热-水-力作用下圆孔花岗岩的动态损伤特征及结构模型

基于深层地热能开采时储能区井筒围岩所处的工程环境,采用高温加热、不同温度水浸泡、加热-循环次数及径向冲击加载的方法模拟井筒围岩经历的高温、遇水、循环采热及热冲击等造成的动力扰动等物理力学条件。同时,以不同内孔直径的同心圆孔岩样模拟深层地热井,采用分离式霍普金森压杆试验系统开展热-水-力作用下圆孔花岗岩的动态力学试验,并结合VIC-3D非接触应变测量及数值模拟分析技术监测冲击过程中圆孔岩样裂隙萌发、形成的历程和表面应变演化的规律,揭示热-水-力作用下圆孔岩样的动态损伤破坏机制。研究结果表明：径向冲击荷载作用下圆孔花岗岩先后经历弹性变形、塑性变形、结构失稳破坏3个典型阶段;内孔直径、加热温度、浸水温度、加热-浸水循环次数4因素都弱化了圆孔花岗岩抗外界荷载的能力,但未改变其整体的变形演化规律;圆孔花岗岩的破坏模式是动态拉伸破坏,先沿冲击方向由内孔壁向岩样外壁,再垂直冲击方向由岩样外壁向内孔壁萌发、贯通裂纹,形成近垂直的两组破裂面。最后,基于圆孔花岗岩的损伤变形特征及历程,在一定假设基础上,建立动态损伤结构模型,推演了结构方程,并结合试验结果确定了方程参数,通过对比分析发现,理论拟合曲线与试验...     

堆石料的剪胀特性与广义塑性本构模型

以三轴试验成果为基础,考虑颗粒破碎引起堆石料剪胀比与应力比之间的非线性关系,提出了能够反映堆石料低围压剪胀、高围压剪缩特性的剪胀方程。在广义塑性理论框架内构造堆石料的塑性流动方向向量和加载方向向量,引入依赖于密实度与平均应力的压缩参数,构造随平均应力、剪应力比和密实度变化的塑性模量,建立了一个考虑颗粒破碎的堆石料弹塑性本构模型。阐述了该模型10个参数的确定方法,并通过模拟不同围压和不同应力路径下堆石料的三轴压缩试验资料验证了模型与参数的合理性。     

PROPAGATION OF TORSIONAL SURFACE WAVES IN VISCOELASTIC MEDIUM

It is well known that an elastic homogeneous half-space does not allow torsional surface waves to propagate. The present paper attempts to find out the possibility of propagation of such waves in a viscoelastic half-space. The study reveals that although the homogeneous elastic half-space does not allow torsional surface waves to propagate, a viscoelastic half-space does so. The wave is damped due to the viscoelastic parameter. It has also been found that as the viscoelastic parameter decreases, the medium becomes elastic and the torsional surface waves ceases to propagate.     

Probabilistic Assessment of Earthquake Insurance Rates for Turkey

A probabilistic model is presented to obtain a realistic estimate of earthquake insurance rates for reinforced concrete buildings in Turkey. The model integrates information on seismic hazard and information on expected earthquake damage on engineering facilities in a systematic way, yielding to estimates of earthquake insurance premiums. In order to demonstrate the application of the proposed probabilistic method, earthquake insurance rates are computed for reinforced concrete buildings constructed in five cities located in different seismic zones of Turkey. The resulting rates are compared with the rates currently charged by the insurance companies. The earthquake insurance rates are observed to be sensitive to the assumptions on seismic hazard and damage probability matrices and to increase significantly with increasing violation of the code requirements.     

乌东德库区泥石流灾害的成因及特征分析

金沙江河谷属泥石流多发地区之一.本文通过金沙江乌东德库区(龙川江 - 坝址段)地层岩性、地质构造、新构造运动、地形地貌以及气候条件等地质环境条件的调查研究,详细分析泥石流灾害的成因、类型以及分布特点.这一分析研究对水电站工程的建设和安全运行具有一定的现实意义.     

单临空面岩体中爆破诱发损伤的数值分析

岩石的抗压强度远大于其抗拉强度,所以在单临空面岩体爆破中,工程技术人员关注的不仅是炮孔附近的塑性压剪损伤,更多的是临空面附近的拉裂损伤,临空面若是地表,可能会影响到施工的安全,甚至造成一定的经济损失。以往这类损伤问题的数值模拟中大多只偏向于一方面：或忽略压剪损伤,或不考虑拉裂损伤,故所得出的结论难以满足工程需要。基于合理的应力修正方式,把现有的岩石拉-压损伤本构以简明的方式嵌入到大型LS-DYNA软件中,对单临空面岩体中的柱形和球形药包爆破问题进行了数值模拟,计算结果表明该法能较好地预测岩体中爆破诱发的拉裂、压缩损伤的分布规律和演化趋势。     

煤层构造变形的综合定量分析

以断裂破坏指数和褶皱构造变形系数为基础,提出了构造变形综合指数新概念,为定量地判识煤层构造复杂程度提供了一种科学方法。      

负压条件下考虑土体损伤和流变的有限元分析

介绍了在负压条件下软基加固的各种理论计算，并采用平面应变有限元法进行分析，计算中考虑了土体的流变和施工扰动引起的损伤。计算结果与某高速公路试验段现场观测的结果比较接近，说明计算方法是合理可行的。     

Productivity optimisation in weak sedimentary formations for improved coal production and roof stability—an approach

Far-field peak particle velocity (PPV) measurements were made in the roof while blasting in coal development drivages at Tandsi Mine, Western Coalfields Limited, India. The roof was fragile at this mine and was posing constant support problems for mining, resulting in low productivity. The PPV measurements have been used to decipher the damage zone in the roof. The extent of damage obtained has been compared to establish the threshold limits for the damage zone. Conversely, the maximum charge per delay that can be exploded is calculated and a suitable blast design has been recommended for maintaining the roof stability and pull. A roof vibration predictor equation has been developed that shows a consistent trend indicating that it may have future use in a similar geo-mining setup. The blast pattern recommended has reduced the damage extent, though marginally, but helped in improving pull. Critical PPV for incipient rock damage in underground coal mine development drivages under fragile roof were computed. The PPV level for incipient crack growth was found to vary from 500 to 800 mm/s while for overbreak it varied from 800 to 1200 mm/s. It was also observed that the location of cut holes, charge concentration and firing sequence were found to be responsible for the difference in their damage potential.     

高温冻结粉土力学特性试验研究

为了探讨高温冻结粉土的力学特性,进行了一系列常规三轴压缩和三轴压缩加卸载试验。结果表明：（1）随着围压的增大,应力应变曲线先表现为应变软化,后应变硬化,最后又应变软化。（2）体积应变曲线均表现为先体缩后体胀,且围压越大,体胀越弱。（3）通过引入改进的双曲线模型,能较好地模拟应变软化和硬化特性。在q-p平面内建立了一个新的强度准则,并利用修正Mohr-Coulomb屈服准则,探讨了黏聚力c和内摩擦角φ的变化规律。根据试验结果,确定了不同围压及不同加卸载循环次数下高温冻结粉土的回弹模量及其损伤变化规律。最后,建立了塑性体积变形和塑性剪切变形之间的关系式和表达式,进一步探讨了高温冻结粉土的剪胀特性。