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Longwall facelines: geology, convergence and powered support rating
141A and vibrational movements of bolts and surrounding rock are described in detail. Results suggest that fully bonded prestressed bolts can accommodate accelerations up to 130g without distress.
893278 Behaviour of a ground anchor supporting a sheet piled wall retaining granular soil McNulty, T A; Little, J A Proc lnt Conference on Foundations and Tunnels, London, 2426 March 1987 V2, P107-111. Publ Edinburgh: Engineering Technics Press, 1987 The behaviour of a pressure grouted, prestressed anchor supporting a temporary sheet pile wall retaining granular materials is reported. Variations in anchor load and changes in free and fixed anchor length were monitored. Distribution of strain along the fixed anchor length suggested that radial stress was around 10X overburden pressure, the high values being due to the method of installation. On excavation below waling level, wall movement was largely attributable to creep of the ground surrounding the fixed anchor length. Extension was accommodated by relaxation of strands rather than horizontal movement of the waling.
893279 Construction, design and application of auger cast soil anchors Gupte, A Proc lnt Conference on Foundations and Tunnels, London, 2426 March 1987 V2, P112-115. Publ Edinburgh." Engineering Technics Press, 1987 The auger cast soil anchor, which involves pumping mortar through a hollow stem as the auger is withdrawn, is described. Simple design formulae are presented for cohesive and cohesionless soils, and mortar and tendon materials suggested. Case studies are illustrated and applications listed.
893280 Numerical evaluation of uplift forces in sands using the trapdoor problem Koutsabeloulis, N C: Griffiths, D V Proc ECONMIG 86, Stuttgart, 16-18 September 1986 V2, 19P. Publ Stuttgart: Unh'ersity of Stuttgart, 1986
Direct rock support methods See also: 893255 893282 Aid for handling powered roof supports Vervoort, A Collier)" Guard V236. Nil, Not" 1988, P394-400 Finite element analysis has been used to study relations between support parameters and occurrence of roof cavities or fall-outs. The 2-D finite element model simulated a longwall mine with a modern shield support consisting of 2 rows of legs and extensible roof bar. The influence of forward inclination and rigidity are considered. Validity of the model was tested using observation of support elements at Winterslag.
893283 Viscoplastic creep of rocks around a lined tunnel Cristescu, N Int J Plasticity V4, N4, 1988, P393-412 A rock support analysis, assuming the rock behaves elastic/viscoplastically while the support is nonlinear, is presented. The case of circular tunnels is considered and formulation of the mathematical problem discussed. The creep of rock around a tunnel with nonlinear supports to limit closure of the tunnel is then studied. It is shown that the ultimate ground reaction is not unique since it depends on the loading history, excavation layout and support design, and onset of failure by dilatancy can be determined. Two kinds of solution are given, a simplified approximate one and a more rigorous general elaborate numerical solution obtained by using computer programs. Auth.
893284 Longwall facelines: geology, convergence and powered support rating Porter, I; Aziz, N [ Min Sci Technol VT, N3, Oct 1988. P243-252
The trapdoor problem, which can be used to model stress distribution around buried plates in sand, has often been physically modelled, but seldom studied mathematically. It is shown that the problem can be tackled simply, using a finite element program which will run on a programmable calculator. Anchor geometry, sand shear strength, friction angle and density are taken into account. Results are compared with some experimental data.
Knowledge of strata-support interaction is necessary to devise optimum support capacity. Empirical relations between convergence, geology and powered support rating are developed, using data from collieries in Scotland and New South Wales. The Scottish coal field uses low load bearing capacity supports due to the 'light' geological structures surrounding the coal measures, whereas in New South Wales the massive sandstone sequence above the coal measures necessitates the use of high capacity supports and firmer control over convergence. Data from the 2 areas are analysed to show how powered support rating and local geological conditions affect the amount of convergence in the central area of a longwall face.
Shotcrete
Grouting
893281 Prediction of time-dependent movement of tiebacks in cohesive soils Liang, R Y K Proc International Symposium on Prediction and Performance in Geotechnical Engineering, Calgary, 17-19 June 1987 P311. 315. Publ Rotterdam: A A Balkema, 1987
893285 Grouting experiences with the Vienna subway construction (In German) Martak, L Geotechnik VII, N4, 1988, P198-209
A finite element program using a time dependent constitutive model for clays has been used to predict the long term deformation and load transfer in a test program. At low load levels the predictions are accurate, but a contact element to model slippage at the soil-grout interface is required at higher loads. Overall prediction of load-deformation, creep rate-time, and strain distribution along the tendon are satisfactory.
During early stages of the metro, strength and permeability of the grout were considered the most important factors, and effects on adjacent structures and groundwater were largely disregarded. As the project expanded, the requirements of durability and groundwater protection became realised. The influence of grout mixture and grout volume has been evaluated. The use of uRrafine cement grouts improves groundwater protection. A theologic model to explain the efficiency of these grouts is proposed, and future research outlined.
