红层软岩变形特性及基床系数取值试验研究

岩体变形特性及基床系数与基础内力、最终变形量和变形的均匀性直接相关,合理确定基床系数值对高层特别是超高层建筑至关重要。以成都市某超高层建筑论证为依托,针对建筑物持力层中风化泥质软岩,在井下平洞内进行不同压板尺寸和形状的平板载荷试验,并取得原位试样进行室内岩块单轴抗压强度、常规三轴压缩试验和直接剪切试验,根据室内及原位试验资料分析了岩体单轴抗压强度、弹性模量、承压板尺寸与基床系数的关系。结果表明：地基基床系数具有随地基岩石单轴抗压强度增加而增加的趋势;较小承压板试验数据离散性较大,较大压板试验数据离散性较小;如果红层软岩基床系数按照规范建议的黏土或砂土经验公式进行修正,会引起较大误差;红层软岩（中等风化泥岩）地基的基床系数与载荷板尺寸间呈双曲线型经验关系,据此建议对建筑物红层软岩地基基床系数进行修正;对红层软岩采用500 mm方形承压板试验获取的基床系数离散性较小。     

单轴循环冲击下花岗岩力学特性与损伤演化机理

为研究循环冲击荷载下黑云母花岗岩的动态力学特性,利用改进的分离式霍普金森压杆,选取4种不同的入射波应力幅值对花岗岩试样进行等幅循环冲击,并对相关机理和试验现象进行探析.结果表明:入射波应力幅值为110.57和90.48 MPa时,随着冲击次数的增加,岩样的峰值应力逐渐降低,最大应变、平均应变率和损伤值均呈现增大趋势;入射波应力幅值为70.82 MPa时,花岗岩的峰值应力随着冲击次数的增加表现出先增强后降低的特性,而最大应变、平均应变率与损伤值则表现出相反规律;入射波应力幅值降为50.69 MPa时,岩样的力学性质基本不变,岩样未见明显的损伤.此外,研究还发现基于岩样静态压缩应力-应变曲线推求的静态裂纹起裂应力,经强度增长比例系数放大后可得到动态裂纹起裂应力,籍此能较好地解释上述循环冲击试验中所观测到的现象.     

Experimental investigation on hard rock fragmentation of inserted tooth cutter using a newly designed indentation testing apparatus

This investigation aims to explore the effects of stress conditions and rock cutting rates on hard rock fragmentation through indentation tests on a newly designed triaxial testing apparatus. This apparatus was designed to realize a triaxial loading and indentation test of cylindrical specimens using inserted tooth cutter. The boreability and crushing efficiency of granite rock was investigated by analyzing the change rules of the thrusting force, penetration depth, characteristics of chippings and failure patterns. Several quantitative indexes were used to evaluate rock boreability in this investigation. The granite rock samples all had a chiselled pit and a crushed rock core. Under initial stress conditions, only flat-shape chippings were stripped from the rock surface when the thrusting force reached 20 kN. The rock cutting special energy had a close correlation with the initial stress conditions and inserted tooth shape. Moreover, a thrusting force prediction model was proposed in this paper. The contribution of this study is that for the first time the influence mechanism of the initial triaxial stress conditions on rock fragmentation is investigated using an inserted tooth and the newly designed testing apparatus. This study has a crucial importance for practical underground hard rock crushing in geoengineering.     

基于FDEM的岩石颗粒破碎后碎片形状的统计分析

针对碎片尺寸和形状会影响岩石强度和变形的问题,采用三维扫描技术获得真实岩石颗粒的表面点云数据,然后通过数字图像处理技术重构数字颗粒,利用连续-离散耦合方法（FDEM）模拟单个颗粒在平板压缩下的断裂破碎. 识别颗粒破碎后所产生的碎片,并进行碎片形状的表征和量化,分析碎片形状与颗粒初始形状、碎片尺寸的关系. 为了准确描述裂纹尖端的应力梯度和损伤演化,进行颗粒有限元网格密度的敏感性分析,结果表明,断裂过程区至少需要5、6个界面单元以减弱网格尺寸的影响. 本研究关注颗粒破碎后所产生碎片的整体形态,忽略断裂引起的碎片表面局部起伏和粗糙变化. 尽管所研究颗粒的初始形状存在较大差异,仍发现颗粒破碎后所产生碎片的形状指标分布具有一些共性特征. 碎片的圆度、扁平率、Domokos因子和凸度对颗粒初始形状的敏感性逐渐增强,并且除了圆度外,其他形状指标分布与碎片尺寸之间并未发现显著的相关性. 不同粒径组碎片的圆度分布表明,较大的碎片棱角更明显.     

