Remedial Measures to Protect Transmission Tower from Excessive Soil Movement : A Case Study

The research background focused on investigating deformation in the T.73 Nonohonis-Kefamenanu transmission tower structure that was suspected to be caused by soil movement due to the tower’s location on a sloped area. To analyze this, various tests were conducted to examine the soil properties and slope stability considered the impact of intense rainfall. The Cone Penetration Test (CPT) results revealed hard soil at depths of 6.8 meters (S1), 8.4 meters (S2), and 7.4 meters (S3), falling within the Silty Sand to Sandy Silt - Sand zone, with qc > 200 kg/cm2. Boring & N-SPT tests indicated hard soil with N-SPT values > 50 at depths of 18 meters (BH-1) and 8 meters (BH-2). The geoelectrical survey using the Wenner-Schlumberger configuration found a groundwater layer at 3-5 meters and suggested the presence of a slip plane. Janbu’s method was used to analyze slope stability, taking into account the complex profiles, layers, and soil characteristics. Modeling results showed minimum safety factors after rainfall (SF 1 = 1.827) and after 30 days (SF 3 = 3.302) following the installation of a 15-meter bored pile foundation with a 50-ton load at the chimney.