OasisLMS

Abstract: In 1990, G. Wayne Clough and Thomas D. O’ Rourke published an article titled “ Construction Induced Movements on In Situ Walls” for an ASCE specialty conference on earth-retaining structures. This article set the stage for industry guidance on designing in-situ walls used for support of excavations. This was determined by their research described in this article reviewing several types of in-situ walls and their measured lateral movement versus the depth of excavation. 35 years later, design software, construction technology, and measuring equipment have progressed to more advanced methods than were possible in the past for the design, construction, and monitoring of in-situ walls.

This paper presents a case study of deep excavation under challenging conditions, using in-situ walls for support of excavation. The project involves the construction of a new 1, 900 MGD flood pump station to replace the Paddy’ s Run Flood Pump Station for Louisville MSD in Louisville, KY. Due to project locational constraints, the new structure was designed within the footprint of the existing levee embankment. Diaphragm walls were chosen for the construction of the pump station structure. These walls serve four purposes: temporary support of excavation for the new flood pump station, permanent foundation for the new flood pump station, levee under seepage cutoff, and embankment stability.

The project approached the design using a variety of finite element models. A 3D numerical model was created in the STAAD structural analysis software package for the purpose of reinforce concrete design of the diaphragm walls, which incorporates the release connections between the wall panels. PLAXIS 2D & 3D models were created to investigate soil-structure interaction. The lateral soil pressures on the diaphragm walls were obtained from these simulations of the staged construction sequence, including the effects of bracing to provide lateral support to each wall.

A monitoring program for the diaphragm walls was implemented to track wall movements during excavation and compare them with predicted values. The field instrumentation in this program included in-place inclinometers and sister bar strain gages. This project provides a unique opportunity to evaluate the accuracy of the models, the quality of the idealized model, and the design analysis methodology.

Mr. ENRIQUE FARFAN; Mr. Adam Hacker

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