香港大学钻孔过程数字监测仪在土钉加固斜坡工程中的应用

介绍了一台新型的能够自动、客观和连续不断地记录和监测钻孔过程的钻孔过程数字监测仪(DPM)。钻孔过程可由一些随时间变化的钻孔参数来表述,这些参数包括钻杆和钻头的位置、位移和转动,以及钻机对钻头施加的各种动力载荷。此便携式监测仪可快速地安装到钻探机或钻孔机上,并且已经在香港防止山泥倾泻的斜坡加固工程中得到应用。通过实例讨论阐述了在风化岩土斜坡中安装土钉的钻孔过程实测结果。这些实测结果是从香港斜坡防护常用的土钉钻孔过程中得到的。这些实测结果表明钻孔过程参数随时间的动态监测可为工程质量管理和控制以及岩土工程设计和检验提供丰富、有利的真实数据和资料。     

风化花岗岩地层旋转钻进中的能量分析

旋转钻进是岩土工程钻探的主要钻进方式,从能量守恒原理出发,对旋转钻进的能量进行分析。同时,在R-20液压式回转钻机上安装数字式钻孔过程监测（DPM）系统,在风化花岗岩地基工程中进行试验,并在监测数据的基础上对钻进能量进行分析计算。研究结果表明,钻进过程中用于破碎岩石的能量主要来自钻进系统的动能,钻进系统用于破碎岩石的能量分配与地层强度特性有关。在风化程度较低或新鲜岩层中钻进时,破碎岩石98%以上的能量来自系统的动能,而轴压力推动钻头位移所给出的能量不到2%;在土层或全风化岩层中,轴压力所做的功达到22%以上,且明显随风化程度的增高而增大,说明钻进系统动能与轴力功可用以表征地层的可钻性,这为实时钻进能量用于地层的识别提供理论依据。     

全自动钻孔过程监测技术在工程勘察中的应用探讨

本文介绍了一种应用于工程地质勘察的由香港大学研制的全自动钻孔过程监测DPM系统。利用DPM现场监测和记录系统,实现了对整个地质钻探过程中重要钻进参数的自动化监测和实时记录,并通过建立区分准则和分析系统实现了原始数据的快速筛选与分析。通过数据的分析,可以更好地了解和分析钻进过程与性能,提高钻进效率,而且为复杂地质情况的准确判断提供了一种可靠的途径。     

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.     

Landslide types and their relationships with weathering in a Calabrian basin,southern Italy

The basin of the Alaco River, in the Serre Massif of Calabria (Italy), is characterized by outcropping Palaeozoic granitoid rocks. The complex neotectonic history of the area and adverse climatic conditions, both active at least since the Quaternary, resulted in deep weathering of the crystalline rocks. Field observations, integrated with laboratory and in situ tests, allowed the weathering profile to be defined following the six-fold scheme proposed by the Hong Kong Geotechnical Control Office. The weathered rocks evidence a wide variety of mass movements, which were mapped over the entire basin. Debris flow-type instabilities dominate in the residual and saprolitic soils, while falls and slides are more significant in the less weathered rocks. In view of the complex vertical and lateral weathering in the rock mass and the high to very high overall susceptibility of the outcropping rocks to landsliding, it is difficult to postulate any direct relationships between individual types of mass movement and weathering grade.     

In situ strength profiles along two adjacent vertical drillholes from digitalization of hydraulic rotary drilling

Drilling speed and associated analyses from factual field data of hydraulic rotary drilling have not been fully utilized. The paper provides the reference and comparison for the utilization of drilling information from two adjacent vertical drillholes that were formed with the same hydraulic rotary drilling machine and bit. The analysis of original factual data is presented to obtain the constant drilling speed during net drilling process. According to the factual data along two adjacent drillholes, the digitalization results respectively include 461 linear zones and 210 linear zones with their constant drilling speeds and associated drilling parameters. The digitalization results can accurately present the spatial distributions and interface boundaries of drilled geomaterials and the results are consistent with the paralleled site loggings. The weighted average drilling speeds from 2.335 m/min to 0.044 m/min represent 13 types of drilled geomaterials from soils to hard rocks. The quantitative relation between drilling speed and strength property is provided. The digitalization results can statistically profile the basic strength quality grades of III to VI from soils to hard rocks. The thickness distributions of four strength quality grades are presented for each individual type of geomaterials along two drillholes. In total, 50.2% of geomaterials from drillhole A are grade IV and 57.4% of geomaterials from drillhole B are grade III. The digitalization results can offer an accurate and cost-effective tool to quantitatively describe the spatial distribution and in situ strength profile of drilled geomaterials in the current drilling projects.     

