冻融作用下人工劈裂砂岩结构面强度特性研究

寒区岩体破坏主要与结构面力学特性及冻融损伤相关。为探究冻融作用下砂岩结构面的强度特性,采用小圆弧刀头劈裂制备贯通结构面,对其进行了冻融循环及剪切试验,得到了结构面的剪切强度、内聚力及内摩擦角的劣化规律。试验结果表明:小圆弧刀头制备的结构面完整、均一,且上下盘吻合度高;岩石的峰值剪切强度与冻融次数呈负相关,与法向应力呈线性正相关;随着冻融循环次数的增加,内聚力减小趋势变缓,内摩擦角无明显变化趋势。研究结果对寒区岩体强度特性分析具有参考价值。

基于JRC-JCS模型的人工劈裂砂岩结构面力学特性研究

为探究人工劈裂结构面与天然结构面力学特性的相似性,解决现场取样困难、难以保证均一性等问题,文章采用人工劈裂方式制备砂岩结构面,并进行三维扫描和室内直剪试验等,根据结构面相关理论、Barton标准剖面线等理论知识,描述了人工劈裂砂岩结构面的相关形态并确定了结构面粗糙度系数,最后基于JRC-JCS模型进行力学参数的估算,并与直剪试验结果对比,分析人工劈裂砂岩结构面的力学特性。结果表明:在粗糙度系数相同时,结构面的抗剪强度与所受的法向应力成正相关;在法向应力相同时,结构面抗剪强度与粗糙度系数成正相关;砂岩结构面的黏聚力和内摩擦角与粗糙度系数呈正相关,其相关系数与粗糙度系数呈负相关,结构面粗糙度系数越小,相关系数越接近于1。研究成果为结构面室内研究工作奠定了基础。

火灾温度变化对隧道砂岩结构影响试验研究

为研究火灾发生时温度变化对隧道围岩内部结构的影响,借助于压汞仪、SEM扫描电镜对砂岩内部结构变化规律进行了室内实验,并从微观结构学角度对其进行分析,研究表明:(1)高温后隧道砂岩围岩内部会产生裂纹,宽度均小于0.01μm;(2)随着火灾温度的升高,砂岩内部首先在孔喉狭窄处表现出黏土矿物膨胀脱水崩解现象,其后依次产生沿晶裂隙、岩桥裂纹、穿晶裂隙;(3)通过研究火灾温度发展岩石内部沿晶裂纹和岩桥裂纹产生规律发现:二类裂纹的阈值温度均为300℃,而穿晶裂纹产生的阈值温度为600℃,随温度升高穿晶裂纹逐步贯通。

构造生长及其它因素对澳大利亚库珀盆地二叠系河成砂岩结构的影响

所谓构造生长意指与沉积物堆积同时产生的微弱地壳运动，要评价这样的因素，其中就必须研究砂岩的后期增积，可流冲刷及盆地区沉积物的分布，气候及地质时代。地层的相互关系，等厚线图及构造图的解释就包括库珀盆地二叠纪的地下构造高。这些是以帕查瓦拉组（蒂拉瓦油田）和图位奇组（大湖－木姆巴油田）薄层年代地层单位的对比关系为基础。木巴地区图拉奇组的C单位是由几层具有循回性的似薄片状向上变细的沉积层序组成，该岩相的相互关系类似于大湖油田附近的下翼地区。不过，在构造顶部区的上翼，河流沉积的层序都是很典型的多层砂岩。这些砂岩在大的地质时代间隔期由于构造生长与曲流河系同时沉积所产生的结果。曲流河系自西南向或北方向穿过大湖－木姆巴局部地区。等厚线图及砂岩百分率图表明，这些河流优先选择向纳帕莫里凹陷搬运的途径。根据蒂拉瓦拉油田的帕瓦拉组2B单位的岩石分析认为，局部地区的沉降速度要略大于大湖和木姆巴油田，结果就导致砂体的连通性增加。虽然穿过油田区向上的层序有时变细，但多层砂岩砂层的发育则出现在该油田西侧的弧形地带，这就是局部构造生长及河流沉积物同时发生断裂所引起的结果。河流成因的储油层广泛分布在沉积盆地中。盆地中出现低速的差异性沉降，则储油层及其分布范围都以薄层状岩体分布于主要沉积中心和边缘附近的构造圈闭内。认识盆地区域性的差异性沉降及河流系结构对油田开发及新油藏的勘探都提供了可靠的保证。

