Testing method of rock structural plane using digital drilling

The rock mass consists of rock blocks and structural planes,which can reduce its integrity and strength.Therefore,accurately obtaining the characteristics of the rock mass structural plane is a prerequisite for evaluating stability and designing supports in underground engineering.Currently,there are no effective testing methods for the characteristic parameters of the rock mass structural plane in underground engineering.The paper presents the digital drilling technology as a new testing method of rock mass structural planes.Flawed rock specimens with cracks of varying widths and angles were used to simulate the rock mass structural planes,and the multifunctional rock mass digital drilling test system was employed to carry out the digital drilling tests.The analysis focuses on the variation laws of drilling parameters,such as drilling pressure and drilling torque,affected by the characteristics of prefabricated cracks,and clarifies the degradation mechanism of rock equivalent compressive strength.Additionally,an identification model for the characteristic parameters of rock mass structural planes during drilling is established.The test results indicate that the average difference of the characteristics of prefabricated cracks identified by the equivalent compressive strength is 2.45°and 0.82 mm,respectively.The identification model while drilling is verified to be correct due to the high identification accuracy.Based on this,a method for testing the characteristic parameters of the surrounding rock structural plane while drilling is proposed.The research offers a theoretical and methodological foundation for precise in situ identification of structural planes of the surrounding rock in underground engineering.

Vertebral Bone Drilling (Puncture) Attenuates the Acute Pain Due to Vertebral Compression Fractures

Purpose: The Investigational Vertebroplasty Efficacy and Safety Trial (INVEST), a randomized blinded controlled study of Vertebroplasty, demonstrated similar improvements in pain between blinded Vertebroplasty and sham-Vertebroplasty groups. The result from the RCT study suggested that the observed efficacy of the Vertebroplasty procedure, instead of representing the cement-mediated reduction in pain, may relate to the vertebral bone drilling per se. The aim of this study was to demonstrate the effectiveness of pain relief of vertebral bone drilling at the site of painful osteoporotic vertebral compression fractures in the acute phase. Materials and Methods: Twenty-six patients with painful osteoporotic compression fractures underwent the vertebral bone drilling. We assessed primary outcome measures in the NRS pain score and RDQ score at day 0 and 3 following the drilling. Comparisons were made by using Wilcoxon signed rank test. Results: The mean baseline NRS and RDQ score, and the mean NRS and RDQ score at day 3 were 7.3 ± 1.2, 15.7 ± 4.2, 4.6 ± 1.4, 7.3 ± 2.2, respectively. Among the patients, we detected significant improvements in NRS pain score and RDQ score at day 3 following the drilling compared with day 0 (P < 0.001). Conclusion: Vertebral bone drilling at the site of painful vertebral compression fractures alleviated the intractable pain due to osteoporotic vertebral compression fractures.

A Statistical Analysis of the Modulus of Elasticity and Compressive Strength of Concrete C45/55 for Pre-stressed Precast Beams

Random behavior of concrete C45/55 XF2 used for prefabricated pre-stressed bridge beams is described on the basis of evaluating a vast set of measurements. A detailed statistical analysis is carried out on 133 test results of cylinders 150 ~ 300 mm in size. The tests have been running in laboratories of the Klokner Institute. A single worker took all specimens throughout the period, and the subsequent measurements of the static modulus of elasticity and the compressive strength of the concrete were performed. The measurements were made at the age of 28 days after specimens casting, and only one testing machine with the same capping method was used. Suitable theoretical models of division are determined on the basis of tests in good congruence, with the use of Z2 and the Bernstein criterion. A set of concrete compressive strength （carried out on 133 test results of cylinders 150 ~ 300 mm after test of static modulus of elasticity） shows relatively high skewness in this specific case. This cause that limited beta distribution is better than generally recommended theoretical distribution for strength the normal or lognormal. The modulus of elasticity is not significantly affected due to skewness because the design value is based on mean value.

Strength weakening effect of high static pre-stressed granite subjected to low-frequency dynamic disturbance under uniaxial compression

This study aimed to elucidate the strength weakening effect of high static pre-stressed rocks subjected to low-frequency disturbances under uniaxial compression.Based on the uniaxial compressive strength(UCS)of granite under static loading,70%,80%,and 90%of UCS were selected as the initial high static pre-stress(σ_(p)),and then the pre-stressed rock specimens were disturbed by sinusoidal stress with amplitudes of 30%,20%,and 10%of UCS under low-frequency frequencies(f)of 1,2,5,and 10 Hz,respectively.The results show that the rockburst failure of pre-stressed granite is caused by low-frequency disturbance,and the failure strength is much lower than UCS.When theσp or f is constant,the specimen strength gradually decreases as the f or σ_(p) increases.The experimental study illustrates the influence mechanism of the strength weakening effect of high static pre-stress rocks under low-frequency dynamic disturbance,that is,high static pre-stress is the premise and leading factor of rock strength weakening,while low-frequency dynamic disturbance induces rock failure and affects the strength weakening degree.

