岭澳核电三期强风化角岩边坡岩体直剪试验研究

采用堆载法进行天然状态与饱和状态下强风化角岩边坡岩体的现场直接剪切试验,获得不同正应力水平下剪切应力-剪切变形关系曲线和剪切强度参数,对其剪切应力-剪切变形关系曲线特征和不同正应力作用下剪应力随正应力的变化规律以及水-力耦合作用对剪切强度与变形特性影响进行了分析。试验结果表明：岩体峰值剪切强度和屈服剪切强度均随正应力的增大而增大;天然状态和饱水状态下剪应力随不同正应力的变化趋势基本相同;岩体剪切强度随含水率的增大而减小,在低法向应力下尤其敏感;水对岩体强度参数中黏聚力c的弱化作用更加明显,同时加大了岩体变形量,延长了岩体变形过程;通过现场直剪试验测得的法向变形可以估算岩体的压缩模量,为边坡稳定性分析提供参数。     

某变形体特征及形成机理研究

变形体位于贵州省铜仁市凉水井镇,斜坡属于典型的软弱基座型缓倾坡内斜坡。基于斜坡工程地质条件及斜坡基本特征,定性分析了斜坡整体变形破坏模式。通过Geostudio2007数值模拟软件,研究斜坡整体变形破坏特征及模式,结果表明:暴雨与天然状态下,因下部泥页岩的塑性变形导致上部灰岩拉裂,斜坡整体失稳模式为塑流—拉裂;暴雨状态下,水对下部泥页岩的软化作用和裂隙充水静水压力及动水压力,加快了岩体破坏,推进斜坡破坏进程。     

水力耦合作用下含三维裂隙类岩石材料的破裂力学行为及声发射特征

水力耦合作用下裂隙岩体的破裂力学行为及声发射特征是关系到地下工程安全建设与灾变预测预警的关键问题。利用水泥砂浆材料及声发射技术开展了室内压缩破裂试验,研究了无水及水力耦合条件下含三维裂隙试件的破裂模式、力学特性、声发射特征以及水压和裂隙倾角的影响,分析了声发射信号主频特征随岩体破裂状态的变化规律。试验结果表明:随裂隙倾角增大,试件破裂模式经历了张拉为主-拉剪复合-剪切为主的转变过程;水压增大增强了试件张拉破裂模式,而剪切破裂模式在一定程度上被削弱;随水压升高,起裂应力、损伤应力和峰值强度均持续降低,水压对起裂应力及峰值强度的影响程度存在阈值(4 MPa);试件破裂过程中声发射撞击率变化呈现明显阶段性特征,从而为起裂和损伤应力判定提供了依据;试件不同破裂状态下的声发射信号呈现不同主频特征,相对高、中、低频波的主频值域区间具有非连续性,低频和高频信号占比与试件破裂状态存在对应关系,因此可为岩体破裂状态的预测预警提供参考信息。     

水压在底板突水中的力学作用

分析了水与水压在底板突水中的力学作用，即水对岩石的软化作用；水压对裂隙介质岩体的力学作用；水压在断层中的水楔作用；突水过程中水流的冲刷扩径作用和水压对突水的动力作用。     

长期浸泡作用下灌浆加固裂隙岩体劣化效应

为分析灌浆加固裂隙岩体在压力水长期浸泡作用下力学性能的劣化效应,在前期碳纤维水泥基复合灌浆材料加固裂隙岩体研究基础上开展了考虑水压力影响的灌浆加固裂隙岩体长期浸泡试验和在不同浸泡周进行直剪试验。研究结果表明,(1) 压力水长期浸泡作用下灌浆加固裂隙岩样的剪应力?剪切位移曲线形态变化趋势明显,剪切刚度逐渐减小,达到峰值抗剪强度时的剪切位移逐渐增大;(2) 随着浸泡周期增加,灌浆加固裂隙岩体的抗剪强度呈先陡后缓的劣化趋势,6个浸泡周期（150 d）后不同法向应力下峰值抗剪强度的劣化幅度为32.6%～39.9%,对应内摩擦角和黏聚力分别降低了19.3%、39.4%,其中前4个浸泡周期（0～90 d）抗剪强度参数劣化幅度占总劣化幅度的90%左右;(3) 水压力作用下裂隙岩样发生溶解、溶蚀、润滑、软化等物理化学作用,浆体中的凝胶体被进入浆体内部的水分子软化,导致裂隙岩体和灌浆体本身的力学性质逐渐劣化,浆体与裂隙面之间的胶结作用、浆体与碳纤维之间粘结性能逐渐减弱,使得灌浆加固裂隙岩体抗剪性能逐渐劣化,剪切破坏面逐渐发展到浆体与裂隙面之间的胶结面。相关研究成果可为灌浆加固裂隙岩体的长期稳定性分析评价提供参考。     