不同卸载速率下煤岩采动力学响应试验研究

深刻认识采动应力路径下岩体力学响应的加载速率效应,是科学界定实际工作面推进最优速率的重要基础。基于平煤矿区煤岩初始地应力环境,定量分析了千米级赋存深度煤岩保护层开采条件下应力演化特征,展开更为符合真实应力状态的不同加载速率下煤岩体力学行为实验模拟,同时与未考虑采动试验结果进行对比分析。研究结果表明：（1）常规三轴压缩试验,试样强度受加载速率影响较小,在1~4 MPa/min时并无明显变化,达到5 MPa/min时强度才有明显的上升,约为115 MPa。（2）随加载速率增加,采动过程中煤岩体强度呈现下降后上升再下降的趋势,1 MPa/min和4 MPa/min加载速率下煤岩体强度达到最大,其峰值应力约为64 MPa,较3 MPa/min提高了12%。（3）低加载速率下试件内部的微小裂隙可以充分发育、扩展,试样裂隙密度随加载速率增加呈减小趋势,其中1 MPa/min约为5 MPa/min的1.61倍,适当降低开采速度可提高瓦斯抽采效率。（4）不同开采速度煤岩在整个采动过程中体积应变不仅出现了相对初始状态的压缩现象,还出现了破坏阶段的体积膨胀,可将其作为采动特征,明显区别于未考虑采动下的体积压缩,且采动下煤岩强度明显偏小,破损程度更大。研究成果可为类似地质条件开展保护层开采设计奠定一定的理论基础。     

粉煤灰掺量对石灰桩性能的影响

目的为了确定粉煤灰石灰桩复合地基设计时无侧限抗压强度技术参数，以及粉煤灰掺入量多少对粉煤灰石灰桩无侧限抗压强度的影响．方法采用试验的方法对粉煤灰石灰桩的力学性能进行实验室试验，并分析了试验所用原材料的化学成分．笔者通过6大组试件试验，研究了不同龄期、不同粉煤灰掺量情况下，粉煤灰石灰桩无侧限抗压强度的变化趋势．结果试验结果表明，粉煤灰石灰桩3d无侧限抗压强度为0．而28d无侧限抗压强度随粉煤灰掺量的增加而减少，当粉煤灰掺量达到80％以上时，28d无侧限抗压强度为0．结论宜取28d的无侧限抗压强度作为粉煤灰石灰桩的强度指标，且粉煤灰掺量越多，粉煤灰石灰桩的无侧限抗压强度越低．     

岩石破碎功、坚固性系数、强度关系的实验研究

为了探索岩石突出等地下工程灾害中的岩石破碎功能关系,以岩石破碎理论为基础,进行了不同岩石的破碎和坚固性捣碎实验、破碎粒度筛分分级实验、岩石单轴抗压强度实验。通过对不同岩石的坚固性系数与破碎比功和单轴抗压强度等实验结果进行了回归,分析了三者之间的关系。研究表明,岩石坚固性系数与岩石破碎比功、岩石单轴抗压强度之间线性相关,同时验证了岩石破碎功能关系符合裂纹学说。实验结果对计算岩石动力灾害中的岩石破碎所需能量提供了实验基础和理论依据。     

花岗岩和大理岩在不同应变率下的冲击试验研究

利用橡胶波形整形器改进后的分离式霍普金森压杆装置,对花岗岩和大理岩在不同应变率下进行了冲击压缩试验。通过试验有效性的验证,证明了数据的可靠性。试验结果表明:应变率明显影响这两类岩石材料的动态力学特性,不同冲击速度下的动态抗压强度、峰值应力、弹性模量表现出显著的率相关性,峰值应变则变化不大,其中分析了花岗岩和大理岩的峰值应力-冲击速度关系以及弹性模量-冲击速度关系,两者呈弱幂函数关系;加载过程中花岗岩表现出更显著的动态脆性,在破坏形态方面花岗岩大多呈轴向劈裂破坏,大理岩破碎程度明显更高呈压碎破坏,并从微观结构方面进行了对比分析。     

不同速率下单双钎头破岩声发射数值分析

选用脆性花岗岩为研究对象,利用岩石破裂过程分析软件RFPA2D,分别对其进行单、双钎头在不同加载速率下的数值模拟试验,得到RFPA2D应力图及相对应同一加载步下的声发射图。结果表明:较单钎头相比,岩石在双钎头协同作用下将会形成应力叠加,且钎头下面的裂纹会对相邻裂纹产生影响,裂纹尖端会产生应力集中,试件破坏释放出的声发射能量和声发射计数更大;随着加载速率的增大,试件释放的声发射总能量增大,且所得竖向载荷增大。     

基于隧道掘进机掘进过程的岩体状态感知方法

针对现有技术无法预先、实时获取隧道掘进机（TBM）掌子面岩体状态参数的问题,提出基于TBM掘进过程监测的岩体状态感知方法. 以吉林引松供水工程TBM施工隧道为依托,分析TBM掘进过程中掘进参数的变化规律,建立TBM掘进参数与岩体参数数据库,研究TBM设备参数和在掘岩体参数之间的相互关系. 分别采用分步回归和聚类分析的方法建立岩机关系模型,利用监测TBM掘进参数实时感知岩石强度、体积节理数和围岩等级等参数. 以石灰岩和花岗岩地层为例,对TBM在掘岩体参数的预测值与实际值进行对比. 结果表明,利用提出的岩体状态感知方法预测的岩石抗压强度UCS和体积节理数与实际值的误差小于18%,预测当前围岩等级与实际岩体状态基本一致,验证了研究结果的准确性.     

