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By P. Davies

The Hillside Smelter presently under construction at Richards Bay, Republic of South Africa, will be, on completion, the fifth largest aluminium smelter in the world. The site selected for this plant is underlain by sandy soils of variable density to depths of 30m or greater. In order to firmly establish pile founding depths required for alternative pile types in the variable subsurface conditions prevailing across the site, a pre-construction test piling programme was conducted incorporating piles instrumented with resistance strain gauges. The results allowed analysis of the relative contributions of end-bearing and shaft friction to the overall bearing capacity of each pile type and permitted comparison with the predictions of conventional static bearing capacity analyses. Conformance with acceptance criteria in respect of allowable pile head movements for single piles was also examined.

Jan 1, 1996

By K. C. Foye

Use of load and resistance factor design (LRFD) of foundations is growing, from offshore applications to bridge applications and beyond. The development of load and resistance factors for design has traditionally relied on calibration to traditional factors of safety. This technique, however, offers little insight into the challenges of pile design. This paper discusses an approach to LRFD factor development that seeks to isolate the various sources of design uncertainty. Using this approach, reliability analysis is used to develop resistance factors for the design of driven pipe piles in sand. These findings shed light on many aspects of the ongoing discussion of how LRFD can be successfully applied to pile design.

Jan 1, 2008

By Subrata Ray

A large no of power stations are being set up in Chandrapur area having coal deposits. Several industries are also coning up in this area. The subsurface is geologically formed under Gondwana system and consists of shale strata at depths ranging from 8 to 12 m. The stress deformation characteristics of shale exhibits wide variation because of it's geological origin. In view of this, a study was conducted on bored cast in-situ piles installed for a Switch yard project to evaluate load settlement characteristics of three test piles to understand the probable engineering behaviour of the material at the tip and the sides. An approach is developed to simulate the load settlement behaviour as observed in the field, theoretically. This is based on the concept of load transfer. The fit is obtained by varying the parameters, thus may be considered as iterative in nature. The theoretical curves closely matched the observed curves. The results of this study are presented in this paper.

Jan 1, 1996

By D. X. Xu

A pump station was constructed at the food of a steep mountain, very close to a riverside. To protect the pump station from being washed out, and to guarantee the stability of the steep hillside behind the pump station and the safety of the foundation pit when the station was built, cast-in-place R.C. diaphragm walls (Fig. 1) were clesigned in front of and on both sides of the pump station. This wall was 130m long, 0.8m wide and 29m deep. The diaphragm walling on both sides of the pump station served to prevent landslides and to fix anchor piles. The 55m long diaphragm walling in front of the pump station served as a temporary shuttering which kept earth and prevented water from permeating when the pump station was under construction. After the pump station project was finished, static blasting method was used to blow up the wall body which was 10m beneath the ground so that the water from the river could come into the pump station. The remaining wall body below this level was kept to prevent soil from being washed out. [ ]

Jan 1, 2010

By Alan J. Lutenegger

A series of tension tests were performed on prototype scale steel pipe piles at two sites to evaluate the influence of scale and pile plugging on the unit skin friction developed in axial tension. The first site consisted of a clean medium dense fine sand above the water table. The second site consisted of a loose silty sand with the water table within about 0.5 m of the ground surface. Pile load tests performed at each of the sites included piles with diameters ranging from 73 mm to 114.3 mm, which may be considered driven "micropiles". At the first site, pile lengths of 6.1 m were used; at the second site, pile lengths of 9.1 m were used. Some of the piles were driven open-ended while others were fitted with a conical tip to form a closed end. During installation, pile plugging measurements were taken on the open-ended piles after each 0.30 m of penetration. The piles were allowed to rest for a period of about 30 days after driving prior to performing the axial uplift load tests to failure. The results indicate that in the medium dense fine sand the unit skin friction developed in tension is dependent on both the amount of plugging that occurs and on the size of the pile, which was not the case for the loose silty sand.

Jan 1, 2000

By Haijian Fan

Currently, deep foundation designs for the service limit state are deterministic in nature. The settlements and lateral deflections of deep foundations are calculated by means of numerical techniques whereby the foundation-soil interactions are characterized by discrete load transfer curves such as t-z or p-y curves. The noted deficiency of the deterministic approach is that the uncertainties arising from various sources, such as soil properties and model errors are not considered. To address this deficiency, a performance-based reliability design methodology is developed using Monte Carlo statistical methods. The performance based design criteria are defined in terms of the specified allowable displacement. The input to the numerical solution techniques, including the soil strength parameters, unit weight of the soil are relevant to the generation of the load transfer curves are treated as random field. The well established random field generator algorithm, local averaging subdivision, is used to generate random samples of input, where the mean values, variances, the probability distribution, and correlation structures are required statistical parameters for these random variables. The objective of the performance based reliability design is to determine the optimized foundation dimensions so that the probability of failure is less than the target probability of failure. The probability of failure by the Monte Carlo approach is simply the ratio of the number of unsatisfactory performance to the sample size. A numerical example for laterally loaded drilled shaft is given to illustrate the application of the methodology. The incorporation of the correlation length is shown to be critical for properly accounting for the site soil spatial variability.

Jan 1, 2017

By V. Tang

In this paper, Chinese economic situation are estimated and prospective developments predicted to assist those US firms who have been trying to do business in China, or are considering to pursue the China market.

Jan 1, 2010