DESIGN OF SOIL IMPROVEMENT WITH VACUUM CONSOLIDATION METHOD (VCM) IN SEMARANG-DEMAK TOLL ROAD PROJECT SECTION 1

• Main Author: Syarifa Amani, Azka
• Format: Final Project
• Language: Indonesia
• Subjects: Teknik sipil
• Online Access: https://digilib.itb.ac.id/gdl/view/74057
• Institution: Institut Teknologi Bandung

Semarang-Demak Toll Road was built to minimize congestion on the Pantura Line and is one of the solutions to the flooding problem in the coastal area of Semarang, because it will be integrated with sea walls to overcome tidal flooding and land subsidence. With soft soil conditions, the construction site of the Semarang-Demak Toll Road needs to be improved. This final project will discuss the design of soil improvement on Semarang-Demak Toll Road zone O (STA 4+600 - STA 4+825). Soil improvement with Vacuum Consolidation Method (VCM) is carried out to accelerate the consolidation time in increasing the bearing capacity of the soil. The selection of the VCM method is based on a large toll road construction area that requires an efficient improvement method because VCM method can minimize the use of resources and heavy equipment. The design of soil improvement using the VCM method begins with the processing of soil data from soil investigation and laboratory testing to obtain soil parameters, and followed by the determination of load parameters. The design of soil improvement also includes Prefabricated Vertical Drain (PVD) design, determination of consolidation vacuum capacity, and stress distribution. Furthermore, modeling is carried out using PLAXIS 2D V20 software with plane strain modeling type, which will be re-evaluated to meet the design criteria for settlement, stability, and liquefaction. This paper will also compare the effectiveness of using the VCM method with the preloading improvement method. The analysis of modeling results consists of settlement analysis, factor of safety, pore water pressure, and excess pore water pressure. To maintain stability during the early construction period, reinforcement with bamboo piles and mattresses was used. VCM ground improvement used square pattern PVDs with a spacing of 100 cm. With this design, the time required to reach 90% consolidation degree decreased dramatically, from 342.87 years to only 20 days. The amount of stress applied by vacuum is 55-75 kPa with stress distribution from the base to the end of the PVD. Based on the design results, the VCM method could shorten the consolidation time by 18%. The service life condition analysis is carried out for 10 years with the working loads, specifically traffic and pavement loads. It was found from the design results that the VCM method has less risk because the applied pressure is isotropic consisting of vacuum pressure and lateral pressure, resulting in a greater factor of safety value than the preloading method. By using a PVD system, the vacuum pressure can propagate to depths beyond the edge of the PVD zone. The vacuum pressure is able to replace the backfill load so that the amount of backfill material required for construction can be less and cause the pore water pressure with the VCM method to be smaller than the conventional backfill method.