Land drainage has been shown to provide significant economic and environmental benefits in agricultural crop production. In Canada, 43 million ha of land is currently under arable agricultural production with about 19% of this land under intensive drainage. One type of drainage system commonly used is subsurface tile drainage. This drainage system consists primarily of a network of buried pipes, which allows shallow groundwater to enter through openings or perforations on the pipe wall. Traditionally, tile drains have been designed to satisfy two main functions: hydraulic and structural. The effects of perforations on the hydraulic performance of tile drains have been studied as early as the 1950s, but perforation effects on the structural performance of buried pipes have not been adequately addressed. Also, the studies have been subsequently shown to have several shortcomings. These include erroneous boundary conditions, limited scope for application, and little or no experimental validation of results.
As a result, guidelines for specifying perforation shape, size, and pattern are vague or virtually non-existent in current design standards and specifications. Thus, there is a gap in knowledge of the design guidelines for perforating tile drains to satisfy a desired level of hydraulic and structural performance. Importantly, there are no guidelines to specify the optimum number of perforations on a tile drain for a given set of drainage conditions. Additionally computational tools such as numerical modelling, with finite element analysis (FEA), is needed to advance the older accepted methods for drainage design and management. This research therefore proposes to use FEA as a relatively new tool for analyzing the influence of perforations on the performance of buried plastic pipes used for agricultural tile drains.
The general objective of this research is to establish a design rationale for specifying perforations in buried plastics pipes for drainage applications. This rationale seeks to merge current design criteria that includes both structural and hydraulic functions of the buried plastic pipes. Thus, the following are the specific research objectives:
- To integrate the hydraulic and structural design criteria for perforating buried HDPE tile drains with a coupled computational model (CCM) using FEA;
- To validate the performance of the CCM using sand tank experiments;
- To assess the hydraulic and structural performance of buried HDPE pipes with various perforation sizes and patterns through simulations with the validated CCM;
- To develop guidelines for establishing perforation standards of buried HDPE pipes.
This research is limited to HDPE drain pipes that are commonly used as tile drains in subsurface drainage systems on agricultural lands. Other types of plastic pipes such as those used in leachate collection systems, storm water drains, and toe drains for embankment are outside the scope of this research. Also, only a fully saturated, steady state flow towards the tile drain will be considered in this research.
Pictures available here.
Naresh Gaj; PhD student
Dr. Chandra Madramootoo; principal investigator