Size effects in the uniaxial compressive properties of 3D printed models of rocks:an experimental investigation

Transparent physical models of real rocks fabricated using three-dimensional(3D)printing technology are used in photoelas-tic experiments to quantify the evolution of the internal stress and deformation fields of rocks.Therefore,they are rendered as an emerging powerful technique to quantitatively reveal the intrinsic mechanisms of rock failure.The mechanical behav-ior of natural rocks exhibits a significant size effect;however,limited research has been conducted on whether transparent physical models observe similar size effects.In this study,to make the transparent printed models accurately demonstrate the mechanical behavior of natural rocks and reveal the internal mechanism of the size effect in rock mechanical behavior,the size effect in 3D printed models of fractured and porous rocks under uniaxial compressive loading was investigated.Transparent cylindrical models with different sizes that contained different fractured and porous structures were printed using the fracture and porous characteristics extracted from natural coal and sandstone.The variation in uniaxial compres-sive strength and elastic modulus of fractured and porous models for increasing model sizes were obtained through uniaxial compression experiments.Finally,the influence of internal discontinuous structural features,such as fractures and pores,on the size effect pertaining to the mechanical behavior of the model was analyzed and elaborated by comparing it with the mechanical properties of the continuous homogeneous model without fractures and pores.The findings provided support and reference to analyze the size effect of rock mechanical behavior and the effect of the internal discontinuous structure using 3D printed transparent models.

Modeling interaction between CO_(2),brine and chalk reservoir rock including temperature effect on petrophysical properties

Carbon dioxide(CO_(2))capture and sequestration through CO_(2)enhanced oil recovery(EOR)in oil reservoirs is one of the approaches considered to reduce CO_(2)emission into the atmosphere.The injection of CO_(2)into a subsurface geological formation may lead to chemical reactions that may affect the formation pore structure and characteristics.In this study,the effect of CO_(2)ebrineerock interaction on the rock petrophysical properties and mineral volume fraction was numerically investigated during CO_(2)injection into a chalk reservoir rock.A 3D numerical modeling and simulation were conducted using COMSOL®Multiphysics commercial software of computational fluid dynamics(CFD)to simulate CO_(2)ebrine core flooding process in a chalk core.The model was validated against a coreescale experimental data from literature.Simulation differential pressure data matched the literature experimental data closely and consistently indicating good agreement between them.Temperature effect on the performance of CO_(2)ebrineechalk sequestration was also evaluated in the present study.Results indicated that porosity was only slightly affected by temperature increase during CO_(2)injection in contrast to permeability that was substantially affected by temperature.Moreover,chemical reactions enhanced as temperature increased leading to significant increase in permeability.Thus,carbonated brine sequestration excelled at elevated temperature due to increased acidity which governs the sequestration process.The developed model maybe considered as a reliable tool to optimize various operating parameters of CO_(2)ebrine sequestration.

Research for time-temperature equivalence effect of rock(Ⅰ):Theory research

In order to know about the rheological properties of rock in a long range of the time scale,method of increasing temperature was brought forward to accelerate the rheological process of rock,which could extend the time scale of experimental test data.Firstly,based on the generalized linear viscoelastic constitutive equation with temperature variable,the creep behavior of rock was divided into three types according to the different strain dependences of the time,that is,Hookean deformation,Newtonian flow,and retarded elasticity.Then the general equivalence relationship between time parameter and temperature parameter was derived for each type of strain.Finally,the relation between time parameter and temperature parameter in the whole creep was considered and the general theory of time-temperature equivalence effect(TTEE) of rock was established.This research reveals: ①The temperature effect on the instantaneous strain could be modified through vertical shift.②The key point of the TTEE of Newtonian flow depends on whether in the study of linear viscoelastic behavior of rock change of temperature is completely equivalent to a shift of the logarithmic time scale or not.③By plotting the results of a creep experiment performed at different temperatures and comparing the curves obtained,one can decide whether the rock considered have TTEE.④The TTEE of the whole creep should satisfy that the horizontal shift function of Newtonian flow and retarded elasticity is consentaneous.

