Experimental study on the modulus of soil reaction for plastic pipes buried in lightweight cellular concrete backfill

Abstract

The modulus of soil reaction, representing the stiffness of a soil surrounding pipes, is a critical parameter in the design of buried flexible pipes. This study conducted plate loading tests on corrugated polyvinyl chloride, smooth polyvinyl chloride, and high-density polyethylene pipes buried in lightweight cellular concrete (LCC) backfills at densities of 400, 475, 550, and 650 kg/m³ to investigate the pipe deformation behavior and moduli of soil reaction. In addition, this study examined the effects of the narrow trench condition on the pipe deformation and modulus of soil reaction. In these tests, the vertical and horizontal diameter changes of pipes under the vertical pressures applied through a hydraulic jack were measured. Test results reveal that the average moduli of soil reaction of plastic pipes within a wide trench backfilled by the LCCs at densities of 400, 475, 550, and 650 kg/m³ were back-calculated as 66, 99, 133, and 205 MPa, respectively, using the modified Iowa formula. Furthermore, the back-calculated moduli of soil reaction for LCCs exhibited linear relationships with their densities and unconfined compressive strengths and were higher than the recommended values for the commonly used soil backfills. Based on the vertical deformation criterion of 5% pipe diameter, the ultimate bearing capacities of flexible pipes buried in wide LCCs at densities of 475, 550, and 650 kg/m³ exceeded 500 kPa. The LCC with a narrow trench exhibited a lower modulus of soil reaction and ultimate bearing capacity but a larger pipe diameter change.

Keywords

Lightweight cellular concrete / Modulus of soil reaction / Plate loading test / Ultimate bearing capacity / Buried plastic pipe

Data availability

The data that support the findings of this study are available from the corresponding author upon reasonable request.

CRediT authorship contribution statement

Yu-qiu Ye: Writing - original draft, Validation, Methodology, Investigation, Formal analysis, Data curation. Jie Han: Writing - review & editing, Project administration, Methodology, Investigation, Funding acquisition, Formal analysis, Conceptualization. Brad Dolton: Writing - review & editing, Resources, Project administration, Funding acquisition, Conceptualization. Md Wasif Zaman: Writing - review & editing, Investigation, Data curation. Robert L. Parsons: Writing - review & editing, Supervision, Investigation.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgement

This study was financially supported by the CEMATRIX Corp. The authors would like to thank technicians David Woody, Kent Dye, and Meyer Carey in the Civil, Environmental, & Architectural Engineering Department at the University of Kansas, for their great assistance in modifying and calibrating the test devices used in this study. The authors also would like to appreciate Ph.D. student Alsharari Turki from the University of Kansas and formerly visiting student Hsin-Ming Wu at the University of Kansas, and Albert Fang from CEMATRIX for their great help on the model tests. Josh Beakley at the American Concrete Pipe Association provided valuable comments and suggestions for the data analysis of soil reaction modulus.

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