Bin Huang

Model test is a common method to study the bearing peculiarity of pile foundation. The influence of overlying soil thickness and overburden pressure on the bearing capacity of soft rock-socketed pile should be considered in the physical model test of mini piles in soft rock. In this paper, the influence of coverage on the bearing characteristics of rock-socketed sections is studied by finite element analysis, and the modelling method of equivalent overburden pressure is proposed. This method can be used to study the carrying peculiarity of soft rock-socketed pile and reveal the failure mechanism of pile tip. The development of pile model test technology considering overburden pressure promotes more scientific design methods for pile foundation.

The failure mode should be taken into account in the analytical solution for pile base resistance. In order to determine the pile’s failure pattern in soft rock, the graphical model test method is used. That the compression zone below the pile base in soft rock is compatible with the spherical cavity expansion is shown. An improved calculation model for the ultimate base resistance may be developed by considering the force balance of the rigid cone under the pile-end in the ultimate stress state and the limit pressure required to expand a spherical cavity. To account for the influence of socket length, the limiting pressure for the spherical cavity expansion in infinite space is adjusted to that in semi-infinite space. The ultimate resistance of a base is computed by factoring in the length effect. The normalization of the base resistance-displacement relation is provided based on the findings of pressure chamber experiments on pile load-settlement, which are independent of socket length and overburden pressure. This semi-empirical technique is verified via the use of pressure chamber experiments and field testing of piles in soft rock.

Using the model test technology of the rock-socketed pile in soft rock in consideration of the influence of the overburden, the physical model test with different overburden pressure and different rock-socketed depth is carried out. The vertical bearing mechanism and law of the rock-socketed pile in soft rock are analysed through the results of axial force distribution, shaft resistance distribution, load sharing ratio of shaft resistance and base resistance, shaft resistance relationship between shaft resistance and displacement, and relationship between base resistance and displacement, etc. Based on the accurate qualitative analysis of indoor model test results, and combined with the measured data and engineering experience at home and abroad, the vertical bearing characteristics of the rock-socketed pile in soft rock are comprehensively interpreted, and the vertical bearing mechanism and its influencing factors of the rock-socketed pile in soft rock are revealed.

Asphalt concrete is a typical rheological material, which is hard brittle at low temperature and reflects soft plastic facture at high temperature; the temperature has a great influence on the mechanical properties of asphalt concrete. In order to eliminate the environmental pollution caused by hot asphalt construction, cationic emulsified asphalt can be used. This paper transforms the temperature control system for static and dynamic triaxial test equipment, which has achieved static and dynamic properties of emulsified asphalt concrete under different temperatures, and researched the temperature sensitivity of emulsified asphalt concrete materials including static stress‐strain relationship, static strength, dynamic modulus of elasticity, damping ratio, and so on. The results suggest that (1) temperature has a great influence on the triaxial stress‐strain relationship curve of the asphalt concrete. The lower the temperature, the greater the initial tangent modulus of asphalt concrete and the higher the intensity; the more obvious the softening trend, the smaller the failure strain of the specimen and the more obvious the extent of shear dilatancy. When the temperature is below 15.4°C, the temperature sensitivity of the modulus and strength is stronger significantly. (2) With the temperature rising, the asphalt concrete gradually shifts from an elastic state to a viscoelastic state, the dynamic modulus gradually reduces, and the damping ratio increases. When the temperature is above 15.4°C, the temperature sensitivity is obviously stronger for the dynamic elastic modulus and damping ratio. (3) The static and dynamic properties of asphalt concrete are very sensitive to the temperature. The test temperature should be made clear for the static and dynamic tests of asphalt concrete. The specimen temperature and the test ambient temperature must be strictly controlled.