Determination of the constant m_(i) in the Hoek-Brown criterion of rock based on drilling parameters

The constant m_(i) in the Hoek-Brown(H-B) criterion is a fundamental parameter required for determining the compressive strength of rock. In this paper, drilling parameters provide a new basis for determining the constant mi. An analytical relationship between the drilling parameters and constant miis established in consideration of the contact response between the drilling bit and the cut rock in the crushed zone.New models are developed to predict the triaxial compressive strength(TCS), internal friction angle φand cohesion c of rock. Drilling tests are carried out on 6 rock types to study the correlation between φ and m_(i). A comparison between the predicted values of rock mechanical properties and the measured values from the laboratory is performed to verify the accuracy of the proposed model(yielding an error less than 10%). The TCSs and constant m_(i) values of fifteen rocks are cited to validate the accuracy of the proposed model. The result shows that the proposed model predicts the TCS and constant m_(i) within a maximum error of 20%. The method can be conveniently applied to the rock mechanical properties.

On the Character and Mechanism of the Drilling Force For SiCw/Al Composite

The results of drilling experiments of SiCw/6061Al composite indicates that the parameter of drilling force F/M (ratio of thrust force to drilling torque) for SiCw/6061Al composite is more than doubled compared with that for 45 steel, the tensile strength of which is nearly the same as that of the composite. The results of tensile and compressive experiments show that the compressive strain is much larger than the tensile strain, and the compressive strength of the composite is larger than tensile strength, which is the reason why F/M for SiCw/6061Al composite is larger than that for 45 steel.

Optimization of Drilling Parameters by Analysis of Formation Strength Properties with Utilization of Mechanical Specific Energy

By increasing the daily needs of human energy, human manipulation of natural energy sources is expanded and encouraged the human society to developing science, knowledge and technology. Mechanical specific energy required energy for drilling the unit of formation volume. This parameter can be used for functional analysis of drilling, drilling bit optimization and investigating of instability has been made during drilling operations. This parameter can be used for decreasing of drilling costs by increasing drilling speed, optimized the useful life of the drilling bit and determine the right time to replace the drilling bit, and in some cases reduced to a minimum amount. In South Pars field in Iran, many wells have been drilled;however detailed statistics processes hadn’t done for optimizing drilling parameters and their impact on mechanical specific energy. By results of these studies, we can analyze performance and drilling parameters such as weight on drilling bit, rotational speed, penetration rate, etc. In the most investigated cases, mechanical specific energy at the final period time of drilling on each wells has been increased gradually due to the speed movement reduction. Although by investigating middle formations in section of 12.25 inch, all existing wells on a platform in one of the phases of Iran’s South Pars field are being studied, which contains formations such as Hith, Surmeh, Neyriz, Dashtak and Kangan. Studies were done in two parts. In the first part, the range of optimized drilling parameters that is increasing drilling speed and reducing the required amount of energy for drilling formation. This process by investigating mechanical specific energy and its relationship with uniaxial compressive strength in five studied formation have been presented. In the second part, correlations to predict the mechanical specific energy in this area by statistical methods by SPSS software, presented and reviewed. Then, by the most appropriate relationship, the most influential drilling parameters on mechanical specific energy have been set. However, for drilling the next wells in this area drilling parameters with the most priority influences on mechanical specific energy, proposed in the optimum range, will be recommended.

Drilling Processes Using Drag Bits and Its Application

This paper proposes an analytical model to describe rock drilling processes using drag bits and rotary drills, and to induce relations among rock properties, bit shapes, and drilling parameters （rotary speed, thrust, torque, and stroke）. In this model, a drilling process is divided into successive cycles. Each cycle includes two motions： feed and cutting. According to this model, drilling torque includes four components generated from cutting, friction, feed, and idle running respectively, the first three items are all proportional to the UCS （uniaxial compressive strength） when the penetration rate is constant. Laboratory tests verified the correctness and effectiveness of the proposed model qualitatively. Especially, the influence of friction on the flank face and the idle running was confirmed. Field experiments were performed. The results showed good correlation between the torque, penetration rate, and UCS. The proposed model and equations engender the possibility of eliminating useless components of cutting forces when investigating the relation between mechanical data and physical properties of rocks.

