Study on determination method of in-situ stress using formation fracturing test and Kaiser effect method

A new method, which is based on formation fracturing test and Kaiser effect method, has been developed for confirming the oilfield in-situ stress in this paper. The new method has been used in a certain oilfield of China and the determined oilfield in-situ stresses is more accurate than that based on one single method.

Influence of deviatoric stress on rockburst occurrence:An experimental study

As mining delves deeper into the crust, it is necessary to investigate the complex rock responses associated with higher stress gradients. Therefore, it is essential to better understand the mechanisms associated with the rockburst phenomenon. However, due to the large-scale and difficult monitoring of real mining excavations, laboratory scale tests must be utilised to determine the conditions conducive to burst. To this end, this research focuses on the implementation of a new rockburst testing apparatus to replicate the stress conditions of a rock mass excavation at the time of bursting. This apparatus allows the determination of rockburst stresses and a relationship between deviatoric stress and in-situ pressure/depth. Using this relationship it is then possible to estimate the standardised stress levels for a certain rock type which might lead to rockburst occurrence. Furthermore, it is demonstrated that with increasing in-situ pressure, the likelihood(measured as a lower differential stress) and the extent(indicated by the increasing range of deviatoric stress) of rockburst increases. These findings provide valuable information about the conditions necessary for bursting in deep mining.

装配式混凝土阶梯钢板式节点应力应变分析

目的研究装配式混凝土阶梯钢板式节点的应力应变分布规律,提出一种装配式混凝土阶梯钢板式节点.方法以混凝土强度和穿心板厚度为参数制作装配式混凝土阶梯钢板式节点,以节点试件的外加梁其两端加载点的竖向荷载和位移、节点的核心区柱应力分布、节点核心区穿心钢板应力分布以及外加梁的应力分布等作为主要量测内容.对试件进行低周往复加载试验.结果穿心钢板的应变大多表现为横向应力应变远大于纵向应力应变,外加梁上梯段钢筋的应变远大于其下梯段钢筋的应变.在其他参数不变的情况下,装配式混凝土阶梯钢板式节点的混凝土强度越高则其主要受力部位的应力应变越小;穿心钢板越厚其主要受力部位的应力应变就越小;节点试件的承载力随混凝土强度提高而增大.其中极限荷载在混凝土强度C20时为110.5 k N,C40则达到228.94 k N,较C20提高107.2%.结论提出的装配式混凝土结构梁柱节点构造具有较好的应用价值,为今后预制装配式混凝土结构深入研究及推广提供试验与理论基础.

Deformation mechanisms in aβ-quenched Ti-5321 alloy:In-situ investigation related to slip activity,orientation evolution and stress induced martensite

The deformation behavior ofβ-quenched nearβTi-5321(Ti-5Al-3Mo-3V-2Cr-2Zr-1Nb-1Fe)alloy was systematically studied using in-situ tensile test monitored by the scanning electron microscopy(SEM).Besides,the electron backscatter diffraction(EBSD)was performed to thoroughly discuss the deformation mechanisms.The results indicated that slip activities,crystal rotation and stress induced martensite transformation were the major deformation mechanisms in theβ-quenched Ti-5321 alloy during in-situ tensile testing.The slip activities were investigated by using the EBSD-trace analysis,which demonstrated that{110}<111>,{112}<111>and{123}<111>slip systems were activated and the{110}<111>slip system dominated.Besides,βgrains rotated about 7.8°to accommodate the increased macrostrain.Notably,the stress induced martensiteα″which was related to the double yielding behavior during tensile process exhibited multiple characteristics.The differentα″variants divided theβmatrix into smallerβblocks with a typical zigzag morphology,in which oneα″variant passed through another one by deflecting its initial growth direction.Moreover,the deformation twinning in martensiteα″and slip bands cutting through martensiteα″effectively accommodated the local strain.These systematically analysis can provide insightful information about the deformation mechanisms in nearβtitanium alloys.

消防云梯计算仿真模型的试验研究

在理解和吸收进口云梯的核心技术基础上,提出了一种国产化进程中建立有限元仿真模型的方法,此方法建立的仿真模型有效真实地再现了进口云梯的结构特性,对于后期的国产化臂架设计和形成我国自己的专业标准具有很好的指导意义.最后,从静态结构的计算和后期测试验证了此设计方法的可行性.

引黄济宁工程拉脊山越岭隧洞超深钻孔地应力梯段测试

引黄济宁拉脊山越岭隧洞长33 km,最大埋深约1 650 m。洞穿青藏高原高大雄峻的拉脊山山脉。为了掌握越岭隧道的不同埋深段地应力量值和方向,在867 m的超深钻孔内采用水压致裂法自250 m以下每50～60 m分不同深度进行了16段地应力测试。结果表明:在测试深度范围内,最大水平主应力值为24. 37 MPa,最大水平主应力的优势方向为NE23°左右,与现代区域构造应力场特征、水平地应力的回归对比分析和数值模拟分析等结果一致,说明测试成果合理可靠。

基于水压致裂法的拉脊山地区深部地应力测试及可靠性分析

拉脊山地区地质构造复杂,深部地应力较高,预测该地区地应力分布,可以有效避免岩爆、软岩大变形等不良地质灾害的影响,为地下建筑工程合理规划提供科学依据。文中依托拉脊山区域的李家峡、龙羊峡、拉西瓦3个水电站的实测地应力数据,采用有限元对拉脊山地区地应力进行模拟预测,并将模拟预测结果与水压致裂法实测结果进行了对比分析。结果表明:拉脊山区域最大主应力方向为北东向,拉脊山地区地应力在深度为400、600、800 m时,最大主应力分别为13~15、20~22、23~26 MPa;测试地应力结果与数值模拟分析结论吻合度较好。通过地应力测试结果可靠性分析,深部地应力实测量值与预测计算结果基本一致(90%以上),说明本次测试结果可靠,也反映了水压致裂法作为深部地应力测试手段是合理的。研究结果可为青藏高原地区地应力的研究和青海省引黄济宁等多个工程的合理规划提供理论依据。

An estimation method on failure stress of micro thickness Cu film-substrate structure

The failure of thin film-substrate structure occurs mainly at the thin film or the interface. However, the characterizing and estimating methods of failure stress in thin film are neither uniform nor effective because there are some complex effects of such as size, interface and stress state on the failure behavior of thin film-substrate structure. Based on the scanning electron microscope (SEM) in-situ in- vestigation on the failure models of the Cu thin film-substrate structure and the nano scratched testing results, the failure stresses in different thicknesses of the Cu film-substrate were characterized, which were compared and confirmed by other methods, such as Stoney formula and other empiric equations. These results indicate that the novel estimating method of failure stress in thin film based on the critical wavelength of surface unstable analysis is better than other methods. The main reason is that the novel estimating method of failure stress in meso thickness film fully considered the effect factors of free surface unstable behavior and elastic anisotropy of thin film. Therefore, the novel estimating method of failure stress assists people to understand the critical interfacial strength and to set up the failure criterion of thin film-substrate structure.