【作者】 刘睦峰；

【导师】 彭振斌；

【作者基本信息】 中南大学 ， 地质工程， 2010， 博士

【摘要】 软岩是地球表面分布最为广泛的一种岩石,是一种特定环境下的具有显著变形的复杂岩石力学介质,给工程施工、结构设计、施工工艺等带来一系列特殊问题。本文结合某工程的地质特征及施工技术难题,选取具有广泛代表性的软岩原样,首次对软岩的相似性材料的组合配方及其试验方法进行探讨,寻求较佳的配合组合来制作室内模拟钻进岩样,以此来探讨大直径软岩钻进技术的改进和工艺参数的优化,取得较好的应用效果,具有重要的工程意义。论文选取岩性材料的模拟方法,将软岩原型选取为三种：泥岩(含页岩、粉砂质泥岩),粉砂岩(含泥质粉砂岩),细砂岩(含粉质细砂岩),经分析比较得出软岩模拟的最优配方号分别是泥岩(A2B2C3,即621#)、粉砂岩(A1B2C2,即437#)、细砂岩(A2B3C1,即355#),较好地模拟出了相应原岩的抗压强度；其三种岩石的内聚力和内摩擦角的变化趋势是相反的,且差别均不大,因此综合其抗剪强度能够符合原岩的强度范围,对模拟试验结果影响不大；模型的密度也尽可能的接近原岩,通过相似比计算均可以模拟原岩密度；模型的弹性模量试验值由于试验水平等原因虽未呈某趋势变化,但其值均在原岩范围内。所以,在室外的大样制作过程中,考虑了模具的承压能力及试验室的制作水平,最终确定模拟大样的尺寸为直径300(mm)、高400(mm)的圆柱体,以保证三轴应力试验机能够顺利制作大样试块和脱模和养护28天后满足钻进模拟试验要求。探讨了机械参数对钻速的影响,根据室内条件和机械参数所起的作用,首先研究了刮刀切削角对钻速的影响。通过改变刮刀的安装角度,使刀片以不同的切削角度切削破碎模块,试验结果表明：泥岩在刮刀安装角度为10°时,碎岩效果最好,钻速最快；而粉砂岩和细砂岩在刮刀安装角度为5°时,碎岩效果最好,钻速最快。其次是钻压对钻速的影响。根据室内实验和现场现场试验数据,采用Microcal Origin软件对实验数据进行加权残差变易法分析,首次拟合出大直径钻孔作业的钻压与钻速的的变化规律为：y=(A-B)/(1+(x/x0)p)+B.现场试验表明钻压控制在100-200kN之间,能取得较好的钻进效果。第三是转速对钻速的影响。根据室内实验和现场现场试验数据并进行回归分析,首次拟合出转速与钻速的的变化规律为：y=a(1-ebx),现场试验表明转速控制在6-8rpm为宜,能取得较好的工效。从钻头的碎岩机理研究出发,探讨了钻头的改进研究。研究认为软岩可归类为塑性岩层和弹—塑性岩层两大类,主要体现为碰撞、压碎及小剪切、大剪切等碎岩方式。在弹—塑性岩层中,每个剪切循环中和各个循环之间,水平力都是跳跃式的有规律地变化着；而在塑性岩层中,水平力没有显著的变化,基本上可以认为是常量。为此,论文主要从钻头刀具形状及材料选择、钻头导向及吸渣水口结构的优化设计、刮刀钻头角度的选择、切削翼板设计、钻头布齿设计等五个方面对新型钻头结构进行论证分析,通过现场试验,改进后的钻头达到了实际需求的效果。一是改进后的导向钻头中心角设置成小于刀翼中心角,将原来的100°改变为80。,增大导向锥的倾斜长度,以提高高速钻进时导向稳定性；二是改进后的刮刀尺寸为长200mm×宽80mm×厚60 mm,硬质合金为YG11C,结构形式是扁棱形,并根据切削角对钻速模拟试验结果,转角翼板的倾角不大于10°；三是工程应用效果评估中,新型刀片的成孔时间将缩短一半左右,其单套刀具的成孔数约普通的3倍,折算到单个成孔的价格性能比,新型刀片较普通刀片高很多；在钻压、转速和其他水力参数相同的条件下,将刮刀在两个项目的施工记录按纯钻进时间进行统计,新型刮刀的的功效提高了一倍以上,并作业区域得到了广泛的应用；四是钻孔参数优化的内容是多方面的,优化的目标不是唯一的,有最低成本指标,也有质量、速度、进尺、工期等其他指标。这些指标与机械设备、地质条件等客观因素有关,又与钻孔施工中采取的诸多措施及参数的选择有关。通过施工组织与管理的风险评估,促进了钻进工艺参数的优化和管理决策水平的提高。一是大直径钻孔灌注桩由于其能适用各种地层条件、能制成各种桩径和桩长、能满足不同承载能力要求等诸多优点,被广泛应用于许多特大型基础工程施工中,尤其是深水、大跨径桥梁基础工程施工中,并不断向超大超深方向发展。由于工程地质条件越来越复杂,施工风险也越来越大。为此,针对工程地质条件的复杂性和不可预知性,着重探讨了风险型的决策方法及其决策方案的风险。二是结合大直径灌注桩施工组织与管理中存在的突出问题,以数理统计及有关计算方法为工具,以系统科学及决策论为理论基础,建立了风险型决策的数学模型,对类似的工程项目具有指导意义。更多还原

