Browsing by Author "Isuranga, SNAMTK"

Now showing 1 - 2 of 2

item: Conference-Full-text
Identification of soil/rock interface using GPR technique for soil nail wall design
(Department of Earth Resources Engineering, 2018-08) Narangoda, SRAIB; Isuranga, SNAMTK; Jeneeshaa, A; Abeysinghe, AMKB; Premasiri, HMR; Samaradivakara, GVI; Abeysinghe, AMKB; Samaradivakara, GVI
Soil nailing is one of the common slope stabilization techniques which has been used in Sri Lanka during the past decade. Due to the advantages of this method, its applications are growing rapidly around the landslide hazard areas in Sri Lanka. Applications of subsurface investigation methods which are used to identify soil/rock interface are limited due to steepness of the slope areas. Since lesser information available about the bed rock geometry, this leads to generate a low cost effective design for soil nailing. The aim of this research is to demonstrate applicability of GPR for optimizing soil nail length. The study area is located near the Nursing Training School Kandy, that has been proposed to be stabilized by using soil nailing technique. GPR readings were taken on the pre-determined traverse lines. Soil/Rock interface identification was done by using survey results together with their interpretation, and geological cross section was produced. GPR imaging indicated that the bed rock level variation at this location is from 15 m to 18 m. It was identified that design length of the soil nail is shorter than depth to the bed rock on the slope with the aid of the diagram. Therefore, it was identified that soil nail length cannot be optimized for the location. The scope of the GPR survey was to find the depth to the bed rock. By using that, length of the soil nail can be optimized and soil nailing process can be performed more efficiently. However, the depth to bed rock level on the slope has to be less than the design length of the soil nail to optimize the soil nail length by means of this technique. This research illustrates the benefits of using GPR to provide understanding about the soil/rock interface in a slope area for the optimization of soil nail length.
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.