利用岩体波速定量划分岩石风化度的试验研究

现行岩石风化度的划分普遍按钻芯定性方法,而定量法则大都以室内岩块试验为基础。为了探索利用原位岩体波速测试方法进行岩石风化度定量划分,在某工程的3个基岩深孔中进行了检层法与超声波法波速测试,以钻孔揭露的岩芯并结合室内波速确定的风化界线为基准,设定风化岩石的岩体波速比,并利用不同方法测定的纵、横波速度换算成波速比来划分岩石的风化程度。试验研究表明,按此方法划分的风化度基本与钻孔揭示一致,而未风化界线偏深的原因在于其岩体波速主要取决于节理裂隙的发育程度。     

岩石风化作用对边坡稳定性影响的研究

风化是引起岩石力学性能劣化的重要因素。本文通过各项试验，研究了风化作用下岩石的力学性能，验证了岩石风化的过程就是改变岩石原有结构、消弱岩石整体力学性能的过程，并得出了风化程度与滑坡发生概率之间的关系。     

三峡地区泥灰质岩石在岩溶和风化过程中力学性质的变化

三峡地区泥灰质岩石的岩溶问题是新近发现的重大工程地质问题。泥灰质岩石具有灰岩和泥岩双重特性，在其中的钙质成分被溶蚀的同时，泥质成分遭受风化，从而使岩性和岩石结构发生变化，岩石的力学强度不断降低，有的岩石己属于较软岩范围。岩溶、风化形成的松散土层具有易滑性，易于发生变形破坏。泥灰质岩石作为移民迁建地基可能因溶蚀、风化而发生地质灾害。防止水向地基的入渗是防治该区地质灾害的关键。     

核电厂厂址岩体完整性评价方法探究

通过福清核电厂岩土工程勘察和环境水文地质调查,对核电厂厂址岩体完整进行性评分析,提出了岩石风化程度的定性和定量划分标准,结合工程实际及现场波速测定、钻探、岩石试验资料及已有资料统计分析,结合工程经验,综合确定了不同风化程度岩体的纵波速度范围值,作为风化程度划分的量化依据之一,为其他工程地质勘察报告提供岩石风化程度的定性和定量划分标准。     

谷坡岩体卸荷带划分量化指标研究

谷坡岩体卸荷在水利水电工程边坡中是一种常见的地质现象，对岩石边坡稳定性及相关岩石工程问题有着重要的控制意义，卸荷带定量划分一直受到水利水电工程勘测与设计的重视。用于卸荷带定量划分的指标很多，比较常用的是反映岩体结构特征的量化指标。根据水利水电工程实践，讨论谷坡岩体卸荷带划分量化指标问题，提出以张开裂隙宽度、张开裂隙累计宽度、波速比作为谷坡岩体卸荷带划分的量化指标。     

石质文物风化程度的超声波CT检测

我国是一个具有悠久历史的文明古国，拥有大量的具有重要历史意义和价值的文化遗产，然而，由于长期的风化作用，导致它们损伤严重，亟须对其风化程度进行评价。超声波测试具有检测分辨率高，对被测物无损伤等特点，使其成为检测石质文物风化程度的有力手段。从理论和办法上，对运用超卢穿透波CT检测石质文物风化程度的方法进行了探讨，提出了一套利用超声波CT法检测现场石质文物风化程度和文物材料丰要力学参数分布状况的方法。利用这套方法对浙江省义乌市南宋古桥——古月桥桥身条石的风化程度进行测试，取得了较好的效果。     

岩石的风化损伤属性与缩小防护煤柱开采机制研究

以大量试验数据、现场测试资料和大规模缩小防护煤柱开采工程实践为依据,研究隐伏煤田基岩风化带的分布特点。结果表明:岩石风化损伤后具有强度降低,塑变能力增强;多趋泥化,裂隙易于弥合,再生隔水能力显著增强,亲水能力强等变异特征以及工程地质特性。重点论述风化带内煤层开采具有移动快、变形大、回缩快和下沉大等覆岩破坏移动演化新特征,获得以泥质岩类为主的风化带岩层受开采扰动的影响,具有阻隔底含水下渗和抑制导水裂隙带继续发展的双重作用和煤岩柱厚度与风化程度是影响导水裂隙带发育高度的主导因素等新的认识。同时,阐述了缩小防护煤柱开采的机制,系统地提出了采空区滞后控水、煤水分流、加大开采高度、物探预测和地质弱面预先加固等一系列确保安全的关键技术保障措施。对类似矿井浅部资源的回收与安全开采具有理论意义和应用价值。     

