探地雷达属性在富水强风化地层中的应用分析

采用探地雷达进行强风化地层隧道超前地质预报时,受现场探测环境、强风化地层的不均匀性以及解译技术制约,造成富水区雷达反射波的解译困难.将探地雷达瞬时属性和频谱属性应用到富水强风化地层研究中,介绍了瞬时属性和频谱属性的原理,并阐述了探地雷达属性在富水强风化地层预报中的可行性.结合工程实例分析研究表明:富水地层的瞬时振幅增强...     

变骨料混凝土与风化片麻岩的强度关系研究

制备不同水灰比的水泥砂浆试件、不同配合比的掺煤渣水泥砂浆试件、不同置入方式的掺铁丝水泥砂浆试件、不同掺入量的掺玻璃纤维水泥砂浆试件以及风化片麻岩试件,试验得到了其单轴抗压强度等力学指标。泰山区域的片麻岩试样分别隶属于未风化、中等风化、强风化和全风化4种风化程度。掺骨料水泥砂浆试件的强度不能达到中等风化程度片麻岩的强度,掺煤渣水泥砂浆不能作为强风化或全风化片麻岩的强度置换材料。掺铁丝七组和掺玻璃纤维六组水泥砂浆试件的抗压强度超过了20MPa,是强风化或全风化片麻岩地基处理的理想置换材料,尤其掺铁丝E组水泥砂浆试件的铁丝掺量、横/竖铁丝置入方式及其对应的基准配合比(C:S:W)1.00:3.95:0.68是推荐的,掺玻璃纤维D、E组水泥砂浆试件的玻璃纤维掺入质量比0、2‰和4‰及其对应的基准配合比1.00:4.29:0.74和1.00:3.95:0.68是科学合理的。注入掺骨料水泥砂浆是提高风化片麻岩地基工程稳定性的有效途径,亦是合理的地基置换材料,变形控制是风化片麻岩建筑地基设计时需要重点考虑的因素。     

金刚石钻进比功及风化花岗岩实时分级研究

基于钻进过程监测系统在不同花岗岩地基金刚石钻进中监测数据,对钻进比功及其变化特性进行分析。结果表明,金刚石钻进比功随岩石风化程度的减弱而增大,具有明显的分区性。在软的全风化及强风化花岗岩中,金刚石钻进比功值低于冲击凿碎比功值;在中等硬度的风化花岗岩中,金刚石钻进比功值与冲击凿碎比功值接近;在硬度较大的微风化花岗岩中,金刚石钻进比功大于冲击凿碎比功。由此可知,在中等硬度的花岗岩中,用冲击凿碎比功来估计金刚石钻进比功才是合适的。这与旋转钻进只适于中硬以下岩层的实际相吻合。最后,提出采用比功变化曲线进行分区,并结合比功均值指标与上界指标对岩体进行实时分级的方法。     

广州某花岗岩地块单桩承载力特征值综合确定

全风化及强风化花岗岩极限侧阻由于其矿物组成及含量不同而差别大,且受地下水及施工工艺的影响较大,难以取值。工程根据静载试验成果,确定其单桩竖向抗压极限承载力,采用规范经验公式,返求全、强风化花岗岩极限侧阻,再与规范经验值对比,综合确定其推荐值,最后根据设计荷载要求,确定单桩竖向抗压承载力特征值。综合确定的全、强风化花岗岩极限侧阻力标准值已经考虑了矿物组成及含量、风化环境、地下水、成桩工艺、泥浆比重等多因素的影响,对特定场地及特定施工工艺下的单桩竖向抗压承载力特征值确定具有直接的指导意义。     

金刚石钻进能量在风化花岗岩地层中的变化特征

利用钻进过程监测系统在风化花岗岩地层中的试验数据对钻进系统的动能、轴力功、黏滞能耗及钻进总能量进行了分析。研究表明,钻具系统的动能在钻进能量中占主导地位,轴力功与黏滞能耗所占的比重很低,钻具系统的动能以及钻进总能量与岩石的风化程度呈负相关,轴力功与岩石的风化程度呈正相关,说明钻进能量与岩石风化程度具有很好的响应关系。最后,从破碎单位体积能耗的观点出发,分析了钻进比功与岩石风化程度之间的关系。研究表明,在全风化及强风化花岗岩地层中,金刚石旋转钻进比功值明显低于冲击凿碎比功;在微风化的坚硬与极坚硬岩石中,金刚石旋转钻进比功则明显高于冲击凿碎比功。这为金刚石旋转钻进中岩石的实时分级与实时判层提供了新的方法。     

预应力锚索装置在高速公路强风化高边坡中的应用

以某新建高速公路风化高边坡加固工程为例,设计3组不同索长和锚固长度下的预应力锚索加固试验,并对试验设计、锚孔现场施工、试验结果等进行了详细分析.结果表明:SY1锚索设计方案只进入外层全风化岩,深度不能满足设计拉力要求,SY2、SY3锚索设计方案均进入全风化岩和砂土状强风化岩,能满足设计拉力要求.     

