Taha Ashoori

ORCID Identifier(s)

0000-0002-5808-8215

Graduation Semester and Year

2018

Language

English

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Civil Engineering

Department

Civil Engineering

First Advisor

Mohammad Najafi

Abstract

Trenchless Technologies (TTs) are alternatives or methods of choice for the construction and renewal of buried pipe or box with little or no surface disruption. Specifically, TTs are used when other traditional methods, such as cut-and-cover methods are not physically possible. Other reasons for TT methods to be increasingly adopted by owners, engineers, and contractors are their low environmental impacts and, based on the project and the site conditions, lower costs per foot of installed pipe, making these technologies much more efficient and versatile with final results within a shorter time span. Trenchless technology methods are divided into two main categories of Trenchless Construction Methods (TCMs) and Trenchless Renewal Methods (TRMs). TCMs are used to install new utilities and pipes underground while TRMs are used to renew, renovate and replace an existing utility or pipe. Trenchless construction method is divided into three categories of Pipe/Box Jacking, Horizontal Earth Boring (HEB) and Tunneling. There are conceptual differences between excavation methods and pipe/liner laying for each method, but all methods have the similar ground displacement pattern since in all methods an overcut excavation (overcut) is created around pipe or box. This overcut excavation is main source of surface settlement (volume loss) and in shallow conditions may cause damage to existing road pavement or railroad bed. The main objective of this research is to compare box and pipe in terms of surface, subsurface and horizontal soil settlement. Trenchless construction methods for this research study include pipe jacking, box jacking and large size manual excavation (hand mining or roadheader) tunnels. Two box jacking projects in sand, one pipe jacking in clay, two centrifuge tests for tunnels in clayey soils and two tunnel constructions by hand mining and open shield tunneling were considered for model validations. Secondary objective of this study is to investigate ground displacement induced by pipe and box in sandy and clayey soil conditions, different construction depths and different pipe and box sizes. Finally, numerical comparison of arching effects over the crown and applicability of empirical methods for predicting surface and subsurface ground settlement for different pipe and box sizes are covered in this research study. Numerical method using Finite Element Analysis (FEA) was used for model simulations to investigate surface and subsurface settlements, effects of box height, box width and overcut for different soil conditions and box/pipe shapes. Pipe and box models in different soil conditions were validated from real-life case histories. The results of this dissertation show that on the average there is 5 to 25% higher surface and subsurface settlements in box over a pipe with the same cross section area of the box, where pipe diameter is considered to be equal to box width. It was observed that settlement in box installations is dependent on ratio of soil cover to width of the box. Different pipe settlement predictive models, such as Gaussian and Modified Gaussian curves, fitted well with the numerical results obtained for box installations.

Keywords

Trenchless technology, Ground settlement, Numerical analysis, Pipe installations, Box installation

Disciplines

Civil and Environmental Engineering | Civil Engineering | Engineering

Comments

Degree granted by The University of Texas at Arlington

Download

Share

COinS