A new classification system for evaluating rock penetrability

This paper presents a new classification system called the Rock Penetrability index (RPi). An evaluation model based on the fuzzy Delphi analytic hierarchy process (FDAHP) has been used for estimation of penetrability and drillability of rocks. For this purpose, five parameters of the rock material, including uniaxial compressive strength, Schimazek's F-abrasivity, mean Moh's hardness, texture and grain size and Young's modulus have been investigated and rated. In the RPi system, a number from 10.25 to 100 can be assigned to each rock, with higher values corresponding to greater ease of drilling and penetration into rock. Based on the RPi classification, rocks are classified into five modes from the view point of penetrability: very poor, poor, medium, good and very good.     

模糊概率模型在岩爆烈度分级预测中的应用

 岩爆是深部高地应力区岩石地下工程中的一种常见地质灾害,对其发生的可能性及其烈度分级预测是地下工程建设中亟待解决的重大课题之一。以模糊概率理论为基础,选取影响岩爆的一些主要因素,如洞壁最大切向应力sq、岩石单轴抗压强度sc、岩石单轴抗拉强度st以及岩石弹性能量指数Wet,并以sq /sc,sc /st和Wet作为评价影响因子,同时将岩爆烈度划分为无岩爆、弱岩爆、中岩爆和强岩爆4个等级,建立岩爆烈度分级预测的模糊概率模型。在此模型中,提出了模糊权重的概念,可充分考虑权重的模糊性。模糊概率模型不仅继承了经典模糊综合评判法的思想和优点,同时也克服了其在实际应用中评价影响因子权重取值的局限性,因而具有明显的合理性。应用该模型对冬瓜山深埋硬岩矿山、秦岭隧道工程以及某大型水电站地下厂房3个典型工程岩爆的实例分析表明,其预测结果与实际情况符合较好。为进一步考察该模型的可靠性与实用性,对国内外23个大型岩石地下工程实例进行计算分析,其预测结果与实际岩爆情况也相当吻合。由此可见,模糊概率模型为深部岩石地下工程岩爆预测问题提供了一种新途径。     

Development of a new classification system for assessing of rock mass drillability index (RDi)

The drilling process and its results are affected by various parameters of the rock material and rock mass. The effects of rock material have been emphasized in various studies; however lack of perfect knowledge of rock mass structural parameters may lead to unpredictable results. This paper presents a new classification system for specifying the rock mass drillability index (RDi). For this purpose, six parameters of the rock mass, including texture and grain size, Mohs hardness, uniaxial compressive strength (UCS), joint spacing, joint filling (aperture) and joint dipping have been investigated by physical modeling and rated. Physical modeling in particular has been used for investigating the effects of joint characteristics on drilling rate. In the proposed RDi system, each rock mass is assigned a rating from 7 to 100, with a higher rating corresponding greater ease of drilling. Based on the RDi rating, the drilling rate may be classified into five modes: slow, slow-medium, medium, medium-fast, and fast.     

岩石破损过程强度变化规律实测研究

 岩石材料强度会随着破裂发展而逐渐衰减,详细介绍自行设计的岩石强度衰减测试方法,试验思路、试件制作及关键技术;通过自行设计的直剪试验,测得常规压缩试验破裂得到的不规则损伤岩块在直剪过程中的剪应力–压应力关系曲线,由其拟合得到库仑强度曲线,并与已有(单、三轴)压缩试验数据线性拟合得到的莫尔强度包络线进行比较,分析讨论岩石在破损过程中材料强度(黏聚力和内摩擦角)变化规律,澄清现有黏聚力和内摩擦角变化规律2种完全相对立观点的适用范围。研究结果表明,由完整岩样进行单、三轴试验测得的黏聚力明显大于不规则岩块直剪试验结果,这主要是岩样在单、三轴压缩破坏过程中产生的损伤所致,而不是试验方法所导致的偏差;黏聚力反映的是岩石本质强度特性,受不同应力状态的影响较小。岩样单、三轴压缩试验测得的内摩擦角小于岩块直剪试验结果,这主要是受到不同应力状态和岩石缺陷分布的影响。在岩石破损过程中,内摩擦角随损伤的发展具有先快速增大至最大值后大幅降低直至保持一定趋势不变的规律。内摩擦角反映的是岩石摩擦强度特性,受不同应力状态的影响较大。黏聚力对应力水平的敏感程度远小于内摩擦角。岩石在破裂前后自身材料强度会产生明显衰减。     

