The design and performance of a deep excavation in Ruabon Marl at Newbridge, Clwyd

SURFACE STRUCTURES:CONSTRUCTION 943323 Effect of transverse load-resisting elements on inelastic e a r t h q u a k e response of eccentric-plan buildings J. C. Correnza, G. L. Hutchinson & A. M. Chandler, Earthquake Engineering & Structural Dynamics, 23(1), 1994, pp 75-89. The accurate evaluation of code torsional provisions for plan-eccentric structures exhibiting inelastic response relies on the adoption of appropriate systems defining both the torsionally balanced (reference) and torsionally unbalanced cases. An issue of particular importance is whether the transverse load-resisting elements oriented perpendicular to the assumed (lateral) direction of earthquake loading should, f o r p u ~ o s e s of realism, be included in model definitions. Clarification of this issue is required in order to advance the understanding of inelastic torsional response behaviour and to assist the interpretation and comparison of previous studies. This paper aims to provide such clarification, based on analyses of a series of models defined rigorously according to code design provisions. It is concluded that for the flexible-edge clement, accurate estimates of additional ductility demand arising from torsional effects may be obtained from uni-directional models only for medinm-period to long-period systems. -from Authors

943324 Design strategies for the seismic retrofit of reinforced concrete frames J. A. Pincheira, Earthquake Spectra, 9(4), 1993, pp 817-842. Due to economical and p r a c t i c a l considerations, the seismic rehabilitation of buildings is generally confined to strategic areas of the structure in which only selected elements are modified or new elements are added. This paper summarizes some of the results of a series of analytical studies conducted on prototype reinforced concrete frames strengthened with some of the most commonly used rehabilitation techniques. Based on the results of these studies, a design strategy that uses lateral drift rather than lateral strength as the main criterion for the design of retrofit schemes is presented. -from Author

943325 Evaluation of a compacted till liner test pad constructed over a g r a n u l a r subliner contingency layer R. K. Rowe, C. J. Caers & C. Chan, Canadian Geotechnical Journal, 30(4), 1993, pp 667-689. The construction and evaluation of a compacted clayey till test pad constructed over a stone layer are described. The geotextiles exhumed from the test liner showed some evidence of construction damage; however, based on the field observations and subsequent laboratory tests, it is coneluded that they performed adequately. -from Authors

943326 The design and excavation of a road cutting in weak rocks: a case history from the Lower Coal Measures of South Yorkshire D. J. Cragg, R. L. Hills & J. A. Naylor, in: The

engineering geology of weak rock. Proc. conference, Leeds, 1990, ed J.C. Cripps & others, (Balkema; ~ngineering Geology S p e c i a l Publication, 8), 1993, pp 385-392. The new A616 Stocksbridge By-pass involves a cutting up to 28m deep through a natural rock scarp formed in heavily jointea and fractured sandstones, siltstones and mudstones of Lower Coal Measures age. The paper describes the process of engineering geological investigation undertaken. lI~itial design considerations for the cutting slopes are outinca. tJetailed oesign considerations included the classic failure modes as well as long term degradation of the rock faces. Engineering geological logging of newly-exposed faces allowed rock mass quality to be classified, and the methods of excavation, final trimming and dentition were tailored to suit the characteristics of each class of rock mass. -Authors

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943327 The 'caves' of the City of Nottingham: their geology, history, extent and implications for engineers and planners J. C. Walsby, D. J. Lowe & A. Forster, in: The

engineering geology of weak rock. Proc. conference, Leeds, 1990, ed J.C. Cripps & others, (Balkema; Engineering Geology S p e c i a l Publication, 8), 1993, pp 479-487. Much of the City of Nottingham is underlain by the Nottingham Castle Sandstone Formation, a moderately weak rock. The sandstone has been excavated during the past c.1000 years to create cavities used for housing storage, shelter and other purposes. That such cavities, have remained stable during many centuries reflects the wide (>>lm) spacing of fault, joint and bedding plane discontinuities within the sandstone. However, the caves pose a potential problem for modem developers, since they may necessitate special foundation design. A recommended code of practice for planners and developers, with particular reference to a register and maps of cave locations produced by the British Geological Survey, is outlined. -from Authors 943328 The design and performance of a deep excavation in Ruabon Marl at Newbridge, Clwyd J. P. Kixkwood & A. Dolecki, in: The engineering geology of weak rock. Proc. conference, Leeds, 1990, ed LC. Cripps & others, (Balkema; Engineering Geology Special Publication, 8), 1993, pp 401-408. The River Dee valley is bridged by a five span high level viaduct supported by piers. The central piers straddle the River Dee and are located within weathered and weak rock materials and generally on steeply sloping sidelong ground. This paper presents a case study for one of these central piers and discusses the design, construction and erformance of a deep excavation in weak Ruabon Marl. It iseusses the geotechnical mapping undertaken, the procurement and validity of discontinuity data in rock slope engineering, rock mass classification systems and the methods o f slope design utilised. The final excavation was achieved at slope angles of the order of 70 to 80 degrees on most faces of the excavation, utilising only rock mesh, drainage and shotcrete as slope restraint methods. The excavations remained open for up to nine months prior to backfilling, with little signs of slope deterioration. -from Authors

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943329 Problems of an earth d a m on weak rocks in outer Himalayas, Punjab, India V . K . Agrawal, G. S. Manhas & Y. P. Sharda, in: The

engineering geology of weak rock. Proc. conference, Leeds, 1990, ed J.C. Cripps & others, (Balkema; Engineering Geology S p e c i a l Publication, 8), 1993, pp 441-446. The main problem in the construction of medium height dams on the poorly lithified and weak U.p~er Siwalik (Lower to Middle Pleistocene) rocks compnsmg alternate bands of sandrock (a poorly consolidated and uncemented sandstone) and clayshale in Kandi Watershed of Punjab State is the low strength of the foundation rocks and their non-groutability. These problems have been successfully tackled by designing these dams as zoned earth fill structures and locating the clay core on impervious clayshale bands which act as a natural cut off. The filters have been zoned in order to guard against piping due to dispersive nature of impervious fill material which has been observed as a regional character. -from Authors 943330 Seismic design of buildings in China Hu Shiping, Earthquake Spectra, 9(4), 1993, pp 703-737. This paper presents a general perspective on the subject of seismic design of buildings m China. The main characristics of Chinese earthquakes, some major earthquake isasters, and a brief history of seismic design in China are descirbed. The paper goes on to relate some new features of the recently promulgated seismic code which include a new design spectrum, how to identify liquefiable soil, the three levels of seismic protection, and the two-phase design. -from Author

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