Study On Meso-Identification Method And Physico-Mechanical Property Of Structure-Disturbed Soil

Natural geologic action and human engineering activity are not only rebuilt many kinds of the geologic disaster, but also leads to the complicated environmental geotechnical problems in the earth's surface. Natural geologic action and human engineering activity such as deep structure peristalsis, mining the underground solid mineral, extraction of groundwater, the exploitation of underground oil and gas resources, underground shield tunneling construction, the deep department geologic condition perturbation which are caused by dewatering and excavate of deeply foundation pit bring collapse and craze of earth's surface and ground sedimentation geologic disasters effect in the meantime, also cause the ground soil and engineering damnify problems of the earth's surface in the great scope.Based on the summary of the practice in the ground fissure site and mining goaf field, the paper put forward the concept of depth disturbance site and studied the physico-michanical property of structure-disturbed soil. At the same time, the major engineering problems had been discussed. Combining with the engineering example in Datum mine area, we mainly study the property feature of structure-disturbed soil and the meso- identification method; also we discussed the deformation behavior and bearing capacity of the site and drew some important cognition as followed:(1)Disturbance of soil structure may leads to the change of physical indices of soil in meso-way. Pilot study had shown that saturate degree is more sensitive to the change than other indices. Model experiment indicated that saturate degree especially submerged in water changed evidently as the sampling position varied, the further study found that saturate degree has the trend of less as the sampling position became more away from the'mine goaf'. Furthermore, there existed more than once drink process when the structure-disturbed soil is in water immersion.(2)The datum of static cone penetrate test (CPT) curve has hierarchical feature. The difference of the datum will be shown as the prospecting hole become more far away from the mine goaf. With the aid of partition functions, we may validate the situation. R/S analysis also indicated that the disturbance caused by mining activities has the property of inherence and sustainability. We may make a further cognition of the characteristic of spatial variation of CPT datum by using fractal and multi-fractal theory.(3)In order to find the stress diffuseness feature in the structure-disturbed site, we designed a simulation test. With the help of digital-image correlation technology, we discovered the displacement field of the structure-disturbed site under the axes load. Difference from the distortion in the semi-infinity elasticity space, the damage of the subgrade in structure-disturbed site has the characteristics of asymmetry, there exist notable lateral deformation near the exhausted area. Result also show that the failure model of the foundation was changed.(4)Based on the understanding of the property of structure-disturbed soil, we established the subgrade destroy model which is on the basis of semi-infinity elasticity space. Formulae of calculating the ultimate bearing capacity of the foundation in structure-disturbed site have been derived, also we illustrate engineering example to validate the result.