Experimental Study of Engineered Cement Plug to Effectively Cure Losses While Drilling in Iranian Oil/Gas Well

Mud losses are one of the most severe problems encountered in drilling. This is commonly known as lost circulation. It can occur in naturally fractured formations and also can be induced in formations through drilling. Mud losses while drilling leading to cost overruns and HSE concerns, primary cement job failure due to not getting the cement up to the desired height resulting in subsequent sustained casing pressure and corrosion, not able to perform work over activity on certain wells due to losses. The objective of this paper is to explain extreme lost circulation problem and introduce cement plug formulation to cure or mitigate this problem. In addition, the cement plug has certain compressive strength that this is proper for use to control lost circulation in field. And finally, the application of a cement plug is described in one well of the Gas Field (National Iranian Oil Company).

微波辐射深井砂岩升温损伤特征与钻进效果对比研究

为了研究微波辐射深井砂岩升温损伤特征与钻进效果,采用恒源煤业标高-940 m回风辅助石门取芯的深井砂岩为研究对象,分析其深井砂岩在相同输入能量微波辐射后温度、质量、纵波波速及钻进实验后的机械钻平均转速、扭矩随不同路径处理下的变化规律。研究结果表明:在模拟试件单面辐射时,高功率短时间(1.4 kW,214 s)比低功率长时间(1.0 kW,300 s)微波辐射后质量变化、试件前侧后表面最高温度变化更大,且波速差值和损伤因子随试件表面温度升高而增大;微波辐射前后测量试件对应5个标记点位置处的纵波波速,发现波速差值和损伤因子较大的地方主要集中在试件表面升温最高的地方;在对比有无受限变形条件下钻进实验效果分析开展了A组微波未辐射、有受限变形(路径1),B组微波功率为1.0 kW、微波辐射时间为300 s、有受限变形(路径2),C组微波功率为1.0 kW、微波辐射时间为300 s、无受限变形(路径3),D组微波功率为1.4 kW、微波辐射时间为214 s、有受限变形(路径4)4种路径的处理方式,得到钻进效果从优到差的路径依次为:路径3>路径4>路径2>路径1;分析得到在相同输入能量有受限变形条件制约下,功率在1.4 kW微波辐射下钻进效率是功率在1.0 kW微波辐射下的1.3倍左右,而有受限变形条件制约下,微波辅助钻进法的效率是无微波辐射常规法的8.5倍左右,即有受限变形条件制约下机械钻进较为困难。研究成果为较弱吸波能力深井砂岩的损伤路径优化及低能耗高效率破岩提供了借鉴与参考。

A Gel-Based Solidification Technology for Large Fracture Plugging

Fault fractures usually have large openings and considerable extension. Accordingly, cross-linked gel materials aregenerally considered more suitable plugging agents than water-based gels because the latter often undergo contaminationvia formation water, which prevents them from being effective over long times. Hence, in this study, aset of oil-based composite gels based on waste grease and epoxy resin has been developed. These materials havebeen observed to possess high compressive strength and resistance to the aforementioned contamination, therebyleading to notable increase in plugging success rate. The compressive strength, thickening time, and resistance toformation water pollution of these gels have been evaluated indoors. The results show that the compressivestrength of the gel can reach 11 MPa;additionally, the related gelation time can be controlled to be more than3 h, thereby providing a safe construction time;Invasion of formation water has a small effect on the gel strengthand does not shorten the thickening time. All considered performance indicators of the oil-based gel confirm itssuitability as a plugging agent for fault fractures.

混凝土灌注桩钻芯法芯样抗压强度结果不确定度评定

本文结合工程实例分析了混凝土灌注桩钻芯法芯样抗压强度试验过程中引入的因素,建立了混凝土芯样抗压强度测量不确定的计算模型,计算出不同因素导致的不确定度分量,从而分别计算A类和B类测量不确定度、合成标准不确定度及扩展不确定度。根据不同因素导致的不确定度分量大小,分析出影响不确定度的关键因素,基于此提出提高抗压强度检测结果准确性的方法。

基于冲击回转钻进的岩石强度随钻识别研究

在隧道掘进施工过程中,数字化钻孔过程监测(drillingprocessmonitoring,简称DPM)系统能够实时快速地获取岩石强度参数,及时指导现场开挖和支护作业。为实时获取隧道开挖掌子面前方的围岩强度,基于搭载于气动冲击回转钻机上的数字化DPM系统地开展现场原位数字钻进试验。通过对钻孔全过程的推进压力、回转压力、冲击压力以及钻杆位移等钻进参数进行实时监测、记录和分析,得到了不同钻孔过程的钻进参数特征,据此对各钻孔过程进行识别,并采用DPM时间序列分析方法分离出纯钻进过程钻进参数,结果表明:纯钻进过程的钻进深度随钻进时间呈分段线性变化;钻机工作压力随钻进时间的变化相对恒定,其对不同钻速段的钻速变化影响有限;同时,钻进速度随岩石强度增加而减小,并建立了岩石强度关于钻进速度的指数关系模型,用以指导工程实践。