Numerical investigation of dynamic response and rupture properties of rock slopes subjected to earthquake triggering

Landslides triggered by seismic activity have led to substantial human and economic losses.Nevertheless,the fundamental physical mechanisms underlying the vibration and rupture of rock slopes during earthquakes remain poorly understood.In this study,finite element method-based numerical simulations were conducted based on the rock slope at Dagangshan Hydropower Station in Sichuan province,China.Firstly,systematic analysis in both the time and frequency domains were performed to examine the seismic dynamic characteristics of the slope.Subsequently,the transfer function method and the multiple stepwise linear regression method were employed to clarify the underlying mechanism and determine critical factors influencing the slope instability during earthquakes.Time-domain analysis reveals that rock slope dynamic response exhibits notable elevation,surface,and local amplification effects.Specifically,the Peak Ground Acceleration(PGA)amplification coefficient(MPGA)is significantly higher at elevated locations,near the slope surface and in areas with protrusions.Moreover,the existence of fracture zones and anti-shear galleries minimally influences the dynamic responses but considerably affect the rupture.Specifically,fracture zones exacerbate rupture,while anti-shear galleries mitigate it.Frequency-domain analysis indicates that the dynamic responses of the slope are closely correlated with the degree of slope rupture.As earthquake magnitude increases,the rupture degree of the slope intensifies,and the dominant frequency of the response within the slope decreases,e.g.,its value shifts from 3.63 to 2.75 Hz at measurement point 9near the slope surface.The transfer function of rock slope,calculated under the excitation of wide flat spectrum white noise can reflect the interrelationships between the inherent properties and the rupture degree.Notably,the peak of the transfer function undergoes inversion as the degree of rupture increases.Furthermore,through multiple stepwise linear regression analysis,four key factors influencing the surface dynamic response of the slope were identified:rock strength,slope angle,elevation,and seismic dominant frequency.These findings provide valuable insights into the underlying mechanisms of rock slope dynamic responses triggered by earthquakes,offering essential guidance for understanding and mitigating seismic impacts on rock slopes.

Effects of amygdale heterogeneity and sample size on the mechanical properties of basalt

Due to the complex diagenesis process,basalt usually contains defects in the form of amygdales formed by diagenetic bubbles,which affect its mechanical properties.In this study,a synthetic rock mass method(SRM)based on the combination of discrete fracture network(DFN)and finite-discrete element method(FDEM)is applied to characterizing the amygdaloidal basalt,and to systematically exploring the effects of the development characteristics of amygdales and sample sizes on the mechanical properties of basalt.The results show that with increasing amygdale content,the elastic modulus(E)increases linearly,while the uniaxial compressive strength(UCS)shows an exponential or logarithmic decay.When the orientation of amygdales is between 0°and 90°,basalt shows a relatively pronounced strength and stiffness anisotropy.Based on the analysis of the geometric and mechanical properties,the representative element volume(REV)size of amygdaloidal basalt blocks is determined to be 200 mm,and the mechanical properties obtained on this scale can be regarded as the properties of the equivalent continuum.The results of this research are of value to the understanding of the mechanical properties of amygdaloidal basalt,so as to guide the formulation of engineering design schemes more accurately.

Fan‐hinged shear instead of frictional stick–slip as the main and most dangerous mechanism of natural,induced,and volcanic earthquakes in the earth's crust

Frictional stick–slip instability along pre‐existing faults has been accepted as the main mechanism of earthquakes for about 60 years,since it is believed that fracture of intact rocks cannot reflect such features inherent in earthquakes as low shear stresses activating instability,low stress drop,repetitive dynamic instability,and connection with pre‐existing faults.This paper demonstrates that all these features can be induced by a recently discovered shear rupture mechanism(fan‐hinged),which creates dynamic ruptures in intact rocks under stress conditions corresponding to seismogenic depths.The key element of this mechanism is the fan‐shaped structure of the head of extreme ruptures,which is formed as a result of an intense tensile cracking process,with the creation of inter‐crack slabs that act as hinges between the shearing rupture faces.The preference of the fan mechanism over the stick–slip mechanism is clear due to the extraordinary properties of the fan structure,which include the ability to generate new faults in intact dry rocks even at shear stresses that are an order of magnitude lower than the frictional strength;to provide shear resistance close to zero and abnormally large energy release;to cause a low stress drop;to use a new physics of energy supply to the rupture tip,providing supersonic rupture velocity;and to provide a previously unknown interrelation between earthquakes and volcanoes.All these properties make the fan mechanism the most dangerous rupture mechanism at the seismogenic depths of the earth's crust,generating the vast majority of earthquakes.The detailed analysis of the fan mechanism is presented in the companion paper“New physics of supersonic ruptures”published in DUSE.Further study of this subject is a major challenge for deep underground science,earthquake and fracture mechanics,volcanoes,physics,and tribology.

