Ground settlements in Singapore

Ground settlements in Singapore

l18A 942452 Stuttgart Urban Railway; current tunnelling measures (In German and English) Berche, H; Kagerer, W; Muller, M Tunnel N4, Aug 1993, P204-21...

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l18A 942452 Stuttgart Urban Railway; current tunnelling measures (In German and English) Berche, H; Kagerer, W; Muller, M Tunnel N4, Aug 1993, P204-213

contemporaneous surface settlement. An analysis is presented of settlement due to longwall mining, geological features which influence it,its prediction, settlement-related damage, and preventive measures.

Expansion of the Stuttgart Urban Railway requires further underground sections. Construction of a 550m tunnel with overburden height from 27m to as little as 6m through gypsum keuper, sandstone, and quarry waste fill is described. In settlement-sensitive locations, an arch of high pressure injected subhorizontal piles was constructed ahead of excavation. Major cavities were filled prior to this work. In loose ground, wall sections were systematically grouted slightly behind drivage to minimise deformation, especially where enlargement was necessary.

942456 Ground settlements in Singapore Broms, B B In: Geomechanics and Water Engineering in Em~iromnental Management, edited by R N Chowdhury P367-397. Publ Rotterdam: A A Balkema, 1992

Groundwater problems 942453 Better times for Storebuelt (In German and English) Wallis, S Tunnel N4, Aug 1993, P186-194 Although initially beset by problems, high penetration rates are now being achieved on the East Channel tunnels of the Great Belt Project. The four earth pressure balanced TBMs are now driving a total of about I km/month since the decision was taken to lower the water pressure in the ground above the tunnel alignment to reduce the working pressure of the TBM. To date, nearly half of the 15km of bored tunnel has been completed in till and marl. 942454 Modelling seepage flow during tunnel excavation Anagnostou, G Proc EUROCK'93, Lisbon, 21-24 June 1993 V1, P3-10. Publ Rotterdam: A A Balkema, 1993 Drawdown due to seepage flow towards a tunnel face is usually inevitable. A new, single step, computationally efficient method to calculate the effect of tunnel excavation on piezometric head distribution, taking into account the excavation advance rate, is proposed. Seepage flow equations are reformulated within a frame of reference which advances together with the tunnel heading. Advance rate becomes another parameter in the equations. The transformed equations are solved using the finite element method. Numerical examples are illustrated.

Surface subsidence, caving and rockbursts See also: 942203, 942237, 942283, 942294 942455 Ground movements due to subsidence and their influence on construction Bell, F G In: Geomechanics and Water Engineering in Environmental Management, edited by R N Chowdlmry P325-348. Publ Rotterdam: A A Balkema, 1992 Coal mining has been carried out over extended periods in many areas. Unmapped abandoned workings exist which present a hazard if a site is to be redeveloped. Surface effects of the abandoned mines (mainly room and pillar) and hazard zoning where they exist are outlined. Most modern coal mining in Europe and the USA is by longwalling, with essentially

Much of Singapore Island is covered by soft marine clay. Settlements have occurred during development as a result of deep excavations or tunnels, groundwater lowering, or construction of fills. Geological and hydrological conditions are outlined. Settlements due to fills and water table lowering depend primarily on compressibility and pretoading of the soil. Settlements due to tunnels or deep excavation depend primarily on shear strength of the soil and depth of the construction. 942457 Fractni character and mechanism of rock bursts Xie, H; Pariseau, W G Int J Rock Mecb Min Sci V30, N4, Aug 1993, P343-350 Microseismic noise rate alone is not a reliable predictor of rockburst, and distribution of event location, a realistic record of damage evolution, should also be taken into account. Distributions of microseismic events have been examined using the number-radius relation. These distributions are found to be fractal. The degree of clustering of microseisms increases with the approach of the main rockburst and corresponds to a decreasing fractal dimension. Fractal dimension thus has potential as a rockburst predictor. Fractal and physical mechanisms of rockburst are analysed using damage mechanics and the fractal concept. Observed seismicity can be well explained. 942458 Non-linear finite element analysis of surface subsidence arising from inclined seam extraction Yao, X L; Reddish, D J; Whittaker, B N lnt J Rock Mech Min Sci V30, N4, Aug 1993, P431-441 A nonlinear finite element analysis package developed to research subsidence in flat seam extraction has been modified to extend its usage to inclined seams. The new model is validated against accepted empirical models and physical modelling data. Effects of dip of the seam and width:depth ratio on subsidence, displacement, stress, and strain distributions are analysed. 942459 Results from microseismic monitoring, conventional instrumentation, and tomogrnpity surveys in the creation and thinning of a burst-prone sill pillar McCreary, R; McGaughey, J; Potvin, Y; Ecobichon, D; Hudyma, M; Kanduth, H; Coulombe, A Pure Appi Geopkys V139, N3/4, 1992, P349-373 The Lac Shortt Gold Mine exploited a thin subvertical orebody, mined in three phases. Rockbursts were encountered when extracting the upper zone from the surface to 500m depth. The third phase involved moving upward from 830m, producing an ever-increasing load on the sill pillar remaining. A monitoring system was installed so the ongoing state of stress and conditions in the rock mass could be followed. Because of the high level of pre-mining stress, increasing stress levels could not be appreciably absorbed by discontinuity closure or tightening, rendering the rock mass highly burst prone.