Numerical simulation on borehole breakout and borehole size effect using discrete element method

Estimation of horizontal stress magnitudes from borehole breakouts has been an attractive topic in the petroleum and mining industries,although there are critical research gaps that remain unfilled.In this paper,numerical simulation is conducted on Gosford sandstone to investigate the borehole breakout and its associated borehole size effect,including temperature influence.The discrete element method(DEM)model shows that the borehole breakout angular span is constant after the initial formation,whereas its depth propagates along the minimum horizontal stress direction.This indicates that the breakout angular span is a reliable parameter for horizontal stress estimation.The borehole size effect simulations illustrated the importance of borehole size on breakout geometries in which smaller borehole size leads to higher breakout initiation stress as well as the stress re-distribution from borehole wall outwards through micro-cracking.This implies that the stress may be averaged over a distance around the borehole and breakout initiation occurs at the borehole wall rather than some distance into the rock.In addition,the numerical simulation incorporated the thermal effect which is widely encountered in deep geothermal wells.Based on the results,the higher temperature led to lower breakout initiation stress with same borehole size,and more proportion of shear cracks was generated under higher temperature.This indicates that the temperature might contribute to the micro-fracturing mode and hence influences the horizontal stress estimation results from borehole breakout geometries.Numerical simulation showed that breakout shape and dimensions changed considerably under high stress and high temperature conditions,suggesting that the temperature may need to be considered for breakout stress analysis in deep locations.

Inversion of breakout data from inclined boreholes for stress state of the upper crust in Jizhong depression

The forward and inverse problems of studying crustal stress state from breakout data of inclined boreholes are concisely stated. direction of the maximum horizontal principal stress (compressive) and relative magnitudes of the horizontal stresses to the vertical stress in the upper crust in two regions of the Jizhong depression, the North of China, are obtained by analyzing the breakout data of 6 inclined wells. To get stable results in the analysis wesearched for the unknown parameters both forwardly and inversely. The results show that the maximum azimuths of the horizontal Principal compressive stresses in the central and southern part of the Jizhong depressionare N86°E and N77°E, respeCtively, while the relative magnitudes of the three principal stresses in the uppercrust (about 1000-4000 m) of the depression are variable. In the centra; part of the Jizhong depression we havefound SH : Sv: SK= 1. 38: 1. 00: 0. 57, where SH, SV and Sh are the maximum horizontal, vertical and minimum horizontal stress, resistively. This indicates that the present stress regime in this area is of strike-slipfaulting type. In the southern part of the depreSSion we have obtained SH: Sv: Sh=0. 80: 1. 00 1 0. 62, indicating a normal faulting stress regime in the shallow Part Of the crust.

Research on the anti-disturbance issues of the breakout prediction system in continuous casting

This paper introduces the function, structure and alarm principles of the breakout prediction system installed for continuous casting in Baosteel＇ s No. 2 Steelmaking Plant. It elaborates on four parameters in the alarm logic,including the temperature changing rate, temperature difference, temperature fluctuation and temperature match of thermocouples. This paper also explains the causes of different disturbances within the breakout prediction system, and the methods used to prevent and eliminate disturbances from radiation, earth, crosstalk, temperature drift and time drift. Finally, the paper summarizes some potential applications of the above technology.

Progress of breakout prediction technique for slab casters at Baosteel

Breakout prediction is one of the important techniques of continuous casting. The software and hardware of the breakout prediction system have been upgraded and revamped time after time since slab casters were put into operation at Baosteel, and its performance and technical indexes have been improved remarkably. This paper reviews the development of the breakout prediction technique of the No. 1 Steelmaking Plant at Baosteel. The newly developed BBPS ^Ⅱ is introduced, and the mould mapping system of the No. 4 slab caster is described. The breakout prediction technique is playing an important role in increasing production capability, improving slab quality and decreasing breakout events.