Experimental studies on gas and water permeability of fault rocks from the rupture of the 2008 Wenchuan earthquake, China

The permeabilities of fault rocks from the rupture of Wenchuan earthquake were measured by using nitrogen gas and distilled water as pore fluids under the confining pressure ranging from 20 to 180 MPa at room temperature. Experimental results indi- cate that both gas and water permeabilities decrease with increasing confining pressure, described by power law relationship, i.e., b = 0.2x10-3kl-0.557. The water permeability is about one order less than gas permeability and also half order smaller than the permeability corrected by the Klinkenberg effect, so-called intrinsic permeability. The differences in the permeabilies imply that the reduction of effective pore size caused by the adhesion of water molecules to clay particle surface and water-swelling of expandable clay minerals contributes to lessening the water permeability besides the Klinkenberg effect. Hence, the liquid permeability of fault rocks cannot be deduced by gas permeability by the Klinkenberg correction reliably and accurately, and it is necessary to use liquid as pore media to measure their transport property directly.

岩棉复合保温外模板承载力及温度效应分析

为了提高建筑外围护结构施工效率及解决传统外保温系统长期存在的易脱落和易着火问题,提出了一种集保温和建筑模板于一体的岩棉复合保温外模板(RW-CIEF)体系。RW-CIEF由内到外依次为内侧加强层、岩棉保温芯材、黏结层、保温过渡层以及外侧加强层。以哈尔滨市为例,基于全寿命周期成本(life cycle cost,C lc)确定了岩棉保温芯材的最佳厚度。采用有限元分析与理论计算相结合的方法探求了RW-CIEF在工程中的可行性,分析了RW-CIEF的抗弯性能、施工承载力及温度效应下的应力和变形,讨论了开槽形式、开槽宽度、开槽深度以及开槽间距对RW-CIEF抗弯性能的影响。结果表明:RW-CIEF的抗弯性能理论计算结果与有限元分析结果有较高的一致性;开槽处理可有效提高RW-CIEF的抗弯性能,综合抗弯性能、热工特性及加工角度,建议开槽形式选用对应开井字槽或对应开纵槽,开槽深度和宽度均为10 mm,开槽间距为150 mm;设计的RW-CIEF满足施工承载力,可保证外围护结构保温工程施工质量;由温度效应产生的最大拉应力和压应力均未超过RW-CIEF的外侧加强层承载力,反映出RW-CIEF出现夏季空鼓或冬季开裂现象的可能性极小。提出的RW-CIEF体系可为外围护结构保温工程及建筑模板工程未来研究方向提供一种新的思路和方法。

王家寨隧道第三系半成岩工程性质及涌水灾害风险分析

为探究王家寨隧道第三系富水半成岩物理力学性质,于现场取样开展颗粒筛分、XRD以及扫描电镜试验,并以现场试样的干密度为基准,制备重塑试样进行三轴压缩试验,研究其矿物组成、微观结构及力学特性,结合Mod-Flow模拟地下水位对隧道进行施工灾害分析。研究表明:1)王家寨隧道第三系半成岩级配不均,具备明显的弱胶结特征,在低含水率下具有明显的水敏性与遇水软化特性。随着含水率增长,试样的抗剪强度呈先增后减趋势,当含水率为11%时达到最大值459.03 kPa;当含水率低于12%时,黏土矿物形成胶结物填充颗粒间隙,使试样黏聚力增大;随着含水率持续增大,大量的自由水赋存于颗粒间隙,造成胶结结构破坏,试样抗剪强度明显下降。2)王家寨隧道涌水模拟结果显示,2段典型的富水段掌子面涌水量分别为2805 m^(3)/d和5025 m^(3)/d,表明在隧道富水段开挖极易发生涌水灾害,且灾害涌水量偏高。3)第三系半成岩水敏性强、遇水易软化的物理力学性质,高压富水环境以及工程扰动是王家寨隧道开挖诱发地质灾害的主要因素。