含方解石脉石炭系灰岩单轴压缩的变形破裂特点

沉积岩形成后由于构造运动和热液运移而导致节理裂隙中晶体生长形成岩脉充填,方解石脉充填节理裂隙后与母岩形成整体,公路隧道及边坡工程中会经常遇到岩体中充填有大量的方解石脉。方解石脉与围岩之间的边界由于形成地质结构,所以对于岩体在应力作用下的力学响应具有重要作用,另外方解石脉的充填厚度也会显著影响到岩体的整体力学行为。本次研究从贵州省惠水至兴仁高速公路工程野外露头采集了含有不同厚度方解石脉的石炭纪石灰岩,考虑到不同厚度方解石脉充填以及区域长期降雨过程中水对岩石力学行为影响这两个重要因素,首先对天然以及饱和后的岩石切片开展了矿物组构的统计分析,然后在实验室制备了标准圆柱形岩石试样并开展了天然以及饱和后的单轴压缩力学实验。通过单轴压缩实验获得了试验过程的全应力-应变曲线,针对破裂后试样采用工业CT扫描及三维重构获得了岩石试样中的裂缝形态特点。经过对饱和以及天然状态下含不同厚度方解石岩脉灰岩的力学行为和裂缝分布的分析发现,由于方解石岩脉厚度和含水饱和度的增加,其单轴受压状态下整体塑性显著增加且强度明显降低,岩石饱和后矿物组构的变化以及方解石脉厚度的增加对其力学行为以及破裂模式有明显影响。另外随着方...     

黄河李家峡典型岩坡变形破坏的水效应研究

黄河上游李家峡段高陡岩坡变形破坏受多种因素控制, 其中水的影响十分明显, 主要包括水的静态效应和动态效应两方面。本文从地下水的软化作用、库岸水压力或静水压力、孔隙水压力, 以及河流冲蚀、边岸再造、降雨引起的动水压力作用和水库泄水引起的动水压力作用等方面, 结合数值模拟手段分别研究了它们对岩坡变形破坏的影响程度和方式。     

某水工隧洞裂隙岩体高水头作用下的渗透性试验研究

结合某抽水蓄能电站高压引水隧洞裂隙岩体的高压压水试验、常规压水试验和室内试验,分析了裂隙岩体在高水头条件下渗透流量与压力关系所反映的岩体渗透特性变化规律;在定量计算基础上探讨了裂隙岩体渗透系数与压力的相互关系。通过对比高压压水试验、常规压水试验和室内试验得到的渗透系数,分析了环境应力状态和压力变化对渗透系数取值影响的原因。研究结果表明,高水头作用下裂隙岩体的渗透系数明显大于低水压条件下的渗透系数,室内试验渗透系数因应力解除影响而大于原位压水试验渗透系数值。     

谷竹高速公路原状片岩抗剪强度的水敏性研究

为了解鄂西北地区水敏性片岩在水作用下的抗剪强度特性,对取自谷竹高速公路现场的原状片岩试样开展了沿其层理面的室内天然状态直剪试验和饱水状态直剪试验,试验结果表明：水对片岩的抗剪强度和破坏特征影响显著;饱水后片岩与天然状态相比凝聚力降低了36.7%,内摩擦角降低了4.6%,残余凝聚力降低了66.7%,残余内摩擦角降低了11.3%;与天然状态的脆性破坏不同,饱水后片岩破坏时具有明显的延性特征。基于试验结果,探讨了水对片岩抗剪强度参数的弱化机制,利用极限平衡方法计算了谷竹高速公路沿线某边坡的安全系数,进而对该边坡在暴雨或连续降雨工况下的稳定性做出了评价。     

温度和含水状态对岩石劈裂强度影响的试验研究

岩土类材料的强度强烈依赖于含水率和温度条件.以兰州兰山砂岩为研究对象,分别进行了不同温度（+20℃、-5℃、-10℃）和不同含水率（干燥、天然含水率和饱和状态）条件下岩石的巴西圆盘劈裂试验.试验结果表明,常温下,岩石抗拉强度随含水率增加而急剧减小,试样饱和时软化、崩解,丧失承载能力;在不同负温条件下,天然含水状态的试样抗拉强度最大,干燥状态下最小;在-10~+20℃范围内,干燥岩石强度随温度升高,抗拉强度增大,含水岩石均是随温度升高,抗拉强度减小,但饱和岩石在-5℃时抗拉强度最大.含水率和温度对岩样强度的影响存在临界值,超过临界值,岩样强度随上述因素反向变化.试验结论为岩土类材料劈裂强度的标准化测试及其工程应用提供了重要的基础数据参考.     

