Pengaruh Penambahan Bubuk Gypsum terhadap Kuat Geser Tanah Berdasarkan Pengujian Triaksial Serta Pemodelan dengan Metode Elemen Hingga

Abstract

Soil is a very important element in a construction which acts as a supporting foundation for all types of construction or construction materials. One of the problems that often occurs in soil is soft soil, one of which is clay. Clay soil is a type of soil with low bearing capacity and shear strength conditions, chemical soil improvement stability is required. Parameters that can be known whether the bearing capacity of the soil is good or not can be seen from the CBR value and the shear strength value. In this study, gypsum powder will be used as a soil reinforcement material because gypsum contains silica oxide as a mineral adhesive which has better properties than organic adhesives because it does not cause air pollution, is inexpensive, fire resistant, is resistant to deterioration by biological factors and is resistant to chemicals. The nature of gypsum powder which when added with water will harden and is expected to increase the density of the soft soil so that its carrying capacity will increase. Gypsum powder was mixed randomly with the soil with gypsum content of 2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18% and 20% of the weight of the soil. This study was conducted to determine how the effect of adding gypsum powder to the soil on the shear strength of the soil, maximum dry density and CBR value. In addition, this study will also analyze the comparison of the results of the soil shear strength parameters between the UCT and Triaxial UU tests and analyze how the results of the laboratory UU Triaxial testing with the UU Triaxial testing simulations carried out in the PLAXIS 2D 201701 program will be compared. The results of this study were the maximum dry density (ℽdmax) of the soil decreased with the addition of gypsum powder where the highest ℽdmax was 1.60 g/cm3 while the lowest ℽdmax was 1.59 g/cm3. The value of shear strength (Su) from the UCT test increased along with the addition of gypsum powder where the lowest Su value was 0.90 kg/cm2 while the highest Su value was 2,98 kg/cm2, an increase of 231%. The increase in the unsoaked CBR value of 285% and an increase in the soaked CBR value is 377%. In addition, the addition of gypsum powder by 20% resulted in an increase in the value of the shear strength (cu) of the Triaxial UU test results of 339% from 1.05 kg/cm2 to 4.61 kg/cm2. The difference in the results of the shear strength of the soil between the UCT and Triaxial UU tests produced is also not very significant. The results of the Triaxial UU modeling with the modeling of the hardening soil model in the PLAXIS 2D program are quite close to the results of testing in the laboratory by producing relatively the same deviatoric stress results at 15% of strain.