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Abstract Abstract：Due to the low in-situ strength and the bedding fracture of the soft compound roof of extra-thick(more than 10 m)，large area roof caving accidents are caused easily if the maintenance of roadway support is inappropriate. Typical engineering examples with in-situ measurements were analyzed with the physical and numerical modelling and the structural form and failure characteristics of extra-thick soft compound roof were studied；the formation of the combined beam of bolts in the lower stratum and the load-bearing arch of cables in the deeper stratum and the arch-beam coupling mechanism were revealed. Under high stress，the deformation of compound roof was affected by the factors such as the stratified structure，the structural plane characteristics and the combination between the layers. The delamination fracture of the compound roof expanded quickly and the failure modes were mainly ones of bent and broken，interface slippage and volume increase. The arch-beam coupled support structure built in extra-thick soft compound roof was found to be the primary structure to maintain the stability of surrounding rocks. And its effect on roof controlling is obvious when compared with the bolt support roadway. The capacity of the stress carrying of the roof raised 77.8% and the reduction ratio of the roadway cross-section decreased 52%. The stability of the support structure was significantly enhanced with the increasing of the density of cables. The combined beam of bolts at the upper layer promoted the formation of load-bearing arch of cables at deeper layers；and meanwhile，the load-bearing arch of cables at deeper layers reduced the pressure，the load and the span of the combined beam of bolts at the upper layer.
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2014, Vol. 33 