砂岩-混凝土结构面剪切特性试验研究及离散元模拟

为从宏、细观角度揭示常法向刚度(Constant Normal Stiffness,CNS)条件下锯齿状砂岩-混凝土结构面剪切机制,首先采用湖南大学自主改造的CNS岩石直剪仪开展3组砂岩-混凝土结构面室内剪切试验.在此基础上,采用刚性墙替代法建立与室内试验相应的离散元数值模型,并引入3个显式运动学方程控制砂岩试样运动轨迹从而实现CNS条件加载,将数值模拟与试验结果对比验证了模型的合理性.随后,开展16个工况的数值剪切试验,通过观察剪切裂纹扩展和力链演化形态,从细观角度揭示结构面破坏模式和荷载传递机制,并从宏观角度分析锯齿几何尺寸(半波长λ、起伏角θ)和加载边界条件(初始法向应力σn0、法向刚度K)对剪切强度和法向膨胀的影响.结果表明:剪切裂纹按照“平稳增加—急剧增加—增幅减小”的发展趋势由结构面区域逐渐向岩石内部扩展,结构面破坏模式随起伏角的增大由滑移磨损向剪断破坏过渡,剪切强度随λ、θ、σn0和K的增加呈指数函数型增加.

神东侏罗纪砂岩微观结构对其力学性质及声波传播速度的影响

为了分析神东侏罗纪砂岩微观结构对其力学性质及声波传播速度的影响,利用偏光显微镜、岩石力学试验系统对砂岩进行研究,同步测定砂岩声波传播速度。结合数理统计方法建立宏观力学特性、声波速度与砂岩内部微观结构之间的定量关系。结果表明:随着碎屑颗粒粒径增加和不均匀系数增大,砂岩的单轴抗压强度、弹性模量和应变相应减小,其力学性质呈减弱的趋势,而泊松比变化趋势不明显;同时随着砂岩碎屑颗粒粒径增加和不均匀系数增大,声波速度也相应减小;对比发现,同一岩石类型侏罗纪煤系砂岩单轴抗压强度与碎屑颗粒平均粒径之间的关系和石炭-二叠纪煤系砂岩相反。

砂岩结构面法向加卸载本构模型研究

鄂西志留系罗惹坪组砂岩结构面法向循环加卸载试验结果表明,在中低法向应力范围内,结构面加载变形曲线呈上凸型,卸载变形曲线呈上凹型,结构面卸载后产生残余变形,形成明显的回滞环。目前已提出的结构面法向变形本构方程都是在试验的基础上总结出的经验方程,因结构面的初始法向刚度和最大闭合变形量难以确定,使模型的计算精度受到一定的限制。因此,针对浅表工程岩体应力状态较低的特性,提出了结构面法向变形的半对数-圆弧线联合本构模型,加载曲线采用半对数模型表征,卸载曲线则采用圆弧线模型表征。其中,半对数函数的模型参数可根据加载试验结果回归分析得出,圆弧线模型方程则由本级加载曲线的起点、终点与卸载曲线的终点三点坐标确定。通过模型计算结果与试验结果对比分析表明,半对数-圆弧线模型计算结果与试验结果相吻合,较好地体现了结构面法向加载曲线为上凸型与卸载曲线为上凹型的特征,重现了卸载-加载过程的回滞圈。新的模型回避了最大闭合变形量和初始刚度的确定难题,并且不需引入新的模型参数,便于实际应用。

