Study On Load/unload Mechanical Properties Of Marbl In Deep Tunnel Stratum And Its Stability Of Surrounding Rocks

The deep underground caverns is used for power station, underground tunnelsand underground storage, security of deep underground excavation engineering, suchas space under high ground stress.Under the high confining pressure effect of rock issignificantly different from shallow engineering mechanical behavior andstress-strain characteristics of rock. It is easy to produce the engineering accidentssuch as instability of surrounding rock when the surrounding rock excavation isdisturbed.For deep underground engineering generally has a long working life, largescale and importance, so the stability problem is more sensitive, once causeproblems of the stability of surrounding rock will bring disastrous damage to theproject, so don’t allow any form of instability.So that the deep rock mass engineeringis facing serious challenges. So it is one of the hot issues to many scholars andengineers researching of.Combining with the silk screen deep secondary hydropower station diversiontunnel engineering background, use the engineering of rock sample to make indoorrock mechanics test, on the stress-strain characteristics of rock under different pathof research.Finally using the rock mechanics parameters obtained from theexperimental analysis of rock mass stability analysis of surrounding rock afterexcavation.Mainly include the following points.(1) To define the concept of "deep" and "deep engineering", introduce thedetermine the critical depth of deep engineering, from the rule of Mohr-coulombstrength criterion to calculate the critical depth. To analyze the original rock stressdistribution and characteristics, include the measured distribution of vertical stress,the horizontal stress and average stress and vertical stress and the relationshipbetween horizontal principal stress and buried depth.From the measured averagelevel of stress analyze the horizontal principal stress valueand the ratio of twohorizontal stress value.(2) By indoor rock mechanics test, study rock under three different addition,unloading mechanics path of stress-strain curve and the damagecharacteristics.Comparing three cases analyse rock deformation parameters andstrength parameters.The rules of the softening of rock under different confining pressure, the variation regularity of residual strength value, and the size of confiningpressure on rock strength and deformation performance are researched. The rock inunloading confining pressure and radial strain under the influence of elastic moduluscurve along with the change of confining pressure are mapped.(3) The deep buried tunnel excavation, a theoretical analysis is made on thestability of surrounding rock and tunnel after excavation could be divided into theplastic zone and elastic zone. The factors of influencing deep surrounding rockstability are concluded.Through the theoretical calculate in different conditions ofsurrounding rock displacement of plastic zone of surrounding rock, and then basedon the plastic displacement of rock mass mechanics test limit value, tojudge thestability of surrounding rock under different strain state.Then use geologicalexploration data to excavate of tunnel stability numerical simulationanalysis.Finally,using the calculated results and the theoretical calculation valuecontrast to judge what kind of state of rock mass strength calculation value is moresuitable for the actual state of surrounding rock.