The results of series field test on piles on strategic oil and gas site in Kazakhstan are presented in this paper. The test include: static load test in accordance with ASTM and Kazakhstan standards (GOST), dynamic load test in accordance with GOST and pile driving analyzer (PDA) in accordance with ASTM. The difference of standards procedures and test results is presented.

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This paper presents an experimental study of the plugging effect on the capacity of open-ended piles installed in sandy soil. Full-scale tests, including dynamic and static axial-compression load tests, were carried out on three instrumented piles with different diameters (508.0, 711.2 and 914.4 mm). To measure the outer and inner shaft resistances acting on the piles, a double-walled system was utilized with instrumented strain gauges on the outside and inside walls of the pile. The results of field tests show that the inner shaft resistance was mostly mobilized at the location between the pile tip and 18 - 34% of the total plug length. It was found that the soil plugging in the lower portion has influence on the inner shaft resistance. In addition, a new design approach that can predict the degree of soil plugging and the inner skin friction is proposed. Based on the plugging measurements, a linear relationship between the PLR and incremental filling ratio (IFR) was proposed. Based on the results of the full-scale field pile load tests, the inner skin friction of the open-ended piles was proposed as a function of the IFR and pile diameter. The proposed method can predict the degree of soil plugging and the inner skin friction of open-ended piles and be selected as convenient option in engineering field.

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An open-ended pile can produce a bearing capacity similar to a closed-ended pile depending on inner frictional resistance, Q_in, which depends on the degree of soil plugging. The degree of soil plugging may depend on many factors including pile outer diameter (D), tip thickness (t), sleeve height (l) and relative density (D_r). In this research, we studied the effects of t, D and l on bearing capacity using laboratory scale model piles. The tests were conducted on a medium dense sandy ground using model piles with different values of D, t and l. The results showed that bearing capacity increases with t, which can be attributed to increase in annular area. They also showed that soil plug height, h is dependent of l for larger diameter piles. The results of incremental filling ratio (IFR) showed that penetration of straight piles (i.e., no sleeve) is closer to unplugged state than the piles with a sleeve. While Q_in is independent of l for smaller diameter piles (D=30 mm), it is dependent of l for larger diameter piles (D=50 mm). The results of Q_in suggested that as large as 50% of Q_t (Q_t is total resistance) is contributed by Q_in even with a small l (e.g., 10 mm) for smaller diameter piles, while Q_in in larger diameter piles increases with l and requires 2D of l to produce a large as 50% of Q_t by Q_in

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Suction caisson is widely used to support offshore structure. However, this type of foundation may not provide sufficient resisting capacity economically under external loads. Recently, to give an increased capacity on the foundation, hybrid foundation concept was proposed to satisfy engineering needs as well as cost reduction of structures. Hybrid foundation concept is combination of skirted mat and suction caisson(s). Suction caisson(s) is fitted on the mat foundation intended to increase load capacity. This paper investigates the behavior of a hybrid suction foundation installed in sand layer for vertical and lateral loads, respectively. A series of centrifuge test have been conducted to assess the load capacity of the hybrid foundation and compared to those of the conventional single suction caisson. The primary goal of this study is to comprehend the effect of the mat compartment on foundation behavior under loading directions, and corresponding bearing capacity. Finally, feasibility of the hybrid foundation for offshore foundation was confirmed.

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In the early stages of design and analysis of structures that are supported by piled foundation, the stiffness of piles is often required to be evaluated. Without going through the complication of pile- soil system, piles can be simulated as springs if the load- settlement behavior of each pile is accurately determined. In this paper, the governing differential equation of pile displacement problem is implicitly solved through a sequence of computation steps. A simple Matlab M- file is built up to perform the computations and present the analysis results. The proposed computation scheme accounts for the nonlinearity of soil mechanical properties and for the non-homogeneity of the soil profile along the pile depth. Consequently, an iterative loop of recalculation and tolerance checking is used and convergence is achieved very rapidly. The procedure is then applied to calculate the pile- settlement behavior of an 1800 mm diameter and about 18m length concrete pile installed in dense to very dense sandy soil. The pile which has a working load of about 6670 kN, is one of the New Hindiya railway bridge piles located in the central part of Iraq. The pile was in situ tested under an axial load of about twice the working load. The results obtained by the proposed computation method compared well (the deviation is less than 10%) with the test results in terms of pile load settlement behavior. This may enhance the reliability of the proposed method.

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This paper presents a method to estimate the bearing capacity of a strip footing embedded in a geosynthetic reinforced granular bed over soft non-homogeneous ground, i.e., increase of undrained shear strength with depth, stabilized with granular trench. Madhav and Vitkar’s solution for bearing capacity of granular trench-supported strip footing in soft ground together with Meyerhof’s punching failure mechanism for dense sand overlying soft clay, extended to include the effect of axial tension in the reinforcement, form the basis of the analysis. A parametric study is performed and charts are developed to quantify the contributions of various parameters on the degree of bearing capacity improvement. The results of the present study are compared with experimental results from literature.

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In this paper, the behavior and performance of two instrumented barrette piles socketed in gravel formation in Taipei are evaluated based on the results of axial loading tests. The tests include two compressive tests conducted on the barrette piles of 44m long. One of the piles with toe grouting was socket 6m into gravel layer and the other pile without toe grouting was socket 3m into gravel layer. The load versus displacement curve at the pile head and t-z curves along the shaft, especially for the part socketed in gravel layer, are main concerns and are presented and discussed in the paper. The t-z curves interpreted from the measured data along depth are also simulated by the hyperbolic model.

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