An experimental program is conducted on model piled rafts in sand soil. The experimental program is aimed to investigate the behavior of raft on settlement reducing piles. The testing program includes tests on models of single pile, unpiled rafts and rafts on 1, 4, 9, or 16 piles. The model piles beneath the rafts are closed ended displacement piles installed by driving. Three lengths of piles are used in the experiments to represent slenderness ratio, L/D, of 20, 30 and 50, respectively. The dimensions of the model rafts are 30cm×30cm with different thickness of 0.5cm, 1.0cm or 1.5cm. The raft-soil stiffness ratios of the model rafts ranging from 0.39 to 10.56 cover flexible to very stiff rafts. The improvement in the ultimate bearing capacity is represented by the load improvement ratio, LIR, and the reductions in average settlement and differential settlement are represented by the settlement ratio, SR, and the differential settlement ratio, DSR, respectively. The effects of the number of settlement reducing piles, raft relative stiffness, and the slenderness ratio of piles on the load improvement ratio, settlement ratio and differential settlement ratio are presented and discussed. The results of the tests show the effectiveness of using piles as settlement reduction measure with the rafts. As the number of settlement reducing piles increases, the load improvement ratio increases and the differential settlement ratio decreases

A three-dimensional moisture diffusion and volume change model Suction heave (SUCH) is described. The model SUCH is capable of predicting soil moisture changes in terms of soil suction and the resulting volume changes (shrink/heave) in expansive soils under a covered area (e.g., flexible slab model) with respect to time when the supporting soil mass is subjected to different edge conditions that commonly cause moisture changes (e.g., climate, trees, ponded water). The moisture movement in unsaturated soils model was based on Mitchell’s diffusion equation for soil suction and the volume changes (shrink/heave) calculation was based on Wray’s model. The model SUCH was validated against field data from four test sites in three countries (i.e., United States, Saudi Arabia, and Australia) with widely varying climatic and soil conditions. In each of these widely diverse sites, the moisture diffusion and volume change model SUCH was shown to be valid.

The behavior of footings resting on soft clays reinforced by floating granular piles is assessed in terms of its bearing capacity and settlement. This paper presents the results of experimental work on model footings resting on soft clay reinforced by floating granular piles. Three model footings of dimensions 10 × 10, 10 × 15 and 10 × 20 cm are tested. The granular piles were installed using the cased-borehole method by compacting granular materials into a preformed hole. In all the studied cases, the length of granular piles and thickness of soft clay bed are constant and equal to 20 cm and 30 cm, respectively. The parameters that were varied are the diameter of the granular piles, the numbers of the granular piles, the area replacement ratio and the materials of the granular piles (i.e., sand and stone). The improvement in the bearing capacity is represented by a nondimensional parameter called the improvement ratio, IR, and the reduction in settlement is represented by a non-dimensional factor, called settlement ratio, SR. The effect of different parameters on the improvement ratio, IR, is presented and discussed. Empirical equations are introduced to calculate the improvement ratio and settlement ratio as a function of area replacement ratio. The results of the tests show that the improvement ratio, IR, increases and settlement ratio, SR, decreases as the number and diameter of granular piles increase or as the area replacement ratio increases. Generally, the IR ratio of footings resting on floating stone piles is greater than that of floating sand piles.