Experimental investigations on influences of ground loss on earth pressure and settlement of adjecent underground retaining structures

Underground excavations often pass through underground retaining structures on one side or between the structures. In most cases, ground loss will be caused. At present, there are more and more collapses caused by excavation. When the ground loss occurs, the development of earth pressure and ground settlement is the decision basis for structural reinforcement or treatment. To obtain the preliminary rules of disturbance influences of the ground loss, the model test setup and the steel rod analogical soil technology are developed. A trapdoor is used to simulate the stratum loss caused by underground excavation and collapse, and the foundation pit excavation is simplified as the translation of the retaining wall. Considering the ratios of trapdoor depth to width, trapdoor depth to distance and trapdoor depth to side limit width, 15 groups of two-dimensional model tests are carried out. The earth pressure of retaining structures is measured by 18 cantilevered loaders on the retaining plate, and the surface settlement curve is obtained by the particle image velocimetry. The results show that ground loss increases the earth pressure at the upper part of the retaining wall and decreases the earth pressure at the lower part of the retaining wall. After the occurrence of the ground loss, if the adjacent foundation pit continues being excavated, due to the disturbance of the soil, there is no "bin effect" of the decrease of the earth pressure at the bottom of the retaining structures, and the earth pressure distribution when the retaining wall translation reaches the active limit state is in good agreement with the Coulomb’s active earth pressure. Under the influences of the superposition effect of the translation of the retaining wall after the ground loss caused by the adjacent underground excavation, the maximum value of surface settlement and the curvature of curve increase with the increase of trapdoor width, and increase with the decrease of trapdoor distance and side limit width. Due to the use of steel rod analogical soil, the test results mainly reflect the earth pressure and deformation characteristics of the sandy soil.