红砂岩路基填料结构特性及路用改良技术分析

为加强红砂岩路基填料结构特性和路用改良水平,提高路基安全性、稳定性,结合工程实践,针对红砂岩路基填料结构特性及路用改良技术进行研究,阐述了红砂岩结构特征,分析了崩解机理及工程特性,总结了红砂岩路用改良技术及工艺原理。试验段检测结果表明,红砂岩改良后路基强度满足施工要求,社会和经济效益可观。

某砂岩微结构分形特征

对某地不同风化程度的砂岩微结构，用扫描电镜(SEM)进行观察，得到数字化的图像。利用编制的微结构图像处理软件对图像数据进行数值分析，得到这些砂岩的微结构分形特征，并求出分维值。分维值可以作为评价岩石内部结构的一个重要参数。

间歇性波浪条件下湖相滩坝砂的结构特征——以东营凹陷南斜坡王73井区沙四段为例

东营凹陷南斜坡王家岗油田王73井区沙四段发育带状展布的滨浅湖滩坝砂体。取心层段砂岩结构分析结果表明,研究区沙四段滩坝砂体在结构上与典型湖相滩坝砂体差异很大,砂体的结构成熟度普遍偏低,具有颗粒分选差、磨圆差、杂基含量高和物性差的特征。粒度分析发现,颗粒的偏度与粒径无直接对应关系。颗粒的平均粒径越大,分选越差。粒度概率累积曲线主要以多段式跳跃组分为主,曲线的斜率低。这些特征表明,研究区沙四段滩坝砂体沉积时的波浪作用很不稳定,波浪发生期和波浪间歇期交替出现,这与湖泊波浪的特征是密切相关的,由此也造成了该区储层物性普遍较差。

砂、泥岩二元结构边坡稳定性分析及防治措施

砂、泥岩二元结构边坡在工程建设中广泛存在,其稳定性问题备受关注。本文针对砂、泥岩二元结构边坡的特点,系统分析了影响其稳定性的因素。在此基础上,提出了一系列防治措施,包括支挡结构设计、排水系统优化、植被护坡、锚喷支护、抗滑桩设置、裂隙灌浆加固以及动态监测与管理等。这些措施的综合应用,可以有效提高砂、泥岩二元结构边坡的稳定性,为工程建设的安全和可持续发展提供保障。

基于交换-单亲遗传算法的砂岩三维显微图像重建

根据二维显微图像中孔隙的统计特征,重建具有相同特征的三维孔隙结构具有重要意义。本文提出用交换算子产生子代个体,替代传统单亲遗传算法中倒位算子、移位算子和突变算子,构建交换-单亲遗传算法。和传统单亲遗传算法相比,该算法能快速更新子代个体的适应值,算法复杂度大大降低。实验结果表明,与常用的模拟退火重建算法相比,交换-单亲遗传算法能有效加快个体能量下降速度,重建结果的统计特征与二维图像更相符,更适合应用于三维重建问题。

砂岩型铀矿找矿目标层识别技术研究

砂岩型铀矿基本为盲矿体,控矿因素复杂,通过单一的方法很难达到预期效果。依据对砂岩型铀矿找矿目标层识别技术研究,从构造变形强度、岩相及砂体发育条件、地层结构、原岩的岩石-地球化学类型、后生蚀变与铀矿化显示等方面分析了铀矿目标层的有利因素:地层倾角5°~30°、发育富含砂体的沉积相带、具备“泥岩-砂岩-泥岩”结构、原岩还原容量大、岩石地球化学分带发育、后生蚀变明显,有铀异常显示。提出了目标层识别的技术流程:(1)以依据构造变形强度判据,确定初选的有利找矿目标层;(2)以沉积特征精选有利找矿目标层,并圈出其各自的重点找矿区域;(3)以地层结构、铀源、氧化还原的地球化学分带和地下水“补-径-排”体系为条件,最终确定重点找矿区域内有利找矿目标层和找矿远景区;(4)以地层成岩度和埋深对确定的有利找矿目标层进行经济技术评价,最终确定重点工作层位。该方法在二连盆地马尼特坳陷铀矿找矿应用中取得了明显突破。

