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Recent developments in geotechnical reliability
Published in K.S. Li, S-C.R. Lo, Probabilistic Methods in Geotechnical Engineering, 2020
A research project was undertaken by Duncan and co-workers at the Virginia Polytechnical Institute to develop load and resistance factors for the design of highway bridge foundations (Barker, et al, 1991). The types of foundation design considered include driven piles, drilled shafts, shallow footings, retaining walls and abutments and tolerable settlements of structures. In the absence of sufficient data, the researchers found it necessary and desirable to base the values of the resistance factors largely on judgment and common sense. LRFD resistance factors have also been proposed for offshore pile foundations (Hamilton and Murff, 1992). Their results show that the new resistance factors yield more consistent safety indices for pile designs relative to those previously designed based on the working stress design concept (API RP2A-WSD). Because of the varying level of biases and uncertainties in the pertinent soil strength, they proposed that different resistance factors are required between operating and extreme load conditions. Moreover, different resistance factors may be also necessary between piles in clay and those in sand.
Soil behavior and critical state soil mechanics
Published in An-Bin Huang, Hai-Sui Yu, Foundation Engineering Analysis and Design, 2017
The main purpose of a foundation is to ensure that the load from the superstructure is properly transmitted to the ground. Retaining walls are built to hold the soil behind it. Civil engineering projects often involve construction through an uneven terrain, or creation of uneven ground due to excavation where the stability of the natural or man-made slope is of concern. The above subjects, as diverse as they may appear, have one thing in common—they all involve unbalanced loading conditions. The analysis or design is to assure that the ground mass remains stable under the given or expected loading conditions and the built structure performs as required. Traditionally, the analysis has been divided into two broad categories, as follows.
Foundations, Framing, Sheathing, and Vapor Barriers
Published in Kathleen Hess-Kosa, Building Materials, 2017
Many of the old stone foundations of yesteryear still remain to this day. While they captivate the log cabin and back-to-nature groups in industrialized nations, today's stone foundations are still the predominant foundation of choice, particularly in Third World countries. Stone foundations may have a long life (e.g., in excess of 100 years)—assuming the soil cooperates. They are not as costly as concrete foundations in time and materials, and stone is certainly the way-to-go in remote wilderness areas.
A numerical study on the behaviour of foundations resting on fibre reinforced soils using an innovative enhanced soil-fibre finite element
Published in Geomechanics and Geoengineering, 2022
Hamideh Mohammadi, Nader Hataf, Mehdi Veiskarami
The bearing capacity failure, excessive settlement and soil erosion are among major problems in the design of foundations. To date, a number of soil reinforcement techniques have been developed to overcome such problems. Examples include deploying continuous geosynthetics, e.g. geocells, geotextiles, geomembranes and discrete reinforcements such as fibres to improve the soil mechanical properties. Attempts have been made in recent years, however a few in numbers, to analyse composite environments such as fibre-reinforced soil media. Binquet and Lee (1975b) apparently were the firsts to study the effect of reinforcement on the bearing capacity of footings. Herrmann and Al-Yassin (1978) used both discrete and composite methods to model reinforced environments. Moroto and Hasegawa (1990) have studied the effect of soil reinforcement by utilising the finite element method (FEM).
Characterisation of geotechnical model uncertainty
Published in Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards, 2019
This Spotlight paper presents a comprehensive review of load test data for various geo-structures and determines the ULS and SLS model statistics in a consistent way with clear references to the supporting databases. In particular, the authors compiled a generic database (PILE/2739) covering many foundation types installed in different soil types. The foundation types covered include small to large displacement piles (e.g. steel H-piles, torque-driven helical piles, driven cast-in-situ piles, and driven closed/open-end concrete/steel piles) and non-displacement piles (e.g. drilled shafts and ACIP piles). The resulting summary (Table 2) represents the most extensive and significant update of Table 3.7.5.1 in the JCSS Probabilistic Model Code (JCSS 2006) to date. It should be pointed out that the model statistics are applicable to any implementations of RBD such as the LRFD, the MRFD (Phoon, Kulhawy, and Grigoriu 2003), or the expanded RBD approach (Wang, Au, and Kulhawy 2011). These model statistics can be used within the First-Order Reliability Method (FORM) to derive a deterministic model partial factor at the design point as well.
Performance evaluation of geocell-reinforced pavements
Published in International Journal of Geotechnical Engineering, 2019
Weak subgrades are the common problem in road construction. Whether it is a temporary access road or a permanent road built over a weak subgrade, a large deformation of the subgrade can lead to deterioration of the paved or unpaved surface. Geosynthetic materials such as geocells have been widely used to reinforce/stabilise the structures with unbound materials such as roads, slopes, retaining walls and embankments. Geocells completely encase the soil and provide all-round confinement, thus preventing the lateral spreading of the soil. Because of this, the soil – geocell layer acts as a stiff mat, distributing the load over a much larger area of the subgrade soil. This helps in reducing vertical and lateral deformations of the foundation soil to a large extent besides increasing the overall load carrying capacity of the foundation soil. Several studies have shown that geosynthetics can extend the service life of pavements (Potter and Currer 1981; Lawson 1992; Haliburton and Barron 1983; Webster and Watkins 1977; Giroud and Noiray 1981; Love 1984; Austin and Coleman 1993; Al-Qadi et al. 1994; Fannin and Sigurdsson 1996; Hufenus et al. 2006; Latha, Asha, and Hemalatha 2010; Veeresh, Mamatha, and Dinesh 2014; Mamatha and Dinesh 2017), reduce base course thickness for a given service life (Webster and Watkins 1977; Giroud and Noiray 1981; Love 1984; Bush, Jenner, and Bassett 1990; Sivakumar Babu and Kumar 2012) and delay rutting development (Potter and Currer 1981; Veeresh, Mamatha, and Dinesh 2014; Mamatha and Dinesh 2017). However, in some studies it is reported that the designed pavement thicknesses are very important and cannot be compromised (Al-Qadi et al. 2012; Veeresh 2013).