基于钻进参数的岩土地层结构识别技术与方法

岩土地层结构是影响工程稳定与安全的重要因素,是地质及岩土工程勘测的主要内容。研发了一种地层地质界面识别系统,阐述了其基本组成和工作原理,建立了钻进过程识别码及岩土地层结构实时识别方法;通过花岗岩地基钻进试验研究,确定了岩体风化等级以及土层/散体、碎裂岩体及整体岩体结构的比能值范围,建立了金刚石钻进比能的地层结构分级标准,比能值分别是土层及散体为0.0017~0.6955 k N·m/cm3,碎裂岩体为0.0258~0.9798 k N·m/cm3,整体岩体为0.0018~2.4935 k N·m/cm3。研究结果表明,该方法与岩土勘测结果一致,可用于地层地质及岩土地层结构的实时识别,为岩土工程智能勘测提供了新的途径。     

Evaluation of the energy efficiency of rotary percussive drilling using dimensionless energy index

This paper sets forth a geomechanics framework for assessing the energy efficiency of rotary percussive drilling using the energy criterion, which has been proposed by Victor Oparin for volumetric destruction of high-stress rocks having nonuniform physico-mechanical properties. We review the long-term research and development in the specified area of science and technology, including research and development projects implemented at the Institute of Mining, Siberian Branch of the Russian Academy of Sciences. A new modified expression of Oparin's dimensionless energy criterion of volumetric rock destruction k is introduced. The range of in situ values is determined for the energy criterion of volumetric rock destruction at the optimized energy efficiency of rotary percussive drilling. The temporo-spatial intervals of geotechnical monitoring are found to control pneumatic drilling energy efficiency at subsoil use objects in Russia. The integrated experimental, theoretical and geotechnical approach to the comprehensive investigation of real-time processes of rock fracture in rotary percussive drilling using the energy concept possesses the necessary geomechanical performance-and-technology potential to create the next level geotechnical monitoring of drilling systems for various purposes, including determination of physico-mechanical properties and the stress-strain analysis of rock mass in full-scale drilling.     

富水砂岩中囊式扩体锚索足尺试验研究

在现场足尺试验基础上,研究了囊式扩体锚索在兰州全风化富水砂岩中的承载特性。试验结果表明,采用水泥浆护壁方式成孔扩孔,即可以防止全风化岩塌孔,又可以将岩屑有效地置换出来。选用合适的高压旋喷压力、复喷次数、进尺速度和水灰比,能够保证扩体段扩径达到设计要求。与普通锚杆相比,囊式扩体锚索在承载力和力学性能方面均有显著提高;通过对锚索扩体段的开挖验证,承压型囊式扩体锚索对周围富水砂岩没有扰动,并且能够在防腐和耐久性方面提供明显的优势。     

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.     

岩石风化程度特征指标的分析研究

岩石风化程度的划分及工程特性研究，对于工程基础面高程的选择以及工程环境或工程材料的利用具有重要意义。关于岩石风化程度划分目前多是采用工程地质定性评价方法，依赖定性的不确定判据进行岩石风化程度划分带有很大随意性。因此，研究和发展定量分析评价方法是必要的。岩石经过风化作用，形成的风化裂隙具有无方向性、不规则发育等特点，与构造作用形成的微裂隙有着本质区别；风化作用改变了岩石的矿物成分，岩石在风化过程中表现出来的阶段性，反映了岩石的不同风化程度。基于对风化岩石显微裂隙的发育状况及其次生充填特点、长石蚀变性质、粘土矿物成分变化等定性资料的分析研究，给出了定量化的统计，建立了岩石风化程度划分的判据。给出的定量指标很好地反映了风化岩石质量，且与反映岩石风化程度的一些物理力学指标存在良好相关性。     

Identification of weathered troughs in granites for tunneling at Daya Bay reactor-neutrino experiment site

Weathered troughs are frequently encountered in granites.They can cause problems to tunneling in the rocks and have to be properly addressed.The structures or spatial shapes of weathered troughs were seldom clarified in the past.In this paper,four weathered troughs are identified by means of geophysical exploration,core drilling,logging,and in-situ stress measurement at Daya Bay reactor-neutrino experiment site in Shenzhen,China.The weathered troughs are exposed on the ground or partially covered by grass and soils,which will threaten the safety of horizontal tunneling at a shallow depth.High electrical resistivity(HER) method is adopted for its feasibility and practicality,in combination with field geological observation,ultrasonic televiewer in boreholes and in-situ stress measurement.By comparing the HER values of completely decomposed to fresh rocks,it is indicated that the HER values of weathered troughs in natural state are 0.4-100 ·m,and the in-situ stress is abnormally lower than those at upper and lower layers.Field investigations show that the depths of the four weathered troughs are 30-182 m,with bottom elevation over 10 m.The volume of each weathered trough is mostly over 1×10 6 m 3 in inverted conic form.The weathered troughs often occur in various kinds of landforms,such as ridges,gullies or gently dipping dish-like depression areas.Faults and boundaries of different granitic plutons as well as joints govern the formation,locations and strikes of these troughs under development.     