1989 Pergamon Press plc. Reproduction not permitted
893278 Behaviour of a ground anchor supporting a sheet piled wall retaining granular soil McNulty, T A; Little, J A Proc lnt Conference on Foundations and Tunnels, London, 2426 March 1987 V2, P107-111. Publ Edinburgh: Engineering Technics Press, 1987 The behaviour of a pressure grouted, prestressed anchor supporting a temporary sheet pile wall retaining granular materials is reported. Variations in anchor load and changes in free and fixed anchor length were monitored. Distribution of strain along the fixed anchor length suggested that radial stress was around 10X overburden pressure, the high values being due to the method of installation. On excavation below waling level, wall movement was largely attributable to creep of the ground surrounding the fixed anchor length. Extension was accommodated by relaxation of strands rather than horizontal movement of the waling.
893279 Construction, design and application of auger cast soil anchors Gupte, A Proc lnt Conference on Foundations and Tunnels, London, 2426 March 1987 V2, P112-115. Publ Edinburgh." Engineering Technics Press, 1987 The auger cast soil anchor, which involves pumping mortar through a hollow stem as the auger is withdrawn, is described. Simple design formulae are presented for cohesive and cohesionless soils, and mortar and tendon materials suggested. Case studies are illustrated and applications listed.
893280 Numerical evaluation of uplift forces in sands using the trapdoor problem Koutsabeloulis, N C: Griffiths, D V Proc ECONMIG 86, Stuttgart, 16-18 September 1986 V2, 19P. Publ Stuttgart: Unh'ersity of Stuttgart, 1986
Direct rock support methods See also: 893255 893282 Aid for handling powered roof supports Vervoort, A Collier)" Guard V236. Nil, Not" 1988, P394-400 Finite element analysis has been used to study relations between support parameters and occurrence of roof cavities or fall-outs. The 2-D finite element model simulated a longwall mine with a modern shield support consisting of 2 rows of legs and extensible roof bar. The influence of forward inclination and rigidity are considered. Validity of the model was tested using observation of support elements at Winterslag.
893283 Viscoplastic creep of rocks around a lined tunnel Cristescu, N Int J Plasticity V4, N4, 1988, P393-412 A rock support analysis, assuming the rock behaves elastic/viscoplastically while the support is nonlinear, is presented. The case of circular tunnels is considered and formulation of the mathematical problem discussed. The creep of rock around a tunnel with nonlinear supports to limit closure of the tunnel is then studied. It is shown that the ultimate ground reaction is not unique since it depends on the loading history, excavation layout and support design, and onset of failure by dilatancy can be determined. Two kinds of solution are given, a simplified approximate one and a more rigorous general elaborate numerical solution obtained by using computer programs. Auth.
893284 Longwall facelines: geology, convergence and powered support rating Porter, I; Aziz, N [ Min Sci Technol VT, N3, Oct 1988. P243-252
The trapdoor problem, which can be used to model stress distribution around buried plates in sand, has often been physically modelled, but seldom studied mathematically. It is shown that the problem can be tackled simply, using a finite element program which will run on a programmable calculator. Anchor geometry, sand shear strength, friction angle and density are taken into account. Results are compared with some experimental data.
Knowledge of strata-support interaction is necessary to devise optimum support capacity. Empirical relations between convergence, geology and powered support rating are developed, using data from collieries in Scotland and New South Wales. The Scottish coal field uses low load bearing capacity supports due to the 'light' geological structures surrounding the coal measures, whereas in New South Wales the massive sandstone sequence above the coal measures necessitates the use of high capacity supports and firmer control over convergence. Data from the 2 areas are analysed to show how powered support rating and local geological conditions affect the amount of convergence in the central area of a longwall face.
Shotcrete
Grouting
893281 Prediction of time-dependent movement of tiebacks in cohesive soils Liang, R Y K Proc International Symposium on Prediction and Performance in Geotechnical Engineering, Calgary, 17-19 June 1987 P311. 315. Publ Rotterdam: A A Balkema, 1987
893285 Grouting experiences with the Vienna subway construction (In German) Martak, L Geotechnik VII, N4, 1988, P198-209
A finite element program using a time dependent constitutive model for clays has been used to predict the long term deformation and load transfer in a test program. At low load levels the predictions are accurate, but a contact element to model slippage at the soil-grout interface is required at higher loads. Overall prediction of load-deformation, creep rate-time, and strain distribution along the tendon are satisfactory.
During early stages of the metro, strength and permeability of the grout were considered the most important factors, and effects on adjacent structures and groundwater were largely disregarded. As the project expanded, the requirements of durability and groundwater protection became realised. The influence of grout mixture and grout volume has been evaluated. The use of uRrafine cement grouts improves groundwater protection. A theologic model to explain the efficiency of these grouts is proposed, and future research outlined.
1989 Pergamon Press plc. Reproduction not permitted