An Experimental Study of the Rate Dependence of Tensile Strength Softening of Longyou Sandstone

It is well-known that the strengths of sandstones measured under fully saturated conditions are smaller than those measured under nominally dry conditions. This strength softening phenomenon has profound implications to rock engineering. In this work we investigate the tensile strength softening of Longyou sandstone from China. Defining the strength softening factor as the ratio of the strength under nominally dry conditions over that under saturated conditions, the static compressive strength softening factor of Longyou sandstone is close to 2 and the static tensile strength softening factor is about 7.9. To further address the applications, where the load may be dynamic, we examine the rate dependence of the tensile strength softening of this sandstone. The dynamic tensile strength is measured using the split Hopkinson pressure bar system in combination with the Brazilian disc sample geometry. The results show that the tensile strength softening factor decreases with the loading rate. Because the saturated sample shows stronger loading rate sensitivity than the dry sample, the softening factor decreases with the loading rate.     

Study on frost heaving characteristics of sandstone under different freezing conditions北大核心CSCD

At present,artificial freezing method has become one of the effective methods for coal mine shaft to pass through water-rich soft rock strata,which can stop the movement of groundwater and limit the deformation of surrounding rock. In order to study the frost heaving characteristics of sandstone under different freezing conditions,frost heaving tests of saturated and dry Cretaceous red sandstone samples under different freezing rates （10 ℃·h-1,5 ℃·h-1,2 ℃·h-1,1 ℃·h-1）and different confining pressures（5 MPa,10 MPa,15 MPa,20 MPa,25 MPa）were carried out by using GCTS（Geotechnical Consulting & Testing Systems）servo-controlled low temperature and high pressure triaxial rock testing system. In this paper,based on the existing theory of physical and mechanical properties of frozen soil,we studied the frost heaving law of sandstone under different freezing conditions and explored the frost heaving mechanism. The result shows that in the process of cooling,the dry rock sample always produce cold shrinkage deformation,while the saturated rock sample first produce cold shrinkage deformation,then produce frost deformation,and finally the deformation tends to be stable. The deformation of saturated rock samples is much larger than that of dry rock samples. The larger the stress level of rock samples at the same temperature is,the smaller the frost deformation is,which shows a linear negative correlation,mainly because the high confining pressure limits the volume expansion of the water phase in the pore inside the rock samples when it becomes ice. The frost deformation of rock samples is mainly affected by confining pressure and water content,while the frost heaving rate is mainly affected by cooling rate. Under this test condition,the higher the cooling rate of sandstone is,the higher the frost heaving rate is,and the relationship between them is approximately linear. For saturated rock samples,the confining pressure reduces the rock frost heaving by limiting the expansion during the phase transformation of ice water,and the temperature affects the rock frost heaving by affecting the freezing rate of pore water and the thermal expansion and cold contraction of rock skeleton. For dry rock samples,the deformation is mainly due to the volume contraction of rock mineral particles caused by thermal expansion and cold contraction effect,and the greater the temperature change,the greater the deformation. Based on the experimental results and theoretical analysis method,a calculation formula of rock frost heaving considering the influence of confining pressure was established. By calculating the frost heave of sandstone samples under different confining pressures,it is found that the calculated values are in good agreement with the experimental results. Moreover,according to the calculation formula of frost heaving,the influence factors of rock frost heaving during freezing can be divided into two categories：internal cause and external cause. The internal cause includes porosity,saturation,volume modulus of ice and rock skeleton,and the external cause includes temperature and confining pressure. For saturated rock,the frost heaving is mainly affected by factors such as confining pressure,temperature and porosity. When the saturation,porosity and freezing rate are low,the rock may only produce shrinkage deformation,because these indicators determine whether the rock produces frost heave or freeze shrinkage. The mechanism of rock frost heaving is very complicated due to the interaction and restriction between the internal and external factors and the dynamic changes of rock micro-structure and mechanical properties during the process of frost heaving. The research results can provide theoretical reference for freezing construction scheme design of deep coal seam mine construction,and also provide a theoretical basis for the study of physical and mechanical properties and engineering application of soft rock in frozen soil area. © 2022 Science Press (China).     