砂岩孔隙结构研究现状

本文综述了砂岩孔隙结构在非常规油气资源勘探与开发中的重要性,并探讨了不同评估方法的适用性。文章首先强调了砂岩孔隙结构对油气储存和流动特性的影响,以及其对提高采收率和优化勘探开发策略的关键作用。接着,文章介绍了间接测定法(如压汞法、半透膜法、离心法)、直接观测法(如铸体薄片法、扫描电子显微镜、计算机断层扫描)和测井资料评价方法(如电阻率法、核磁共振法、声波时差法)等技术,并分析了它们的优势与局限性。最后,文章得出结论,砂岩孔隙结构的研究对油气资源的有效开发至关重要,有助于保障能源安全、推动技术进步、保护环境以及实现社会经济的可持续发展。随着技术的发展,未来有望进一步提升油气资源的开采效率,实现资源的充分利用,为全球能源的持续发展贡献力量。This article reviews the importance of sandstone pore structure in the exploration and development of unconventional oil and gas resources and discusses the applicability of different evaluation methods. The article first emphasizes the impact of sandstone pore structure on the storage and flow characteristics of oil and gas, as well as its key role in improving recovery rates and optimizing exploration and development strategies. It then introduces indirect measurement techniques (such as mercury injection, semi-permeable membrane, and centrifugation methods), direct observation methods (such as thin section casting, scanning electron microscopy, and computed tomography), and logging data evaluation methods (such as resistivity, nuclear magnetic resonance, and sonic time difference methods), and analyzes their advantages and limitations. Finally, the article concludes that the study of sandstone pore structure is crucial for the effective development of oil and gas resources, contributing to energy security, technological progress, environmental protection, and sustainable socio-economic development. With technological advancements, it is expected that the efficiency of oil and gas resource development will be further improved in the future, realizing the full utilization of resources and contributing to the sustainable development of global energy.

A novel model for assessing the pore structure of tight sands and its application

Pore-structure poses great influence on the permeability and electrical property of tight sand reservoirs and is critical to the petrophysical research of such reservoirs.The uncertainty of permeability for tight sands is very common and the relationship between pore- structure and electrical property is often unclear.We propose a new parameterδ,integrating porosity,maximum radius of connected pore-throats,and sorting degree,for investigating the permeability and electrical properties of tight sands.Core data and wireline log analyses show that this newδcan be used to accurately predict the tight sands permeability and has a close relation with electrical parameters,allowing the estimation of formation factor F and cementation exponent m.The normalization of the resistivity difference caused by the pore- structure is used to highlight the influence of fluid type on Rt,enhancing the coincidence rate in the Pickett crossplot significantly.

PDC钻头地质录井方法探讨

为了解决PDC钻头钻井给地质录井所带来的难题,文章从分析PDC钻头的特点、破碎岩石的机理入手,探讨了PDC钻头的录井方法,就相应的录井工具选择、取样方法、资料收集和判断地层的方法提出建议。重点介绍了综合分析法、砂岩微观结构判断法、色谱法、反推法、热水实验法和间接资料法六种方法。

