含预制缺陷类岩体模型破断试验与分析

doi:10.11872/j.issn.1005-2518.2020.02.129

Abstract

Abstract:

In the process of formation of natural rock-mass，a large number of cracks，holes and other original defects often occur in interior，the internal defects of rock have a significant impact on the mechanical properties of rock-mass.Therefore，it is important to study the initiation，propagation and fracture of cracks in defective rock materials and rock-mass materials for practical engineering.Hence we explored the influence of the change of internal defects from cracks to holes on the fracture mode and characteristics of rock-mass materials by combining theory with experiment.Firstly the mechanical model of uniaxial compression was constructed and the stress at the hole edge was solved by using the conformal angle mapping method，then the uniaxial compression test was carried out on the defective rock samples made of cement mortar materials.The rock-mass specimens were made by mixing 325^#white cement，river sand，and water at a mass ratio of 5∶5∶2，the size of the defective sample after forming is 200 mm×150 mm×50 mm.The defects were created by inserting 3D printing materials into cement mortar paste and removing them during curing，the long axis 2a is 40 mm，the short axis 2b is change values for 1，10，20，30，40 mm，hence the corresponding m [m=（a-b）/（a+b）] values were 0.95，0.60，0.33，0.14 and 0.Uniaxial compression of defect specimens by using the rock mechanics servo-controlled testing system after standard conservation were carried out.The test results show that：（1）Under uniaxial compression，when m is 0 the uniaxial compressive strength of the defective rock-mass is the lowest.The uniaxial compressive strength of the defective specimen increases gradually with the increase of m value，and the peak strength of the defective specimen decreases gradually with the increase of m value.（2）In the process of uniaxial compression fracture of defective rock-mass，the initial tension crack is initiated at the end of the short axis of the defect.With the increase of m value，the initiation position gradually moves to both ends of the long axis，and the crack develops along the direction of the principal stress.Under the action of continuous load，shear cracks are initiated near or far from the long axis of the defect，and the shear crack propagates continuously with the increase of load.In the later stage of crack propagation，spalling phenomenon at the end of the long axis when the m value is large.（3）After uniaxial compression fracture the defective rock-mass will have two fracture modes, namely shear failure and tension-shear mixed failure.When m is greater than 0.60，the failure mode is shear failure，others will happen tension-shear mixed failure.

Key words: uniaxial compression, defect, rock-mass material, stress solution, strength characteristic, fracture mode, propagation of cracks

CLC Number:

TU45

Xuxu ZHANG,Shijiao YANG,Jiajun ZENG,Ke LUO,Chengzhi PU. Fracture Test and Analysis of Rock-Mass Model with Prefabricated Defects[J].Gold Science and Technology, 2020, 28(2): 255-263.

Figures/Tables 10

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Fig.4

Table 1

Physical and mechanical parameters of rock-mass"

参数	数值	参数	数值
密度 $ρ$ /(kg·m^-3)	2 178	黏聚力 $c$ /MPa	4.09
单轴抗压强度 $σ$ _c/MPa	22.25	泊松比 $ν$	0.27
单轴抗拉强度 $σ$ _t/MPa	3.50	内摩擦角 $φ / (°)$	36.24
弹性模量 $E$ /GPa	6.44

Table 1

Fig.5

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Fig.9

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Fracture Test and Analysis of Rock-Mass Model with Prefabricated Defects

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