Mechanical properties of rock under coupled static-dynamic loads

Li, Xibing; Zhou, Zhen; Zhao, Fei; Zuo, Yujun; Ma, Chunde; Ye, Zhouyuan; Liang, Hong

doi:10.3724/sp.j.1235.2009.00041

Cited by 81 publications

(45 citation statements)

References 7 publications

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“…Especially for rocks at depths of 1000 m and more below the ground surface, abnormal phenomena (e.g., rockburst, zonal disintegration, core discing) become more prominent, leading to an enormous challenge to the traditional rock mechanics (Qian 2004;Zhou et al 2005). Traditional fracture criteria and strength theories are not applicable when the rocks are under the dynamic load superimposed with static pre-load, because the measured total rock strength is different from the summation of the rock dynamic strength and the static pre-load (Li et al 2008b). Therefore, it is necessary to investigate the dynamic properties of rocks subjected to static pre-load.…”

Section: Introductionmentioning

confidence: 99%

Dynamic Fracture Properties of Rocks Subjected to Static Pre-load Using Notched Semi-circular Bend Method

et al. 2016

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A dynamic load superposed on a static pre-load is a key problem in deep underground rock engineering projects. Based on a modified split Hopkinson pressure bar test system, the notched semi-circular bend (NSCB) method is selected to investigate the fracture initiation toughness of rocks subjected to pre-load. In this study, a two-dimensional ANSYS finite element simulation model is developed to calculate the dimensionless stress intensity factor. Three groups of NSCB specimen are tested under a pre-load of 0, 37 and 74 % of the maximum static load and with the loading rate ranging from 0 to 60 GPa m 1/2 s -1 . The results show that under a given pre-load, the fracture initiation toughness of rock increases with the loading rate, resembling the typical rate dependence of materials. Furthermore, the dynamic rock fracture toughness decreases with the static pre-load at a given loading rate. The total fracture toughness, defined as the sum of the dynamic fracture toughness and initial stress intensity factor calculated from the pre-load, increases with the pre-load at a given loading rate. An empirical equation is used to represent the effect of loading rate and pre-load force, and the results show that this equation can depict the trend of the experimental data. Keywords Fracture toughness Á Pre-load Á SHPB Á NSCB Á FEM List of symbols BD Brazilian disc ISRM International Society for Rock Mechanics CCNSCB Cracked chevron notched semi-circular bend NSCB Notched semi-circular bend SHPB Split Hopkinson pressure bar a The length of the notched crack of the NSCB specimen A 0The cross-sectional area of the bar BThe thickness of NSCB and CCNSCB specimen E 0The Young's modulus of the bar material f D The scale factor of dynamic fracture toughness over the static fracture toughness f Dp The scale factor of dynamic fracture toughness with pre-load over the static fracture toughness K I The stress intensity factor for mode-I fracture in NSCB specimen K IcThe quasi-static fracture toughness K IdThe dynamic fracture toughness K I_totalThe total fracture toughness K I_preThe stress intensity factor due to the pre-load P 1The forces at the incident end of the specimen P 2The transmitted end of the specimen P dynamicThe dynamic load P maxThe maximum value of the load P preThe pre-load P totalThe total load P(t)The time-varying loading force RThe radius of NSCB specimen R S The radius of diamond-impregnated blade saw SThe span of the supporting pins Y(a/R)The dimensionless stress intensity factor e iThe incident stress wave & Kaiwen Xia

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Section: Introductionmentioning

confidence: 99%

Dynamic Fracture Properties of Rocks Subjected to Static Pre-load Using Notched Semi-circular Bend Method

et al. 2016

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“…Some recent experimental studies of rocks under combined static and dynamic loading have been performed. Li et al (2008aLi et al ( , b, 2010 presented a modified split Hopkinson pressure bar system, which could simultaneously apply static pressure and dynamic impact loading. Although the effects of both the static axial and confining pressures were introduced in their study, only the effects of the axial pressure were investigated.…”

Section: Introductionmentioning

confidence: 99%

Numerical SHPB Tests of Rocks Under Combined Static and Dynamic Loading Conditions with Application to Dynamic Behavior of Rocks Under In Situ Stresses

2016

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A modified split Hopkinson pressure bar (SHPB) numerical testing system is established to study the characteristics of rocks under simultaneous static and dynamic loading conditions following verification of the capability of the SHPB numerical system through comparison with laboratory measurements (Liao et al. in Rock Mech Rock Eng, 2016. doi:10.1007/s00603-016-0954-8). Three different methods are employed in this numerical testing system to address the contact problem between a rock specimen and bars. The effects of stand-alone static axial pressure, stand-alone lateral confining pressures, and a combination of them are analyzed. It is determined that the rock total strength and the dynamic strength are greatly dependent on the static axial and confining pressures. Moreover, the friction along the interfaces between the rock specimen and bars cannot be ignored, particularly for high axial pressure conditions. Subsequently, the findings are applied to determine the dynamic behavior of rocks with in situ stresses. The effects of the magnitude of horizontal and vertical initial stresses at varied depths and their ratios are investigated. It is observed that the dynamic strength of deep rocks increases with increasing depth or the ratio of horizontal-to-vertical initial stresses (K). The dynamic behavior of deeper rocks is more sensitive to K, and the rock dynamic strength increases faster with depth in areas with higher K.

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“…[18][19][20][21][22][23][24]. Conventional wisdom indicated that knowledge of the ejection velocity of the burst rock fragments is the key to further predicting rockburst risks and designing a corresponding protective support system [25][26][27][28].…”

Section: Introductionmentioning

confidence: 99%