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The demand for a load distributive compression anchor (LDCA) in construction sites has been increasing, owing to its high bearing capacity and removable steel strands. As an LDCA comprises multiple anchor bodies and unbonded steel strands, the load applied to the strands generates a distributive compressive stress in the grout, preventing high concentration of grout–ground shear stress. Unlike in the conventional anchors, in an LDCA, independent load transfer of each anchor body induces interference effect between adjacent anchor bodies. Therefore, for an efficient design of an LDCA, it is necessary to investigate the load transfer mechanism considering the effect of multiple anchor bodies. In this study, a series of anchor pull-out field tests was conducted for LDCAs consisting of a single anchor body, and double and triple anchor bodies spaced by 1, 2, and 3 m. According to the test results, the LDCA showed a stiffer load–displacement behavior with an increase in the number and spacing of the anchor bodies. The multiple anchor bodies of the LDCA generated an overlapping of the grout axial load and induced its rapid dissipation, increasing the grout–ground shear stress. This interference effect was more clearly observed with a decrease in the anchor body spacing.

As an LDCA consists of multiple anchor bodies and unbonded tendons, the load applied to the tendon is transmitted to grout and ground by the movement of each anchor body installed along the anchor length. Therefore, the load transfer behavior of LDCA is affected by the interference between adjacent anchor body, and the effect of multiple anchor bodies should be considered in the LDCA design. This study performed a series of pull-out field tests on LDCAs installed in soft rock. LDCAs were designed to have various number and spacing of anchor bodies to investigate the effect of multiple anchor bodies. Furthermore, the test results were compared with the results of pull-out field tests conducted on weathered rock to examine the effect of ground conditions. The load-displacement relationship showed that the grout failure occurred in the LDCA installed in soft rock, and thus the ultimate bearing capacity was smaller than that of the LDCA installed in weathered rock. Additionally, the grout axial load distribution indicated that the LDCA installed in soft rock expressed tensile stress in the grout due to the effect of multiple anchor bodies leading to the tensile failure on the grout.

The traction force of a tracked unmanned ground vehicle (UGV) depends on the soil thrust generated by the shearing action on the soil-track interface. In the development of soil thrust, because the continuous-track system consists of a number of single-track systems connected to each other, interference occurs between the adjacent single-track systems through the surrounding soil. Thus, the total soil thrust of the continuous-track system is not equal to the sum of the soil thrust of each single-track system, and the interference effect needs to be carefully considered. In this study, model track tests were conducted on model single-, double-, and triple-track systems according to relative density of soil and shape ratio (i.e., the length of the track plate to grouser depth). The test results indicated that the interference effect reduced soil thrust due to the overlapping shear zones between adjoining single-track systems. The loss of soil thrust increased as the relative density of the soil increased and the shape ratio decreased. Based on these findings, a soil thrust multiplier that can be utilized to assess the soil thrust of a continuous-track system was developed.

As the soil traction of the track system consisting of a track plate and protruded grousers is generally higher than that of a comparable wheel system, underwater tracked vehicles are the favored platforms for heavy-weight remotely operated vehicles (ROVs). When an underwater tracked vehicle moves on the seafloor, the track system laterally transmits an engine torque to the soil-track interface, resulting in slip displacement and an associated soil thrust acting as a traction force. Therefore, to evaluate the mobility of underwater tracked vehicle, it is critical to evaluate the soil thrust of the track system based on the soil-track interaction. Unlike the soil thrust of sandy soils, a reliable soil thrust assessment method accounting for the failure mechanism of clayey soil has yet to be developed in spite of its significance. An experimental study on the mechanism of the soil thrust of clayey soil was thus performed. Model track experiments were conducted on a model track system with clayey soil. Based on the experiment results, the mechanism of the soil thrust of clayey soil was investigated and was compared with the mechanism of soil thrust derived from the previous soil thrust assessment methods using sandy soil. Particular attention was given to the development of a new soil thrust prediction model for the track system on clayey soil using the limit equilibrium analysis technique.

When an off-road tracked vehicle travels, shearing action and ground sinkage occur on the soil&ndash, track interface, severely affecting the tractive performance of the vehicle. Notably, ground sinkage, which is induced by the vehicle&rsquo, s weight (static sinkage) and longitudinal forces in the direction of travel producing slip (slip sinkage), develops motion resistance, directly restricting the tracked vehicle&rsquo, s performance. Thus, it is critical to consider both static sinkage and slip sinkage to assess the tractive performance of a tracked vehicle. In this research, model track experiments were conducted to investigate slip sinkage. The experimental results showed that the slip sinkage increased as the slip ratio increased, but the rate of increase decreased. The slip sinkage was found to increase as the density of the ground decreased and imposed vertical load increased. The experimental results were used to calculate normalized slip sinkage, and an empirical equation for slip sinkage in terms of slip ratio was developed. This equation will allow vehicle operators to predict the slip sinkage and associated motion resistance for given soil and vehicle conditions.

The track system is generally applied for heavy off-road vehicles. While moving on the off-road, the track system horizontally transmits an engine torque to the soil-track interface, resulting in slip displacement and an associated soil thrust acting as a traction force. As soil thrust is developed on the bottom and the side of the track system (hereinafter referred to as “bottom thrust” and “side thrust”, respectively), it is imperative to evaluate both the bottom thrust and the side thrust to assess the off-road tracked vehicle’s performance. Unlike the bottom thrust, however, the mechanisms of the side thrust have not been fully understood. To address this, this study aimed to evaluate the side thrust for off-road tracked vehicles. A new mechanism for the side thrust was theoretically investigated based on the punching shear theory. A series of model track experiments were conducted on a model track system with silty sand. From the experiment results, the shapes of the failure surface were observed, and the side thrust was measured for verification purposes. Particular attention was given to the development of a side thrust prediction model for the heavy off-road tracked vehicles based on the proposed mechanism.