Geotechnical centrifuge modelling is an advanced physical modelling technique for simulating and studying geotechnical problems. It provides physical data for investigating mechanisms of deformation and failure and for validating analytical and numerical methods. Due to its reliability, time and cost effectiveness, centrifuge modelling has often been the preferred experimental method for addressing complex geotechnical problems. In this ZENG Guo-xi Lecture, the kinematics, fundamental principles and principal applications of geotechnical centrifuge modelling are introduced. The use of the state-of-the-art geotechnical centrifuge at the Hong Kong University of Science and Technology (HKUST), China to investigate four types of complex geotechnical problems is reported. The four geotechnical problems include correction of building tilt, effect of tunnel collapse on an existing tunnel, excavation effect on pile capacity and liquefied flow and non-liquefied slide of loose fill slopes. By reporting major findings and new insights from these four types of centrifuge tests, it is hoped to illustrate the role of state-of-the-art geotechnical centrifuge modelling in advancing the scientific knowledge of geotechnical problems.

This paper presents a study of flow characteristics in high-lift siphon drains. A laboratory test was conducted to investigate the effects of hose diameter and flow velocity on siphon drainage. Three types of water flow were observed and analyzed. The experimental results show that the flow characteristics of siphon drainage are significantly influenced by the hose diameter. Water flows in the form of a wall pressing flow in a large diameter siphon hose (e.g., larger than 5.0 mm) under low flow velocity, which leads to discontinuous siphon drainage. However, water flows in the form of an integral slug flow in a small diameter siphon hose (e.g., smaller than 4.0 mm) under low flow velocity, which leads to continuous siphon drainage. Based on experimental observations, a thermodynamic derivation of the threshold of siphon hose diameter for continuous siphon drainage was analytically conducted. In slope engineering, a 3.6 mm polyurethane (PU) hose is recommended for siphon drainage.

The mechanical performance of textile reinforced concrete (TRC) thin-plate under high temperature conditions was investigated using three-point bending tests. The influence of polypropylene (PP) fiber addition on the out-of-plane load capacity of TRC thin-plate after high temperature treatment was also studied. The results showed that the thermostability of TRC thin-plate with textile impregnated with epoxy resin was not good, but that the out-of-plane load capacity of TRC thin-plate after high temperature treatment could be improved by increasing the plate thickness or the textile distribution rate. Under normal temperature and a high temperature of 120 °C, the out-of-plane load capacity of specimens could be increased and cracks better distributed by mixing the TRC with PP fiber. However, the out-of-plane load capacity of TRC thin-plate under a continuous high temperature of 200 °C was not much affected by the addition of PP fiber. The result of a microcosmic scanning electron microscope (SEM) test showed that the main reason for the interfacial adhesive failure between the textile and the original concrete substrate was the degradation of the epoxy resin under high temperature.

Based on the finite element method (FEM) and the Lagrange equation, a novel nonlinear model of a double disc rotor-seal system, including the coupled effects of the gravity force of the discs, Muszynska’s nonlinear seal fluid dynamic force, and the mass eccentricity of the discs, is proposed. The fourth order Runge-Kutta method is applied to solve the motion equations of the system and numerically determine the vibration response of the center of the discs. The dynamic behavior of the system is analyzed using bifurcation diagrams, time-history diagrams, axis orbit diagrams, Poincaré maps, and amplitude spectrums. With the rotor speed increasing, the system presents rich forms including periodic, multi-periodic, quasi-periodic, and chaotic motion. We also discuss the effects of the distance between the two discs, the mass of the discs, seal clearance, seal length, and seal drop pressure on the dynamic behavior of the system. The numerical results demonstrate that a symmetrical disc structure, small disc mass, proper seal clearance, long seal length and high seal drop pressure can enhance the stability of a double disc rotor-seal system. The results provide a theoretical foundation for the design of multi-stage sealing systems.

Nowadays, brake disc manufacturers are seeking new finishing techniques to offer economical solutions to their customers and so become more competitive. The elimination of the surface spiral pattern after turning operation is a challenge to avoid braking problems at the early life of the component. This paper presents a practical low-cost solution to finishing this kind of component. Concretely, a detailed study of the brushing process as an alternative solution to the conventional grinding process is performed. The limited literature regarding this topic implies the necessity of a full study of the process prior to any industrial application. The influence of process variables on the final surface was analyzed in this work. In addition, the tool wear and tool life behavior, the influence of the abrasive type used and the originating forces during the process were taking into account. Once the process was established, various prototypes were finished in order to check the feasibility of the process and to pass the required quality control. Results show that brushing is a feasible and economical alternative for brake disc finishing. The surface quality obtained was shown to be equal or better than grinding, with reduced costs and manufacturing time.

The aim of this study is to characterize the interfacial fracture toughness of a micro-lattice core based sandwich structure from quasi-static to dynamic rates of loading. The modified three-point bend (MTPB) sandwich beam was used to characterize the interfacial properties of these sandwich structures. Dynamic tests were undertaken of up to 3 m/s using a purpose-built instrumented drop-weight impact tower. Data reduction was accomplished through the use of a compliance calibration procedure similar to that used for characterizing the delamination resistance of composites. The flexural properties of sandwich beams were investigated through three-point bend tests at a cross-head displacement rate of up to 3 m/s. A detailed examination of the impact region highlighted the failure processes in these systems and this was related to the data from the quasi-static flexural tests. The globalized deformation and energy absorption during progressive were also discussed.

A riverbed topographic survey is one of the most important tasks for river model experiments. To improve measurement efficiency and solve the riverbed interference problem in traditional methods, this study discussed two measurement methods that use digital image-processing technology to obtain topographic information. A new and improved approach for calibrating camera radial distortion, which comes from originally distorted images captured by our camera, was proposed to enhance the accuracy of image measurement. Based on perspective projection transformation, we described a 3D reconstruction method based upon multiple images, which is characterized by using an approximated maximum likelihood estimation method (AMLE) considering the first-order error propagation of the residual error to compute transformation parameters. Moreover, a theoretical derivation of 3D topography according to grey information from a single image was carried out. With the diffuse illumination model, assuming that the ideal grey value and topographic elevation value are positively correlated, we derived a novel closed formula to explain the relationship of 3D topographic elevation, grey value, grey gradient, and the solar direction vector. Experimental results showed that our two methods both have some positive advantages even if they are not perfect.