resultful measure to increase the bearing capacity of soft or liquefiable foundations. The centrifuge model test and finite element method were employed to investigate the bearing capacity and deformation behavior of the stone column-reinforced foundation. Study shows that the modulus of the reinforced foundation exhibits significant anisotropy. A bulging deformation area is identified in the reinforced foundation where obvious horizontal deformation of the stone column occurs. The ratio of the column stress and soil stress is observed to change violently in this area. A homogenization technique is consequently deduced by employing the column-soil stress ratio as a key variable. The definition of the column-soil stress ratio is extended to reasonably describe the column-soil interaction under different stress levels and its approximation method is given. Based on the Duncan- Chang E-nu model, a simplified method using the homogenization technique is proposed for the stone column reinforced foundation. The proposed homogenization technique and simplified method have been validated by the centrifuge model tests and finite element analyses. This method properly addresses the nonlinear spatial characteristic of deformation and the anisotropy of the stone column reinforced foundation.

Deep soil mixing (DSM) is a widely used ground improvement method to enhance the properties of soft soils by blending them with cementitious materials to reduce settlement and form a load-bearing column within the soil. However, using cement as a binding material significantly contributes to global warming and climatic change. Moreover, there is a need to understand the dynamic behavior of the DSM-stabilized soil under traffic loading conditions. In order to address both of the difficulties, a set of 1-g physical model tests have been conducted to examine the behavior of a single geopolymer-stabilized soil column (GPSC) as a DSM column in soft soil ground treatment under static and cyclic loading. Static loading model tests were performed on the end-bearing (l/h = 1) GPSC stabilized ground with Ar of 9 %, 16 %, 25 %, and 36 % and floating GPSC stabilized ground with l/h ratio of 0.35, 0.5, and 0.75 to understand the load settlement behavior of the model ground. Under cyclic loading, the effect of Ar in end-bearing conditions and cyclic loading amplitude with different CSR was performed. Earth pressure cells were used to measure the stress distribution in the GPSC and the surrounding soil in terms of stress concentration ratio, and pore pressure transducers were used to monitor the excess pore water pressure dissipated in the surrounding soil of the GPSC during static and cyclic loading. The experimental results show that the bearing improvement ratio was 2.28, 3.74, 7.67, and 9.24 for Ar of 9 %, 16 %, 25 %, and 36 %, respectively, and was 1.49, 1.82, and 2.82 for l/h ratios of 0.35, 0.5, and 0.75 respectively. Also, the settlement induced due to cyclic loading was high under the same static and cyclic stress for all the area replacement ratios. Furthermore, the impact of cyclic loading is reduced with an increase in the area replacement ratio. Excess pore water pressure generated from static and cyclic loads was effectively decreased by installing GPSC.

A novel MgO-mixing column was developed for deep soft soil improvement, utilizing in-situ deep mixing of MgO with soil followed by carbonation and solidification via captured CO2 injection. Its low carbon footprint and rapid reinforcement potential make it promising for ground improvement. However, a simple and cost-effective quality assessment method is lacking. This study evaluated the electrical properties of MgO-mixing columns using electrical resistivity measurements, exploring relationships between resistivity parameters and column properties such as saturation, strength, modulus, CO2 sequestration and uniformity. Microscopic analyses were conducted to elucidate the mechanisms underlying carbonation, solidification, and electrical property changes. The life cycle assessment (LCA) was performed to assess its carbon reduction benefits and energy consumption. The findings reveal that the electrical resistivity decreases rapidly with increasing test frequency, remaining constant at 100 kHz, with the average electrical resistivity being slightly higher in the upper compared to the lower section. Additionally, electrical resistivity follows a power-law decrease with increasing saturation. Both electrical resistivity and the average formation factor exhibit strong positive correlations with unconfined compressive strength (UCS) and deformation modulus, enabling predictive assessments. Furthermore, CO2 sequestration in MgO-mixing columns is positively correlated with electrical resistivity, and the average anisotropy coefficient of 0.96 indicates good column uniformity. Microstructural analyses identify nesquehonite, dypingite/hydromagnesite, and magnesite as significant contributors to strength enhancement. Depth-related changes in electrical resistivity parameters arise from variations in the amount and distribution of carbonation products, which differently impede current flow. LCA highlights the significant low-carbon advantages of MgOmixing columns

Previous studies have demonstrated that reducing earthquake-induced damage to central columns in underground structures can effectively prevent the collapse of overall structures. Truncated columns (TC) are less likely to experience severe damage during lateral deformation because the partial release of the constraints at both ends of the columns helps maintain their integrity. This approach can effectively enhance the seismic performance of the overall underground structures. In this study, pushover and shaking table tests were conducted to investigate the seismic performance of a subway station using TC columns compared to that using the cast-in-place columns (CC). These tests aimed to examine failure modes, structural stiffness, lateral deformation and load-bearing capacities, acceleration and deformation responses of the underground structures. The results from the pushover tests indicated that the initial stiffness of both structures-those with TC and with CC-was equivalent. On the other hand, the shaking table tests showed no significant differences in the dynamic responses of the two types of underground structures under small earthquakes. However, the vertical ground motions exacerbated damage to the structures. Although the lateral load-bearing capacity of the structure with TC is somewhat lower, the movements between the column ends and beams during loading enhance the structure's ability to adapt to the deformation of surrounding soil due to the release of column end constraints. As a result, the seismic resistance of the overall underground structures is improved. It is important to note that the ceiling slab and sidewalls in the structures with TC are more likely to crack during earthquakes, thus requiring additional efforts to prevent leakage. The findings of this study provide experimental evidence that supports the seismic control of underground structures.

After sand liquefaction, buried underground structures may float, leading to structural damage. Therefore, implementing effective reinforcement measures to control sand liquefaction and soil deformation is crucial. Stone columns are widely used to reinforce liquefiable sites, enhancing their resistance to liquefaction. In this study, we investigated the mitigation effect of stone columns on the uplift of a shield tunnel induced by soil liquefaction using a high-fidelity numerical method. The liquefiable sand was modeled using a plastic model for large postliquefaction shear deformation of sand (CycLiq). A dynamic centrifuge model test on stone column-improved liquefiable ground was simulated using this model. The results demonstrate that the constitutive model and analysis method effectively reproduce the liquefaction behavior of stone column-reinforced ground under seismic loading, accurately reflecting the time histories of excess pore pressure ratio and acceleration. Subsequently, numerical simulations were employed to analyze the liquefaction resistance of saturated sand strata and the response of a shield tunnel before and after reinforcement with stone columns. Additionally, the effects of densification and drainage of the stone columns were separately studied. The results show that, after installing stone columns, the excess pore pressure ratio at each measurement point significantly decreased, eliminating liquefaction and mitigating the uplift of the tunnel. The drainage effect of the stone columns emerged as the primary mechanism for dissipating excess pore pressure and reducing tunnel uplift. Furthermore, the densification effect of stone columns effectively reduces soil settlement, particularly pronounced around the stone columns, i.e., at a distance of three times the diameter of the stone column.