Mechanical properties and energy mechanism of red sandstone under hydro-dynamic coupling effectEI北大核心CSCD

A series of impact experiments is conducted on natural, soaked and saturated red sandstone samples. The effect of hydro-dynamic coupling on dynamic strength, deformation characteristics and energy mechanism of samples is analyzed by comparing with that of dry samples. Experimental results indicate that dynamic compressive strength and peak strain of samples are mainly affected by the water content and impact load, while the peak modulus is obviously influenced by the water content. The water softening effect leads to loosen expansion of granular structure, which further results in cementation weakening. In addition, the meso-mechanical effect of pore water might lead to low strength and high strain of samples at high strain rate. The strength of samples is strengthened and the plastic deformation is decreased by the effect of strain rate. A large amount of total absorbed energy U prior to the peak stress is transformed to the releasable strain energy U-c,but a small portion of U is transformed to the dissipation energy U-d. he strain energy of each part increases with the increase of the pulse intensity, however the variation with the water content is largely different. A modified brittleness index BIM (ratio of U-d to U-e) shows that both the water content and pulse intensity have a threshold resulting in the response of plastic deformation quite different. The effective impact energy index (K-eff) shows that the strain rate effect significantly influence the impact tendency of dry and saturated samples. Water softening effect reduces the effect of strain rate, but the strain rate effect is enhanced when the saturation is reached.     

孔隙压力作用下煤岩破裂及声发射特性的数值模拟

运用嵌入孔隙压力的岩石破裂过程分析RFPA2D系统,对孔隙压力作用下煤岩的变形强度特性进行了数值试验研究。数值试验结果表明,在孔隙压力一定时,随着围压的增加,煤岩的杨氏模量、抗压强度都随之增高;而当围压一定时,随着孔隙压力的增加,煤岩的杨氏模量、抗压强度则稍有降低,而且峰值强度后的应力-应变曲线有呈现脆性的趋势。此外数值模拟还研究了不同围压及孔隙压力作用下煤岩的声发射特性     

考虑围压影响的岩石峰后应变软化力学模型

试验表明,随着围压增加,岩石峰后残余强度和割线模量增加,如何模拟围压对岩石峰后应变软化力学行为的影响是岩石峰后力学行为研究的关键。利用Z. Fang[1]提出的峰后强度下降指数描述围压对岩石峰后残余强度和割线模量的影响,与摩尔-库仑模型结合,建立了考虑围压影响的岩石峰后应变软化力学模型。在FLAC环境下,利用Fish函数方法开发了相应的数值计算程序。数值算例研究了Tennessee大理岩在不同围压下的应变软化过程,模拟结果与试验数据基本一致,表明建立的模型合理,可以应用于岩石峰后软化过程的模拟。     

孔隙水压力对锯齿状结构面剪切蠕变特性的影响

为探究孔隙水压对岩体结构面剪切蠕变特性的影响,自主研制了结构面一体化制作模具和多功能剪切流变仪,开展了孔隙水压力下锯齿状结构面的剪切蠕变试验,分析了孔隙水压对结构面蠕变变形、蠕变速率和长期强度的影响。试验结果表明：不同孔隙水压力下的结构面先后经历了瞬时变形阶段、减速蠕变阶段和稳定蠕变阶段,并且孔隙水压力的增大促进了结构面非线性特征的发展;随着孔隙水压力的增大,结构面瞬时位移、蠕变位移和稳态蠕变速率逐渐增大,而蠕变时长、破坏应力和长期强度均呈现明显降低的趋势。根据试验结果,考虑孔隙水压力对模型参数的影响,将蠕变模型中的瞬时剪切模量、黏性剪切模量以及黏性系数替换为孔隙水压力的函数,构建了能够反映孔隙水压力影响的结构面蠕变模型,并对模型参数进行辨识,将试验曲线和理论模型曲线进行对比,验证了模型的正确性和适用性。研究成果对富水区岩体长期稳定性分析提供一定的理论指导。     

