Hollow Inclusion Strain Gauge Geostress Measuring Instrument in Deep Borehole and its Application Example

摘要

An example of our the deep borehole hollow inclusion strain gauge geostress measuringrninstrument and its assistive tools will be described, which were used for deep borehole geostressrnmeasurement；and an example is given. Traditional instruments based on stress-release theory onlyrnapplied to shallow boreholes, and did not apply to deep boreholes. Our newer instruments havernimproved, and a deep borehole hollow inclusion strain gauge geostress measuring instrument wasrndeveloped. It integrates hollow inclusion strain gauges, strain recording apparatus and electronicrncompass with a micro-probe, which can be installed at a predesigned position in the boreholernwhen measuring geostress. Using this this technology, geostress data of Zhangjiangrnobservational borehole in Shanghai at a depth of 365 and 385 m were obtained. The results showrnthat the maximum principal stress direction in the surveying area is near EW direction, and the valuesrnof the maximum principal stresses are between 8.5 MPa and 9.0 MPa. The minimum principal stressrndirection is near vertical, and the values of the minimum principal stresses are near equal to thernoverburden pressure. Measurement results show that deep borehole hollow inclusion strain gaugerngeostress measuring instrument is suitable for deep borehole 3D geostress measurement.