Probabilistic considerations for the design of deep foundations against excessive differential settlement

Abstract

Current foundation design practice for serviceability limit states involves proportioning the foundation to achieve an acceptably small probability that the foundation settlement exceeds some target maximum total settlement. However, it is usually differential settlement that leads to problems in the supported structure. The design question, then, is how should the target maximum total settlement of an individual foundation be selected so that differential settlement is not excessive? Evidently, if the target maximum total settlement is increased, the differential settlement between foundations will also tend to increase, so that there is a relationship between the two, although not necessarily a simple one. This paper investigates how the target maximum total settlement specified in the design of an individual foundation relates to the distribution of the differential settlement between two identical foundation elements, as a function of the ground statistics and the distance between the two foundations. A probabilistic theory is developed, and validated by simulation, which is used to prescribe target maximum settlements employed in the design process to avoid excessive differential settlements to some acceptable probability.

Assessment of soil spatial variability for linear infrastructure using cone penetration tests

“…Soil variability is a major issue in geotechnical engineering (Honjo, 2011); it typically causes uncertainty in the interpretation of site investigations and has important, but different, implications for different geotechnical structures. The influence of spatial variability has been studied, by way of the use of theoretical and numerical models, in relation to shallow, strip and pile foundations (Jaksa et al, 2005;Suchomel & Masín, 2010;Naghibi et al, 2016), retaining walls (Sert et al, 2016), liquefaction of hydraulic sand fills (Wong, 2004;Hicks & Onisiphorou, 2005;Popescu et al, 2005) and slope stability (Griffiths & Fenton, 1997;Hicks & Samy, 2002;Hicks & Spencer, 2010;Li et al, 2016). It has been shown, especially for embankments (Spencer & Hicks, 2007;Hicks & Spencer, 2010;Hicks et al, 2014;Hicks & Li, 2018), that the spatial variability of material properties, the problem geometry and the combination of the two are significant factors influencing the stability of slopes and the failure mode.…”

Probabilistic assessment of pile group response considering superstructure stiffness and three-dimensional soil spatial variability

“…For pile groups with caps of various thickness, the design concern becomes the differential settlements (∆). A recent study [7] investigated the differential settlements between two piles installed in spatially variable soils, and suggested that ∆ is largest when θ is approximately equal to the spacing (s) between the piles. In their study, the soil is elastic and the spatial variation of Young's modulus is isotropic (θ ln x = θ ln y = θ ln z ).…”

“…The designs of large pile groups or piled rafts are often controlled by differential settlements, which may cause distortion or tilting of the structure. However, in previous studies of probabilistic analyses of piles and pile groups [e.g., 1,2,3,4,5,6,7], there have been limited discussions on the uncertainties associated with these aspects of piled foundation response, and their interrelationship with spatial variability of soil properties and influence of superstructure. This may be partly attributed to the complex interaction effects in the system.…”

Design, construction and analysis for super-wide, deep and large foundation pit

“…Therefore, it is very popular in various engineering design fields. During several years, the continuous development of computer technology, people continue to develop a variety of finite element analysis software [16][17]. In solving the complex conditions of foundation pit engineering method, the application of numerical analysis software is also quite common.…”