酸性干湿循环下充填节理岩石劣化性能试验研究

为探究酸性干湿循环作用对充填节理岩石的损伤劣化规律,首先对预制充填节理岩石进行酸性和中性环境下不同次数的干湿循环前处理,再采用万能试验机和分离式Hopkinson杆（split Hopkinson pressure bar,简称SHPB）装置对其进行单轴压缩试验和动态冲击试验,对充填节理岩石纵波波速、静态抗压强度以及动态抗压强度的劣化效应进行分析,并进一步分析酸性和中性环境干湿循环作用下充填节理岩石动态冲击的破坏形态。结果表明,随着干湿循环次数的增加,无论是酸性环境还是中性环境,充填节理岩石的波速值、静态抗压强度以及动态抗压强度不断减小,劣化程度不断加剧,其中酸性干湿循环作用对静态抗压强度的劣化最显著;此外发现干湿循环作用下充填节理岩石静态、动态抗压强度与波速值之间均存在一致性较强的线性关系;酸性环境干湿循环作用下充填节理层粉化程度和两侧岩石破碎程度更严重。研究成果可为酸性环境干湿循环作用下工程岩体稳定性分析提供科学依据。     

不同岩性火山岩孔隙度压力敏感性及其影响因素：以长岭断陷火山岩为例

为了解不同岩性火山岩孔隙度的压力敏感性,笔者选取长岭断陷安山岩、角砾凝灰岩和凝灰岩的代表性岩样,分别进行3.4、8.3、13.1、17.9、22.8、27.6、32.4、37.2 MPa多个覆压条件下的气体法孔隙度测量。结果表明,随着压力的增大,3种岩性岩样的孔隙度呈不同幅度的减小,幅度减小程度由大到小的岩性依次为凝灰岩、角砾凝灰岩、安山岩;说明凝灰岩的孔隙压力敏感性较强、角砾凝灰岩的孔隙压力敏感性居中、安山岩的孔隙压力敏感性最弱。经X射线衍射全岩分析、偏光显微镜下岩石薄片鉴定、高压压汞仪实验和基于CPMG脉冲序列的核磁共振实验分析显示,岩石组份、颗粒分选、孔径分布是影响孔隙压力敏感性的关键因素;塑性矿物体积分数越大、颗粒越小、孔径越小,相应孔隙度的压力敏感性越强。     

南京秦淮东河黄马青组(T2h)砂岩水致劣化特征分析

南京秦淮东河新开河道在铜家山地段穿越黄马青组（T₂h）砂岩,形成高度最大达70 m的高边坡。根据现场调查和钻探结果,在近地表处,岩石中裂隙发育,岩体完整性差,而在深部,根据钻孔取芯结果,岩体中结构面胶结强度高,岩体完整性好。钻孔取岩芯样进行干湿循环试验发现,样品在干燥-饱和循环条件下,一般循环5次以上就易发生崩解,而在自然吸水-干燥循环条件下,循环20次以上仍可以保持完整。分析认为,岩石中小开裂隙发育。根据扫描电镜（SEM）对微观结构分析结果发现,饱和条件下,岩石中小开裂隙进水后导致结构面胶结物软化,并可能造成岩石开裂、吸水膨胀,即水对岩石的劣化作用是物质软化和岩石结构破坏的双重机制;而在自然吸水条件下,小开裂隙中未进水,水对结构面的软化作用较小。矿物分析结果表明,岩石中含有较多的黏土矿物,是导致岩石浸水软化的重要原因。经过干湿循环后,岩石波速下降、致密程度降低,塑性特性增强。多次循环后岩石的单轴抗压强度和弹性模量均呈明显下降趋势,岩石破坏时的变形量随循环次数增大而下降,岩石的孔隙压密和弹性变形过程逐渐消失,加载后迅速进入塑性变形阶段,且破坏速度加快。     

循环荷载下软黏土不排水强度弱化分析的动力有限元ABAQUS实现

在波浪循环荷载作用下饱和软黏土地基出现孔隙水压力升高,并导致不排水强度弱化,严重影响防波堤的承载性能。考虑静偏应力影响,基于最大孔隙水压力发展模型和正常固结软黏土不排水强度公式,推导出软黏土不排水强度随循环荷载作用次数和应力水平变化的动态折减规律。结合软黏土不排水强度动态折减规律和M-C屈服准则,在有限元软件ABAQUS上实现软黏土不排水强度循环弱化分析的数值开发和动力运算过程。运用该动力有限元方法对天津港防波堤地基软黏土的动、静三轴试验进行数值模拟运算。结果表明,最大孔隙水压力发展曲线以及循环荷载作用后不排水强度的数值预测结果与动三轴试验结果吻合良好。另外,动力有限元方法（DFEM）能够表示土体强度在循环荷载作用下的具体弱化过程。