Damage failure of cemented backfill and its reasonable match with rock mass

In order to study the failure mechanism of backfill and the reasonable matches between backfill and rock mass, and to achieve the object of safe and efficient mining in metal mine, four types of backfills were tested under uniaxial compression loading, with cement?tailing ratios of 0.250:1, 0.125:1, 0.100:1 and 0.083:1, respectively. With the help of the stress?strain curves, the deformation and failure characteristics of different backfills with differing cement?tailing ratios were analyzed. Based on the experimental results, the damage constitutive equations of cemented backfills with four cement?tailing ratios were proposed on the basis of damage mechanics. Moreover, comparative analysis of constitutive model and experimental results were made to verify the reliability of the damage model. In addition, an energy model using catastrophe theory to obtain the instability criteria of system was established to study the interaction between backfill and rock mass, and then the system instability criterion was deduced. The results show that there are different damage characteristics for different backfills, backfills with lower cement?tailing ratio tend to have a lower damage value when stress reaches peak value, and damage more rapidly and more obviously in failure process after peak value of stress; the stiffness and elastic modulus of rock mass with lower strength are more likely to lead to system instability. The results of this work provide a scientific basis for the rational strength design of backfill mine.

Classification of tight sandstone reservoirs based on NMR logging

The traditional reservoir classification methods based on conventional well logging are inefficient for determining the properties,such as the porosity,shale volume,J function,and flow zone index,of the tight sandstone reservoirs because of their complex pore structure and large heterogeneity.Specifically,the method that is commonly used to characterize the reservoir pore structure is dependent on the nuclear magnetic resonance(NMR)transverse relaxation time(T2)distribution,which is closely related to the pore size distribution.Further,the pore structure parameters(displacement pressure,maximum pore-throat radius,and median pore-throat radius)can be determined and applied to reservoir classification based on the empirical linear or power function obtained from the NMR T2 distributions and the mercury intrusion capillary pressure ourves.However,the effective generalization of these empirical functions is difficult because they differ according to the region and are limited by the representative samples of different regions.A lognormal distribution is commonly used to describe the pore size and particle size distributions of the rock and quantitatively characterize the reservoir pore structure based on the volume,mean radius,and standard deviation of the small and large pores.In this study,we obtain six parameters(the volume,mean radius,and standard deviation of the small and large pores)that represent the characteristics of pore distribution and rock heterogeneity,calculate the total porosity via NMR logging,and classify the reservoirs via cluster analysis by adopting a bimodal lognormal distribution to fit the NMR T2 spectrum.Finally,based on the data obtained from the core tests and the NMR logs,the proposed method,which is readily applicable,can effectively classify the tight sandstone reservoirs.

Nuclear magnetic resonance T_2 spectrum:multifractal characteristics and pore structure evaluation

Pore structure characteristics are important to oil and gas exploration in complex low-permeability reservoirs. Using multifractal theory and nuclear magnetic resonance （NMR）, we studied the pore structure of low-permeability sandstone rocks from the 4th Member （Es4） of the Shahejie Formation in the south slope of the Dongying Sag. We used the existing pore structure data from petrophysics, core slices, and mercury injection tests to classify the pore structure into three categories and five subcategories. Then, the T2 spectra of samples with different pore structures were interpolated, and the one- and three-dimensional fractal dimensions and the multifractal spectrum were obtained. Parameters a （intensity of singularity） andf（a） （density of distribution） were extracted from the multifractal spectra. The differences in the three fractal dimensions suggest that the pore structure types correlate with a andf（a）. The results calculated based on the multifractal spectrum is consistent with that of the core slices and mercury injection. Finally, the proposed method was applied to an actual logging profile to evaluate the pore structure of low-permeability sandstone reservoirs.

Study on the cutting plane friction law of sandstone

The friction characteristics of rock damage plane have important impact on the stability of block structure formed after the stratum is broken. The mechanics properties of rock damage plane are described by parameters such as roughness coefficient, wall compress strength and basic friction angle. These three coefficients for fine grain sandstone and medium granular sandstone and grit sandstone are test. The friction stress is researched at the condition of different normal compressive stress acting on the tension damage plane. The friction law of tension damage plane of sandstone abided by is summed up. This law will provide scientific basis for block structure stability judging in basic roof stratum and roof pressure intensity calculating.