弱化矿岩破碎动力系统的能量转化和时效特性

基于弱化性质矿岩典型的非线性负指数本构关系和灾变特性,分析了灾变和非灾变两种破碎动力学模式下能量转化和时效特性随机构刚度的变化情况。结果表明,低机构刚度诱发的灾变破碎模式会急剧降低破碎动力系统的能量传递效率和破岩时效。从能量利用和破岩功效角度考虑,破碎动力系统不宜采用低机构刚度;给出了机构刚度设计适宜的选用范围。

三轴压缩条件下具有层理性页岩的力学性质及声发射演化

为探寻深部不同埋深应力条件下页岩的力学性质和破坏形态,利用MTS 815岩石力学测试系统开展页岩在常规三轴加载下的声发射试验。试验结果表明:60°层理倾角页岩压缩试验中,峰值应力、峰值轴向应变、弹性模量、泊松比与围压大小成正比;莫尔—库仑准则下所使用60°层理页岩的破裂方位角理论值在62°附近,实验值比理论值稍微偏大,整体在62°附近窄幅波动,页岩破裂模式为沿弱面的剪切破坏;页岩试样横向应变系数的改变与膨胀特性有关,10 MPa下,试样体积应变持续增大,岩石体积缩小,60 MPa试样的体积应变达到了-0.31%,岩石体积膨胀。围压越大,试样的膨胀特性越显著;页岩声发射定位点的多少与振铃计数率大小、能率高低具有良好的一致性。围压增加,累计计数和定位点的总量呈减少趋势,最大能率和累计能量随围压增加而减小。

基于多尺寸结构面的循环剪切力学特性及其抗剪强度研究

岩石结构面的抗剪强度具有强烈的尺寸依赖性,开展结构面多尺寸试验对于研究大尺寸结构面力学特性具有重要的理论价值和实践意义。针对过往研究较少的循环作用下结构面力学特性尺寸效应问题,首先基于立方体劈裂试验获得不同粗糙度的近天然岩石结构面,然后运用三维扫描技术获得结构面点云数据,进而采用三维打印技术制作不同尺寸结构面树脂模型,最后,通过倒模法制作试样并进行室内试验,研究不同法向应力下结构面尺寸效应的规律以及不同粗糙度和不同法向应力对结构面抗剪强度的影响。基于黏着摩擦理论-Barton经验公式,提出了一个可以考虑结构面尺寸效应的峰值抗剪强度公式。研究结果表明:岩石结构面的峰值抗剪强度具有明显的负尺寸效应,且峰值抗剪强度的改变对小尺寸大法向应力和大尺寸小法向应力下的结构面更为敏感;低法向应力下的残余剪切强度具有明显的负尺寸效应,而高法向应力下的残余剪切强度随着结构面尺寸的增大,从正尺寸效应变为负尺寸效应。

Experimental study on the mechanical properties of rocks at high temperature

The mechanical properties of marble, limestone, and sandstone as well as the stress-strain curve, the varying characteristics of the peak strength, the peak strain and elastic modulus were studied by using the MTS810 Rock Mechanics Servo-controlled Testing System under the action of temperatures ranging from room temperature to 800°C Results show that (1) the peak strength and elastic modulus of marble fluctuate at the temperature from normal to 400°C; and they decrease gradually over 400°C (2) With the rise of the temperature, the peak strength and elastic modulus of limestone show downward trend from normal temperature to 200°C have little change from 200°C to 600°C and decrease sharply over 600°C (3) The peak strength of sandstone shows a downward trend while a little change for elastic modulus at normal temperature to 200°C and from 200°C to 600°C, the peak strength of sandstone increases while a little change for elastic modulus; the peak strength and elastic modulus decrease rapidly at the temperature over 600°C. (4) The peak strain of limestone shows little change at normal temperature to 600°C, however, the peak strain increases rapidly over 600°C; and for marble and sandstone, the peak strain decreases with the rise of the temperature from normal temperature to 200°C, the peak strain increases rapidly over 200°C. The result can provide valuable references for the rock engineering design at high temperature.

