冻土力学发展的新领域——深土冻土力学

Based on the practice of artificial freezing engineering in deep alluvium and simulation tests, it is found that there exists an obvious difference between frozen soil mechanics for shallow alluvium and for deep alluvium. The concept of frozen soil mechanics for deep alluvium, its research topics and methods are presented in this paper.     

Overcoming flood and desiccation made by implementing artificial recharge toward absorption reservoir

Flood and desiccation are perceived as two most critical and influential disasters which contradict between causes and consequences. Flood occurs when the water surface could no longer flow the whole water flow, thus, the water flooded. Contradicted to that, desiccation occurs when the water flow contains a low volume of water deposit, thus, the water requirement exceeds the available potential. That condition was caused by land utilization as the consequences due to the increased land requirement for housing or industrial needs. An attempt to overcome the flood, nowadays, is implemented mostly in a structural way, through building canals, implementing rivers normalization, building gateways or building flood control pump which are more directed toward the flood direction in order to increase the surface flow in an immediate maner to the sea. However, the effort to overcome the flood its self, could be more effective if followed by an effort to increase the soil ability to absorb natural recharge or artificial recharge or by refilling the water into the earth surface. Absorption reservoir used as one of technology alternatives （artificial recharge） could also be used to support the attempt to overcome flood and desiccation. Absorption reservoir is a dam which was designed according to the basic principles, such as the bottom surface of the reservoir that has a high permeability surface; the surface of the reservoir water is higher （higher aquifer） along with a high permeability, considering the availability of water source that has been absorbed and its quality; considering the aquifer category on the water absorption dam;     

岩石空心圆柱扭剪仪试验能力

针对自行研制的岩石空心圆柱扭剪仪可独立控制4个加载参数（轴力、扭力、内围压和外围压）的功能,通过数学和力学分析,系统地整理出几种易于实现且符合实际工程的应力路径及加载方式：在轴力与内围压满足一定关系的前提下,可以获取岩石的抗拉强度,提供一种新型测量岩石抗拉强度的方法;通过控制内外围压及轴力,可以进行常规三轴试验与真三轴试验,克服了现阶段岩石真三轴试验中试验装置复杂、试样加载面摩擦大的缺点;在轴力与内、外围压分别满足一定关系时,可以分别实现平均应力p不变与中主应力系数b不变的应力路径,用于研究应力主轴旋转对岩石力学性质的影响。上述应力路径的实现对岩石力学性质的研究以及现阶段岩石室内试验的发展具有重要意义。     

考虑结构性的冻融作用对黄土湿陷系数的影响

结构性是黄土的基本属性,黄土的湿陷特性与其结构性之间有着必然的联系。针对冻融作用对不同结构性黄土湿陷性的影响,以水泥作为模拟土颗粒间的联结材料制备了人工结构性土,开展了不同水泥含量的人工结构性土与相应的原状土、重塑土的湿陷试验,分析了结构性、冻融作用、初始含水率、湿重度及荷载大小对湿陷系数的影响规律。试验结果表明：冻融前后,人工结构性黄土的湿陷系数均比原状土、重塑土的湿陷系数小,且随着水泥含量的增加,湿陷系数有所减小;冻融之后,各土样的湿陷系数几乎均有所增加,但增加的程度和土样初始结构、含水率、干密度（压实系数）及竖向荷载关系密切,尤其当含水率接近最优含水率和土样为重塑土或水泥含量较低的人工结构性土时,冻融后湿陷系数增大幅度显著。在标准荷载200 kPa下,冻融前后原状土、重塑土的湿陷系数与其湿重度之间基本呈较好的线性负相关关系,而人工结构性黄土湿陷系数与湿重度之间并不呈线性关系;竖向荷载为50 kPa时,重塑黄土和5%水泥含量黄土的湿陷系数与冻融次数之间存在着较好的对数关系。以水泥作为土颗粒间联结材料,制备的人工结构性土是否能很好地代替原状土反映结构性黄土的湿陷特性,还需更进一步深入研究。     

