Piled Raft - An Effective Foundation Design Method for High-Rise Buildings in Ho Chi Minh City, Viet Nam

Abstract

Nowadays, the wave of construction of high-rise buildings, which usually use the concept of piled group foundation in their design, has increased in Ho Chi Minh City as well as other cities in Viet Nam. In this study, settlement, the load shared by the raft, and the behavior of the piled raft were considered via monitoring settlement and the Poulos-Davis-Randolph (PDR) method where the settlement of a varying number of piles, the pile length, and raft embedment were determined. The results of settlement monitoring of a high-rise building in Ho Chi Minh City showed that the foundation design of this building was conservative, with a ratio of allowable-to-actual settlement of 9.3. In the simplified method, the proportion of load share by raft was 2.8% (which was ignored in the piled foundation concept), with the settlement results being in good agreement with the measurement results. The parametric analysis indicated that the piled spacing/piled diameter was 5 -7 times the recommended optimum value. Furthermore, increasing the pile length decreased settlement. The pile length was equal to 30 times the pile diameter, which was effective for the settlement ratio. In addition, the raft load share reached 30% of the applied load when the raft was put in the second layer of stiff-to-very-stiff clay. The study indicated the simplified method was effective for evaluating the preliminary conditions of the foundation, settlement, and that a piled raft was feasible for Ho Chi Minh City's subsoil geology.

Load Sharing Mechanism of Bamboo Pile Mattress for Reinforced Embankment

“…11 The effects of mattress layer number n More mattress layers imply more bamboo mattress thickness. The less significant effects of thickness are supported by previous reports in [18,26,27]. They published both experimental and numerical results to show that raft thickness and rigidity had an insignificant influence on pile raft foundation systems.…”

“…S∞ and SF∞ are associated parameters at s/L = ∞ (bamboo mattress with no pile condition). This result is in line with [15], the used of more piles decreased embankment settlement [16][17][18]. However, increasing pile spacing with the same number of piles and raft area should expand the pile coverage area [19].…”

“…Closer rows of the piles reduce settlement by up to 0.7 times when s/L = 0.1. Further lowering of s/L < 1, increasing L causes less settlement than lowering s.This result is in line with[15], the used of more piles decreased embankment settlement[16][17][18]. However, increasing pile spacing with the same number of piles and raft area should expand the pile coverage area[19].…”

Load-Displacement Behavior of Single Pile in Sand Using Physical Model Test and Finite Element Method

“…Therefore, piles must be used as a foundation to support the weight of the high-rise building and to transfer that weight to firmer soil layers at a deeper level. A raft is usually used as a medium for conveying forces from the high-rise building to the piles [1][2][3][4][5][6][7]. Parameters describing the behavior of the raft, expressed as its moment and shear, are required to specify the reinforcing steel design, and they are commonly calculated using the plate on springs method, by simulating the raft as a thin plate element and the piles as springs, with the analysis undertaken using a general structural analysis computer program [8].…”

“…A raft is usually used as a medium for conveying forces from the high-rise building to the piles [1][2][3][4][5][6][7]. Parameters describing the behavior of the raft, expressed as its moment and shear, are required to specify the reinforcing steel design, and they are commonly calculated using the plate on springs method, by simulating the raft as a thin plate element and the piles as springs, with the analysis undertaken using a general structural analysis computer program [8]. Pile springs are commonly modeled with linear elastic behavior, with the pile spring stiffness or elastic constant of the pile springs (kp) being determined based on the load on the pile head per settlement.…”