Behavior Of Rafts Research Articles

Piled raft foundations: design and applications

In situations where a raft foundation alone does not satisfy the design requirements, it may be possible to enhance the performance of the raft by the addition of piles. The use of a limited number of piles, strategically located, may improve both the ultimate load capacity and the settlement and differential settlement performance of the raft. This paper discusses the philosophy of using piles as settlement reducers and the conditions under which such an approach may be successful. Some of the characteristics of piled raft behaviour are described. The design process for a piled raft can be considered as a three-stage process. The first is a preliminary stage in which the effects of the number of piles on load capacity and settlement are assessed via an approximate analysis. The second is a more detailed examination to assess where piles are required and to obtain some indication of the piling requirements. The third is a detailed design phase in which a more refined analysis is employed to confirm the optimum number and location of the piles, and to obtain essential information for the structural design of the foundation system. The selection of design geotechnical parameters is an essential component of both design stages, and some of the procedures for estimating the necessary parameters are described. Some typical applications of piled rafts are described, including comparisons between computed and measured foundation behaviour.

Small rafts of xenon physisorbed on Pt(111)

The behavior of small rafts of xenon (<50 particles) is illustrated. Events which involve collective motion of raft atoms are shown to occur. These events are persistent below a transition temperature and are not persistent above this temperature. A video of the events is available.

The use of retinoic acid to probe the relation between hyperproliferation-associated keratins and cell proliferation in normal and malignant epidermal cells.

When cells from normal human epidermis and from the human squamous cell carcinoma line SCC-13 were seeded on floating rafts of collagen and fibroblasts, they stratified and underwent terminal differentiation. Although the program of differentiation in SCC-13 cells was morphologically abnormal, the cultures resembled normal epidermal raft cultures by expressing the terminal differentiation-specific keratins, K1/K10, and by restricting their proliferative capacity to the basal-like cells of the population. In addition, the differentiating cells of both normal and SCC-13 raft cultures expressed keratins K6 and K16, which are not normally expressed in epidermis, but are synthesized suprabasally during wound-healing and in various epidermal diseases associated with hyperproliferation. While the behavior of normal and SCC-13 rafts was quite similar when they were cultured over normal medium, significant biochemical differences began to emerge when the cultures were exposed to retinoic acid. Most notably, while the SCC-13 cultures still stratified extensively, they showed a marked inhibition of both abnormal (K6/K16) and normal (K1/K10) differentiation-associated keratins, concomitantly with an overall disappearance of differentiated phenotype. Surprisingly, the reduction in K6/K16 in retinoid-treated SCC-13 cultures was not accompanied by a decrease in cell proliferation. Using immunohistochemistry combined with [3H]thymidine labeling, we demonstrate that while the expression of K6 and K16 are often associated with hyperproliferation, these keratins are only produced in the nondividing, differentiating populations of proliferating cultures. Moreover, since their expression can be suppressed without a corresponding decrease in proliferation, the expression of these keratins cannot be essential to the nature of the hyperproliferative epidermal cell.

A molecular dynamics study of the behaviour of xenon physisorbed on Pt(111): Coverages less than one monolayer

In recent He beam studies of Xe adsorbed on Pt(111) at less than monolayer coverages the xenon has been found to exist in incommensurate and commensurate phases both rotated by 30° with respect to the substrate. We present here molecular dynamics studies of small rafts of xenon particles on Pt(111). We find evidence that the corrugation of the xenon-platinum potential of interaction can lead to an incommensurate phase but that, using reasonable interaction potentials, the corrugation cannot lead to a commensurate phase which can exist over a range of temperatures. A variety of molecular dynamic studies of raft behaviour are presented.

The behaviour of an impermeable flexible raft on a deep layer of consolidating soil

AbstractAnalytic solutions to the problem of the time‐settlement behaviour of raft foundations have been limited in the past to flexible or rigid loadings, and have treated the foundation as being completely permeable. In this paper, solutions are presented for smooth circular rafts of any flexibility causing consolidation of a deep homogeneous clay layer, where the raft may be considered permeable or impermeable.Results for the time‐dependent behaviour of contact stresses, pore pressures, raft displacements and moment in the raft are presented.

Time-settlement behaviour of rafts of finite flexibility : Proc 4th Australia-New Zealand conference on geomechanics, Perth, Western Australia, 14–18 May 1984 V1, P159–164. Publ Barton: Inst of Engineers, 1984

A method is presented for computing the time-settlement behaviour of circular rafts of finite flexibility, resting on soil layers of finite depth. Results are presented for the time-settlement behaviour of rafts on soil layers of various depths, as well as for the development of moment in the raft with time. (Author/TRRL)

The time‐deflection behaviour of a circular raft of finite flexibility on a deep clay layer

The behaviour of a flexible circular raft resting on a deep clay layer is examined. The clay is idealized as a porous elastic medium, and a solution is obtained by calculating the response of the soil to a general reaction distribution and then determining the precise form of the distribution by invoking displacement compatability at the raft- soil interface. Results are presented for the time- deflection behaviour of rafts of various stiffnesses along with examples of the moment distributions and differential deflections which develop in the raft as consolidation of the clay layer proceeds. (Author/TRRL)

Influence of soil inhomogeneity on raft behaviour : Technical note. 6F, 2T, 7R. SOILS AND FOUNDATIONS, V14, N1, MAR. 1974, P61–70

Influence of soil inhomogeneity on raft behaviour : Technical note. 6F, 2T, 7R. SOILS AND FOUNDATIONS, V14, N1, MAR. 1974, P61–70