流纹岩天然裂隙网络几何特征分析

 天然岩石中裂隙的统计分析是其力学性能研究的基础,裂隙发育几何特征与岩石所处的应力状态密切相关。基于裂隙网络在长度和方向上的相关性,提出一种综合考虑裂隙长度和倾角的裂隙网络几何方向贡献参数?,可以准确计算裂隙网络的优势发育方向?p,进一步计算得到描述裂隙网络随机程度的随机参数?,将其用于泥巴山隧址区流纹岩裂隙网络的分析。研究结果表明,裂隙网络几何贡献参数?和随机参数?具有明确的几何物理意义,裂隙网络几何贡献参数?可以较为准确地计算裂隙网络的综合优势角?p,随机参数?可定量评价裂隙网络发育的随机程度,?越小裂隙网络优势方向越明显,三者之间存在定量关系。研究成果为复杂天然裂隙网络统计提供了一种有效的方法,为进一步开展裂隙性岩石力学特性研究奠定基础。     

节理裂隙岩体地基输电线路基础承载性能现场试验研究

针对输电线路工程中节理裂隙发育的岩石地基,结合新疆节理裂隙岩体地基220~750k V输电线路工程荷载特点,根据以往理论研究与试验研究成果,选择软岩地基的全风化、强风化等不同风化程度,开展覆盖层厚度(2m-3m)的岩石复合基础上拔、水平、上拔+水平的现场真型试验,分析基础的荷载位移变化规律、钢筋的应力应变规律,监测上拔破坏岩体裂缝产生、扩展及贯通的全过程,研究岩石基础在不同覆盖层厚度条件下的承载特性。     

润扬大桥风化花岗岩工程特性与影响因素研究

由于风化会对岩石强度、刚度和耐久性产生重大影响，故在岩石工程勘察设计中需对其进行重点研究。风化是润扬大桥花岗岩类基岩岩体质量和桥基选址与设计的控制因素之一。系统的地质分析和多种测试结果表明，桥区风化壳厚度的变化很大，岩性以及地壳升降、断裂切割、卸荷作用、江水下切与入渗等地质作用是控制花岗岩风化作用及其风化岩分布的主要因素；桥区花岗岩易风化、卸荷敏感，处于化学风化的早期阶段：细密的蚀变裂隙对岩石强度起着控制作用。在此基础上讨论了风化带来的主要岩土工程问题以及桥型方案、基础选址与设计、地基参数取值以及风化因素控制等方面的工程对策。     

Influence of weathering on the engineering properties of Harsit granitic rocks (NE Turkey)

Weathering and hydrothermal alteration of the granitic rocks in the Eastern Black Sea Region (NE Turkey) are important phenomena affecting the engineering projects in the region. The study investigated the probable paths of rock-forming mineral transformations due to weathering in the Harsit granitoid rocks, the changes of the major oxides as a consequence of weathering and the effects of weathering on the engineering properties. To identify the changes in the major oxides, the volume concentrations were considered in relation to the dry density. Chemical leaching during weathering was shown to be significant in changing the minerals. It was concluded that the engineering properties of the weathered granitic rocks can be most reliably predicted by P-wave velocity.      

Deep weathering of a group of thick argillaceous limestone rocks near Three Gorges Reservoir,Central China

Rock mass characterization is one of the most basic and important tasks in rock mechanics and engineering. Literature review indicates that although there are many publications available on weathered rocks, there are few reports in English on weathered argillaceous limestone rocks and their chemical and mechanical properties. This paper presents a case study of characterizing a group of highly weathered thick argillaceous limestone rocks. Most importantly, they can be easily and quickly decomposed into soils after they are exposed due to excavation. Consequently, they would substantially lose their mechanical strengths. Geohazards such as landslides and sinkholes could occur in uncovered highly weathered argillaceous limestone rocks. The problematic weathered rocks were found during the development of a new town in upper mountains above the Three Gorges Reservoir on Yangtze River in Central China in the past 20 years. The factual data are presented on the changes of chemical compositions and mechanical properties of the weathered argillaceous limestone rocks due to chemical weathering. Some empirical correlations are given to quantify the changes in their uniaxial compressive strength and deformation moduli in terms of their contents of calcium carbonate. The data and findings presented in the paper can be useful to future urban development in geologically poor mountainous environments occupied by highly weathered argillaceous limestone rocks in the world.     

