Creep and long-term strength are important time-dependent behaviors of rock. To study the time-dependent behavior of hard rock under different confining pressures, conventional triaxial tests and multistage creep tests were conducted on the greenschist in the Jinping II Hydropower Station at different confining pressures. Based on the test results, the characteristics of axial, lateral, and volumetric creep were analyzed, and the creep properties under different confining pressures were also studied in detail and evaluated quantitatively by a simple model. Meanwhile, a new method is proposed by which the long-term strength can be determined using the inflection point in the isostrain-rate curve. The test results revealed that the creep was weakened and the ratio of long-term strength to instantaneous strength decreased with increasing confining pressure, during which the deformation of the rock sample transitioned from brittle to ductile. It was found that the duration of the transient creep stage decreased and the lateral strain was more sensitive to the creep stress than the axial strain when the confining pressure increased. It is also observed that the long-term strength determined by the inflection point method is consistent with those estimated by the creep rate in multistage creep tests, and the accuracy of the method proposed in this research is verified.

The axial compressive performance of novel L‐shaped and T‐shaped concrete‐filled square steel tube (L/T‐CFSST) column was assessed in this study. Ten L/T‐CFSST columns were tested to failure under axial load. The experimental data were used to determine various failure modes, bearing capacities, and load‐displacement curves. The test parameters included the section form, steel tube thickness, steel yield strength, and slenderness ratio. The axial compressive performance of the L/T‐CFSST column proved favorable, and each square steel tube showed strong cooperative performance. The failure mode of the stub column specimen (H/D ≤ 3) was strength failure caused by local buckling of the steel tube and that of the medium‐long column member (H/D > 3) was instability failure caused by overall bending of the specimen. A finite element analysis (FEA) model was established and successfully validated by comparison against the test results. Based on the FEA model, parametric analyses were conducted to investigate the effects of steel tube thickness, concrete strength, steel yield strength, and slenderness ratio. The ultimate loads obtained from the experiments and FEA were compared to the results calculated by the available design codes. A formula was established to calculate the axial compressive strength and stability bearing capacity of the L/T‐CFSST column accordingly. The calculation results are in close agreement with the FEA and experimental results, and the proposed formula may provide a workable reference for practicing engineers.

The soil discharged by an earth pressure balanced (EPB) shield machine reflects ground loss and controls surface settlement. In engineering, the discharge was mainly estimated by weighing the tunnelling spoil, however, human disturbance and information lag bring serious hidden security risks to tunnel construction. Through the analysis of conveying flow and force of screw conveyor, an energy model of interaction between screw conveyor and soil discharged was proposed and verified experimentally. Then, the energy model was combined with the discharge equation and the force balance equation, and a semi-analytical method to fast estimate the soil discharged of the EPB shield machine was proposed. Taking an EPB shield construction project as an example, according to the data of earth pressure, the torque and the rotation of the screw conveyor recorded by EPB shield machine, the real-time soil discharged of EPB shield machine can be accurately estimated. The mean absolute error (MAE) of this method is 3.177 × 10³ kg compared with the measured weight of tunnelling spoil, which verifies the rationality of the method and provides a method for further effective evaluation and control of ground loss.