Slope Risk Management System on Toll Road: A case study Semarang-Salatiga Section

Landslide is a geohazard event which can be caused by several factor, such as high rainfall intensity, slope geological feature and the slope geometry itself. Tropical wet climate and typical geomorphology of Indonesia derives landslide event as common disaster during the wet season. Nowadays, the paradigm in road slope management has changed to put the Slope as an Asset, like other infrastructure. In this case study, a slope risk management system was created to assist road slope managers in planning periodic monitoring and maintenance. As the building have the BIM System, the slope can also be digitalized as GeoBIM. Based on case studies, this system can be used to inventory and create an electronic database of road slope assets. Furthermore, the road slope assets are assessed and prioritized based on geological hazards and economic consequences. In the end, each slope asset will have routine maintenance schedules, costs, and a historical data of repairs and damage. Therefore, the slope asset can be handled effectively and efficiently

Residual Strength Parameter Method for Slope stability on a Toll Road with Expansive Clay

The decreasing stability phenomenon needs to be considered during the design of cut slopes on problematic soil. Excavation slope of toll road construction tends to fail when it lies above clay-shale strata. Certain common correlations and ordinary analytical methods are not recommended for safety calculation. This study is intended to find out the characteristic of clay-shale and proper slope inclination design on Semarang Batang Toll Road. The behaviour of a clay-shale area on the cut slope of Batang-Semarang toll road segment STA 438+000–STA 439+000 was identified. The degradable and expansive properties caused slope failure of the initial design with an inclination of 1 H: 1 V. Laboratory tests found that the soil had a clay faction > 40% and can be categorized as high plasticity (LL > 50%). An empirical approach determined that the residual shear strength decreased to phi < 6 degrees. To describe the swelling after the excavation stage, the flow deformation was determined by a finite element simulation. During the swelling phase, the pore water pressure was maintained at a certain value, and a gentler slope fulfilled the minimum safety factor with an inclination of 1 V: 3 H. Furthermore, the shear strength of the clay-shale was reduced to that for a fully softened material, and all the slope factors for safety moved to a critical state. According to the simulation, the minimum suggested slope inclination is 5 H: 1 V. This approach is important for the maintenance of pore water pressure and the prevention of an additional reduction in the shear strength so as to avoid slope failure on clay-shale regions in the yielding stage

ANALISIS GEOLOGI TEKNIK PADA KEGAGALAN BENDUNG CIPAMINGKIS, BOGOR, PROVINSI JAWA BARAT

Bendung Cipamingkis terletak pada Desa Jatinunggal, Kecamatan Jonggol, Kabupaten Bogor, Provinsi Jawa Barat. Bendung ini dibangun pada tahun 1980 dan merupakan infrastruktur irigasi yang vital karena mengairi sekitar 7805 Ha sawah yang terdapat pada Kabupaten Bogor dan Kabupaten Bekasi. Inisiasi kegagalan bangunan tercatat pada Maret 2016 dimulai pada bagian mercu dan pintu pengambilan hingga kegagalan total terjadi pada April 2017. Penelitian ini difokuskan pada identifikasi parameter geologi teknik untuk memahami penyebab kegagalan Bendung Cipamingkis. Metodologi penelitian ini terdiri dari studi lapangan dan uji laboratorium. Tahap studi lapangan berupa pemetaan geologi dan pemboran geoteknik. Tahap uji laboratorium berupa penentuan parameter keteknikan antara lain slake durabilityindex dan free swell index digunakan untuk mengkonfirmasi ketahanan batuan dan pendugaan nilai pengembangannya (expansivity). Dari hasil penelitian didapatkan bahwa bendung ini berdiri di atas batuan dasar berupa dominan batulempung dan zona sesar mendatar menganan. Hasil laboratorium menunjukan slake durability index 0 - 3.88 % dan free swell index > 50 % dan LL yang berkisar antara 60% - 80%. Dengan adannya orientasi zona sesar mendatar yang tegak lurus dengan as bendung, memungkinkan rekahan-rekahan menjadi jalur termudah untuk air melalui bangun bendung hingga terjadinya erosi dan terbentuk saluran pembuluh. Nilai LL yang tinggi (> 50%) membuat karakteristik mekanik batulempung bergeser pada fase softening – residual strength walaupun dari data SPT menunjukkan nilai yang baik. Faktor lain yaitu bahwa batulempung pada daerah tersebut memiliki tingkat ekspansifitas yang tinggi. Kata Kunci: Bendung, Batulempung, Sesar, Kegagala