| In recent years,the underground space development in engineering continues going into deeply,what's the depth of mining reaching 1000 m and the maximum depth of diversion tunnel of Jinping hydropower project is 2525 m.As these projects emerged,bringing the special environment with high ground temperature?high pressure?high water pressure and high atmospheric pressure,while the excavation unloading also attributes the engineering rock mass into rock burst ejection.Given these special circumstances in the actual project,the study of the rock under temperature in rock failure of morphological changes and mechanism has playing an important role in engineering practice.This article concludes some uniaxial compression test,tensile test and true triaxial unloading test,whereby the study including rock burst proneness index in different modes of temperatures and the temperature effects about rock brittle failure,simulating the brittle rock destruction under rock brittle destruction and the process of rock ejection in unloading way.Mainly achieved results in this following:(1)Granite uniaxial compression tests shows that real-time heating 20?~100? interval,with the temperature riseing,the peak intensity increases as overall trend.But from 40? to 50?,due Internal expansion rock crystal significant difference exists,and the overall strength decreased.The tensile strength and the storage limit granite decrease with increasing temperature.And granite brittleness index with increasing temperature gradually rises,and to enhance the rate increases with increasing temperature.(2)Test at 40? ~ 220? range once warmed showed: below 160?,granite compressive strength increases with increasing temperature and after heating 160? ~ 220?,the strength of rock showed a downward trend.Analysts believe that after the heating process below 160?,most granite internal evaporation,enhance the rock strength;and 160? ~ 220? heating rock samples can produce thermal damage,which causes the compressive strength decreased.Brittleness index as the temperature rises firstly increased downward trend.Characteristics of granite from the destruction of the analysis,each specimen were cut composite sheet damage.At a temperature of 40? ~ 140?,it is tensile and shear destruction.And there is two or more pieces of tension fractures.The temperature between 160? to 220?,all appear two very distinct X-type Crack.And there are major shear surface and sub-surface of a weak cut.(3)Under the action of heating cycle(6 times)in the range of 40? ~ 100?,the tensile strength and compressive strength of rock increases as the temperature increased,but tensile strength with increasing temperature moderate trend.(4)By two different heating method performed granite ejection true triaxial unloading test,the first one for process temperature,approximate simulation of ground temperature tunnel excavation will rock samples heated to the set temperature after exposure triaxial tests at room temperature;the second is equivalent temperature brittleness index finger and granite rock in the temperature combined with different heating method(after a warming or the cycle warming)for real-time at different temperatures warmed stars.The temperature corresponds to the same index value.Monitoring rock sample free surface temperature analysis of damage,ruptured due to the temperature difference between the activities,at 20? ~ 100?,under the process temperature and equivalent temperature mode with temperature increases.(5)In hard rock ejection true triaxial unloading test,when the test mode in accordance with process temperature(at 20? ~ 100?),along with rock sample temperature,the initial airport after unloading rock surface rupture(tiny cracks and fissures)shows a decreasing trend,in rock's final burst,but as the temperature rises and becomes strong,the board split phenomenon is more pronounced,ejected out of the rock cuttings are larger in size and more.These phenomena describes in the test's temperature range,with the temperature increasing the brittle rock's activity is being more,and rock storage before final rupture strain energy also being higher,this will leading to more intense rock burst.From the acoustic emission rate and AE energe: initial compaction deformation stage low-energy acoustic emission activity rate of production,the elastic deformation stage is in the period of calm what the rate releasing into the plastic deformation stage.With the emergence and expansion of energy will have micro-cracks lower acoustic emission activity occuring,the main high-energy acoustic emission activities are concentrating in the later stages of nonlinear failure;as process temperature,and the energy of rock acoustic emission count rate also increased,80? and 100?,have two peaks stage,AE energy is being more dense?and more higher amplitude,indicating the internal crack motion at this time.(6)At the range of 20?~100? in the process temperature and equivalent temperature patterns,with increasing temperature the granite peak intensity shows a rising trend,and fracture properties of rock samples at the time of failure,as well as AE counts and AE exhibit substantially consistent regularity on a wide range of energy.So the crack movement in rock's internal is becoming severe.And in the numbers of rock sample's fracture,occurred at 60? and 80?,the equivalent temperature is more than the process temperature;Temperature difference at the value between the damage to rock's back and forth stage,at 40?~100?,the process temperature is greater than the equivalent temperature,thinking when rock sample destroyed,the process temperature mode being higher at rock's stored energy and elastic strain during rockburst being released the more,so the more dissipated energy occurs at that time by a percentage in the form of generating heat.Also at 40?~100?,for receiving granite in the compaction stage to stage of plastic deformation of the acoustic emission count,the equivalent temperature on the scale and magnitude are stronger than the process temperature;at the range of 40?~80?,the stage from instability to the peak intensity,the AE counts in the process temperature is stronger than the equivalent temperature.And at 100?,both in the monitored AE counts and AE energy are extremely close. |
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