Engineering geological mapping for empirical design evaluation of Tunnel 10 of Jakarta - Bandung high-speed railway, Indonesia

An engineering geological mapping was carried out at the construction site of the Tunnel 10 of Jakarta Bandung High-Speed Railway to obtain data and information of the engineering geological conditions, particularly the rock masses. This research aims to determine the rock mass classes at the tunnel construction site and recommend the tunnel support system based on the Rock Mass Rating (RMR) and the Japan Society of Civil Engineers (JSCE) systems. This research is expected to better understand the rock mass classes, which were previously determined based on the newly applied Basic Quality (BQ) system for the tunnel support empirical design. The results showed that the research area consisted of young volcanic products, namely moderate to highly weathered tuff breccia and andesitic breccia. The uniaxial Compressive Strength (UCS) of rock mass varies between 1-25 MPa. The RMR value ranges from 21 to 40, indicating disintegrated and poor rock mass quality. The proposed tunnel support system is the combination of shotcrete, steel support for top heading and bench support, arch sidewall, and invert concrete.

On the issue of formalization of the creation of special geotechnical maps

Today in the scientific and technical literature of Kazakhstan as well as abroad there are a significant amount of works which have been devoted to engineering-geological mapping. By means of specialized maps it is obviously possible to assess geological profile of building ground in general, and separate sites of project facilities. The assessment of geological profile of territory of cities is impossible without geoinformation technologies at the present time. Improvement of mapping services and technologies of GIS software are widely used for engineering-geological mapping, development plan of territories, forecasting dangerous natural processes and assessment of various risks. However introduction of geoinformation technologies and special engineering-geological mapping in the Republic Kazakhstan is underdeveloped and does not play a leading role in engineering practice. The article addresses formalization of the process of creating special geotechnical maps in GIS as a certain step-by-step description of the process, based on a number of principles that determine the characteristics of map indicators and the methods of mapping. Special geotechnical maps are a basis for the decision of practical problems connected with an arrangement of constructions on the building ground, a detailed planning and project formulation of building blocks. The analysis of the existing methods of assessing geological profile of the built-up territory of the city was given in order to optimize the survey and engineering work on the construction of foundations, an example of the developed geoinformation database for the analysis of geotechnical properties of soils and the development of special geotechnical maps was given in addition. Also examples of types and the reasons of deformations of buildings and constructions caused by variations in the bases of foundations , besides the research works of the authors who developed their own methods of conducting engineering and geological surveys and special geotechnical maps have been analyzed and the concepts as «engineering-geological maps», «special geotechnical maps» have been defined.

Surface and subsurface engineering geological mapping for empirical designs of excavation method and support system of Tunnel 6 of Jakarta-Bandung high speed railway, Indonesia

Empirical design of support system at the Tunnel 6 of the Jakarta – Bandung high-speed railway was based on the Basic Quality (BQ) system, which had not been adopted in Indonesia. This research was carried out to better understand the rock mass quality at the tunnel construction site by comparing rock mass quality determined by the BQ system to that determined by two more popular rock mass classifications, namely the Geological Strength Index (GSI) and Rock Mass Rating (RMR). Surface and subsurface engineering geological mapping were carried out and tunnel excavation method and support system were proposed. The engineering geological model of the BQ, GSI, and RMR systems showed that the sedimentary rock masses of the Miocene Jatiluhur Formation generally had poor to very poor quality, while those of the Quaternary Volcanic Formation had very poor to good quality. Based on the RMR, the stand-up time values of the sedimentary rock masses were predicted to be relatively low as compared with those of the Quaternary Volcanic Formation, implying requirement of a relatively quick support system installation after excavation. In general, a combination of systematic bolt, shotcrete and steel ribs is the recommended support system for this tunnel.

Evaluasi Kondisi Geologi Teknik dalam Pembangunan Embung

Pucang Village was consisted of eruption materials of Merapi Volcano. The relatively high coefficient of permeability of the materials consisting this area caused rainwater to directly infiltrate into the ground. Evaluation of engineering geological conditions was conducted for construction of a detention pond in this area, which had limited water supply for daily activities. The evaluation was conducted on results of a 1:10.000 scale of engineering geological mapping and analyses of 1:10.000 scale of geological disaster maps produced by previous researchers. The engineering geological mapping involved mapping of morphological condition and active geomorphic process, lithological condition, existence of geological structure, and water source location. The evaluation results showed that the proposed location met the land suitability criteria for detention pond construction based on the morphological condition and active geomorphic process, existence of geological structure, and water source location, but did not meet those based on the lithological and vulnerability to Merapi Volcano eruption disaster. Construction of impermeable layer to prevent water seepage into the ground and periodic removal of sediment in the base of the detention pond were suggested to be carried out to keep the detention pond functioning properly.

Insights from the Engineering Geological Mapping of Four Basement Rocks Derived Soils

Due to the rapid expansion and associated construction of civil engineering structures on the Federal University of Technology, Akure (FUTA) campus, there arose an urgent need for an engineering geological mapping of the underlying soils (residual soils). Generalized geological mapping revealed four types of basement rocks namely migmatite-gneisses, granites, quartzites and charnockites. Results from the fifty (50) soil samples from twenty-five test pits collected all over the spread of the campus coverage of 6.4 km2revealed that the campus is underlain by soils of granular and clayey composition, generally lateritic, having reddish to brownish colour. Engineering geological tests such as natural moisture content, particle size analysis, consistency limits, California bearing ratio and consolidation were carried out on the soils following standard procedures revealed that the values of natural moisture content do not generally follow a consistent pattern and varied from location to location. The grain size characteristics curve, displayed 84% and 16% subsoils are of well graded and poorly graded type respectively. The soils were grouped into CL (low plasticity), CI (medium plasticity) and CH (high plasticity) from consistency limits results. Compaction characteristics of the subsoils revealed 36% and 64% representative of fair to good and poor to very poor foundation materials respectively. Soils with settlement rates greater than 1mm/year were designated as high settlement subsoils. 72% and 28% of the subsoils fell into hard to stiff and soft categories from the shear strength characteristics respectively, and classified as c-ø soils. California Bearing Ratios values range from 10 – 70, indicating their suitability for pavement construction. Conclusively, areas underlain by migmatite-gneiss and charnockite-derived soils, and granite and quartzite-derived soils possessed low and high strength characteristics respectively which can be attributed to their textural characteristics. The subsoils of the entire campus spread are however capable of bearing very substantial loads.