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Abstract Pipe-roofing technology has been widely used to develop larger or more complicated underground spaces in urban cities in Japan. Rapid installation of roof pipes plays an important role in reducing underground construction cost and improving construction safety. Pipe-roofing has been attracting more attention to engineers and is one of the auxiliary construction and temporally support methods with less disturbing surrounding ground. However, ground conditions are very complicated and unknown and also a lot of underground utilities and facilities on the surface have been already constructed in the project sites. Cutting tool wear or failure due to hard rock layer or hard stones such as cobbles and boulders leads to tunneling work stoppage and in some cases, unforeseen obstacles make tunneling stop. This paper describes the recent pipe-roofing technology and the development of a micro-tunnel boring machine (MTBM), considering ground conditions. A newly developed MTBM shows many outstanding features in pipe-roofing under difficult ground conditions. 1. Introduction Our society depends very much on infrastructures such as roads, railroads, gas, electric power, water, sewer system, communication line, and so on. Sewage coverage has already reached 78% in Japan, and the market for constructing the sewage system is saturated especially in urban areas (Matsui et al., 2015). A new trend in this field is urban renewal, utilizing more underground spaces. Required underground spaces are becoming much larger or much more complicated shape. However, underground in urban areas is already congested with many utilities as well as many buildings on the surface. In order to keep ground stability during construction of underground spaces, pipe-roofing technology has been used at the project sites these days. Ground conditions and used construction system play an important role in reducing the construction cost and improving safety. Unfortunately fully understanding the ground conditions is very difficult or impossible in spite of pre-geological survey. Difficult ground conditions, machine troubles, or unexpected obstructions in the ground sometimes stop the tunneling operation. This paper describes the recent pipe-roofing technology and the development of a micro-tunnel boring machine (MTBM) used in pipe-roofing considering ground conditions. 2. Pipe-roofing using a micro-tunnel boring machine (MTBM) Fig. 1 shows an example of pipe-roofing works that before constructing an underpass beneath the existing freeway, a lot of pipes are installed to control surface settlement or ground failure during the underpass construction afterward. After pipe installation, the installed pipes are filled with concrete in order to reinforce the strength of the pipe roof structure. Now, it is recognized that pipe-roofing is one of auxiliary construction and temporally support methods without severe ground settlement or collapsing surrounding ground. Currently, underground spaces such as tunnels, subway stations, pedestrian underpasses etc., in urban areas are larger and more complicated shape and constructed near existing facilities and structures both in the underground and on the ground surface. Therefore, pipe-roofing has been attracting close attention of engineers as a supplementary construction method.
- Machinery > Industrial Machinery (1.00)
- Construction & Engineering (1.00)
- Transportation > Ground > Rail (0.34)
Abstract The Jurong Series of rocks in Singapore primarily comprise weakly metamorphosed sedimentary rocks that have been folded and faulted. The Series occupy a large proportion of the western side of Singapore where many major civil engineering works underground are underway or are planned. Although many geotechnical investigations have been conducted and several projects have been completed published data on the properties of these rocks is sparse. Geotechnical investigations have been carried out on project specific basis and there has not been a collation of material or mass properties in the public domain. For example, interpretative reports have described the rocks qualitatively as water-bearing with highly conductive features. In practice claims have arisen regarding expectations of strength and conductivity and these are difficult to resolve in the absence of an adequate data base. The Series includes diverse rock materials such as conglomerates, sandstone, siltstone, claystone, limestone and tuff amongst others. These rocks have a wide range of properties. The authors have collected basic properties of strength of rock material for different types of rock and for various grades of weathering and in situ conductivity from packer tests with the intention of providing basic data illustrating the broad range of properties of these rocks to which others may add subsequently. 1. Introduction The Jurong Series of rocks (Jurong Rocks) are found extensively over the western side of Singapore. They primarily comprise sedimentary rocks that have been subjected to a low grade of metamorphism and subjected to weathering in situ. The rocks of the Jurong Series are complicated because they comprise several formations with diverse lithology. They are extensively and intensively folded, sheared and faulted. Because of their complexity, determination of engineering properties can be very difficult (Zhao. 2001). In particular packer tests to determine conductivity yield widely ranging values within short distances and strength tests vary widely between adjacent specimens even when taken from the same run of core.
Abstract Japan Atomic Energy Agency (JAEA) is operating two underground research laboratory projects in order to establish a firm scientific basis for safe geological disposal of high-level radioactive waste (HLW). One of these, the Mizunami Underground Research Laboratory (MIU) project, is focused on crystalline rock. Grouting for reducing water inflow is an essential countermeasure technology utilized during construction of underground facilities. To achieve high quality seals with grouting technology, it is of great importance to select the most appropriate grouting methodology, e.g. injection pressure, pattern of grout holes, as well as grout material, and all taking into consideration the geological conditions. Status of grouting in the Mizunami Underground Research Laboratory is as follows:Post-excavation grouting test in the Ventilation Shaft at GL.-145m and in the galleries at -300m depths. Suspension type calcium-silica and solution type water glass were used for post-excavation grouting in the sedimentary rock at Ventilation Shaft. Lugeon values, hydraulic conductivity, water head, and inflow in the zone, assessed pre- and post-injection, were used to evaluate the effectiveness of post-excavation grouting and considered useful. Liquid-type colloidal silica was applied for grouting tests at Ventilation Shaft side of the gallery at GL.-300m. The colloidal silica gel seemed to be stable for water pressures of at least 5 MPa. Pre-excavation grouting in the Ventilation Shaft at GL.-200m, -420 and -440m depths. An umbrella type, diverging pattern of injection holes suitable for a shaft were drilled, and Ordinary and super-fine Portland cement were used for grouting. The results suggest that current pre-excavation grouting technology is effective for reduction of groundwater inflow into excavations and that hydraulic conductivity in the surrounding rock mass can be reduced by more than one order of magnitude. Pre-excavation grouting in the galleries at GL. -300m and -500m depths. The results suggest that current pre-excavation grouting technology using Ordinary and super-fine Portland cement are effective for reduction of groundwater flow into the galleries.