Engineering property test of kaolin clay contaminated by diesel oil

Engineering property of kaolin clay contaminated by diesel oil was studied through a series of laboratory experiments.Oil contents(mass fraction) of 4%,8%,12%,16% and 20% were selected to represent different contamination degrees,and the soil specimens were manually prepared through mixing and static compaction method.Initial water content and dry density of the test kaolin clay were controlled at 10% and 1.58 g/cm~3,respectively.Test results indicate that since part of the diesel oil will be released from soil by evaporation,the real water content should be derived through calibration of the quasi water content obtained by traditional test method.As contamination degree of the kaolin clay increases,both liquid limit and plastic limit decrease,but there's only a slight increase for plasticity index.Swelling pressure of contaminated kaolin clay under confined condition will be lowered when oil-content gets higher.Unconfined compressive strength(UCS) of the oil-contaminated kaolin clay is influenced by not only oil content but also curing period.Increase of contamination degree will continually lower UCS of the kaolin clay specimen.In addition,electrical resistivity of the contaminated kaolin clay with given water content decreases with the increase of oil content.However,soil resistivity is in good relationship with oil content and UCS.Finally,oil content of 8% is found to be a critical value for engineering property of kaolin clay to transit from water-dominated towards oil-dominated characteristics.     

磷块岩地下开采的岩爆机理及处理对策

中国某磷块岩矿床地下开采过程中,采场顶板及巷道有明显的岩爆现象发生. 通过现场岩爆的实地调查,了解现场岩爆的发生频度及发生规律,在岩爆区域现场采样进行室内微观实验分析,发现磷块岩宏观力学行为很大程度上符合其微观结构构造和矿物组成的微观力学行为,微观裂纹试验发现磷块岩晶界弱面为白云石与胶磷矿之间的接触晶界. 现场研究发现,岩爆多发生在爆破后环境干燥的区域,且多发矿段为白云石含量较高的岩层. 提出了岩爆的产生判据,并给出了岩爆的防治对策.     

Experimental study on the mechanical properties and consolidation mechanism of microbial grouted backfill

Backfill mining technology is the practice of returning waste materials underground for both disposal and geotechnical stability, however, a challenge with current technologies is that they commonly require cement-based binders which have a relatively high environmental impact. Finding alternatives to cement-based binders can improve environmental performance and this paper proposes microbial grouted backfill (MGB) as a potential solution. In this paper, the effects of the cementation solution concentration (CSC), volume ratio of bacterial solution to cementation solution (VRBC), particle sizes of the aggregates, and the number of grouting batches on the mechanical properties of MGB are studied. The experimental results show that MGB strength increased, up to a peak value, as CSC was increased, before decreasing as CSC was increased further. The results also show that MGB strength increased, up to a peak value, as VRBC decreased, before decreasing as the VRBC was decreased further. The peak strength was achieved at a CSC of 2 mol/L and a VRBC of 1:9. The strength of the MGB also increased as the number of grouting batches increased. Graded MGB samples showed the highest UCS, 25.12 MPa, at particle sizes of 0.2 to 0.8 mm, while full (non-graded) MGB samples displayed mean UCS values ranging from 1.56 MPa when the maximum particle size was 0.2 mm, up to 13 MPa when the maximum particle size was 1.2 mm. MGB samples are consolidated by the calcium carbonate that is precipitated during microbial metabolism, and the strength of MGB increases linearly as calcium carbonate content increases. The calcium carbonate minerals produced in MGB materials are primarily calcite, with secondary amounts of vaterite.     

