MECHANISM OF STRAIN ENERGY CONVERSION PROCESS FOR MARBLE DAMAGE AND FRACTURE UNDER HIGH STRESS AND
RAPID UNLOADING
HUANG Da1，2，3，TAN Qing1，HUANG Runqiu2
(1. College of Civil Engineering，Chongqing University，Chongqing 400045，China；2. State Key Laboratory of Geohazard Prevention and Geoenvironment Protection，Chengdu University of Technology，Chengdu，Sichuan 610059，China；3. Key Laboratory of New Technology for Construction of Cities in Mountain Area of Ministry of Education，Chongqing University，Chongqing 400045，China)
Abstract：Based on energy theory and marble test of unloading confining pressure before peak strength under high stress，the whole process of strain energy conversion is researched，including absorbing strain energy for axial compression，dissipating strain energy for plastic deformation and cracks propagation，expending strain energy for circumferential deformation，storing and releasing elastic strain energy. The mechanism of strain energy conversion for marble specimens? damage evolution is revealed. The elastic strain energy stored is more than strain energy dissipated before the peak；and the quantity of strain energy dissipation can be significantly increased only near the peak. The stress quickly drops companying with elastic strain energy being rapidly released and strain energy fast dissipated for plastic deformation and fracture expansion after the peak. The rate of strain energy conversion obviously increases with the increasing unloading rate whenever before and after the peak，especially more intensely after the peak. The influence of initial confining pressure on the rate of strain energy conversion is closely related to unloading rate；and the rate of strain energy conversion clearly increases with the increasing initial confining pressure when the rate of unloading is faster；but the change is not obvious relatively when the rate of unloading is slower. The increasing initial confining pressure significantly enhances elastic strain energy storage before the peak. The rate of elastic strain energy release is far larger than that of strain energy expenditure for circumferential deformation；and the strain energy absorbed for axial compression is almost equal to that dissipated for plastic deformation and cracks propagation. So，the hard rock often presents the characteristics of tensional fracture or rip with the orient proximately perpendicular to unloading orientation，even rock burst appears. The mechanism of strain energy dissipation and release for marble damage and fracture under rapid unloading and high stress is that the elastic strain energy stored is more than the strain energy dissipated before the peak；and the elastic strain energy is quickly and largely released and dissipated after the peak；and companies with expending the strain energy for relatively fast confining tensile deformation towards unloading orientation.
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HUANG Da1，2，3，TAN Qing1，HUANG Runqiu2. MECHANISM OF STRAIN ENERGY CONVERSION PROCESS FOR MARBLE DAMAGE AND FRACTURE UNDER HIGH STRESS AND
RAPID UNLOADING. , 2012, 31(12): 2483-2493.
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2012, Vol. 31 