Study on tectonic stress of Zhongyuan oil field with wellbore breakout data

Recording curves of four-arm caliper logs obtained from 36 wellbores in Zhongyuan oil field have been processed and analysed with computer programs. Orientations of principal stress axes in Dongpu seg,where theZhongyuan oil field is located, are inferred from dominant azimuths in which severe bore wall breakouts tookplace. The result shows that the maximum horizontal principal compressive stress axis in the northern part ofthe seg lies in the direction of N(79±6°)W, while in the southern part it is in N (79°±18°)E, retaining a didference of about 22°between the former and the later. A two dimensional finite element simulation using alinear elastic plane stress model indicates that the clock-wise rotation of the principal stress direction in thenorthern Dongpu seg relative to that in its surroundings may be attributed to the softness of the seg rocks andits geometry of narrow northern and wide southern part. The magnitude range of the maximum and minimumhorizontal principal stresses is estimated from the most shallow depth at which the radially unsymmetric elongation of a wellbore initiates. Finally, evidences showing local variation of stress state with sites and depths are presented.

An investigation of machine learning techniques to estimate minimum horizontal stress magnitude from borehole breakout

Borehole breakout is a widely utilised phenomenon in horizontal stress orientation determination,and breakout geometrical parameters,such as width and depth,have been used to estimate both horizontal stress magnitudes.However,the accuracy of minimum horizontal stress estimation from borehole breakout remains relatively low in comparison to maximum horizontal stress estimation.This paper aims to compare and improve the minimum horizontal stress estimation via a number of machine learning(ML)regression techniques,including parametric and non-parametric models,which have rarely been explored.ML models were trained based on 79 laboratory data from published literature and validated against 23 field data.A systematic bias was observed in the prediction for the validation dataset whenever the horizontal stress value exceeded the maximum value in the training data.Nevertheless,the pattern was captured,and the removal of systematic bias showed that the artificial neural network is capable of predicting the minimum horizontal stress with an average error rate of 10.16%and a root mean square error of 3.87 MPa when compared to actual values obtained through conventional in-situ measurement techniques.This is a meaningful improvement considering the importance of in-situ stress knowledge for underground operations and the availability of borehole breakout data.

Numerical Simulation and Prediction for Sticking Type Breakout Behavior in Slab Contiuous Casting

A two-dimensional heat transfer model was developed to calculate the mould wall temperature field under normal operations condition and to determine its changing behavior when breakout occured. On the numerical simulation of sticking type breakout process and the breakout related wall temperature evolution, parameters of prediction were suggested.

小零食大市场 量贩零食店的崛起与突围

近年来,随着国家整体经济实力的提升和消费者需求的变化,我国休闲零食市场不断发展,在向前推进的浪潮中,量贩零食店更是凭借丰富的商品和低廉的价格迅速崛起,并席卷下沉市场。尤其是2022-2023年,各种品牌量贩零食店在我国低线城市遍地开花。文章探讨了我国量贩零食店的特点、崛起原因,并针对当前激烈竞争如何成功突围提出建议对策。

Molten Steel Breakout Prediction Based on Thermal Friction Measurement

By measuring the pressure and piston stroke of hydraulic servo cylinders in the oscillation system of a caster mould,friction between mould and shell can be determined.The condition of solidified shell can be monitored by thermocouples fixed to the mould.Breakouts,whether caused by shell cracking,shell sticking or entrained impurities,can therefore be predicted and effectively avoided through monitoring the change characteristics of friction and thermocouples temperature during the process.

寒门子弟向上流动的驱动力——一个农村“80后”阶层突围者的自我民族志

寒门子弟能否向上流动是衡量社会平等开放程度的重要标志。寒门子弟向上流动的驱动力是什么?作者以局内局外双重视角和夹叙夹议的方式凸显个人反思,呈现个人成长叙事和学理思考两条主线,旨在回答底层苦难经历与教育奋斗、阶层突围的密切关系。物质条件的窘迫、农业劳动的艰辛、家人的耳提面命等能促使寒门子弟早早洞悉自己的命运,不仅使其养成自律克制、勤俭节约、孝顺懂事的品格,也驱使其加强时间管理、锤炼心志和移情父母并与之结成命运共同体,还激发出强烈的向上流动意愿和内驱力;重要他人的助力、环境文化的熏陶、社会结构机会、特定机缘与情势是助推寒门子弟阶层突围的外驱力,与底层家庭原因引发的内驱力共同驱动寒门子弟实现阶层突围。因此,底层也有自己独特的文化资本,成为寒门子弟取得高学业成就的密钥,进而脱离“子承父业”的泥沼,解除阶层代际传递的“魔咒”;底层家庭要注重子女抗逆力的培养,促使其养成正确的认知和积极的心态,形成良好的个性品质,从而积极地、理性地应对逆境;寒门子弟要相信“读书改变命运”,积极发挥主观能动性,努力创造条件,将有限的家庭资本转化为学业成就;社会应重视教育在促进弱势群体子女向上流动中的中介作用,进一步加大欠发达地区基础教育投入,进一步完善弱势家庭子女就学政策,对教育机会竞争中的弱势群体予以帮扶,进而帮助更多寒门子弟找到突破阶层代际传递的“黑匣子”,实现阶层突围。

