ABSTRACT:

A test conducted on buried HDPE pipe has been examined using finite element analysis to investigate a number of potential modeling choices. Issues considered include stress dependent response of granular materials, shear failure of the soil surrounding the flexible compressible pipe products, and the materially nonlinear response of the polyethylene. Elastic, visco-elastic and viscoplastic models are employed to characterize the thermoplastic pipe material. The performance of the different models in these simulations of buried pipe behavior is examined through comparative study. Measurements of pipe strain, soil stress and pipe deflections obtained from the laboratory tests are reviewed, as are solutions obtained using a closed form analytical solution based on linear elasticity. Conclusions are drawn regarding which techniques are most suitable for conducting parametric studies and undertaking installation design for pipe buried under these conditions.

INTRODUCTION

Thermoplastic pipes are now in common use worldwide in gravity flow and pressure pipe applications. Research is therefore underway to develop limit states design for buried thermoplastic pipe. Linear finite element analysis, using reduced material modulus, has been used to model the time dependent soil-pipe interaction (Katona, 1988; Hashash et al. 1990). Laboratory facilities which simulate pipe burial have been developed so that limit states can be investigated experimentally, Moore et al (1996). New constitutive models have been developed to enable researchers to predict the linear and nonlinear time dependent response of polyethylene (Moore and Hu, 1996; Zhang and Moore, 1997). This paper examines the extent of nonlinearly observed in a laboratory test of pipe response in a biaxial pipe test cell.

LABORATORY BIAXIAL CELL TEST

The test was conducted on plain thermoplastic pipe in a biaxial pipe cell. The cell was devised to model the biaxial field stresses experienced by deeply buried pipes (Moore et al. 1996).

This content is only available via PDF.
You can access this article if you purchase or spend a download.