Browsing by Author "Perumal, M"

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item: Conference-Full-text
Incident of ground collapse up to daylight and recovery actions taken in shallow Ranwediyawa tunnel in Sri Lanka
(Division of Sustainable Resources Engineering, Hokkaido University, Japan, 2024) Perumal, M; Wanigasekara, WADID; Isuranga, SNAMTK; Narangoda, SRAIB; Iresha, H; Elakneswaran, Y; Dassanayake, A; Jayawardena, C
The Ranwediyawa tunnel was constructed under the Mahaweli Water Security Program (MWSIP) to minimize the social impacts on the villages, where the irrigation canal runs through the village. The tunnel was slightly redirected from the original canal path which was planned to run through the village road having a deep excavation over a length of 620m with a mixed ground condition. The area has a high ground water table and seasonally varies slightly due to the area's weather pattern with varying topography and which has a deep open excavation from 12m to 18m for the construction of cut & cover conduit. Having a shorter period of design the Ranwediyawa tunnel was designed with a ground cover varying from 9m to 20m, including 5 support classes according to the RMR classification. Both tunnel portals start with completely to slightly weathered rock and move into moderately weathered to fresh rock. Both tunnel drives were driven by mechanical excavation with NATM concept with few small chimney collapses, however, a major collapse occurred once the upstream drive reached the rock-type boundary and it was developed to daylight. This paper describes the details of the initial excavation procedures, the major geological conditions and the recovery procedures which were taken to complete the tunnel excavation. Also, this paper covers special arrangements made by the Contractor in the shortage of resources available in the project as the incident occurred during the spreading of the COVID-19 period. The tunnel drive successfully passed this weak geological area with long pipe roofing support before the tunnel excavation after two months with a few days of site closure due to the identified worker getting COVID-19 in the tunnel team.
item: Conference-Full-text
A Study of groundwater recovery following tunnel construction in the upper highland complex – a case study on the Ranwediyawa tunnel
(Division of Sustainable Resources Engineering, Hokkaido University, Japan, 2024) Dissanayake, HM; Perumal, M; Lees, DJ; Iresha, H; Elakneswaran, Y; Dassanayake, A; Jayawardena, C
In Sri Lanka, understanding the hydrogeological conditions is vital when constructing tunnels, especially geological regions such as the Highland Complex, where groundwater supports local communities and agriculture. While some recent data sheds light on groundwater reduction during tunneling, little is known about the recovery process. The Ranwediyawa tunnel construction, part of the Mahaweli Water Security and Investment Program (MWSIP), offered an opportunity to monitor groundwater impact closely. During excavation, considering seasonal variations, a reduction in groundwater levels was recorded, and following tunnel completion and installation of the waterproof lining, the groundwater recovery was monitored. The hydrogeological conditions of the Highland Complex present unique challenges as groundwater is vital for local communities and agriculture, so tunneling activities must be carefully managed to minimize disturbance. This paper outlines the planning, monitoring, and construction carried out for this project. Our findings stress the importance of comprehensive planning and monitoring during tunnel construction, understanding hydrogeological conditions and implementing effective waterproofing measures, to minimize environmental impact and ensure no disruption in domestic water supply and agriculture sustainability. It is hoped that the data and insights gained from this project can be used in future tunnel projects in similar hydrogeological settings, enhancing infrastructure project resilience and safeguarding groundwater resources for future generations.