漳州沿海岩石的风化规律及存在的工程地质问题

本文对不同岩性岩石的风化规律及存在的主要工程地质问题的分析研究,并且提出预防和处理的措施建议,可为工程规划建设和基础设计提供依据。进而消除或者降低风化岩土工程地质问题给岩土工程带来的危害。     

平遥古城墙基外侧砂岩的风化速度研究

岩石风化的研究一直受到地貌学家、地质学家和岩土工程学家的关注。暴露于自然环境下的石质文物(特别是不可移动文物)可认为是在当地环境下经历了一段较长时间的风化试验。作者利用自行研制的、具有较高精度的仪器,量测了平遥古城墙基底部的砂岩经过638 a自然风化后的风化丧失深度,得其风化丧失深度和最大风化丧失深度分别为8.03～32.30 mm和11.80～46.97 mm,并以此计算出相应风化速度分别为0.0125～0.0506 mm.a-1和0.0185～0.0737 mm.a-1。比较砂岩的风化速度,发现其受朝向控制:朝南、朝西、朝东和朝北的砂岩的平均风化速度值分别为0.0481,0.0377,0.0286和0.0220 mm.a-1。笔者认为上述风化速度的差异是由不同朝向的砂岩受到的太阳辐射不同造成的。     

土工测试与勘察技术研究进展

文章总结国内外近年来在土工测试与勘察技术领域的研究进展,主要包括土工室内测试技术,土工离心模拟技术,岩土工程勘察技术,原位测试技术等。分析表明,随着各类工程建设呈现高、大、深、重的趋势,传统的土工测试技术已发生根本改变,考虑“水-热-力”耦合、震动、风化、高压、波浪、冲刷等复杂工况的大型土工室内试验及离心机设备,以及电子测量、光纤测试、电磁测试、声波测试、激光扫描、无线传感、物探等先进勘察技术,在岩土工程领域已得到广泛应用。     

Weathering of metapelites from the Quadrilátero Ferrífero mineral province,southeastern Brazil

Low-grade metamorphic rocks are known for their low mechanical strength and high weatherability. In the Quadrilátero Ferrífero, an important mineral province located in southeastern Brazil, this set of features results in frequent issues with mining and road slope instability, mainly associated with phyllites. Despite the significant iron ore production that occurs in this province, little is known about the geotechnical properties of the materials constituting the weathering front. Here, we report work aimed at investigating the changes in the basic properties of phyllites at four weathering grades. The methodology used included the field classification and mapping of four weathering grades in order to assess their spatial distribution on a road slope, as well as sampling for geological characterization by petrography and X-ray diffraction (XRD). In addition, the authors performed a physical characterization of all weathering grades, including index properties, mercury porosimetry, and strength data obtained with a Schmidt hammer both in the field and in the laboratory as well as using the point load test (PLT). Results showed the relevance of structural features such as discontinuities and metamorphic foliation observed in the weathering morphology in situ, with different weathering intensities occurring along the slope. Changes in the porosity and pore size distribution in the weathering front were nonlinear, as were resistance variations. The difficulty involved in performing the macroscopic identification of weathering grades due to the very fine texture of the rock as well as microstructural heterogeneities are likely causes of the observed variability in phyllite properties. This fundamental knowledge may aid the prediction of short-term and long-term scenarios for slope stability based on rock weatherability.

     

Automatic monitoring of rotary-percussive drilling for ground characterization—illustrated by a case example in Hong Kong

