Variability of N-SPT-Correlated Undrained Shear Strength of Alluvial Deposit in Doplang Region, Central Java, Indonesia

Sugeng Krisnanto (Geotechnical Engineering Research Group, Faculty of Civil and Environmental Engineering, Institut Teknologi Bandung, CIBE Building Level 5, Jalan Ganesa No. 10, Bandung 40132, Indonesia)
Masyhur Irsyam (Geotechnical Engineering Research Group, Faculty of Civil and Environmental Engineering, Institut Teknologi Bandung, CIBE Building Level 5, Jalan Ganesa No. 10, Bandung 40132, Indonesia)
Rendy Dwi Kartiko (Applied Geology Research Group, Faculty of Earth Sciences and Technology Institut Teknologi Bandung, Jalan Ganesa No. 10, Bandung 40132, Indonesia.)
Arif Rahman Hakim Sitepu (Civil Engineering Graduate Program, Faculty of Civil and Environmental Engineering, Institut Teknologi Bandung, Jalan Ganesa No. 10, Bandung 40132, Indonesia.)
Mohammad Anwar Fathoni (Civil Engineering Graduate Program, Faculty of Civil and Environmental Engineering, Institut Teknologi Bandung, Jalan Ganesa No. 10, Bandung 40132, Indonesia.)
Ina Asha Nurjanah (Civil Engineering Graduate Program, Faculty of Civil and Environmental Engineering, Institut Teknologi Bandung, Jalan Ganesa No. 10, Bandung 40132, Indonesia.)
Shafira Annisa Putri (Civil Engineering Graduate Program, Faculty of Civil and Environmental Engineering, Institut Teknologi Bandung, Jalan Ganesa No. 10, Bandung 40132, Indonesia.)
Lindawati Lindawati (Civil Engineering Graduate Program, Faculty of Civil and Environmental Engineering, Institut Teknologi Bandung, Jalan Ganesa No. 10, Bandung 40132, Indonesia)
Maudy Anisa Fanani (Civil Engineering Graduate Program, Faculty of Civil and Environmental Engineering, Institut Teknologi Bandung, Jalan Ganesa No. 10, Bandung 40132, Indonesia)
Alexander Wicaksono Budiarto (Civil Engineering Graduate Program, Faculty of Civil and Environmental Engineering, Institut Teknologi Bandung, Jalan Ganesa No. 10, Bandung 40132, Indonesia)
Idrus Muhammad Alatas (Civil Engineering Department, Institut Sains dan Teknologi Nasional (ISTN), Jalan Moh. Kahfi II, Jakarta 12640, Indonesia)

Journal of Engineering and Technological Sciences
Vol. 55 No. 6 (2023)

The need to better quantify the variability of soil shear strength and its relations with the factor of safety is increasing in Indonesia. However, this aspect has not yet been studied thoroughly. This paper presents an attempt to quantify the variability of undrained shear strength in relation with the factor of safety of an alluvial deposit in the Doplang region, Central Java, Indonesia. A relationship between the undrained shear strength, su, and N-SPT for the deposit was found as su = 3.4 N-SPT. The variability of the undrained shear strength was quantified utilizing the coefficient of variance, s/m (the sample standard deviation, s over the mean, m) of the N-SPT correlated undrained shear strength. The variability of the undrained shear strength was investigated for the soil near ground surface. The deposit had a value of s/m ranging from 0.15 to 0.25 near ground surface. The variation of s/m tended to follow normal and lognormal distributions. Relationships among the coefficient of variance, the probability of failure, and the factor of safety in terms of soil strength for normal and lognormal distributions were developed. For the value of s/m near ground surface, the relationship between the probability of failure and factor of safety was obtained.