大连地区风化泥灰岩的工程特性

简述了大连地区泥灰岩的分布特征及风化程度，讨论了在不同的地质环境中全风化泥灰岩(或残积土)的工程地质特性。     

南京地区火成岩的分布特征及岩土工程勘察

南京火成岩分布普遍,岩浆岩种类齐全。区域岩浆活动具有活动时间长,活动期次多,涉及范围广,活动形式多样等特点。因火成岩的成因及风化程度不同,其抗压强度相差很大,从极软岩到较坚硬岩均有分布。火成岩的风化带一般较厚,有的全风化及强风化带可能超过20m。进行岩土工程勘察时,应注意查明火成岩的分布变化规律,确定稳定可靠的基础类型。     

某核电站强风化花岗岩原位直剪试验研究

强风化花岗岩在某核电站厂址区普遍发育,研究其剪切强度对于核岛边坡及常规岛地基的稳定性评价具有重要意义。由于该岩体风化不均匀,常夹有中等风化及微风化较硬夹层或球状风化体,扰动后即碎裂,现场取样和室内试样的难度较大,而且目前进行岩体强度参数反分析的资料相对匮乏。本文作者通过设计堆载式加荷直剪试验方法,并经野外大量现场试验,获得了强风化花岗岩原位直剪的剪应力—应变关系曲线,对强风化花岗岩的剪切强度性质进行了相应的理论分析,为工程区强风化花岗岩设计输入提供了可参考的c、φ值,保证了工程的可靠性,也避免过于保守,并为类似工程积累了经验。     

浅谈回旋钻机深孔钻桩成孑L质量控制

本文就强风化层花岗岩层与中风化花岗岩层多层交锗以及岩面倾斜的地质地段进行钻孔桩的施工．论述了传统的单导向圈的回旋钻机钻头改为双导向圈回旋钻机钻头以及增加配重块有利于保证钻孔质量的特点。     

The relationship between physical and chemical weathering indices of granites around Seoul,Korea

In order to assess the relationship between chemical weathering indices and physical properties of granite, physical and chemical analyses were performed on both natural and artificially weathered granite samples from the Seoul area, where the pH of the rainfall occasionally drops to below 5. The results suggest that slake durability, uniaxial compressive strength, Ruxton ratio, Parker index, modified weathering potential index, chemical alteration index and loss on ignition effectively revealed changes of the degree of chemical weathering. However, the study showed no such good correlation between chemical and physical properties except dry density against loss on ignition and modified weathering potential index against uniaxial compressive strength. It is recommended that both physical and chemical indices should be used for the classification of weathering grade for the granites in the Seoul area.

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Utilisation d'arènes granitiques pour la fabrication de béton en terre

Completely weathered granites are abundant materials and, as a first approximation, their composition is such that treatment with lime should be quite satisfactory, whether they are used for road-building or to produce stabilized blocks for low-cost housing. Three types of completely weathered granite were selected. Their mineralogical and geotechnical properties, and the rocks from which they originate, are described. The completely weathered granites studied differ:

- in the particle size distribution;

- in the mineralogy of their clayey fraction;

- in the degree of weathering affecting them.

The aim of the treatment was to obtain a material having sufficient mechanical strength and insensitivity to water. The results reveal differences among the materials. On dry test specimens, the best results are obtained with the completely weathered granites having the highest clay content, while in saturated test specimens, we find that the mineralogy of the clayey fraction is a factor: the test specimen that performed best had the highest clay content, but its clayey fraction contained no smectites. It is shown, however, that the harmful effects appear only above a threshold that varies with the percentage of lime, and the performance of one of the specimens, artificially enriched with its own fines, which contained smectites, was improved. We propose a relation between the saturated strength values and the quantity of binding agents formed, as assessed on the basis of a mild acid attack. To conclude, on the whole, completely weathered granites can benefit from treatment with lime, whether the purpose is road-building or the production of stabilized blocks. But optimization of the treatment product-performance couple depends on a detailed knowledge of the materials.     