In mountainous regions comprising weathered soils and rocks, it is important to delineate the spatial distributions of geomaterials with different weathering and decomposition grades in depth. This paper presents a methodology to cost-effectively and accurately identify the subsurface zones of volcanic weathering. The methodology consists of in situ digital monitoring and a number of associated data analysis methods. The in situ digital technique is the drilling process monitor. It can automatically, objectively and continuously measure and record parameters associated with the full drilling process of a rotary-percussion drilling machine when it is being used to drill a production hole (such as probe holes and soil nail holes) in the ground. The data analysis methods are used to identify relevant factual data from the full drilling process data for zoning. The calculations are simple and straightforward tasks. Factual data presented in the paper illustrate that the proposed methodology can be a simple and cost-effective tool to record and utilize by-products of current normal drilling practice for ground investigation, geotechnical design and verifications, drilling construction management, as well as drilling quality control. The proposed methodology offers great potential in furthering the geotechnical knowledge and engineering practice in Hong Kong and many other mountainous regions comprising weathered soils and rocks. There is also significant potential for other applications in civil and mining engineering through estimation of the mechanical properties of rock from the monitored drilling data.     

张河湾上水库边坡细砂岩变形模量原位试验研究

变形模量是岩土工程力学特性的一个重要指标,现场压板荷载试验计算变形模量是最直接有效的方法。河北张河湾抽水蓄能电站上水库边坡施工开挖后全强风化细砂岩出露较多,对沥青混凝土面板的变形影响较大,通过对不同风化程度的细砂岩取样进行细砂岩变形模量试验,为工程设计提供地质依据。     

高密度电法和土壤氡测量在滇中某地岩土工程勘察中的应用

在滇中某场地岩土工程勘察中投入高密度电法和土壤氡测量对拟建工程影响较大的浅部持力层结构进行探测,推断了软弱下卧层、基岩起伏、风化壳、岩溶和活动性断裂等不良工程地质。结合同期开展的钻探和开方剥离等验证工程对此次物探效果进行对比分析,总体来看探测效果较好,成果为后期工程建设提供有利技术支撑。     

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。     

The influence of mineralogical textural and chemical characteristics on the durability of selected sandstones in Istanbul, Turkey

 The paper describes the analyses and geotechnical testing of sandstones taken from a road cutting to the north east of Istanbul, Turkey. Samples were carefully selected in the field in order to obtain material representative of the complete weathering profile. Although unconfined compressive strength, point load index values and Schmidt hammer rebound numbers were obtained, the slake durability test provided the closest correlation with weathering grade. Received: 4 February 1998 · Accepted: 15 June 1998     

Study of the unexpected collapse of the Ampurdán tunnel (Spain) using a finite elements model

This paper presents the case study of the Ampurdán tunnel that suffered an unexpected partial collapse during construction due to the weathering of the claystone groundmass after excavation and wetting by infiltration water. To overcome the problems encountered, a finite elements model was used to understand the behaviour of the tunnel and surrounding ground to determine the geotechnical properties that lead to failure, allowing engineers to choose suitable procedures for the construction of the tunnel. The parametric study performed simulated the deformations measured in situ and related to the tunnel collapse. The geotechnical parameters used for the weathered claystone, when compared with the intact portion, correspond to a wide range of reductions between 8 % in the apparent density and in the effective friction angle, up to 40 % in the effective cohesion and 56 % in the Young modulus.     

Mechanical properties and behaviour of soils under the triaxial test,the Yamauchi landslide,Japan

A series of consolidated undrained triaxial tests have been undertaken on material from the Yamauchi landslide in northern Kyushu. The samples were obtained from two specially drilled boreholes. Both the logging and the geotechnical test results indicate a wide variation which is probably attributable to the differing degree of weathering/hydrothermal alternation. Two types of stress strain and pore-water pressure responses were observed during the test. Two failure modes were identified – plastic and semiplastic. Electronic Publication     

压实花岗土的试验研究

对压实花岗土进行了三轴固结排水试验、复合应力路径试验、p定值试验和η定值试验。并利用Yasufuku模型对试验结果进行了预测比较。试验及预测结果表明，利用Yasufuku模型预测的结果与实测结果基本一致，但在η定值试验中显现出了一定的出入。     

Risk evaluation of rock mass sliding in El-Deir El-Bahary valley,Luxor, Egypt

The temple of Hatshepsut is considered as a most interesting ancient architectural monument and its stability is of real concern to human civilization. The temple is completely incised into the rock mass of Gebel Gurnah which is composed of Esna shale overlain by highly fracture Thebes limestone. Recently, two rock falls have occurred. A geotechnical characterization of the site around the temple was carried out. The present work aims to evaluate the probability of further limited circular failures in the Esna shale. This evaluation is achieved by using a near circular failure model based on the behaviour of intact rock, in conjunction with the CSIR rock mass classification system which gives the reduced mechanical properties due to the increase in discontinuity sets and weathering of the rock mass of the mountain around the temple.     