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。     

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.

     

Geological and geotechnical characteristics of Xiaolangdi dam, Yellow River, China

In order to construct a 154 m high, 1,650 m long earth filled dam across the Yellow River at Xiaolangdi, China, site investigations including in situ and laboratory tests, Landsat imaging, geological mapping, geophysical survey and drilling were undertaken. Two special investigation techniques were employed. To ensure full recovery of the intercalated clays and siltstones in the Permian and Triassic deposits, a sleeve drilling technique was introduced while to establish the long-term stress conditions in the tunnels, radial resistance testing was undertaken. The paper focuses on the geotechnical characteristics of the Quaternary sands and gravels, which in the channel of the valley are up to 70 m thick, and discusses the influence of the Triassic and Permian bedrock.     

DEM investigation of weathered rocks using a novel bond contact model

The distinct element method(DEM) incorporated with a novel bond contact model was applied in this paper to shed light on the microscopic physical origin of macroscopic behaviors of weathered rock, and to achieve the changing laws of microscopic parameters from observed decaying properties of rocks during weathering. The changing laws of macroscopic mechanical properties of typical rocks were summarized based on the existing research achievements. Parametric simulations were then conducted to analyze the relationships between macroscopic and microscopic parameters, and to derive the changing laws of microscopic parameters for the DEM model. Equipped with the microscopic weathering laws, a series of DEM simulations of basic laboratory tests on weathered rock samples was performed in comparison with analytical solutions. The results reveal that the relationships between macroscopic and microscopic parameters of rocks against the weathering period can be successfully attained by parametric simulations. In addition, weathering has a significant impact on both stressestrain relationship and failure pattern of rocks.     

对岩土工程勘察钻探及编录的认识

指出岩土工程勘察钻探及编录是一项取得第一手资料的重要环节,它直接影响到最终勘察报告的质量,并从外业钻探和编录的实际经验出发,从钻探设备、技术人员、岩土特征等方面,对钻探编录的几个要点进行了提示和分析,以供从业人员参考。     

Pressurised TBM tunnelling in mixed face conditions resulting from tropical weathering of igneous rock

Weathering is a process that turns rock into soil. Deep weathering is prevalent in tropical and sub-tropical areas. The resulting sub-surface conditions can be very onerous for tunnelling, with tunnel drives commonly encountering a significant proportion of mixed face conditions, comprising partly rock and partly soil. Problems that have been encountered have included: inability to maintain the face pressure, ground loss, sinkholes, slow rates of tunnelling, rapid tool wear, damage to tools, mixing arms and other parts of the TBM, very frequent and long interventions, clogging and blow-outs. The nature and extent of the problems on any particular tunnel have depended on the type and design of the TBM, the nature of the rock and the proportion of the tunnel in mixed ground. In Singapore this has resulted in a change from mainly EPB to mainly slurry tunnelling in weathered igneous rock; however, predominantly EPB TBMs have been used in weathered sedimentary rock. Information from EPB and slurry TBM drives is used to illustrate the issues involved.     

CFG桩施工造成环境岩土工程问题的研究

长螺旋钻管内泵压CFG桩,是近10年来发展起来的一项复合地基新技术。然而当该技术应用到郑州地区的某些区域时却出现了环境岩土工程问题。根据多年的施工经验,对其进行了研究,得出长螺旋钻管内泵压CFG桩施工引起的环境岩土工程问题与施工工艺和施工场地的岩土工程条件有关。     

Weathering of the massiac gneiss (massif central,France)

Weathering profiles of gneissic rocks in tropical and temperate climates are here compared and represent a most relevant concern for geotechnical engineering. The understanding of the physico-chemical weathering processes is very important for an adequate interpretation of the geotechnical behaviour of those materials. The weathering profile of the Massiac gneiss developed in a temperate climate, is described in relation to its mineralogical and textural changes, as well as the characterization of the main index tests and geotechnical parameters as strength and deformability. The relevance of anisotropy in the different weathering grades is evaluated.