双轴加载下成组裂隙参数对类岩石试件力学性质的影响规律

煤矿深部地层岩巷围岩裂隙分布复杂,裂隙参数对岩体力学性能影响较大。为研究深部地层裂隙岩体在掘进扰动条件下的破坏规律与力学性能,制备不同裂隙倾角和长度的成组裂隙类岩石试件,开展模拟煤矿深部巷道掘进扰动的双轴加载试验,研究类岩石试件力学特性及其影响因素。研究结果表明:成组裂隙试件强度受预制裂隙的倾角影响明显,当预制裂隙倾角为30°~45°时,试件的起裂应力和峰值应力为最小值,当裂隙倾角为90°时,试件的起裂应力和峰值应力最大。在双轴固定比例加载的条件下,裂隙倾角和长度均会对试件的强度产生影响,其中裂隙倾角对试件强度的影响最为明显,裂隙长度的影响较小。

煤岩组合体动力破坏响应研究进展述评

目前,煤炭资源已进入深部开采阶段。随着开采深度的增加,冲击地压发生的频次和烈度显著提高。围绕矿山冲击地压防治中的岩石力学等问题,许多学者从煤岩组合体的角度开展了系统性的基础研究。首先介绍了不同因素影响下煤岩组合体的力学性质,煤岩组合体的抗压强度、抗拉强度、弹性模量介于煤和岩石组分之间,更偏向于煤组分的力学性质。总结了煤岩组合体在不同条件下的能量积聚、能量释放等特征,煤岩组合体受载阶段可分为应变能快速积累、应变能增速放缓和应变能快速释放3个阶段,煤岩组合体的峰前积蓄能量和峰后耗散能量随抗压强度、加载速率、围压的增大而增大。分析了岩石强度、煤岩硬度差、能量差、煤岩比例、倾角、加载速率、外界载荷条件对冲击效应的影响,岩石强度越大、煤岩硬度差越大、能量差越大、煤岩比例越大、煤岩倾角越大、加载速率越高,冲击效应越强。研究了煤岩组合体破坏过程的声发射能量、振铃计数、声发射总数等特征,煤岩组合体受载时声发射信号具有明显的阶段性特征,可划分为平稳区、活跃区和爆发区,声发射活动可以作为评估煤岩组合体损伤状态的指标。总结了煤岩组合体不同条件下的破坏形式及失稳机制,煤岩组合体受载条件下积聚大量的能量,煤组分中积聚的能量较多,对于组合体的破坏起主导作用,岩石组分中的能量对组合体的破坏起到一定的加速和促进作用。最后讨论了煤岩组合体岩石组分的破坏机制和煤岩的界面效应,并且指出了高渗透压、高温条件、强动载扰动下煤岩组合体的力学性质和冲击效应是煤岩组合体未来重点关注的研究方向。

隧道施工防突岩盘破坏三维力学特征试验研究

隧道施工开挖遇前方存在突水突泥致灾构造时,如隔水/隔泥岩土盘厚度小于最小安全岩土盘厚度时,隔水/隔泥岩土盘在致灾构造中地下水/黏土压力的作用下失稳破坏,致灾构造中地下水或致灾构造中黏土突出形成突水/淤泥灾害。本文采用隧道中最为常见的砂岩和灰岩制作长宽一定、厚度不同的完整和预设裂隙试件,进行集中荷载作用下的破坏试验,探索砂岩和灰岩防突岩盘三维力学特征及最小安全岩盘厚度和水头的联系。结果表明:砂岩岩盘破坏形成的裂纹呈“X”型,灰岩岩盘呈“树枝”型;砂岩岩盘裂纹沿尺寸较大的方向产生,存在原生裂隙时裂纹尖端向大尺寸方向扩展;灰岩岩盘裂纹沿着长对角线产生主裂纹,在裂隙较深处出现次生裂纹,裂纹主要沿一端进行扩展;随着长度的增加,完整砂岩岩盘最大横向应力呈现“驼峰”型曲线,裂隙砂岩盘最大横向应力呈现“山峰”型曲线,完整和裂隙灰岩岩盘最大横向应力呈现“单峰”型曲线,横向应力在某一长度时最大横向应力出现极值;随着厚度的增加,曲线最终呈现“单峰”型曲线,在某一厚度下,抗破坏力最强,砂岩和灰岩板破坏时的水头与厚度均呈幂指数的关系。

