Why is perforated pvc pipes used in gravity dams

We know in constructing hydroelectric power plants,we have to built dams or reserviors in order to store water.

A dam is constructed over the runoff of any river due to which seapage of water occurs which we need to divert otherwise it will weaken our dam structure,In order to do that we use pvc perforated pipes such that we can accumulate water through its little pores and make its way out of dam structure.

Plastic pipe used in embankment dams serves different purposes than pipe used in water and sewer applications. Failure of plastic pipe in water and sewer applications rarely results in loss of life. However, failure of plastic pipe in dams can have catastrophic consequences. Removal and replacement can be difficult, time consuming, and costly. Plastic pipe used in dams must be conservatively designed to provide for a long service life, strength to accommodate all loading conditions and foundation movements, and have adequate access for cleaning and inspection. For a discussion of the importance of good design and construction and the ramifications that can result if these are lacking, see the Introduction of FEMA’s Technical Manual: Conduits through Embankment Dams (2005). Recommendations in this document are based on well founded engineering principles fundamental to the safety dams. However, in some cases, a distinction is made between plastic pipe used in significant/high hazard potential dams and low hazard potential dams. Significant and high hazard potential dams require stringent and conservative design measures, because failure or misoperation could result in loss of human life or economic damages. Generally, this is not the case for low hazard potential dams. While low hazard potential dams could certainly benefit from the design measures discussed in this document, some measures may be considered overly conservative for this type of structure. The designer of low hazard potential dams needs to carefully consider the requirements of their particular application. Plastic pipe has been used in the construction and renovation of conduits and drainpipes within embankment dams (i.e., earthfill and rockfill) since about the 1980’s. The term “conduit” as used in this document refers to conduits used for outlet works, spillways, and siphons in embankment dams. These types of conduits regulate or release water impounded by the dam and are grouped together as “embankment conduits.” The term “drainpipe” is used to refer to toe drains that act as a downstream extension of the dam’s internal drainage system to collect and transport seepage passing through the dam or foundation to a desired outfall location. Plastic pipe has also been used for decants and drainpipes in tailings disposal and slurry impoundment facilities since about 1980. Plastic pipe is lightweight, abrasion resistant, and inert to most forms of chemical attack. This facilitates installation and benefits durability and service life. Plastic pipe is often used in toe drain systems for collecting and measuring seepage and safely discharging it into a channel located downstream from the dam. Plastic pipe is commonly used for toe drain construction, since it is relatively inexpensive, readily available in many diameters, can be manufactured with slots or perforations, and can be rapidly installed (figure 1). Another frequent use of plastic pipe is for the sliplining of deteriorating outlet works conduits. Plastic pipe is preferred for sliplining due to its ease of installation, ability to re-establish the watertightness of the conduit, and improved hydraulic performance. Dam designers and dam safety officials often rely upon precedent and recognized guidelines to design critical features of dams; therefore, many dam designers and dam safety officials have been reluctant to use plastic pipe. Currently, the primary source of design information for plastic pipe is from manufacturers. However, most of this information is targeted to sewer and water pipe installations and does not address the unique factors involved in using plastic pipe within embankment dams. Most dam designers have never had training on the behavior of plastics and must weigh decisions on the use of plastic pipe by considering the initial costs, operating requirements, maintenance costs, dependability, and long-term performance. Some State dam safety officials have attempted to address the use of plastic pipe in their policies and regulations since the early 1990’s. Their efforts have resulted in imposing various design requirements, including reinforced concrete encasement, restrictions on the use of plastic pipe, and use restrictions based upon dam hazard classification. However, because of the many potential benefits, more projects are being designed and constructed using plastic pipe. The manufacture of plastic pipe will continue to evolve, based on the requirements of the engineering community. Continued improvements in manufacturing processes will provide products with enhanced strength, durability, and efficiency. This document is intended to serve as a guide for dam designers and dam safety officials to address the unique design requirements of plastic pipe used in dams for embankment conduits and drainpipes. This document provides the reader with detailed procedures for design, inspection, maintenance, renovation, and repair for plastic pipe applications used in embankment dams. This document specifically addresses plastic pipe applications involving embankment conduits and drainpipes in traditional water-retention embankment dams. The information in this document also applies to the design and use of plastic pipe for conduits and drainpipes in tailings or mine waste-disposal impoundments. However, chapter 7 discusses how the unique characteristics of these impoundments can affect the design of plastic pipe when used for this application. This document does not address other uses of plastic pipe often associated with embankment dams, such as instrumentation (e.g., piezometer riser pipes), relief wells (relief wells are considered part of the foundation drainage system), and structure underdrains (i.e., drains located under spillway floor slabs). Also, this document does not address plastic pipe used to deliver tailings or slurry to a mine-waste-disposal impoundment. However, some portions of this document may have limited applicability to these uses of plastic pipe.

What are pvc perforated pipes?

PVC perforated pipes are the pipes which have little pores all over its surface such that seepage gets accumulated into the pipe.We need manholes at every instant such that if there is any blockage we will be able to remove it.we have to instal pvc perforated pipes at every structure such that there will be no seapage left inside the dam structure otherwise which will affect it.Their size is generally 1m dia.

PVC perforated pipes

 

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