ANALISIS AMBLESAN TANAH AKIBAT PEMBEBANAN DAN PENGAMBILAN AIRTANAH DENGAN STUDI KASUS DI DAERAH MUKTIHARJO LOR, KECAMATAN GENUK, KOTA SEMARANG

• Main Author: HERMAWAN, WAWAN
• Format: Theses
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/41627
• Institution: Institut Teknologi Bandung

Phenomena of land subsidence have occurred in many large cities in the world which were built on Quaternary sediments, such as Bangkok, Shanghai, San Joaquin and Jakarta. These phenomena have also happened in one of the provincial capitals of Indonesia, namely Semarang. The differences of the scale of the land subsidence occured were strongly related to the geological conditions and the development of city land use. In this study, the analyzes performed were based on: a) land subsidence due to loading of infrastructure development by mean of the approach of The Terzaghi’s one-dimensional consolidation theory, and b) land subsidence due to groundwater depletion in the period October 2010 - October 2013 based on the approach theory of Biot consolidation through a finite element method. Based on stratigraphic conditions, the study area is dominated by clay layers which consist of very soft sandy clay layer (10.5 to 28.1 m) and firm-stiff clay layer (28.1-82 m). The values of OCR <1 on whether sandy clay layer or firm-stiff clay indicate that the consolidation processes are very likely still to occur at this area. The value of compression index (Cc) showed that the clays at the study area have high values of compression index, so it is estimated that the compression within these layers will easily occur if the stress increases. Due to the small value of the coefficient of consolidation (Cv) which is 0.00032 to 0.00060 cm2/sec, the dissipation procesess from these layers became quite slow and in turn the processes of consolidation became longer as well. The value of land subsidence in the study area based on the benchmark is 12 cm, while the results of the land subsidence analysis due to loading of infrastructure development is 0.61 cm and due to the groundwater depletion is 5.40 cm. Therefore, the total of land subsidence due to the natural consolidation is estimated 5.99 cm. Geological condition in the study area gave significantly effect to the value of natural consolidation as a causing factor of land subsidence, which is composed of a very thick clay layers with the OCR value < 1 and has high to very high compression index values.