堆石料劣化及其对大坝安全运行影响的研究

在现有土石坝工程中,一些易风化的软岩已被广泛应用于坝体的填筑,在坝体长期运行过程中,堆石料含水率和温度变化的影响等会造成其力学性质的劣化,随着全球大气环境污染加剧,酸雨对其力学性质的影响也将日趋显著。堆石料是天然形成的,一般而言已有的生命周期可能比大坝的使用周期长得多,但在某些情况下岩石的力学特性会在很短甚至几个月内发生较大变化,堆石料力学性质的劣化会使其强度参数降低从而导致大坝安全稳定性下降,同时使坝体产生附加后期变形。现有的大坝设计中把岩体分成全风化、强风化、弱风化等,一般只考虑风化的现状,很少考虑工程建成以后岩体因风化而对其寿命和功能的影响。随着科技的进步,特别是环境岩土工程的进步,对风化现象从定性描述到定量研究的条件正在逐步成熟。针对单线法和双线法两种试验方法,分别提出了一个能够考虑堆石料风化影响的计算模型,可用于定量分析大坝使用周期内的坝体应力变形特性的变化,在此基础上对大坝内易风化软岩的分区布置进行了探讨。     

Cluster analysis for the determination of the undrained strength tendency from SPT in mudflows and residual soils

The standard penetration test (SPT) remains one of the most commonly used field tests to obtain the shear strength properties of soils, the undrained strength (c_u) being one the most SPT-N-correlated parameters for geotechnical applications. The overall N-value-c_u correlations show a direct relationship between them, characterized by presenting an equation formed by a constant value multiplied by N. More recently, the use of c_u in geotechnical engineering has been of great interest in the evaluation of the influence of the undrained strength variability with depth on slope stability analysis. Therefore, an evaluation of the variability with depth of the N-value is made according to the geological origin. However, the (N₁)₆₀ values obtained from the SPT have different limitations due the possible “outside of tendency” data known as outliers caused by random factors such as: rock fragments content, weak zones and variations in the state of weathering, which may ultimately affect the estimation of the c_u function with depth. Therefore, a cluster analysis of the SPT data was performed in order to identify the values that affect the best-fitting mathematical SPT-N function with depth. These analyses were implemented to the (N₁)₆₀ values obtained from multiple SPTs in two distinct geological units, mudflows and residual soils, in order to study the influence of the geological origin in the SPT and, therefore, of the shear strength tendency with depth. It was found that the best clustering method to identify the SPT tendency and the state of weathering in residual soils is the Ward method. For mudflows, the best cluster algorithm is the single method; however, it is concluded that for large areas, the use of a unique cluster method is not recommended. For most projects, the undrained shear strength showed a nonlinear tendency with a squared Z (where Z is the depth in meters) function being common among all geologies. The function gradient for residual soils is about twice when compared with that of the mudflows, mainly due to the overburden pressure and to the decrease in the state of weathering with depth, which increases shear strength in the former type of soils.

     

深圳地区第四系主要地层特征探讨

深圳地区三面临海,地势东南高西北低,可分为三个地貌带．各带地貌类型复杂。河流短小众多,降雨量丰沛,河流属雨源型。其径流量、流量和洪峰与降雨量密切相关。洪峰暴涨暴落。第四系沉积厚度及种类各地相差悬殊．与下伏基岩密切相关。位于燕山晚期侵入的中粗粒花岗岩区的河流上游风化壳厚度大,水土流失严重,下游淤浅严重,第四系沉积层厚度大...     