脊形PDC齿的机械性能和破岩效果

以地层特性为依据有针对性地选择PDC异形齿,可以降低其失效的概率并提高其机械钻速和进尺。为了综合对比脊形PDC齿的机械性能和破岩效果,对165斧形、135斧形、三刃3种脊形PDC齿的耐磨性能和抗冲击性能进行测试,随后选择花岗岩进行3个吃入深度的单齿切削试验和不同压力下的全尺寸钻头模拟钻进试验,并与普通圆形齿的结果进行对比。结果表明:3种脊形PDC齿的耐磨性能均优于圆形齿的;165斧形齿与三刃齿的抗冲击性能优于圆形齿的,而135斧形齿的冲击点缺少材料支撑,其抗冲击性能较差。在相同吃入深度下,脊形齿的切向力与法向力均低于圆形齿的相应力,且脊角越小切削力越小。135斧形齿的机械钻速最快且适合高钻压;与165斧形齿比较,三刃齿在≤20.0 kN的低钻压下机械钻速较快,在>20.0 kN的高钻压下机械钻速较慢;圆形齿的机械钻速最慢,所适合的钻压也较低。同时,当脊形齿的脊角变化时,其冲击点的材料支撑也发生改变,进而影响其抗冲击性能;且脊角变化会改变前方岩石内部的应力集中,进而改变其破岩效果。

碳酸盐岩溶蚀效应及力学特性

针对不同赋存环境下溶蚀对碳酸盐岩力学特性的影响,采用自主研发的岩石动水压力溶蚀试验设备,开展多因素影响下碳酸盐岩溶蚀及单轴抗压强度试验,研究碳酸盐岩溶蚀效应、力学性质劣化规律及化学损伤。试验结果表明,不同赋存环境下岩样出现了不同程度的力学损伤,其抗压强度和弹性模量在溶解后有所下降,溶蚀率越高,峰值应力和弹性模量越低,进而提出劣化度拟合关系式,得到影响岩样抗压强度敏感度的各因素,依次为pH值、温度、时长、流速、动水压力及溶蚀后岩样的微观结构和矿物成分组成。

川中地区中二叠统茅口组储层特征及有效物性下限

储层有效物性下限是识别有效储层、确定储层有效厚度的关键参数,是提交天然气地质储量的一项必要研究内容。川中地区中二叠统茅口组储层有效物性下限常类比川东地区下三叠统飞仙关组、上二叠统长兴组碳酸盐岩储层,但其区域地质条件、沉积环境、成岩作用、岩石类型等均存在明显差异,严重影响了地质储量估算的精度,制约着该区茅口组气藏的勘探开发。本次研究基于钻井、测井、岩心、分析化验等资料,系统分析川中地区茅口组气藏储层特征,综合利用最小流动孔喉半径法、产能模拟法、单层试气法确定储层有效物性下限。研究结果表明:(1)川中地区茅口组储集岩类包括细晶云岩、少量砂屑云岩、灰质云岩以及云质灰岩;(2)研究区储集空间以各类溶蚀孔洞为主,裂缝和喉道是重要的渗流通道,储渗空间类型多、几何形态复杂,具较强的非均质性;(3)受溶蚀孔洞及微裂缝发育等因素影响,采用全直径样品实验结果反映研究区物性水平,总体表现为低孔低渗、局部发育高孔渗段的特征;(4) 3种方法综合确定储层有效孔隙度下限为1.97%,渗透率下限0.009 0 mD,为识别有效储层、确定有效储层厚度、估算地质储量等提供参考依据。

中低应变率范围内花岗岩单轴压缩特性的尺寸效应研究

利用变频动态加载岩石力学试验系统对直径为50 mm,长度分别为50,75,100,125 mm的花岗岩试样进行中低应变率范围内的加载试验。研究结果表明:(1)试样强度具有显著的应变率依赖性,随着应变率增大,压缩强度近似以乘幂关系增大。(2)静载和准动态加载条件下,岩石强度基本上随试样长度的增加而减小。(3)不同应变率加载条件下,直径为50 mm的试样,长径比不小于2时,方能取得基本稳定的试验结果。(4)峰值应变随试样尺寸的增大逐渐减小。(5)割线模量E50和线性段弹性模量Et随试样尺寸的增大而增大,且Et>E50。(6)破裂形式具有显著的应变率效应,随着应变率的增高,破碎程度加大;其尺寸效应则表现为:应变率<10-3s-1时,随着尺寸的增大,破裂形式表现为劈裂–锥形破裂–剪切破裂的过程;应变率>10-2s-1时,破裂形式则直接由锥形破裂变为剪切破裂。