Measures for Reducing the Rate of Breakout of Slab Casters

In order to reduce the rate of breakout of slab caster, improve the operating rate and ensure the stability of the caster, measures including the tundish casting auto-start, the mold level automatic control system optimization, the SEN one-button automatic quick-change technology, the mold breakout forecast system optimization, the mold oscillation parameters optimization, the mold taper measurement optimization and the mold powder management have been adopted by a steel plant of WISCO. As a result, the breakout rate of slab caster was significantly reduced to be zero level in the first 3 years, which is a new record for all steelmaking plant in China.

ChatGPT赋能CSCL:未来图景与突围路径

CSCL作为培养高阶思维发展的一种新型学习方式,已经历了30年的颠簸历程,但因跨学科的特征致使其发展与探索呈现复杂性。随着以ChatGPT为代表的生成式AI迅速渗透各行各业,为CSCL的创新发展带来了曙光。为此,文章首先进行了ChatGPT的基本概述,并从内容生成、语境理解、语言转译及场景复刻刻画了其应用优势。然后,文章基于对CSCL手册的分析与思考,融合ChatGPT的特征与能力,从影响CSCL发展的外延与核心两个层面,依据复刻境脉、助力变革、面向多元、支持学习、辅助教学、解密黑箱六个维度,构建了ChatGPT赋能CSCL发展的未来图景。最后,文章提出了基于ChatGPT的CSCL生态创新发展的突围路径,以期为CSCL的创新发展与教育领域内ChatGPT的理论探索与实践应用提供参考。

A discrete element exploration of V-shaped breakout failure mechanisms in underground opening

V-shaped breakouts,which may appear in underground opening during excavation,are the results of two different failure mechanisms:tensile spalling and shear fracturing.This study uses discrete elements in exploring the conditions that would lead to different breakout mechanisms under plane strain conditions.The test tunnel of the Mine-by Experiment in Lac du Bonnet granite batholith is adopted as the base problem.In order to carry out the study,some fundamental issues need to be addressed.First,an exponential softening bond that enables the incorporation of fracture energy is adopted.In order to obtain a reasonable ratio between the uniaxial compressive strength,rc,and the uniaxial tensile strength,rt,discrete disc particles are tied together to form an irregular shape clump as the basic discrete element.This effort is supported by a successful reproducing of test results from Lac du Bonnet granite in DEM modeling.The issue of sensitivity of discrete particle size on results is examined.The reduction of strength with increase in specimen size is also modeled.After the calibration work is completed,the Mine-by tunnel behavior is studied.Finally,this study shows that a reduction in rc/rt ratio,under the same setup,would cause the failure mechanism to transit from tensile spalling to shear fracturing in V-shaped breakouts.

Relationship between rock macro-and micro-properties and wellbore breakout type

This study numerically investigates the effect of material micro-and macro-parameters on the failure mechanisms and geometry of a wellbore breakout.The analysis of the borehole breakout is essential in addressing wellbore stability,well completion,and sand production problems.The three-dimensional discrete element method(DEM)was used in the simulations.The numerical tool was used in numerical model simulations of drilling through sandstone in cubic samples at the laboratory scale subjected to pre-existing far-field stresses.Besides,a series of triaxial testing simulations were performed to relate the micromechanical parameters to the macromechanical material properties.The results showed that the geometry of the breakout is affected,among the material micro-parameters,by the particle contact modulus,bond normal and shear strengths,particle crushing strength,and particle size distribution.Further,it was found that the macro-parameters including Young’s modulus,friction and dilation angles,and uniaxial compression strength(UCS)also affect the type of breakout.