节理产状对岩石单轴抗压强度的影响研究

运用岩石破坏过程分析RFPA^2D系统,采用控制变量法,分别研究了节理不同位置、方向和迹长对于岩石试件单轴抗压强度的影响。结果表明:试件节理位置对应值(裂纹尖端到受压面的距离)与抗压强度值有近似的线性关系;岩石试件中所含节理倾角不同时,试件的破坏模式不同,随着倾角的增大,试件的强度先降低随后增大;随着节理迹长与试件直径比值的增大,试件强度随之减小。数值模拟结果同物理试验结果相吻合,研究结果对于深入揭示断续节理岩石在单轴压缩下损伤破坏机制具有重要参考价值。     

未确知测度模型在岩爆烈度分级预测中的应用

 针对岩爆烈度分级预测评价中诸多因素不确定性问题,应用未确知测度理论并结合工程实际,根据岩爆的特点及成因,选取最大切应力sθ、单轴抗压强度sc、单轴抗拉强度st及岩石的弹性能量指数Wet,并以应力系数sθ/sc、岩石脆性系数sc/st及弹性能量指数Wet作为岩爆烈度分级的评价指标,建立岩爆烈度分级预测的未确知测度评价模型。以国内外18组工程岩爆分析初始数据进行分级判别,根据实际情况建立各评价因子的未确知测度函数,对其进行定量分析,并利用熵计算各评价指标的权重,依照置信度识别准则进行等级判定,最后得出岩爆烈度分级预测的评价结果。并与模糊综合评判法、属性综合评判法、灰色聚类法、物元分析法及实际情况的结果进行比较。为进一步考察该模型的有效性与实用性,运用该模型对秦岭隧道工程的岩爆实例进行分析。研究结果表明：该模型判别预测结果与实际岩爆情况较吻合,且方法科学合理,意义明确,为岩爆烈度分级预测提供一种新思路。     

Estimation of uniaxial compressive strength from point load strength,Schmidt hardness and P-wave velocity

Uniaxial compressive strength is considered one of the most important parameters in the characterization of rock material in rock engineering practice. The study investigated correlations between uniaxial compressive strength and point load index, P-wave velocity and Schmidt hardness rebound number together with the effects of core diameter size. A total of 150 core samples at five different diameters (54, 48, 42, 30 and 21 mm) were obtained from sandstone, limestone and cement mortar. Ten saturated samples at each diameter (length:diameter ratio 2:1) were prepared from each of the three materials. The best correlations were found between uniaxial compressive strength and point load or Schmidt hammer values. The closest relationship was observed for the 48 mm diameter cores.      

Point-load strength: An index for classification of rock material

Point-load strength (Is) as a measure for the determination of rock strength and for estimating uniaxial (unconfined) compressive strength (UCS) are described and both put together and used for rock strength classification of brittle and hard rocks. The estimated point-load strength values of specimens of varying sizes and also the values corrected to a standard thickness of 50 mm, and the resultant point-load strength values (Is-50) have been used to estimate the uniaxial (unconfined) compressive strength which correlates well with actual recorded uniaxial (unconfined) compression test results. Using graphical and mathematical relationships between the observed and estimated UCS and Is values, a conversion factor of 16 is obtained for estimating uniaxial (unconfined) compressive strength values from point load strength results. A nomogram for computing point-load strength index and a system for the classification of rock material are presented.     

基于组合权重–理想点法的应变型岩爆五因素预测分级

基于理想点法的基本理论,综合考虑了岩爆发生机理,选取围岩洞壁最大主应力与岩石单轴抗压强度的比值、围岩洞壁最大切向应力与岩石单轴抗压强度的比值、岩石单轴抗压强度与岩石单轴抗拉强度比值、岩石弹性能指数以及岩体完整性系数作为评判预测指标,通过层次分析法和熵权理论计算主客观权重,综合确定各个指标的权重系数,构建了应变型岩爆组合权重–理想点法预测分析模型。通过统计相关工程案例,利用模型进行工程实例分析,验证了该模型的可行性与适用性。基于岩爆预测分级模型,开发了相应程序,可以为类似工程岩爆预测与等级划分提供重要支撑。     