基于NMR技术的孔隙结构与充填体强度关联机制

充填料浆凝固后形成的充填体中含有大量的孔隙,孔隙对充填体力学性能的影响尚不明确。为探究充填体内孔隙结构与充填体单轴抗压强度(Uniaxial compressive strength, UCS)的关联机制,利用十二烷基硫酸钠(Sodium dodecyl sulfate, SDS)调节充填体内的孔隙含量,采用低场核磁共振技术(Nuclear Magnetic Resonance, NMR)测试充填体内部孔隙的横向弛豫时间,利用压力机测试充填体的UCS,利用扫描电镜(Scanning electron microscope, SEM)获取充填体破坏面孔隙结构的微观图像,对孔隙的孔径分布进行了分析,对孔径的分形特征进行了研究,结果表明：充填体内孔隙总量随着养护龄期的增加逐渐降低,且SDS掺量越高,样品在14d与28d时的孔隙总量越接近；多害孔隙的占比随着养护龄期的增加明显降低,且与样品的UCS呈负相关,无害孔隙、低害孔隙、有害孔隙的占比在各龄期间变化较小；SDS掺量为所用水泥质量的2‰时对样品的UCS最有益；孔径在5nm-130nm区间的孔隙数量具有较为明显的分形特征,而孔径不在该区间的孔隙数量不具有分形特征；水泥水化反应产物呈簇状,簇状产物因生长、发育、延伸而挤占了孔隙空间是孔隙总量、多害孔隙数量随养护龄期增加不断降低的微观原因。研究结果可以为更全面的理解充填体强度提供理论支撑。     

The mechanical properties of coastal soil treated with cement

The influences of cement type, cement content, and curing time on the unconfined compression strength （UCS） of soil-cement were investigated. The influence of groundwater on UCS of soil- cement was also studied. The experimental results indicate that the soil treated with high grade cement presents a higher UCS. Additionally, the UCS of soil-cement presents linearly increased with the cement content. A logarithm correlation between UCS and curing time presents to forecast the strength development. Compared with the UCS of samples immersed in distilled water, those immersed in groundwater oresent a hizher value.     

矿山排土场散体岩土的强度变形特性

在对排土场散体物料块度分布规律研究的基础上 ,通过若干矿山排土场散体物料力学性质试验 ,研究了排土场散体物料应力应变特性 ,建议了合理的计算模式 ,系统分析了岩性和散体物料粒径等因素对散体强度的影响     

裂纹扩展过程红外热像实验及数值模拟研究

采用花岗岩材料通过红外热像和数值实验的方法,对两预制裂纹导致的岩石中新裂纹孕育、繁衍、萌生、扩展和贯通机制,以及由此引起的试样宏观强度变化等进行分析.通过红外热像遥感观测方法以及数值模拟对7块预制双裂纹的试样进行了实验研究.结果表明,裂纹扩展过程中,脆性破裂的声发射前兆不明显,在主破裂发生之前有小规模声发射现象,但释放的能量不多,只有在主破裂发生时产生大量声发射,特别是岩爆类型的破坏.试样破裂过程中有红外异常现象,在破裂处会出现明显的高温区和高温条带,并指出斑状花岗岩在破裂前主要表现为高温前兆.     

一种基于TBM掘进参数的现场岩石强度快速估算模型

基于隧道掘进机(tunnel boring machine, TBM)现场实际掘进参数与岩石强度的相关性,提出一种现场岩石强度快速估算模型。该模型详细分析了开敞式TBM现场实际掘进参数的趋势,建立了其与岩石单轴抗压强度(uniaxial compressive strength, UCS)的拟合关系式;根据回归系数R²排序:0.761 2(贯入度指数)> 0.759 5(推力)> 0.691 5(掘进比能)>0.598 6(扭矩)> 0.561 5(贯入度),确定采用贯入度指数(field penetration index, FPI)快速估算岩石强度UCS。与以往岩石强度经验模型对比,该估算模型更具针对性和适用性。研究成果为TBM工程岩石强度的快速估算提供了一种新的切实可行的思路。     

建筑物混凝土垃圾试样的物理力学性能分析

对兰州市雁滩某高层住宅地下室底板混凝土的钻芯取样进行抗压强度测定．通过试样破坏及曲线分析,判断其破坏形态,根据实验强度推定混凝土结构的实际抗压强度值;并对该底板部分混凝土破碎、筛分,做相关物理性能试验．为后期再生混凝土的研究提供参数依据．     

单轴压缩条件下花岗岩声发射事件空间分布的分维特征研究

基于声发射事件空间分布的柱覆盖分形模型,利用MTS815 Flex Test GT岩石力学试验系统和PCI-2声发射（AE）三维定位实时监测系统,对瀑布沟水电站地下厂房花岗岩单轴压缩损伤破坏过程中声发射事件空间分布的分形特征进行了研究。结果表明,声发射事件随应力增加逐渐活跃,加载初期声发射数量较少,应力接近峰值强度时,声发射事件累计数曲线呈指数上升。声发射事件的空间分布随应力增加是一个降维过程,其空间分维D在3~2内变化,峰值强度时,其值最小。弹性阶段后期,岩石内部微破裂开始向破坏面集聚,声发射空间分维D下降幅度明显增大。声发射空间分维恰当地表征了声发射事件空间分布的复杂程度。研究结论揭示了岩石声发射事件空间分布的分形特征,室内试验结果与文献对岩爆研究结果相吻合,可为现场监测应用提供理论指导。