Artificial neural network model for prediction of rock properties from sound level produced during drilling

In many rock engineering applications such as foundations, slopes and tunnels, the intact rock properties are not actually determined by laboratory tests, due to the requirements of high quality core samples and sophisticated test equipments. Thus, predicting the rock properties by using empirical equations has been an attractive research topic relating to rock engineering practice for many years. Soft computing techniques are now being used as alternative statistical tools. In this study, artificial neural network models were developed to predict the rock properties of the intact rock, by using sound level produced during rock drilling. A database of 832 datasets, including drill bit diameter, drill bit speed, penetration rate of the drill bit and equivalent sound level (L_eq) produced during drilling for input parameters, and uniaxial compressive strength (UCS), Schmidt rebound number (SRN), dry density (ρ), P-wave velocity (V_p), tensile strength (TS), modulus of elasticity (E) and percentage porosity (n) of intact rock for output, was established. The constructed models were checked using various prediction performance indices. Goodness of the fit measures revealed that recommended ANN model fitted the data as accurately as experimental results, indicating the usefulness of artificial neural networks in predicting rock properties.     

Soft rock pillars

Summary Soft rock pillars can be designed by several methods available in the mining literature. All of these methods include the effect of shape, or geometry, on the average strength of specimens and pillars. All of the pillar design methods include some measurement of the strength of specimens of the pillar rock. The most common rock specimen strength property measured is the unconfined compressive strength. However, the average strength of triaxially confined rock specimens is much greater than the unconfined specimen strength, which can be more important to pillar strength. The estimation of the strength of a pillar is complicated by the decrease in rock specimen strength with increase in specimen size.Editor's note: In common with North American engineering practise, the paper uses English units throughout, where feasible conversions are included in the text. Where not, the following factors may be used: 1 inch=25.4 mm; 1 ft=0.3048 m; 1 lbf/in.^–2=6.895 kn/m^–2; 1Tonf.=8.896 kN.     

岩土材料极限分析上界法的讨论

现行的极限分析上界法,尽管求解结果合理,但理论上却存在一些矛盾：如试验证明,关联流动法则不适用于岩土材料,而现行解法却采用了关联流动法则;传统分析中假设体积不变,但计算中却出现大于实际的体积剪胀变形;按关联流动法则,应力特征线与速度滑移线重合,但在分析中却采用速度方向与应力特征线方向成 角;实际土体破坏时,破坏面上同时存在着剪切力 和正应力 ,但在计算中却反映不出摩擦功。近年在中国日益兴起的广义塑性力学理论为岩土材料的极限分析方法提供了科学的理论基础。作者提出了基于广义塑性力学的极限分析上界法,消除了上述矛盾,并获得了正确的计算结果。通过同经典算法的比较,证明了两种方法的计算结果几乎是一致的,但现行方法计算简便,因而,可作为一种实用的计算方法。论文还对上述两种算法作了系统的分析与比较,指出了它们求解的相同点与不同点。     

新安县人工增雨效益评估办法

根据作业云回波面积和强度的变化,可定性判断人工增雨是否有效。对有效增雨,可根据高炮有效控制半径,计算出影响面积;根据作业区样本点作业后比作业前的降水平均增量和对比区样本点作业前后雨量平均变化量,可确定作业区平均增雨量(mm);根据增雨量,可计算出影响区增雨质量,并由此计算出经济效益。     

绿片岩三轴流变力学特性的研究(Ⅰ):试验结果

为了解锦屏一级水电站坝基绿片岩的流变力学特性，采用岩石全自动流变伺服仪对绿片岩进行了三轴压缩流变试验。基于试验结果，研究了绿片岩在不同围压作用下的轴向应变以及侧向应变随时间的变化规律，讨论了流变特性对岩石应力一应变曲线的影响，探讨了不同应力水平下的轴向以及侧向流变速率变化趋势，分析了不同围压下流变的破裂机制，掌握了绿片岩三轴流变的基本规律，从而为该水电站工程流变数值分析时参数的辨识提供了可靠的依据。