Most of the hydraulic structures in Korea were built before 1970, with 69.4% of them having a service life exceeding 50 years. Ordinary Portland cement (OPC), which is currently in general use for the construction of these structures, is continuously facing price increases. In addition, considerable amounts of greenhouse gases generated during the manufacturing process cause environmental problems. Therefore, in this study, ZA-SOIL, a material developed by recycling inexpensive blast furnace slag powder and desulfurized gypsum, was mixed with sodium silicate and silica sol in a liquid state and evaluated as an alternative to OPC. The compressive strength and environmental characteristics of the ZA-SOIL product were experimentally compared with those of OPC to evaluate its applicability as a grout material. The results indicated that the compressive strength of the developed ZA-SOIL was 3.23, 2.88, and 1.25 times higher than that of OPC after 3, 7, and 28 d of curing, respectively. In addition, ZA-SOIL satisfied all prescribed criteria and was found to be environmentally stable. Further evaluation of the field applicability of ZA-SOIL revealed that the electrical resistivity increased after reinforcement, depending on the depth, and the permeability coefficient (k) sharply decreased. Therefore, ZA-SOIL, developed by recycling inexpensive circulated resources, shows potential as an OPC substitute.

Tunnel structures that pass through active faults are prone to serious damage under the action of fault displacement. When the tunnel cannot avoid active faults, a series of disaster reduction measures need to be taken to reduce the impact of fault displacement on the tunnel. In current work, firstly, a three-dimensional numerical analysis model was established, and the numerical model was validated through existing centrifugal model experiments. Then, by comparing the damage response of articulated tunnels and integral tunnels under fault action, the energy dissipation mechanism and disaster reduction effect of articulated design method were researched, and the key parameters in the articulated design method, such as the longitudinal position, elastic modulus and length of flexible joint and the length of lining segment, were further analyzed for their influence on the disaster reduction effect. Finally, considering the possibility of groundwater seepage during tunnel operation in areas with abundant water, a variable cross-section disaster reduction method based on the articulated design was proposed, and the disaster reduction effect under different parameter influences were discussed. This work can provide meaningful references for the disaster reduction design method of sand tunnels under the action of bedrock normal fault dislocation.

In this study, a design method using system stiffness influence factor (IF) was established to characterize the excavation-induced wall and ground movements with changes in groundwater level (GWL). The established factor for quantifying wall and ground behavior in this study considering GWL was regarded as an important aspect to prevent failures and ensure stable support systems design for the target structure. Irregular excavation configuration, common in urban areas, was considered using the three-dimensional finite element (FE) analysis, as well as different GWLs and various influence parameters for wall and support systems. Wall deflection and surface settlement were shown to decrease as the groundwater level was lowered and system stiffness was increased, especially with larger wall bending stiffness, higher wall embedment depth, and reduced vertical and horizontal strut spacings. These effects were particularly noted within re-entrant corner zones due to the corner stiffening effect. The influence of individual parameters was evaluated and quantified using the IF. A modification procedure for the IF was introduced to incorporate the effects of groundwater level, and the proposed method was shown to effectively predict wall deflection and ground settlement. Case example data confirmed the validity of this method, and its applicability in enhancing and optimizing excavation design was demonstrated. Overall, the proposed approach was offered as a practical and innovative framework for the design of excavation support systems under the influence of groundwater.

The shape of natural rock and soil particles is distinct and their orientation may prefer a certain direction, and determining the influences of particle shape and initial particle orientation on dry and immersed granular collapse is of great significance to prevention of geological disasters such as subaerial and submarine landslides. Using the superquadric DEM and the coupled CFD-DEM, the dry and immersed collapse process of granular columns with different particle shapes (aspect ratio A and blockiness B) and different initial particle orientations 𝜃 are simulated. The results show that, compared with the case of A = 1 (spherical), the collapse of particles with larger A (elongated) or smaller A (platy) results in a shorter final runout distance and a higher final deposit height. The collapse of particles with larger B (more angular) also results in a shorter final runout distance and a higher final deposit height. The collapse of particles with 𝜃 = 0° (approximately horizontal) produces an obviously smaller final runout distance, and progresses in a particular way that some particles being first squeezed out from the lateral free surface followed by the gradual slide of particles in the upper parts. For platy ellipsoidal particles, the collapse of particles with 𝜃 = 135° (leaning on the fixed wall) generates the longest final runout distance. Whereas, for elongated ellipsoidal particles, the collapse of particles with 𝜃 = 90° (approximately upright) generates the longest final runout distance.

Biopolymer-based soil treatment (BPST) has recently been introduced as a new ground improvement method for environmentally friendly and sustainable development. Numbers of research have investigated BPST effects on the soil hydraulic conductivity, while there are lack of studies considering in-situ stress (i.e. vertical confinement and groundwater pressure) conditions. In this study, the effect of gellan gum BPST on the hydraulic conductivity behavior of sands was assessed using a pressurized permeability test apparatus which allows separate vertical confinement and pore pressure control. The hydraulic conductivity of gellan gum biopolymer-treated sands were measured with different biopolymer contents, vertical confinement levels, and pore water pressure conditions. Laboratory test results show that the hydraulic conductivity of gellan gum-treated sands attribute to 1) biopolymer-particle bonding, 2) biopolymer hydrogel induced pore-clogging, and 3) hydrogel alteration due to pore pressure increase, where gellan gum BPST is postulated to be an effective manner for ground hydraulic conductivity control in geotechnical engineering practice.

This study proposed a new "grouting-soil-pier interaction transmission model", using work done on soil per linear meter to reflect the impact of soil displacement on the bridge pier. Exploring the relationship between grouting volume, soil displacement, and bridge pier displacement, the relationship between bridge pier horizontal displacement and grouting volume is divided into three zones: linear, nonlinear, and ineffective. A continuous transition from linear to nonlinear behavior is formulated, thereby elucidating the entire progression of pier displacement. For the present project, In the range of grouting distance [0, 5] meters and volume [0, 120] cubic meters, a proportional relationship is observed. Field tests show that the error between derived and measured slopes of pier displacement is under 10%, validating the model. Further exploration reveals that the maximum bending moment and maximum soil displacement occur at the same depth, which corresponds to the silt layer. Under different pile deflection conditions, the ratio of work done on soil per linear meter to pile strain energy varies, indicating different energy transfer efficiencies.