Settlement Prediction of Footings Using VS

Hyung Cho,Nam Kim,Dong Kim,Heon Park

doi:10.3390/app7111105

Abstract

The shear wave velocity (VS) is a key parameter for estimating the deformation characteristics of soil. In order to predict the settlement of shallow footings in granular soil, the VS and the concept of Schmertmann’s framework were adopted. The VS was utilized to represent soil stiffness instead of cone tip resistance (qc) because the VS can be directly related to the small-strain shear modulus. By combining the VS measured in the field and the modulus reduction curve measured in the laboratory, the deformation characteristics of soil can be reliably estimated. Vertical stress increments were determined using two different profiles of the strain influence factor (Iz) proposed in Schmertmann’s method and that calculated from the theory of elasticity. The corresponding modulus variation was determined by considering the stress level and strain at each depth. This state-dependent stress-strain relationship was utilized to calculate the settlement of footings based on the theory of elasticity. To verify the developed method, geotechnical centrifuge tests were carried out. The VS profiles were measured before each loading test, and the load-settlement curves were obtained during the tests. Comparisons between the measured and estimated load-settlement curves showed that the developed method adequately predicts the settlement of footings, especially for over-consolidated ground conditions.

Highlights

The design paradigm of civil structures is currently shifting to performance-based design (PBD)instead of the traditional safety factor-based design
This study aims to develop a new approach for predicting the load-settlement behavior of shallow footings based on the VS and nonlinearity of soil
There is a certain limitation of the developed method normally-consolidated (NC) granular soils even though most sites where the construction of the for normally-consolidated (NC) granular soils even though most sites where the construction of shallow foundation is suitable have slightly- or heavily-consolidated ground conditions with the shallow foundation is suitable have slightly- or heavily-consolidated ground conditions with substantial bearing capacity

Summary

Introduction

The design paradigm of civil structures is currently shifting to performance-based design (PBD)instead of the traditional safety factor-based design. In PBD, greater emphasis is placed on controlling structural deformation to assure the serviceability and durability of civil structures [1] rather than using safety factors for design. A number of methods have been introduced to predict the settlement of shallow foundations Most of these methods are based on the theory of elasticity and focus on the determination of soil compressibility. In order to determine the compressibility of soil (i.e., stiffness or modulus) the selection of stiffness is commonly made on the basis of penetration resistance. Parameters such as the N value and qc value, derived from a standard penetration test (SPT) and cone penetration test (CPT), respectively, are generally utilized to determine the stiffness of soil layers. Meyerhof [2], Peck &

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