中小直径钻芯法在水利薄壁构件强度检测中的应用

水利薄壁构件强度检测方法多样化,钻芯取样属于常用的方法。文章结合水利工程实例,重点研究中小直径钻芯法在强度检测中的应用要点,提出钻芯方案,进行试验设计和试件加工,分析试件的破坏形态,根据实测抗压强度评价薄壁构件的强度是否达标。经研究,在评价薄壁预制构件的抗压强度时,高径比为0.71的D70H50芯样试件检测结果具有可靠性,能够较为准确地反映薄壁构件的强度,并减轻钻芯引起的薄壁构件损伤,研究内容可供同仁参考,有效做好薄壁构件强度检测工作。

超小直径芯样检测混凝土抗压强度可行性试验研究

JCJ/T 384-2016《钻芯法检测混凝土强度技术规程》中规定的用来检测混凝土抗压强度的最小芯样直径不能小于70mm,而实际工程中,尤其是一些装配式混凝土预制构件,比如预制叠合板、预制叠合剪力墙等的厚度较小,一般只有50mm~60mm,此时如果采用钻芯法检测混凝土抗压强度就不可能,所以有必要对直径小于50mm的超小直径芯样检测混凝土抗压强度进行研究。通过对30.5mm、35mm和42mm的超小直径芯样试件进行混凝土抗压强度检测,对比分析其与标准立方体试件和100mm、75mm直径芯样之间的强度变化关系,研究使用超小直径芯样检测混凝土抗压强度的可行性。

多峰分布的岩石单轴饱和抗压强度统计分析方法及应用

越南某火力发电厂下伏中等风化岩石单轴饱和抗压强度fr呈现多峰分布,极差大、离散性大,正态分布假设下的统计量与实际情况存在偏差。笔者以fr样本分位数为切入点,探讨fr水平、垂直分布规律以及统计成果应用。结果表明:fr在水平方向的分布与地层沉积韵律、层厚、层面倾角等直接相关,fr在垂直方向的分布与取样深度无明显相关性;基于各钻探回次的fr样本分位数,可通过贝叶斯公式及全概率公式估算钻进成功率,可用于钻进工艺选择以及风险评估;通过线性规划模型可得到钻进工艺配置的最优方案。该统计分析方法对样本分布特性无特殊要求,易于实现,具有一定的工程应用价值。

基于压缩感知的井下钻具状态预警方法研究

在井下振动信号向高频采集发展趋势下,井下振动采集模块需要存储和传输的数据量逐渐增大。为了解决井下数据存储和上传压力大的问题,并对井下钻具的运行状态进行预警,提出了将压缩感知理论和支持向量机(Support Vector Machine,SVM)模型融入于井下振动信号的存储、传输和状态预警中。研究了一种原子数自适应的稀疏字典建立方法,用少量稀疏特征表达完整信号;建立了观测矩阵将原始信号投影到低维空间上,实现信号的压缩方法;应用改进的布谷鸟算法(Improved Cuckoo Search,ICS)对SVM模型进行参数寻优,训练好的ICS-SVM模型实现了钻具状态预警。应用结果表明,压缩感知技术可以将井下振动数据压缩至12%,数据重构误差为0.1772,ICS-SVM模型对钻具状态预警成功率达到98%。研究结果达到了缓解井下振动数据存储和上传压力的目的,可帮助工作人员更好地进行实时钻井操作和状态预警。

钻芯修正回弹法在混凝土抗压强度检测中的应用

为了优化混凝土抗压强度检测在实际工程中的应用,提高检测结果的准确性,增加检测数据的精度,本文提出了钻芯修正回弹法,对比了回弹法和钻芯法的优缺点,指出了规范文件中要求使用钻芯修正回弹法的情况,重点介绍了钻芯修正回弹法的完整过程。通过在工程实例中进行应用得出,利用钻芯修正回弹法可提高检测数据的精度与准确性,为混凝土抗压强度检测工作在实际工程中的应用提供保障。

超长大直径钻孔桩基础现场压缩静载荷测试分析

文中以某桥梁工程为例,对静载作用下不同类型桩的沉降量时程响应曲线以及荷载随深度的传递机制进行分析。结果表明,相同荷载水平下,2号桩的沉降量与1号桩相比降低了55.3%~67.8%。所有荷载水平下,钻孔灌注桩的桩身轴力随着深度的增加呈现不断下降的趋势。相同荷载条件下,钻孔灌注桩的桩身轴力略高于1号桩的桩身轴力,最大荷载水平下,2号桩的桩端部支撑百分比高于1号桩的端部支撑百分比。随着施加荷载水平的增加,钻孔灌注桩的桩侧摩阻力呈现先快速增加后平稳的趋势。相同荷载水平下,2号桩的桩侧摩阻力大于1号桩的桩侧摩阻力。总之,桩越长,钻孔灌注桩的承载能力越强。