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The dynamic characteristics of the flow around the pile directly determine the distribution law of the force of the flow on the pile, which is the basis of the calculation of the flow load of the hydraulic structure. At present, the model test and numerical simulation methods are mainly used to study the flow characteristics around the pile. There are problems of model scale effect and test accuracy in the laboratory model test, and inherent problems in the numerical simulation method, such as the determination of medium parameters, mesh division, and boundary conditions. Therefore, the research results cannot reflect the actual situation of the interaction between water flow and pile. This paper developed a field test system for measuring the hydrodynamic pressures on surface of piles which are the vital foundations of wharves under superhigh Reynolds number. And the analysis methods of in-situ data, which can realize the multifunction including calibration and transformation for test data, frequency and time-domain statistical analysis process, were put forward according to the theory of stationary random process and mathematical statistics method. A representative frame wharf located in the upper reaches of the Yangtze River was performed as a case study, and the developed system was utilized to operate the in-situ test on this practice. Application showed that the field test system and the analysis methods can be applied to obtain the more accurate distribution of the pile surface hydrodynamic pressure. And the drag coefficient in wharf field ranged from 0.30 to 0.40. These findings in this paper may provide significant technical support for the in-situ test in similar structures and some reference for drag force calculation of flow around pile in the engineering design.

The shear capacity of the steel-concrete interface (SCI) of concrete-filled steel tubular piles (CFSTs) degrades due to the cyclic shear action of external loading and unloading and can result in a reduction in the bearing capacity. To explore the shear strength degradation characteristics of the steel-concrete interface under cyclic shear, cyclic shear tests for three roughness types and under four different normal stresses were carried out by using a large-scale repeated direct shear test system. The characteristics of the shear load-displacement curve and failure mode of the SCI under external cyclic shear were analyzed, and the influence of the roughness and normal stress on the SCI shear strength degradation was explored. The results indicate that the CFSTs experienced shear failure in the first three shear cycles and then exhibited wear failure. The peak shear load of the SCI increases exponentially with increasing normal stress and decreases logarithmically with increasing cyclic shear time. A larger interfacial roughness and normal stress results in a faster interfacial shear strength ratio (τfn/τf1) weakening during the first three shear cycles, and with an increase of the cyclic shear times, the weakening rate is reduced.

The failure of vertical concrete shafts in the deep alluvium zones is always a troublesome technical problem in coal mines. There is lack of practical failure criteria for such shafts. Therefore, the method of establishing failure criteria of shafts based on the method of ultimate strain was proposed. By regarding concrete as a frictional geomaterial, the formula for the plastic ultimate strain of concrete was constructed according to the theory of generalised plastic mechanics. Furthermore, the ultimate strain when concrete failure was determined using numerical limit analysis method. The numerical limit strain analysis method can be used as a quantitative failure criterion for a concrete shaft. It can directly determine the limit state and failure position. By exploring the shaft deformation during the reduced groundwater level of quaternary aquifers by applying numerical limit analysis method, the failure procedure of concrete shaft was reproduced. It was revealed that the damage to the soil around the shaft preceded that to the shaft; the reduction in groundwater level of aquifers can damage the shaft, while the stress-relief groove delays the failure of the shaft and shifts the failure zone to a greater depth. On condition that water level decreased by 25 m, the sand layer at a burial depth of 158–174 m was damaged; in the case that water level was reduced by 27 m, the shaft at a burial depth of 181–182 m was damaged. After setting a stress-relief groove on the shaft, failure occurred when the groundwater level was decreased by 38 m, implying that the stress-relief groove can release the vertical stress on the shaft.

The static and dynamic compression mechanical properties of the prefabricated artificial filled rock joints specimens with different fillings and different joint thicknesses are tested, respectively. Then, the strength, deformation, wave propagation and energy dissipation laws of the filled joints are analyzed. The experimental results show that the static and dynamic compression strength of filled joints increases with the strength of filling materials while decreases with the filling thickness. The deformation characteristics of filled joints under static and dynamic compression are positively correlated with the properties of filling materials and the thickness of filled joints. With the increasing of the filling thickness, the reflection coefficient increases while the transmission coefficient decreases. With the increase of the strength of the fillings, the reflection coefficient decreases while the transmission coefficient increases. The energy dissipation ratio decreases with the increase of the filliing thickness and increases with the increase of the strength of the filling material.

In the geotechnical engineering, the tensile failure of soil is disregarded for a long time. Actually, the tensile strength of soil is very low and the tensile failure really occurs, especially in the slope engineering. The limit height and active earth pressure of slope will change when considering the effect of tensile failure. In this paper, we try to figure out the limit height and active earth pressure of slope by using the new numerical limit analysis method, the ultimate strain method. The results, without considering tensile failure and with considering tensile failure, are compared with the analytical solutions. It is proved that the ultimate strain method is credible and feasible in the slope engineering. The result shows that the tensile strength has a great influence on the limit height of the unsupported slope, but little influence on supported slope. It also has obvious influence on the active earth pressure of supported slope when the value of tensile strength is small, and the smaller the tensile strength the larger the influence. But the earth pressure becomes stable when the value of tensile strength is over 10 kN, and it is much close to the one calculated without considering the tensile failure.