Diagnosis and reduction of mine roof failure. Part 2

I IgA This simulauon ,*as achieved in such a v,a,. that material '.alues v, ere modified after each run, according to stress distribunon. until the simulation reached an equdibrium condition. MSC N A S T R A N finite element method program was used for the simulation. The effect of a ,,ield pillar system v, as anal.,,zcd in comparison with a regular pillar system The results agreed v, ith the field measurement in terms of stress distribution and floor heave. Auth. 863329 Physical model study of a long-all mine Park. D W: Kicker, D C .Win Sci rechnol ~'3. .VI, Oct I9A'5. P51-61 .-\ ne'a physical model for Iongwali mining is de,,eloped combining features of the "sandbox" n'odel with a new concept for excavation of mine openings using a special tooi. The model is used to examine stress distribution around a long,xall face in chain pillars as v, ell as in the panel. Reproducible results are obtained. ,,~hlch enable a successful simulation by the model o( the mode of stress changes in chain pillars, and measurement of the de,.elopment of panel front abutment. Auth. 863330 Combined boundary element-finite element analysis of lined openings. Technical note Gioda. G; Carini. A Rock ),lech VD';. .\4. Oct-Dec 1985. P293-202 An analysis of lined openings in elastic media is presented. The solution is based on the sub-di',ision of the liner into a mesh of finite elements, and on the coupling between finite element and boundary segment discretizations in terms of "nodal' forces and dispk~cements. Both cases of perfectl', rough and perfectly smooth liners are considered. Equations go,,erning the problem soluuon are discussed and the main characteristics of the relevant matrices and vectors arc illustrated. Results are shown concerning some typical test examples of both deep and shallo~ lined openings.

Underground excavation failure mechanisms 863331 Diagnosis and reduction of mine roof failure. Part 1 Moebs. N N: Stateham, R M Coal Min l"22..V2. Feb I985. P52-55 The probable causes of persistent roof failure, based on :.he occurrence, character, and distribution of the mine fails, are outlined. Two principal categories for classifying failures are proposed - geology-related and stress-related - as well as a number of sub-categories. Suggestions to avoid further roof failure, including supplementary support, destressing and reduction of mine air humidity, are presented. 863332 Diagnosis and reduction of mine roof failure. Part 2 Moebs. N N; Stateham. R M Coal Min I'22, .V3. March 1985. P42-48 Roof failures attributable to geologic defects or character of rock are subdivided into those caused by low rock strength, mmsture sensitivity, bedding plane spacing, or minor structures. These topics are examined in detail, establishing the identity and suggesting methods to pre'.ent or control each type of roof (allure. (

863333 Failure of coal pillar ribs and possible methods of control O'Beirne. T J: Shepherd. J Proc 4th Australia-New Zealand Conference on Geomechanics, Perth, ~'estern Australia, 14-18 .flay 1984 I2. P661-66'. Publ Burton lnst of Engmeer~, /9.~4 From in,.estigations of the stability of coal r~bs at se~.eral collieries, it 'xas concluded that failures appear to be due to ,,ertical tensile fractures leading on to "bucklin,2 and kinking" failures and possibly even shear failures. It" cleat directions can be identified for ~irgin blocks of coal, then rib stabiht,', cain be improved b~ la',ing out entries at a high angle to the principal cleat trend. A knov, ledge ot" the fracture ,;~stems in pillar ribs :,; a prerequisite for the design of pillar ~,orkings and the choice of an optimum support system,

Tunnels See also-363014. 863180, 863215. ~6322 ~ 863334 Slashing tunnelings costs Gnilsen. R ('/r Engng..% Y V55, .VII..Voc 1985. P38-41 A tunnel complex on the Washington DC Metro, US.-',. ~as constructed at reduced cost by adopting the Ne~ Austrian Tunnelling Method instead of the conventional US practice of reinforced concrete liners. Excavation was b', blasting, v, ith ground ahead of the space supported b~ spiling. Tunnel support was by rock bolts and shotcrete. A three dimensional -finite element analysis of the excavation procedure v~as undertaken using the computer programs P A T R A N and A D I N A Examination of the results was simplified by the use of a colour graphics display of the stress field. 863335 Soil tunnel test section: case history summary Hansmire. W H; Cording. EJ d Geotech Engng Div ASCE VIII, NIl..Vm. 19,~5. P1301/320 During the construction of two tunnels for the Washington DC Metro, USA. through primarily sand and gravels, threedimensional soil displacement about the advancing shields, and tunnel lining load and displacement were monitored. Extraordinary settlements were observed for the first tunnel and a significant change was made in the construction procedure for the second tunnel. The construction methods, soil displacements and volume changes, ground movement in relation to construction and the deformation and loading on tunnel linings are presented and discussed. 863336 NATM construction of WMATA's Vcheaton station and tunnels Heflin, L Iq: Le Fevre, G T Tunnlg Technol Newsl N50, June 1985, PI-/O An expanded version of a paper presented at the 7th Rapid Excavation and Tunneling Conference held June 16-20, 1985. in New York. The second project in the US to use the NATM is the subway station at Wheaton. Maryland. and associated tunnels that form part of the system being constructed b.v the Washington Metropolitan Area Transit Authority tWMATA). Description is given of the e',aluation of its design, the computer modelling and analysis, and the rock classification scheme dividing the site materials into categories. The progress of construction to date is noted. Only three significant ground failures have occurred. Se'.eral ne~ or

1986 Pergamon Press Ltd. Reproduction not permitted