Project geotechnical engineering: systems methodology considerations

Systems methodology considerations for project geotechnical engineering are discussed. Emphasis is on general systems and related geotechnical principles, issues and limitations. After an introduction, the paper outlines geotechnical programme management as a framework for defining, organizing and controlling the geotechnical engineering process. Then, following the logical order of elements in project geotechnical engineering, the paper discusses programme development, followed by site characterization and analysis, and design and implementation. The paper concludes with a discussion on additional general methodologies: uncertainty, updating, values, innovation and impediments. The objective is to provide a broad conceptual framework which can be used as needed to help guide realistic integration and implementation of the diverse and often convoluted efforts of project geotechnical engineering.     

Caractéristiques des masses et marnes du gypse et de leurs faciès d'altération dans la région parisienne méthodologie des études géotechniques

The author presents the principal results of a research project concerning a geological formation widely represented in the natural region of Parisis, North of Paris, which is dreaded by geotechnicians: masses and interstratified marls of ludian gypsum. The impossibility of making ground observations essential to a thorough study of the phenomena of weathering of the gypsum, and notably its substitution, led to the work being undertaken along the following lines:

-Modelling of the geological infractructure of the gypseous slopes.

-The quest for indicators of the lithology and distribution of the residual masses and interstratified marls of gypsum, and the valuable role of diagraphs of natural radioactivity.

-The incidence of the weathering of the gypsum on the mechanical (pressiometric) characteristics of the gypseous areas.

-A methodology of geotechnical surveys on gypseous sites.

A progressive approach is proposed, beginning with a feasibility study, followed by a detailed study of the evolutive nature of the site, essential to the establishment of a suitably adapted project, and concluding with a mechanical characterisation necessary for the structural design of foundations.     

Climate as the most important factor determining anti-fungal biocide performance in paint films

The effect of Pigment Volume Content (PVC) on fungal growth on acrylic paint formulations with and without biocide, exposed to weathering in three different climatic regions in Brazil for four years, was studied. Latex paints, with PVC of 30%, 35% and 50%, were applied to autoclaved aerated concrete blocks pre-covered with acrylic sealer and acrylic plaster. They were exposed to equatorial, tropical and temperate climates in north, south-east, and south Brazil. Cladosporium was the most abundant fungal genus detected in the biofilm on the surfaces of all paint formulations at all sites after four years. Heaviest fungal colonization occurred in the tropical south-east and lightest in the temperate south of the country, but more phototrophs, principally cyanobacteria, were detected in the equatorial region. PVC and presence of biocides were shown to be of less importance than environmental conditions (irradiance, humidity and temperature) for biofilm formation and consequent discolouration. These results have important implications for testing of paint formulations.     

Altérabilité, gonflement et propriétés d'indices des marnes néogènes de la dépression de Grenade (Sud de l'Espagne)

The geotechnical features of the three members of the Neogene of the Grenade basin (South Spain) are described from 170 samples. The upper member shows 30 meters of soil with 46–90% silt, 5–52% clays (34 to 82% smectitic), high durability-high plasticity and high swelling potential. In the upper 10 meters, some very local layers of silts and gypsum are observed and at the bottom 20 meters of detritic deposits. The middle member is composed by 80 to 250 meters of marly soils with 40–92% of silt fraction, 5 to 60% of clay fraction (40 to 100% illitic), high weathering index and low swelling potential. Some turbiditic and evaporitic deposits, several tens of meters thick, are also locally interlayered. The upper member is composed by 100 meters of detritic-carbonated soils with 0–88% of sand fraction and 5–57% of clay fraction (30–80% smectitic). The weathering index and the swelling potential are similar to the middle member, even with its higher smectitic contain and because of the swelling inhibition derived from the higher carbonate and sulfate proportions.