泉州地区花岗岩残积土地质特征与岩土工程评价

泉州地区广泛分布的花岗岩残积土,由变质-混合岩、酸性-中酸性火山岩和花岗岩风化而成,是一种成分复杂、物理力学指标变化区间很大的特殊性土体,其工程性质主要受母岩及其风化程度的影响,与风化残积物中的成分、结构,特别是粗颗粒含量关系密切,并具有随深度规律变化的特征。本文所称的花岗岩属花岗岩类岩石,包括变质-混合花岗岩、酸性-...     

The alteration degree of the metacrystalline rocks based on UAI,Bolu (Turkey)

The geomechanical properties of the metacrystalline rock masses vary due to alteration. The Devonian aged Yedigoller formation crops out in the Asarsuyu valley (Bolu, Turkey). The aim of this study is to investigate the alteration degree of the amphibolite and metagranodiorites based on their geomechanical and petrographical properties. The P-wave velocity is 1,613–5,588 m/s and the unconfined compressive strength varies between 12.75 and 99.86 MPa. Several weathering products occurred due to carbonisation, oxidation and sericitation. These rocks, subjected to hydrothermal effects, are classified as “fresh” to “completely altered” according to the unified alteration index (UAI). In addition, the values of the loss on ignition, modified weathering potential index and chemical index of alteration were taken into account for supporting the alteration process. Since the main process is hydrothermal alteration, the rocks which were exposed to alteration are weathered on the slopes after excavation. Weathering classification and the chemical indices indicate this process. Thus, UAI is concluded to be more suitable and credible in order to evaluate the hydrothermal alteration process of such crystalline rocks numerically.     

Weathering indices and their applicability for crystalline rocks

In the recent past, several weathering indices have been proposed to characterize the extent of weathering and weatherability depending upon the nature and requirement of the study. The weathering index provides a quantitative measure of the extent of weathering of rock; hence it can provide input to the prediction models to assess the strength and deformational properties of rocks and classifications of weathered rock material. In the present study some of the important weathering indices, broadly categorized as chemical, (micro) petrographical and engineering weathering indices, are reviewed and studied experimentally for three common rocks of India, namely granite of Malanjkhand, basalt of Nagpur and quartzite of Delhi, along with results of other rocks reported by other researchers. The study reveals that none of the existing chemical weathering indices is valid for genetically different common rock types and useful for engineering purposes. However, loss on ignition (LOI) may provide an approximate estimation of altered minerals (clays and hydroxides) in tested rocks. It has also shown good correlation with petrographic indices and engineering index properties. Among the petrographic indices, crack density (ρ_cr) and unsound constituent (an input to the micropetrographic index) indices provide good correlation with engineering index properties. To quantify the extent of weathering in terms of strength degradation due to weathering in rock, an index is suggested – strength ratio (R_s) – which is the percentage of uniaxial compressive strength (σ_c) of weathered rock with respect to σ_c of fresh rock. Its significance is shown statistically through the relationships with other indices for several rock types including sedimentary and metamorphic rocks. Electronic Publication     

柏叶口水库坝址基岩风化的综合判定

通过勘察研究,阐述了工程场区岩体风化类型及岩体强风化带、弱风化带、微风化带在空间上的分布及其规律,分析了岩体风化波速比Kw、岩体完整性系数KV和RQD值之间的相关性,确定了综合划分工程场区岩体风化带的定性和定量指标。     

润扬大桥锚碇基岩摩阻力试验研究

采用室内试验和现场剪切试验等手段研究了润扬大桥南北锚碇基底基岩-混凝土胶结面的强度，并根据试验研究成果及现场实际情况，综合分析多种影响因素，研究确定整个锚碇范围内基底摩阻力情况。