Adrin Tohari already know, when a landslide will occur. The movement of soil on the slopes will occur when the water table in the area rise above its slip plane. Departing from these facts, Adrin and a number of other researchers from the Geotechnology Research Center at the Indonesian Institute of Sciences (Pusat Penelitian Geoteknologi LIPI), Bandung create a mechanism to stabilize the slopes with the siphon method.The innovation was named Technology of Groundwater Extraction with Gravity for Slope Stability or in Bahasa Indonesia called 'Teknologi gravitasi ekstraksi air tanah untuk kestablian Lereng' abbreviated 'ThE GREATeST.' The innovated anti-landslides researcher team was consisted of Adrin Tohari, Arifan Jaya Syahbana, Khori Sugianti, and Nugroho Aji Satria.
Adrin claim the groundwater treatment technology was the most effective and economical method than the other strengthening slope methods such as pile, drill, or gabions. The device can be applied on steep slopes and ramps.
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| Cross-section images of the Groundwater Extraction with Gravity Technology. (Picture from: KORAN TEMPO 4430) |
The other engineered method to lower the deep soil water level on a steep slope conditions can also be done by drilling a large size with horizontal drilling for pipe installation. However, its construction cost was expensive and difficult way to gentle slopes.
On steep slopes with shallow ground water level, a decrease in the water can be done by installing a horizontal pipe. "But the performance is easily clogged pipelines plant roots and soil material carried by the water flow," he said.
ThE GREATeST, which was initiated eight months ago, has been tested on the slopes of the LIPI's Earth Conservation and Information Office (UPT Balai Informasi dan Konservasi Kebumian LIPI) at Karangsambung, Kebumen, Central Java. At that location, move fairly gentle slope, which is 15 degrees. "It is evident that the tool can work. Now stay refinement," said Adrin.
In the rainy season, the soil water level on the slopes of the ranges of 40-50 centimeters below the soil surface. That means the slopes are prone to landslides. They must suppress the water level was up to 2.5-3 meters in accordance with the measurement of the depth of soil slip plane. According Adrin, ground water level should be below the plane skidded to prevent landslides.
To test ThE GREATeST, they dig the hole diameter of 10 centimeters depth of 4 m, and then insert the PVC pipe diameter of 7.6 centimeters. Porous pipe that will facilitate the entry of ground water. Water suction filter is also included in the pipe at a depth of 3 meters. "Its function is to filter water-borne dirt," said Adrin.
Filter pipe connected to the pneumatic tube. The pipe that was used to the compressor that ran up the hole and stretched along the slope below the soil surface. Pneumatic hose serves to channel ground water entering the filter. Ground water entering the wellbore and the filter will push water up through a pneumatic tube. The hose connected to the water level control system and discharged through a pipe flushing. The research team still needs to improve automatic flushing system to get rid of air bubbles, so that the water can smooth out.
Of the field test, the valve pipes proved less potent as an open spigot, it could fail due to dirt and water-borne materials. Filter pipe without valves and suction hose diameter 8 mm showed the best results. "The groundwater dropped from 0.4 meters to 3 meters from the ground, with a maximum water flow measured at 87.6 liters per hour," said Adrin.
According to team, the technology is suitable for the slope without occupancy that could landslides, such as the slope on the side of the railroad tracks, roads, and highways. On the slopes which have an occupancy, this technology could also be applied, but it will have an impact on the decline in the water table wells. The problem can be overcome by building a water tank in the outlet pipe, so that the ground water can still be used citizens.
Adrin said, the slopes that are prone to landslides in the area that its soil composition derived from young volcanic eruptions, so the power is low because it has not compacted. In addition to the soil material is easily removed, easily saturated soil water. Slope soil sediment that is easy to expand and contract due to weather also prone to landslides. "When the drought cracked soil, during the rainy season becomes mush," he said . Ground such that, for example, is on the side of the Cipularang highway's 91-92 KM. *** [EKA | ANWAR SISWADI | KORAN TEMPO 4430]
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