基于Hoek-Brown准则的板岩强度特征研究

 建立在岩体各向同性基础上的Hoek-Brown经验强度准则被广泛地应用于地下和边坡工程的设计与安全评估。但Hoek-Brown准则不能直接用来处理层(片)状岩体如板岩或页岩以及含有1或2组优势结构面岩体的强度问题,因为这类岩体往往沿层(片)理或优势结构面破坏,必须对准则加以改进。基于对Hoek-Brown经验破坏准则的深入研究,通过对层状岩体完整岩石试件定义的改进,提出用Hoek-Brown准则的一个很重要的参数,即完整岩石试件的单轴抗压强度 来表征层状岩体强度随层面倾角的变化规律以及应用Hoek-Brown准则来分析层状岩体强度的方法。按照该方法对南水北调西线工程场区不同层面倾角板岩岩石试件进行单轴、三轴压缩试验。根据对试验结果的统计分析,确定不同层面倾角板岩岩体的Hoek-Brown经验破坏准则的相关参数,建立不同层面倾角板岩岩体的Hoek-Brown强度准则。此外,还获得完整岩石试件的单轴抗压强度 随层面倾角的变化规律,建立南水北调西线工程场区板岩岩体的Hoek-Brown经验破坏准则的统一表达式,并预测围压为10,15,20和25 MPa下南水北调西线工程场区板岩岩体的三轴强度随层面倾角的变化规律。本文的工作可以为类似工程提供借鉴。     

煤层顶底板岩石点荷载强度与拉压强度对比试验研究

 利用自主研制的点荷载仪,通过室内对煤矿顶底板常见岩性岩石进行点荷载试验、单轴抗压试验、抗拉试验对比分析,研究由点荷载强度快速准确确定单轴抗压强度及抗拉强度的方法。试验结果表明：点载荷强度较低的粗砂岩极易受到加载速率和加载方向影响,其预测值与实际值的误差相对较大;而对于点荷载强度较大的岩石,3种强度的线性相关性较高。点荷载试验的应用,为煤矿顶底板岩石强度确定及岩体分类提供了重要依据。     

多类混凝土和各向同性岩石损伤比强度准则

针对已有损伤比变量下的损伤比强度理论仅适用于混凝土且偏平面略有内凹等不足,基于多轴应力下混凝土损伤比强度理论的一般形式,根据已有试验资料关于普通混凝土、再生骨料混凝土、轻骨料混凝土和各向同性岩石破坏包络面的特征,建议考虑Lode角和静水压力对受压损伤比影响以及考虑材料类型对受拉损伤比影响的六参数损伤比变量表达式,且损伤...     

岩石隧道掘进机的施工预测模型

分析了岩石隧道掘进机的破岩机理,介绍了自上世纪70年代以来发展的一系列施工预测模型,包括单因素预测模型、综合预测模型(CSM模型和NTNU模型)、岩体分类预测模型(QTBM模型)、概率模型、模糊神经网络模型。单因素预测模型中包括的主要岩石材料参数有岩石单轴抗压强度、抗拉强度及岩石的总硬度;CSM模型主要是基于线性切割试验机岩石试验数据,其初始预测模型中包括岩石单轴抗压强度及抗拉强度;NTNU模型是一套完整的预测模型,包括掘进速度、进度预测、刀具的磨损预测及经济分析,在它的施工进度预测模型中,考虑到了岩石的可钻性、孔隙度及岩体节理的密度及方向;QTBM模型源自于Q系统,加入了一些与隧道掘进机及与掘进速度相关的参数;概率模型是基于一个庞大数据库的类比模拟模型;模糊神经网络模型是一种黑箱模型,克服了输入与输出之间的不确定性关系。     

低温条件下花岗岩力学特性试验研究

 从辽宁锦州拟建地下储库工程现场钻取典型花岗岩岩芯,进行不同冻结温度(－10 ℃～－50 ℃)和不同含水状态(干燥和饱和)的单轴及三轴压缩试验,分析岩石的变形破坏规律、干燥和饱和状态抗压强度以及三轴剪切强度参数c,j 值随温度的变化关系。试验结果表明：(1) 无论干燥还是饱和试样,微风化花岗岩单轴及三轴抗压强度随着低温温度的降低而提高,但呈现非线性增加的趋势,得到花岗岩抗压强度随低温温度变化的非线性关系拟合式,并认为微风化花岗岩存在一个抗压强度趋于稳定的温度界限值,此值约为－40 ℃;(2) 微风化花岗岩在干燥和饱和条件下,黏聚力c值随温度的降低而增大,在干燥条件下尤为明显。干燥条件下,微风化花岗岩内摩擦角随低温温度降低变化较小,摩擦角基本保持在57°左右,饱和条件下,微风化花岗岩内摩擦角随温度降低而增加, 由－10 ℃～－50 ℃增长幅度约为3.43%。该研究成果可为液化天然气(LNG)的低温地下存储提供一定的力学参数依据。     

