Development Of Measuring Instrument For Rheological Stress Recovery Method

Getting accurate in-situ stress measuring data is the precondition of developing deep engineering safely and efficiently.Influenced by sedimentary environment and tectonic movement,surrounding rock in deep roadways and tunnels is usually soft and broken.Traditional in-situ stress measuring methods are hard to conducted with high productivity in this working condition.Rheological stress recovery method is an innovative in-situ stress measuring method aiming at this kind of surrounding rock.Based on dramatic rheology mechanical property of deep soft rock with high in-situ stress,adopt the method of embedding pressure transducer inside borehole to measure initial in-situ stress of surrounding rock.Base on the in-situ stress measuring theory of rheological stress recovery method,generally considering in-situ stress measuring methods and devices domestic and overseas,develop the whole in-situ stress measuring instrument.Specific research contents as follows:(1)After summarising current in-situ stress measuring methods and prevalent pressure transducers,considering requirements of long-distance signal transmission and pressure transducer minimisation during in-situ stress measurement with rheological stress recovery method,put forward throught about replacing vibrating-wire three-dementional pressure transducer with fiber bragg grating six-direction pressure transducer to conduct rheological stress recovery method in deep soft and broken surrounding rock,ensuring scientificity and practicability of rheological stress recovery method during in-situ stress measurement.(2)According to measuring theory of rheological stress recovery method,decide 6 measuring directions of pressure transducer and relevant stress calculation formulas,accomplish the design of transducer's integral structure;according to fiber bragg grating sensing theory,accomplish structure design of pressure transducer's sensing element including belleville spring type,cantilever beam type,clamp type and arched beam type,and put forward working principles referring to these sensing elements respectively;then adopt proper manufacturing materials to produce fiber bragg grating six-direction pressure transducers with different structures.(3)Based on Chinese regulation of metrological verification and expected goal of instrument development,conduct testing experiment with sensing elements inside the transducer to make sure their practical working performance,getting sensing property indexes and metering error indexes of 4 kinds of sensing elements and evaluating relevant class of accuracy degree;according to the test result,finally adopt arched beam sensing element as the core sensing structure of transducer because the class of accuracy degree of all measurement indexes of this sensing element reaches 2.0 which presents that this sensing element has hign accuracy;the test result of Creep behaviour presents that it possesses good long-term stability.(4)Based on fiber bragg grating six-direction pressure transducer,develop matched fiber grating demodulator and pressure transducer fixing device;fiber grating demodulator adopt intrinsically safe type of anti-explosion design,meeting using requirement for measuring instrument with coal mine environment and avoiding excessive mass of measuring instrument when adopting design of flame-proof type;pressure transducer fixing device consist of locating part,pushing part and fixing part with locating part ensuring three-dimensional gesture of pressure transducer in borehole,pushing part considering roughness of borehole in surrounding rock and designing three-direction pulley possessing stretch and rotating functions,and fixing part ensuring that the position of pressure transducer does not change during measurement.