The dynamic response law of a pile foundation in liquefied soil has always been a significant issue in the field of seismic engineering. This paper is based on a shaking table test of 2×2 straight pile groups and 2×2 inclined pile groups in nonliquefied sand and saturated sand with different thicknesses. The bending moment of pile in nonliquefied sand and saturated sand with different thicknesses was studied by applying the qian'an wave with a certain frequency and acceleration. It shows that the liquefaction of sand will cause the bending moment of pile body to increase. Under the same working condition, the bending moment of inclined pile is smaller than that of straight pile. The difference of bending moment at the bottom of pile is larger, and the difference is more obvious with the increase of the thickness of liquefied sand. Therefore, the inclined pile is more resistant to external load than the straight pile.

The research on the shaft resistance governing by the sliding and shearing mechanism between the pile-rock interfaces is always a hot issue in the research of rock-socketed pile. All existing theoretical methods assumed that the normal stiffness of the bore wall of rock around the pile is constant which based on the elastic solution of cylindrical cavity expansion in a finite medium during the increasing of the relative displacement of the pile-rock interface. However, rock is not an ideal elastic material. In order to illustrate this problem, this paper combined the cavity expansion theory and the original Hoek-Brown failure criterion conducted an elastoplastic analysis of rock-socketed piles during the relative displacement of the pile-rock interface increases and derived the stress field and displacement field in the elastic and plastic phase. And, based on a case validation illustrated the difference between the elastic and elastoplastic solution of the normal stress increment with different radial displacement of the pile-rock interface and stated that only using the elastic solution of normal stiffness will overestimate the increment of normal stress at the pile-rock interface, and then overestimate the shaft resistance which will cause the design unsafety.

Although the application of sheet piles has been expanding to non-temporary structures recently, their vertical performance has not been well understood as they have long been used for temporary retaining structures in which their horizontal performance is the main concern. In addition, the extra time and cost required for conducting the conventional load test has been a barrier to improve the situation. In this paper, simplified methods of static compressive and tensile load test using a press-in machine are introduced. Results of the simplified load test on five pressed-in piles in a soft alluvial soil are reported.

FRPC pile is a new type of composite pile formed by combining FRP material with traditional material. It has good physical and chemical erosion resistance, light weight, high strength and other advantages. Based on the particle image velocity measurement (PIV) technique, this paper studies the interaction between sand soil and FRPC pile by applying bidirectional horizontal load on the FRPC model pile embedded in sand soil. In the process of loading the FRPC model pile, a CCD high-speed industrial camera is used to take gray image of sand deformation around the test observation surface pile. DH3816 Strain Collecting Instrument was used to collect pile side strain, and image processing software PIVview2C was used to get displacement cloud picture. By analyzing the distribution of total displacement, horizontal displacement and vertical displacement of sandy soil under different loads, the micro mechanism of FRPC pile and sandy soil is clarified. The distribution of pile side moment was studied, and the macro mechanism of FRPC pile and sandy soil is clarified.

It is significant in practical design that rationally analyzing and comparing the relationship in terms of magnitude between the sum of thrust in double-row piles and the thrust on single-row piles in large-scale landslide control project. According to the transfer coefficient method based on limit equilibrium principle, the sum of upslope thrust on double-row piles and upslope thrust on single-row piles, as well as the sum of net thrust upon double-row piles and net thrust upon single-row piles are analyzed and compared. The results show that the relationship between the sum of thrust on double-row piles and the thrust on single-row piles is closely correlated with the position of the rear piles, with the ratio of resistance force in front of the piles over the thrust behind piles, and with the load transfer factor of thrust between soil slices. When the rear piles are located at the resisting section of the slip surface, the sum of the upslope thrust on double-row piles is greater than the upslope thrust on single-row piles. If the entire slip surface is a plane, the sum of net thrust upon double-row piles does not exceed that on single-row piles.

In the construction of offshore civil engineering structures or the exploitation of energy and mineral resources in the shallow part of the seabed, it is necessary to investigate mechanical properties of the foundation ground or various characteristics of reservoirs and mineral deposits. Thus, Vibro Sampling and Cone Penetration Test (VS-CPT) was devised for economical and effective submarine geotechnical investigation of the surface layers, about 20 mbsf. To examine an appropriate shape of the probe, model probes were made and driven into the model sand ground. As the results demonstrated that the drivability and sample recovery were not bad when the aperture ratio of the probe, Ra, was 0.5 or higher, a prototype apparatus (Mark 1) was manufactured with Ra = 0.67. Driving test using a vibratory hammer on a saturated dense sand ground, however, revealed that the tip of the sampler was clogged in the surface layer, and the drivability was low. In addition, the cone resistance is found not suitable for sounding as its measured values were zero.

Casting bored piles in Karst areas is often problematic, since the concrete can penetrate through cave systems or underground stream channels, resulting in poor construction quality of bored piles with insufficient bearing capacity. A new type of bored pile is proposed to cast the concrete within a rubber/geotextile bag in the bored hole, which can restrict the loss of concrete through stream channels in Karst areas. In this study, model-scale laboratory tests were conducted to assess the feasibility of casting rubber/geotextile bag-sealed bored pile and to evaluate its bearing behavior. The measured results for a bag-sealed pile within Karst regions and a normal pile with equal diameter in a uniform ground without stream channels were compared. It demonstrates that casting bored pile within a big is an effective solution to increase the bearing capacity of pile under static loads. The ultimate bearing capacity of bag-sealed pile is about 1.5 times that of equal-diameter pile. The settlement of bag-sealed pile is much smaller than that obtained for equal-diameter pile under the same loading conditions.