- Research Report > New Finding (0.68)
- Research Report > Experimental Study (0.54)
- Geology > Rock Type > Sedimentary Rock (0.50)
- Geology > Rock Type > Igneous Rock (0.36)
- Geology > Geological Subdiscipline > Geomechanics (0.30)
- Water & Waste Management > Solid Waste Management (1.00)
- Energy > Oil & Gas > Upstream (0.90)
- Energy > Power Industry > Utilities > Nuclear (0.49)
Abstract Shafts have a key role as access, transportation, and ventilation routes in mining, tunneling, and underground construction. In addition, the high-level radioactive waste disposal planned in Japan will require the shafts that are deeper than several hundred meters. In recent years the raise boring method is widely employed for shaft excavation in limestone quarries in Japan; however, this method possibly encounters serious troubles in fractured or weathered rock masses, such as collapse of shaft walls, stoppage of excavation, and breakage of tools. These troubles lead to an extension of construction period and an escalation of budget. Therefore, it is essential to understand the rock mass conditions around a shaft before or during excavation. In this study, an estimation method of rock strength from the excavation data of a tunnel boring machine (TBM) was applied to the shaft excavation with a raise boring machine (RBM) in a limestone quarry. Rock strengths were estimated from the thrust force and cutting depth and from the torque and cutting depth during shaft excavation with the RBM; the two strengths show a similar trend from the bottom of the shaft to the surface. In addition, the depth at the low rock strength was coincident with that at argillaceous or cracked shaft walls. The ratio of the two estimated strengths is probably an important index that alerts collapse of shaft walls and stoppage of excavation. This study validated the applicability of the estimation method of rock strength to the raise boring method. 1. Introduction Shafts have a key role as access, transportation, and ventilation routes in mining, tunneling, and underground construction. In addition, the high-level radioactive waste disposal planned in Japan will require the shafts that are deeper than several hundred meters. These vertical or inclined shafts are excavated with the drilling and blasting (D & B) method or the mechanical method, in a similar way to horizontal tunnel excavation. The D & B method is suitable for hard rock breakage and has been used for shaft excavation; however, the operation is non-continuous, and problems on safety, noise, and vibration possibly occur. The mechanical methods include the raise boring, the down reaming, the boxhole boring, and the shaft boring modified from the horizontal tunnel boring (Bilgin et al., 2014). As described in the next section, in recent years the raise boring method is widely employed in limestone quarries in Japan. This method requires no explosives and no rock supports under ideal rock mass conditions, and hence realizes safe and rapid shaft excavation. In contrast, excavation in fractured or weathered rock masses may cause serious troubles such as collapse of shaft walls, stoppage of excavation, and breakage of tools. Therefore, it is essential to understand the rock mass conditions around a shaft before or during excavation with the raise boring method. However, few reports have been published on the mechanisms and the excavation data of the raise boring method (Shaterpour-Mamaghani and Bilgin, 2016; Shaterpour-Mamaghani et al., 2016).
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Carbonate Rock > Limestone (0.72)
- Water & Waste Management > Solid Waste Management (1.00)
- Energy > Oil & Gas > Upstream (0.67)
Abstract In this paper, the forces acting on tunnel lining due to dry condition and groundwater pressures were studied. Firstly, the effect of the forces acting on tunnel lining under dry condition was studied numerically for the Sabzkouh tunnel as an actual case study. This tunnel is a deep tunnel that is bored through Zagros Mountains in Iran by a hard rock Tunnel Boring Machine (TBM). Secondly, the effect of hydrostatic pressures on tunnel lining was evaluated. The lining of a bored tunnel usually consists of precast concrete segments that are reinforced by steel bars. These segments must be capable to withstand all loads caused by earth (e.g. rock and water pressures), construction conditions (e.g. thrust forces) and utilization (e.g. traffic loads) without unallowable deformations. A Finite difference code was used to analyze Sabzkouh tunnel lining. The final results show that the values of bending moments, axial forces and shear forces in the precast concrete lining can be reduced under fully-drained conditions, although, the drainage is more effective in weak rocks rather than strong rocks. 1. Introduction In recent years, mechanized tunneling has developed increasingly, and the benefits of full-face tunnel boring machines have been recognized. Design methods for segmental tunnel linings used in mechanized tunnel constructions typically employ numerical bedded beam models and/or classical analytical solutions for the determination of structural forces (i.e. moments and shear and axial forces) and simple load spreading assumptions for the design of the reinforcement in joint areas (Gall et al., 2018). Basically, the forces acting on the tunnel lining depend on construction procedures and in many cases, these forces enhances during construction rather than after construction. The measurement of the induced bending moments and normal forces are difficult, but the numerical analyses give more reliable results than analytical and closed form solutions. The behavior of lining segments is affected by the complex construction features, for example the sequential excavation process and backfill grouting. Therefore, developing a framework to accurately predict the lining forces and deformations is essential for the purpose of structural safety and optimum design (Zhao et al., 2017).
- Geology > Rock Type (1.00)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Materials > Construction Materials (0.89)
- Energy > Oil & Gas > Upstream (0.69)
- Water & Waste Management > Water Management > Water Supplies & Services (0.46)