A study of the weathering of the bukit timah granite part a: Review,field observations and geophysical survey

The Bukit Timah granite exhibits a full range of weathering grades. Examination of these exposures shows that the weathering has been rapid. Field observations and geophysical surveys show that the rock has been weathered up to 70 meters depth, and that the main mechanisms of weathering is chemical decomposition. The humid tropical condition in Singapore with high annual precipitation has produced secondary weathering of the residual soil. The weathering profiles suggest that the weathering of the Bukit Timah granite is stratified with weathered layers and a sharp boundary between the residual soil and the slightly to moderately weathered granite. This paper (Part A) is a review of current weathering classification systems for weathered rock. Some results from field observations and geophysical surveys are also presented in the paper. A weathering classification and determination method is proposed for the Bukit Timah granite. Results from field and laboratory investigations of the weathering of the granite and material properties will be presented in Part B.     

Stress ratio effect on fatigue life of tropically weathered rock

This paper investigates the fatigue life of weathered granite and weathered sandstone using a stress ratio of R = 0.17. A small stress ratio is adopted to control data discrepancy between weathered rocks for which stress amplitude is known to affect the fatigue life. The range of varying static strength between weathered rocks, especially for highly weathered rock (grade IV) which has lower static strength, resulted in adopting this small stress ratio. The details of rocks tested, including microscopic petrographic characterization as well as their physical properties obtained from laboratory work, is also explained in this paper. Weathered rock specimens from slightly weathered to highly weathered (grade II, grade III and grade IV) granite and sandstone were used during the investigation. The specimens were representative of rock collected in Sungai Buloh (granite) and Puncak Perdana (sandstone) in Selangor, Malaysia. In order to eliminate the influence of frequency and waveform, all rock specimens (54 in total) were tested under a cyclic compression load with a frequency of 1 Hz using a constant sinusoidal waveform. Result shows that grade IV specimens are the least affected by the small cyclic stress ratio as compared to grade II and grade III specimens. The number of cycles to failure is not dependent on rock weathering grade; it is greatly related to the petrological and microstructure of the individual rock. However, the weathering degree of a rock does contribute to the weakening of the rock's structure, consequently affecting the life of the rock.     

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-...     

“Plagioclase solution degree index”: a new index to evaluate the weathering degree of granite

The weathering degree of rocks has an adverse influence on their strength and deformability characteristics, which in turn influences the industrial uses of rock. The need to develop a weathering index that reveals their mechanical and engineering geological behaviors is thus pertinent to enable the building of more accurate models for forecasting geological hazards. Granite weathering in the Ma On San, Shek Kip Mei and Kwun Tong areas of Hong Kong was studied using scan electron microscope (SEM) images to observe mineral shapes for detailed identification of the weathering degree of completely decomposed granite (CDG). Plagioclase images captured from the SEM were subsequently analyzed and processed with the use of a microstructural image processing system. The results of the analyses indicate that plagioclase, though sensitive to weathering, still remains in CDG and is preserved at different weathering degrees. Hence, it provides a possibility for evaluating the weathering degree more accurately. Thus, a new index referred to as the plagioclase solution degree index is proposed to evaluate the weathering degree of granite.     

Weathering grade classification of lesser Himalayan granites,Western India

Lesser Himalayan granites show various stages of weathering. Primary cracks, grain boundaries and joints have initiated and controlled the weathering processes and resulted in the decomposition of the granites. Feldspars and mica act as key minerals for the initiation of weathering. Later stages of weathering are dominated by the varying nature of weathered clay.     

风化岩石的破碎分形及其工程地质意义

利用分形统计的方法,对风化花岗岩矿物成分的粒度分布特征进行了分析和统计,并根据分析的结果指出,岩石的风化破碎过程具有分形特征。其粒度分布的双对数曲线为多段折线,不同斜率的折线段对应不同的分形维。因此,分形维至少有2个数值,一为结晶颗粒粒度分形维,一为碎裂颗粒粒度分形维。同时,根据试验结果和理论分析得到,碎裂粒子的累积频率分布也符合指数分布,并给出了用指数分布系数求解碎块的碎裂概率的理论计算公式。随后,讨论了碎裂分形维和岩石强度与颗粒结构的关系,并以岩石的降维碎裂演化,得到以分形维描述的岩石风化速率。     

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。