回归泮塘 从荔湾湖公园西北区景观提升议景观的微地理再造

荔湾湖公园是位于广州荔湾传统城区的著名老公园,一方面,在当下城市文旅活化的潮流趋势中,它呈现了固有之魅力风采,另一方面则表现为各类历史和现实问题层叠累积而“遭遇”的现实窘境。为其寻找突围策略,是景观提升规划设计的诉求与挑战。文章通过解读历史文献与图像中的荔湾人文地理风貌,分析了传统地理景观作为城市基底与社会记忆的重要属性,并以其作为城市历史保护研究与活化的一种方法,通过地景重塑,再造泮塘的地理肌理和褶皱,并从空间规划、地形改造、风景构筑改建、植被提升等专项,提出具备岭南想象力与文化复魅可能的概念方案。

论残雪《突围表演》的先锋性

先锋文学是在20世纪80年代由西方传入我国的。从整个文化思潮背景来看,80年代中国文坛受西方哲学、美学影响最大,尤其是西方现代主义,如尼采、弗洛伊德、萨特、福克纳、乔伊斯、伍尔芙、卡夫卡等大师的影响,中国作家在此基础上结合本土创作实际形成的一种“先锋”流派即现代主义风格,属于西方思潮中国化的成果。《突围表演》作为残雪先锋文学的代表作,处于本土创作与现代主义二者共同的子集当中,在文体的开创、语言的延异以及对人的异化状态的展示层面,均达到了一定高度,其目的是在除却形式的狂欢后,最终回到人本身。

我国民族传统体育文化网络传播困境与突围进路

在全民健康概念深入人心的时代背景下,民族传统体育文化的有序传播能够呼应民众身心发展需要与社会发展诉求,而在当今开放共享的“互联网+”传播形势下,其网络传播热度存在的高开低走现象引人深思,民族传统体育文化的网络传播要着重巩固前期的传播基础与成果,接续新时代的传播进程,稳中求进,致力于弘扬中华优秀传统文化与增进人民身心健康,进一步增强中华文明传播力与影响力。本文运用文献资料法、访谈法等,结合相关传播学理论,探究我国民族传统体育文化网络传播困境与突围进路。研究发现:民族传统体育文化网络传播困境主要表现在传播内容、传播方式、传播技术和传播平台四个方面,其突围进路应注重内容为王予以深耕,方式为重予以凸显,技术为用予以交融,平台为翼予以借力。

基于机器视觉的35kV开关室复合机器人设计

为提升高压开关室智能运维水平,文中设计了一款开关室复合机器人。首先,文中从总体上论述了产品结构和信息流设计方法。其次,在控制流程方面,阐述了一键顺控倒闸、紧急分闸、带电检测、视频巡视4类典型操作的实现方法;在软件算法方面,介绍了点云特征识别和仪器仪表识别的算法设计方法。最后,通过试验验证了所设计的系统具有较好的稳定性、准确性和可靠性,具备较大的推广应用价值。

四川LZ页岩储层现今地应力方向及主控因素——以龙一段为例

现今地应力场方向是影响页岩储层压裂改造效果的主要因素之一,进行现今应力场方向展布特征及其主要影响因素分析对页岩气开发应用具有重要的意义。利用古地磁结合波速各向异性法、微地震监测法、测井资料3种方法来判别地应力方向,对LZ地区地应力方向平面展布特征及主控因素分析。结果表明:宽缓向斜处3种解释方法都适用,准确度和可信度排序为岩心实验测试、偶极横波测井、电成像测井。断裂影响区域偶极横波测井不再适用,岩心实验测试结果可信度大于电成像测井。裂缝发育强构造变形区域对3种方法解释结果均有影响,需多种方法结合分析;LZ地区龙马溪组现今最大主应力方向变化范围在90°~125°。得胜、宝藏、云锦向斜的最大主应力方向在约115°,福集向斜最大水平主应力方向偏转最大,在80°~100°,可能与西侧华蓥山断裂逆冲兼具走滑有一定关系。断裂规模越大其扰动范围和强度越大。Ⅰ、Ⅱ、Ⅲ、Ⅳ级断裂最大扰动范围分别为1100、850、500、300 m。紧闭背斜褶皱变形区,受褶皱顶部派生的拉张应力影响,地应力方向沿着褶皱轴向偏转,靠近褶皱顶部,受拉张应力影响大,偏转角度最大。研究成果可为后期水平井井位轨迹优化及压裂改造工程提供理论支撑。