Evaluation of group effect of pile group under dragload embedded in clay

Abstract

A simple semi-empirical analysis method for predicting the group effect of pile group under dragload embedded in clay was described assuming an effective influence area around various locations of pile group. Various pile and soil parameters such as the array of pile group, spacing of the piles (S), embedment length to diameter ratio of piles (L/D) and the soil properties such as density (γ), angle of internal friction (φ) and pile-soil interface friction coefficient (µ) were considered in the analysis. Model test for dragload of pile group on viscosity soil layer under surface load consolidation conditions was studied. The variations of dragload of pile, resistance of pile tip and the layered settlement of soil with consolidation time were measured. In order to perform comparative analysis, single pile was tested in the same conditions. The predicted group effect values of pile group under dragload were then compared with model test results carried out as a part of the present investigation and also with the values reported in literatures. The predicted values were found to be in good agreement with the measured values, validating the developed analysis method. The model test results show that negative skin friction of pile shaft will reach 80%−90% of its maximum value, when pile-soil relative displacement reaches 2 mm.

Mathematical Model and Analysis of Negative Skin Friction of Pile Group in Consolidating Soil

“…Example Case Studied by Kong et al One 3 × 3 piles group with pile spacing equals 4.0 ( equal to 0.041 m) Arrangement of pile group and the code of typical piles, (a) rectangular arrangement (b) hexagonal arrangement.was presented by Kong et al[19] (for the position of piles, refer toFigure 7(a)). The model piles were driven to 0.7 m clay, approximately 0.2 m above the silt layer.…”

Dragload and downdrag performances of inclined pile group embedded in consolidating soil

“…When the soils surrounding the pile settle more than the pile under surcharge load or groundwater table lowering conditions, negative skin friction (NSF) may occur. The development of dragload and downdrag in the pile could cause engineering problems like pile foundation failure or pile damage, difference settlement.Many researches have been carried out on dragload of vertical pile foundations through field tests (Fellenius [1] ), model tests (Toma et al [2] , Lee et al [3] , and Kong et al [4] ) and numerical simulations (Chow et al [5] , Lee et al [6] , Comodromos et al [7] , Hoque et al [8] , and Kong et al [9] ), and influence factors including pile arrangement, surcharge load, consolidation time, pile spacing, and pile positions, etc were analyzed. Some focused on downdrag of vertical pile group (Ng et al [10] and Lam et al [11] ).…”