Measured performance of slurry walls

Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2002.Includes bibliographical references (p. 355-361).This thesis evaluates the measured performance of 29 slurry wall supported excavations in Boston, Chicago, Washington DC, and San Francisco - most of which have been constructed since 1980. Each of these case studies includes data on the initial site conditions (soil profile and properties, groundwater conditions and location of adjacent facilities etc.) and designs for support of the excavations. The main goal is to relate construction records to the measured performance of the lateral earth support systems. The principal parameters of interest are the induced ground deformations (and their effects on adjacent structures) and observations of groundwater flows. The actual monitoring data always include inclinometer measurements of lateral deflections within the diaphragm wall and/or adjacent soil. However, other information such as surface settlements, building settlements, heave of the sub-grade or piezometric data were only archived for some of the projects (nearly all in Boston). Even fewer projects contain measurements of structural forces in either the diaphragm wall or bracing system. These data have been grouped according to the soil profile, toe fixity of the wall and type of bracing system (tie-back anchors, prestressed cross-lot and top-down). Most of the projects have succeeded in allowing only small wall deflections, often less than 0.2% to 0.3% of the total excavation depth, and similar magnitudes of the maximum surface settlements. Larger wall movements did occur in several projects but have been linked to either inadequate bracing (poor tieback design or inadequate pre-stressing of rakers), lack of toe embedment or ground softening inside the excavation (installation of drilled caissons or load bearing elements). Unexpectedly large surface settlements in one project (Dana Farer) were clearly linked to ground loss during tieback installation. Several other reported cases of leakage (through panel joints and/or tiebacks) have been repaired by grouting. Given the limited availability of archival data, the thesis has focused on the interpretation of lateral deflections. Wall deformations have been sub-divided into rigid body translation, rigid body rotation and bending modes. Empirical correlations have been proposed for estimating each of these components.b y Dimitrios C. Konstantakos.M.Eng