基于单轴剪切破坏的岩石M–C准则参数反演分析

基于岩石单轴压缩试验中出现的不同剪切破坏形式,应用极限分析法推导出岩石单轴抗压强度与黏聚力及内摩擦角的关系式。结合矿区岩石单轴、三轴试验结果,验证以岩石M–C准则参数计算单轴抗压强度关系式的正确性,据此关系式获得的结果与试验结果差值在6%~10%之间。采用实例进行岩石黏聚力和内摩擦角的反演分析,以岩石实际单轴剪切破坏形式和试验结果为依据,两两结合联立计算得到岩石的黏聚力和内摩擦角。实例表明:基于单轴剪切破坏形式和单轴抗压强度值计算岩石黏聚力和内摩擦角的方法准确,具有实用价值,该关系式也揭示了岩石试样破坏类型与岩石力学参数间的内在关系。     

Modelling of shear strength of rockfills used for the construction of rockfill dams

This paper presents the results of examination of shear properties of rockfills used for the construction of rockfill dams. Based on the results of a large number of experiments, mathematical model of the shear strength of the rockfill was derived, as a function of normal stress, initial compaction and uniaxial compressive strength of intact rock material. Using this model it is possible to make a realistic assessment of the shear strength of a rockfill for the Preliminary Design. The experimental data used for modelling were obtained by direct shear tests performed in the majority at the “Jaroslav Cerni” Institute for Development of Water Resources in Belgrade, Serbia.     

广州轨道交通六号线金沙洲段灰岩的水岩相互作用对岩体强度的影响

本文通过对广州轨道交通六号线的金沙洲段部分岩样的单轴抗压强度、抗剪强度进行统计和计算,分析了地下水的水岩相互作用对于研究区灰岩岩体的强度影响,得到这种作用在局部对岩体强度的影响相当大--使得岩块单轴抗压强度的最大损失为81.3%、结构面抗剪强度的最大损失为78.5%,但是这种腐蚀损伤的程度在岩体中是相当不均匀的.     

Determination of in situ uniaxial compressive strength of coal seams based on geophysical data

The central issue for pillar design in underground coal mining is the in situ uniaxial compressive strength (σ _cm). The paper proposes a new method for estimating in situ uniaxial compressive strength in coal seams based on laboratory strength and P wave propagation velocity. It describes the collection of samples in the Bonito coal seam, Fontanella Mine, southern Brazil, the techniques used for the structural mapping of the coal seam and determination of seismic wave propagation velocity as well as the laboratory procedures used to determine the strength and ultrasonic wave velocity. The results obtained using the new methodology are compared with those from seven other techniques for estimating in situ rock mass uniaxial compressive strength.      

A generic method for rock mass classification

Rock mass classification (RMC) is of critical importance in support design and applications to mining, tunneling and other underground excavations. Although a number of techniques are available, there exists an uncertainty in application to complex underground works. In the present work, a generic rock mass rating (GRMR) system is developed. The proposed GRMR system refers to as most commonly used techniques, and two rock load equations are suggested in terms of GRMR, which are based on the fact that whether all the rock parameters considered by the system have an influence or only few of them are influencing. The GRMR method has been validated with the data obtained from three underground coal mines in India. Then, a semi-empirical model is developed for the GRMR method using artificial neural network (ANN), and it is validated by a comparative analysis of ANN model results with that by analytical GRMR method.     

Some remarks on shear strength measurement along joints in rocks with a rigid behaviour

Rock slope analyses cannot be performed without a knowledge, or at least, a reliable estimation of the shear strength of the potential failure surface. Some of the parameters concurrent to determination of the shear strength along joints of rocks with a rigid behaviour are considered, for the purpose of making this determination as quick and accurate as possible. Some remarks are especially developed, based on experimental data, covering joint wall compressive strength, the uniaxial compressive strength of the rock material, the basic friction angle and joint roughness.