Mechanism and practice of rock control in deep large span cut holes

Deep large span cut holes are difficult to stabilize. The 7801 cut hole in the Lu'an Wuyang Mine was used as this project's background. The main factors affecting large span cut hole stability are analyzed. Pre- stressed bolting theory was used to design a roof control method for a large span roadway. By reducing the span and applying equal strength coordinated supports the rock could be stabilized. The control prin- ciples and methods are given herein along with the analysis. A double micro arch cross section roadway is defined and its use in solving the current problem is described. Beam arch theory was used to build a model of the double micro arch cross section roadway. A support reverse force model for the arch foot intersection was also derived. A support method based upon reducing the width of the large span in the cut hole is presented. These results show that the reduced span of the roadway roof plus the use of cable anchors and single supports gives an effective way to control the large span cut hole. On site monitoring showed that the reduced span support from the double micro arch cross section roadway design had a significant effect. The roadway surface displacement was small and harmful deformation of the cut hole was effectively controlled. This will ensure its long term stability.

Evaluation of the analgesic,sedative-anxiolytic,cytotoxic and thrombolytic potentials of the different extracts of Kalanchoe pinnata leaves

Objective:To evaluate the analgesic,neuropharmacological,cytotoxic and thrombolytic potentials of the aqueous,ethanol and ethyl acetate extracts of Kalanchoe pinnata leaves.Methods:At the dose of 400 mg/kg body weight,the analgesic activity of the extracts were evaluated by the acetic acid-induced writhing and formalin-induced persistent pain tests while neuropharmacological activity was evaluated by the open field,hole cross and elevated plus maze tests.The cytotoxic potential was observed by brine shrimp lethality bioassay and the thrombolytic potential was investigated by clot lysis test.Results:The aqueous extract significantly suppressed the number of writhing(96.78%)as well as the formalin-induced persistent pain on the early phase(46.92%)and on the late phase(40.98%).Again in case of hole cross and open field tests,the locomotor activity was decreased significantly(P<0.001)mostly by the ethyl acetate extract.Furthermore,the sedative-anxiolytic activity was supported by the increased percent(P<0.01)of frequency into the open arm on elevated plus maze test.Besides,the extracts showed moderate lethality and thrombolytic activity.Conclusions:The findings showed that activities are comparable to the standards and in some cases are stronger than the standards.Therefore,based on the results,it is evident that it has great analgesic and sedative-anxiolytic activity with moderate cytotoxic and thrombolytic potential.