Abstract
Piles act as settlement reducers in case of connected piled-raft foundation and hence decrease the settlements of the raft. The design concept of the connected piled-raft foundations is to lessen the number of piles and utilize the bearing capacity of the system piled raft. Due to significant straining actions at the pile head-raft connection, an alternative technique is proposed to disconnect the piles from the raft. A granular layer (cushion) beneath the raft is incorporated. The disconnection has a beneficial effect on reducing axial load compared to connected piles. For small piled rafts, nonconnected piled rafts show less stiffness than connected piled rafts, and the soil is highly stressed and shows greater raft settlement. In the case of the large piled raft, nonconnected piled rafts show greater settlement efficiency. Cushion stiffness was realized to be more substantial for a nonconnected piled raft with shorter piles than one with longer piles. The results show that the load transfer mechanism in a nonconnected piled raft is mainly governed by the thickness and stiffness of the cushion layer and by the stiffness of the subsoil.
Highlights
For given load circumstances, shallow foundations are acceptable foundations when suitable bearing stratum is present at a shallow depth. e use of deep foundations is required if the load from the structures would lead to excessive settlements
Numerical modelling was used to evaluate the effectiveness of nonconnected settlement reducer piles under the raft foundation (NC) in terms of settlement efficiency ratio, load sharing ratio of piles, and axial load distribution along the pile length. is research compares the performance of connected settlement reducer piles (PR) with nonconnected piles
It reduces the settlement by up to 40% for 16 nonconnected piles. e following conclusions can be drawn for conducted parametric studies: (i) Nonconnected piled raft foundation system is likely to be governed by the interposed layer stiffness and thickness
Summary
Shallow foundations are acceptable foundations when suitable bearing stratum is present at a shallow depth. e use of deep foundations is required if the load from the structures would lead to excessive settlements. Most conventional projects rely on assuming that piles were designed to carry the entire load of the structures In this case, a large number of piles were utilized. In [4], it is considered that for competent design of rafts with settlement-reducing piles, 80% of the pile capacity mobilization can be assumed under working load In this regard, a lower factor of safety can be applied to the geotechnical capacity of the piles, and the bearing capacity of the raft is adequate on its own. Most of them do not incorporate the effect of cushion and load sharing and carrying mechanisms of piles in a nonconnected piled raft foundation. The effects of variation in cushion thickness, pile number, raft thickness, cushion and subsoil stiffness on load sharing and settlement efficiency of nonconnected piles are studied in detail
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