【Abstract】 Soft rock, the most widely distributed type of rock in the Earth’s surface, a complex rock mechanics media that become significantly deformed in a specific environment, has brought a series of special issues to the construction, structural design and construction technology. based on the geological features and technical difficulties in a construction project, this study selected a sample of broadly representative raw soft rocks to, for the first time, explore the combination formula and testing methods of similar materials of soft rocks, to seek optimal combination formula for the production of indoor simulated drilling rock samples, and finally to improve the large-diameter soft-rock drilling technology and optimize the process parameters. The application results have important engineering significance.The simulation methods adopted for selecting lithologic materials identify three types of prototype soft rock:shale (including shale, and silty mudstone), siltstone (including muddy siltstone) and fine-grained sandstone (including silty fine-grained sandstone). By analyses and comparisons, the optimal formula of simulation of soft-rock were obtained, which are:mudstone (A2B2C3, No.621), siltstone (A1B2C2, No. 437) and fine-grained sandstone (A2B3C1, No.355), with their corresponding compressive strengths of the original rocks well simulated. An opposite trend has been found in each of the three types of rocks between its cohesion and internal friction angle, without significant differences. This, taking into consideration their shear strengths that fall within the intensity scope of the original rocks, has no significant impact on the simulation tests. The density of the samples was kept as close to that of the original rocks as possible, through similarity ratio calculations. The experimental values of the elastic modulus of the models fell within the scope of that for the original rocks, although they could not show a trend as constrained with experimental conditions. Therefore, in outdoor bulk sample production process, taking into account the pressure bearing capacity of the sample and the production capacity of the laboratory, the simulation of large sample was determined to be a cylinder with a diameter of 300 (mm) and a height of 400 (mm), in order to ensure that a triaxial stress test machine can smoothly produce bulk sample test block and the stripping and maintenance of 28 days to meet the drilling simulation test requirements.The paper discusses the role of mechanical parameters on the drilling speed.1) According to indoor conditions and the role of mechanical parameters, it experimented on the impact of scraper blade’s cutting angle on the drilling speed by changing the blade angle, so that the blade could cut and break the modules from different perspectives. The test results showed that, in terms of rock breaking effect and drilling speed, the blade had the best performance with an angle of 10°for mudstones, and 5°for sandstones.2) The impact of drilling pressure on the drilling speed:Based on laboratory experiments and on-site field test data, using Microcal Origin software, the experimental data are weighted residuals Variation Analysis for the first time fitting a large-diameter drilling operations drilling pressure and drilling speed of change of the:y = (A-B)/(1+(x/x0) p)+B. Field test showed that when WOB controlled between 100 and 200kN, the drilling can achieve the better results.3) The impact of speed on the penetration rate:Based on laboratory experiments and on-site field test data and regression analysis, the first drilling fitting out the speed and speed of change of the:y= a (1-ebx), field tests show that speed controlled within 6-8rpm is appropriate and can get better ergonomics.Based on the drill’s rock-breaking mechanisms, the paper has explored on how to improve the function of drills. Studies suggest that soft rocks can be categorized as plastic soft rock formations and-elastic-plastic rocks, with their characteristics mainly reflected in the rock-breaking modes such as collision, crushing and small shear and large shear. In the elastic-plastic rocks, in each cutting cycle and between the various cycles, the horizontal force leaps and changes regularly, whereas in plastic rocks, the horizontal force, without significant change, basically can be considered constant. This paper therefore analyzed and argued for an improved structure of the drill from five aspects including: the shape and material selection for the cutting blade, drill-oriented and smoke residue nozzle structural optimization design, the choice of blade angle drill, cutting flange design and drill cloth tooth design. Through on-site testing, the improved drill bit achieved the expected results.1) For the improved drill, the central angle for the guiding drill bit is smaller than that of the blade-wings, a decrease from the original 100°to 80°, which increases the inclined length of the guiding cone in order to improve the stability of orientation in high-speed drilling; 2) The improved scraper blade is sized 200mm long,80mm wide and 60mm thick, made of hard alloy YG11Cin a flat diamond structure, and based on the simulated testing results of penetration rates against cutting angles, the inclination angle of the flange is not greater than 10°; 3) In the effect evaluation of the engineering applications, the new blade can half the time for hole forming, and the number of holes formed using a single set of the new tools is about three times as many as that using common tools, i.e., converted into a unit cost per hole, the new blade is far more cost-effective than common ones. In the same conditions of WOB, rotational speed and other hydraulic parameters, statistics of the net drilling time and progress of two projects has proven that the efficacy of the new scraper has more than doubled, and therefore the new tool has been widely used in the operating areas; 4) The objectives and content of the optimization of drilling parameters are multiple dimensional, including many indicators such as minimum cost, quality, speed, footage, duration and others. These indicators are again related to some physical conditions such as mechanical equipment and geological conditions, as well as various measures taken and parameters selected in the construction projects.Trough risk assessment on construction organization and management, the paper promotes the optimization of drilling process parameters and management decision-making.1) Applicable to a variety of formation conditions and different pile diameters and lengths and capable of meeting different bearing capacity requirements, as well as many other advantages, large-diameter bored piles are widely used in many large foundation engineering constructions, especially in deep water and long-span bridge foundation engineering constructions, and these foundations continue to grow towards an extra-ultra-deep direction. The risks associated with construction are growing as engineering and geological conditions become increasingly complex. To address the complexity and unpredictability of engineering and geological conditions, this paper discussed risk-based decision-making methods and risks of decision-making program.2) In view of the outstanding issues in the construction organization and management of large-diameter bore piles, using mathematical statistics and calculation methods, and based on systems science and decision-making theory, this paper has proposed a mathematical model for risk-based decision-making, which could be used to guide similar projects.更多还原