بررسي آزمايشگاهي اثر مشخصه‏ هاي هندسي و مكانيكي لوله مكش‏ بر كارايي روش هيدروساكشن در تخليه رسوب

Experimental Investigation of the suction pipe geometrical and mechanical characteristics effect on the sediment removing efficiency of hydrosuction method

رسوبگذاري مخازن موجب بوجود آوردن مشكلاتي مانند كاهش حجم و عمر مفيد مخازن، كاهش حجم كنترل سيلاب، گرفتگي آبگيرها، تونل‏ها و توربين‏ها و ديگر مسائل مرتبط مي‏شود. علي‏رغم توسعه چندين روش براي حل اين مسئله، نرخ رسوبگذاري مخازن سدهاي دنيا بيانگر وجود داشتن اين مشكل مي‏باشد. در دهه گذشته روش‏هاي جديدي ارائه شد كه از بين آن‏ها روش هيدروساكشن لوله مكش دفن‏شونده بيشتر مورد توجه گرفته است. هدف از اين تحقيق، بررسي آزمايشگاهي اثر فاصله بين روزنه‏هاي تحتاني و چگالي قسمت انحناء لوله مكش بر كارايي روش هيدروساكشن لوله مكش دفن‏شونده مي‏باشد. در اين تحقيق روزنه‏ها به سمت بالادست و پايين‏دست انحناء امتداد يافته‏اند. به‏‏منظور يافتن ارتباط بين كارايي روش با فاصله بين روزنه‏هاي تحتاني و چگالي قسمت انحناء لوله مكش، آزمايش‏هاي متعددي بر لوله مكش با قطر داخلي 61 ميليمتر، نسبت قطر روزنه‏ي تحتاني به قطر لوله مكش برابر 25/0 و فاصله نسبي 5/0، 75/0 و 1 بين روزنه‏هاي تحتاني انجام شد. نتايج نشان داد، اثر افزايش چگالي قسمت انحناء لوله مكش بر كارايي ابتدا افزايشي و سپس كاهشي است. بطوريكه با افزايش چگالي از 77/1 به 16/2 كارايي صعودي است و سپس با بيشتر شدن چگالي كارايي نزولي مي‏شود. همچنين، كاهش فاصله بين روزنه‏ها موجب افزايش كارايي روش هيدروساكش مي گردد و در فاصله نسبي 2 ، بيشترين غلظت متوسط خروجي با مقدار 58/1 درصد مشاهده شد. بعلاوه نتايج نشان داد، روش هيدروساكشن قادر است تا 5 برابر حجم رسوباتي كه در محل قرارگيري لوله مكش ته‏نشين شده‏اند را تخليه نمايد.

The purpose of constructing and using a dam reservoir is storage and conservation of water. Sedimentation declines this object and can arise many problems such as reduction in capacity for flow regulation, reservoir lifetime and flood control volume, blocking intakes in reservoirs and damage of tunnels and turbines, and many other types of sedimentrelated problems can occur both upstream and downstream of dams. Several techniques have been proposed to prevent entrance of sediment to the reservoirs and removing deposited sediment from reservoirs. However, actual observations of world reservoirs sedimentation rates have revealed that the problem still remains. The “burrowingtype sediment removal suction pipe method” is widely considered among the new methods introduced in the last decade. This study investigated the suction pipe geometrical and mechanical characteristics on the efficiency of the burrowingtype sediment removal suction pipe method. The the suction pipe geometrical and mechanical characteristics of this experimental study includes the bottom holes spacing ratio and suction pipe bends part’s density. The suction pipe with different density at its bend part, used as a new technique conserving distance between bottom holes and sediment. The average concentration of suction flow during the experiment time known as the efficiency of the Hydrosuction sediment removal method. In this research, A series of experiments are carried out to reveal the effect of the bottom holes spacing and density of suction pipe bend part of the Hydrosuction method efficiency. The suction pipe used in this research is a flexible PVC pipe with an internal diameter of 61 mm. The ratio of bottom hole diameter to pipe diameter is 0.25, and the spacing ratio between bottom holes varies from 0.5 to 1. This study, also, used a layout of holes that the bottom holes extended both the upstream and downstream of the pipe bend part. This research also investigates the time series of suction flow concentration and suction cone volume. The results showed that the decrease of the bottom holes spacing ratio from 1 to 0.5 increases the efficiency of the method and the suction flow has its maximum average concentration (efficiency) at spacing ratio 2, with an amount of 1.58 %. Also, the density of pipe bend part has a remarkable effect on Hydrosuction method efficiency. Examination of pipe bend part density showed tha, with the increase of density of bend part from 1.77 to 2.16, the efficiency increases and it decreases just the pipe bend part density’s dimensionless parameter have greater value than 2.16. Suction flow concentration showed that, mostly, the maximum concentration occurs at the beginning of the test and then the concentration curve has an ascending branch, a maximum point and descending branch, respectively. After commencing the test, the suction flow concentration has a rapidly increasing trend untill the pipe reaches to the level of reservoir bottom, then the concentration decreases gradually. Volume ratio of flushing cone to sediment filled under suction pipe location has its maximum value at holes spacing ratio of 2 that its value, in this research, reaches to 5.