Stress and strength of reinforced concrete shaftlining

254A dimensional, nonlinear incremental finite element code is discussed. Its application to describe plane strain, cyclic loading and pressurized thin cylinders is illustrated. Improvements are considered. 904456 Pore size distribution of nonwoven geotextiles Prapaharan, S; Holtz, R D; Luna, J D Geotech Test J VI2, N4. Dec 1989, P261-268 Permeability, soil retention and resistance to clogging are important design parameters for granular or geotextile filters. Pore size distribution of geotextiles was measured by mercury intrusion porosimetry,following basic procedures laid down in ASTM D 4404 for soils and rocks. Results are consistent with those from the Image Analyser. PSD of compressed fabrics, the usual in-site case, can be measured by testing a specimen compressed to a known thickness between perforated plates. Permeabilities calculated from PSD data are in good agreement with experimental values. 9O4457 Stress and strength of reinforced concrete shaftlining Sun Wenruo; Yang Junjie Proc International Symposium on Modern Mining Technology, Taian, October 1988 P440-449. Publ Taian: Shandong Institute of Mining and Technology. 1988

mechanics based model is presented which takes into account the specific experimental parameters of in situ stress testing. It considers pressure drop at the fracture inlet and pressure distribution within the hydraulic fracture. It uses analytical solutions for both stress intensity calculations and fluid transport evaluations. 90446O Applications of fracture mechanics to some mining engineering problems Singh, R N; Sun, G Min Sci Technol VIO, NI, Jan 1990, P53-60 Rock is a complex material with natural fractures and flaws, and use of a fracture mechanics approach can compensate for inadequacy of some conventional methods of analysis. Fracture mechanics principles are applied to a number of mining problems: fragmentation by blasting, rock cutting, coal dust control, rock slope stability, rock fracture formation,and the prediction of the size of the fracture zone around mine openings for use in support design. 904461 Numerical and experimental investigation for determining fracture toughness of Welsh limestone Singh, R N; Sun, G Min Sci Technol VIO, NI. Jan 1990, P61-70

Model tests have been carried out on reinforced concrete shaft linings. Results suggest the steel reinforcement does little to improve load bearing capacity and that current design methods are overconservative. The strength of the concrete, which is dependent on concreting quality, and ratio of wall thickness to radius arc the most important

Mode I fracture toughness of Welsh limestone was determined in bending tests on half disc specimens in a servo-controlled stiff testing machine. Crack tip stress intensity and the three dimensional nature of the fracture were studied using the finite element code PAFEC. Results indicate the fracture toughness is dependent on specimen size and crack length, but little influenced by specimen thickness or moisture content.

Snow and ice mechanics

904462 Probabilistic compressive strength of sound dry granite Kittl, P; Leon, M; Diaz, G; Lillo, A Rock Mech Rock Engng V23, NI, Jan-March 1990, P21-28

904458 Micromechanics of ice fields - !: microscale constitutive laws Ostoja-Starzewski, M; Jessup, R G Pure Appl Geophys VI34, N4. Feb 1990. P781-802 A theoretical model of the mechanics of tightly packed ice is presented which includes random microstructural effects. It examines both discrete and continuous viewpoints. Kinematics of ice fields in general are first outlined, then mechanics of the discrete ice field with a single characteristic size in the microscale tens to hundreds of metres. A planar graph representation is presented to describe the ice field's mieromechanisms by the discrete fields of deformation and interaction force. This forms the basis for derivation of various microscale constitutive laws, and Monte Carlo simulation models and macroscopic response studies.

Fracture-Statistics Mechanics, or Probabilistic Strength of Materials, introduced by Weibull in 1939, is applied to constant uniaxial compression of granite. Different functions of cumulative probability of fracture which may be used are described. Results indicate that all fracture stresses belong to a single group which shows two functions of specific risk of fracture. The material is a binary compound made of two materials characterised by different Weibull parameters.

Fracture mechanics 904459 Interpretation of hydrofrac pressure recordings using a simple fracture mechanics simulation model Rummel, F, Hansen, J lnt J Rock Mech Min Sci V26, N6. Dec 1989, P483-488 Most hydrofracturing data interpretations consider only singular pressure values of characteristic pressurisation phases, and are based on idealised assumptions. A new, fracture

F~ 1990 Pergamon Press plc. Reproduction not permitted