Title

Stress Transfer from Rocking Shallow Foundations on Soil-Cement Reinforced Clay

Abstract

Equivalent-static pushover analyses with a three-dimensional (3D), nonlinear, finite-difference model are used to investigate the static and seismic stresses imposed on soil-cement grid reinforcements in soft clay profiles by overlying structures supported by shallow footings. The goal is to evaluate the potential stress concentrations in the soil-cement grid during foundation rocking and the potential for large foundation settlements associated with the local crushing of the soil-cement. The numerical analyses are first validated using data from dynamic centrifuge experiments that included cases with and without large foundation settlements and localized crushing of the soil-cement grids. The experimental and numerical results indicate that the stresses imposed on the soil-cement grid by the overlying structures must account for foundation rocking during strong shaking and stress concentrations at the soil-cement grid intersections. The numerical analyses provide reasonable predictions of the structural rocking loads and the zone of the expected crushing or lack of crushing, but underestimate the accumulation of foundation settlements when the seismic demands repeatedly exceed the soil-cement strength. The simulated moment-rotation and uplift behavior of the footings under monotonic lateral loading are reasonably consistent with the dynamic centrifuge test results. Parametric analyses using the validated numerical model illustrate how the stress transfer varies with the area replacement ratio, the thickness of the top sand layer, the properties of the bearing sand layer, and the relative stiffness of the soil-cement and the surrounding soil. A design model for estimating the stresses imposed on a soil-cement grid by rocking foundations was developed and shown to provide a reasonable basis for assessing whether or not local damage to the soil-cement grid is expected.

Department(s)

Civil, Architectural and Environmental Engineering

Comments

Support for this work was provided by the National Science Foundation ( NSF ) through the George E. Brown, Jr. Network for Earthquake Engineering Simulation (NEESR) under Grant No. CMMI-1208117, the Pacific Earthquake Engineering Research Center ( PEER ), and Hayward Baker, Inc.

Keywords and Phrases

Dynamic kinematic loads; Dynamic response; Rocking foundation; Single degree of freedom system; Soil-cement grid reinforcement

International Standard Serial Number (ISSN)

0038-0806

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2019 Elsevier B.V., All rights reserved.

Publication Date

01 Aug 2019

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