HYPERSALINE ENVIRONMENTS AND GENERATION OF PETROLEUM

Not only the mudstones and carbonates deposited in hypersaline environments, but also evaporites can be source rocks of petroleum. They all have a peculiar composition of hydrocarbon such as the strong predominance of phytane, the richness in gammacerane, the frequent preference of even carbon number n-alkanes, and have a generative potential for less mature oils in diagenesis of organic matter.     

Ductile–brittle‐transition phenomenon in polypropylene/ethylene‐propylene‐diene rubber blends obtained by dynamic packing injection molding: A new understanding of the rubber‐toughening mechanism

For a more complete understanding of the toughening mechanism of polypropylene (PP)/ethylene‐propylene‐diene rubber (EPDM) blends, dynamic packing injection molding was used to control the phase morphology and rubber particle orientation in the matrix. The relative impact strength of the blends increased at low EPDM contents, and then a definite ductile–brittle (D–B) transition was observed when the EPDM content reached 25 wt %, at which point blends should fail in the ductile mode with conventional molding. Wide‐angle X‐ray diffraction (WAXD), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM) were used to investigate the shear‐induced crystal structure, morphology, orientation, and phase separation of the blends. WAXD results showed that the observed D–B transition took place mainly for a constant crystal structure (α form). Also, no remarkable changes in the crystallinity and melting point of PP were observed by DSC. The highly oriented and elongated rubber particles were seen via SEM at high EPDM contents. Our results suggest that Wu's criterion is no longer valid when dispersed rubber particles are elongated and oriented. The possible fracture mechanism is discussed on the basis of the stress concentration in a filler‐dispersed matrix. It can be concluded that not only the interparticle distance but also the stress fields around individual particles play an important role in polymer toughening. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2086–2097, 2002     

固体材料的变形—断裂转变

总结评述了固体材料表现出韧或脆性,也即变形和断裂及其相互转变的力学条件。收列大量事例以说明变形—断裂转变的各种表现形式及各种条件参数的影响。提出一种能概括各种变形和断裂行为的变形—断裂转变示图。总结表明,材料的断裂行为主要受尺寸参数D和性能参数(K_c/σs)~2控制,在不同的状态条件下,可表现为弹性变形、弹性断裂、弹塑性变形、弹塑性断裂、塑性流动或倒塌、全塑性断裂等多种力学行为。     

Mathematical modelling of rock bolt systems I

The main goal of the paper is to give a variational formulation of the behaviour of bolt systems in rock mass. The problem arises in geomechanics where bolt systems are applied to reinforce underground openings by inserting steel bars or cables. After giving a variational formulation, we prove the existence and uniqueness and some other properties.     

Grid method: Application to the characterization of cracks

In this paper we present an application of the grid method to the assessment of crack initiation and growth in brittle materials. It is shown that a grid deposited on the surface of a structure can be utilized to characterize the crack location and opening. Furthermore, one single picture only is required to carry out a control over a predefined area. First, the principle of the method is introduced, showing that a periodical pattern encoding a cracked surface can be analyzed by signal processing. The phase modulation of the grid can be calculated very accurately for any small deformation of the structure. Discontinuities due to cracks are easily detected on the phase field and the crack width is proportional to the amplitude of the discontinuity. Secondly, the performances of the method are presented, mainly depending on the spatial frequency of both the pattern and the sampling. It is shown that good results can generally be obtained with few setting difficulties and equipment investment. Finally, we sum up some basic recommendations for the practical use of the technique.     

圆宝山隧道炭质板岩大变形段初期支护结构受力特性研究

为了准确掌握丽香铁路圆宝山隧道炭质板岩大变形段初期支护结构受力特性,结合深埋炭质板岩隧道大变形特点,通过调查分析发现炭质板岩具有显著的各向异性特征,在地下水、高地应力及施工扰动等复杂因素作用下表现出显著的蠕变特性,从而导致隧道发生大变形。同时,对圆宝山隧道展开围岩变形及初期支护受力监测,监测结果表明,薄层炭质板岩段围岩的变形速率、变形量整体上较中厚层炭质板岩段围岩大,且达到稳定所需的时间更长;围岩压力与钢拱架应力基本呈从拱顶到拱脚减小的趋势,且围岩压力最大值出现在拱肩,而钢拱架应力最大值分布位置不固定,常见分布位置为两侧拱墙上下,这与钢拱架因发生扭曲而设置横支撑基本吻合;变更支护参数后,围岩的时效特性有明显改善,尤以薄层炭质板岩段围岩最为明显,同时围岩压力分布更加均匀,钢拱架出现拉应力现象不再集中。基于上述研究成果,选择I18型工字钢焊制钢架、设置间距为0.6m、喷射厚为27cm的C25混凝土作为初期支护,同时采用"弱爆破、短进尺"的掘进方式,以达到控制深埋炭质板岩隧道围岩变形的目的。     

软岩流变的一种新的试验研究方法

 研制了用于软岩流变的蠕变-松弛耦合试验仪，探讨了利用单级 加载和逐级加载两种方式确定软岩流变参数和长期强度的蠕变-松弛耦 合试验原理. 有关的具体试验表明，该仪器操作简便, 稳定性好，所得 结果客观、可靠，可在工程中推广应用.     

沟谷坡面风沙起动规律研究

根据坡面风沙受力情况,以滚动模式建立了坡面风沙起动的风速公式.计算分析了相同风向条件下不同坡度风沙的起动风速和相同坡度条件下不同风向风沙的起动风速,并与平面风沙起动计算风速和实测风速进行了比较.计算分析表明,在风向一定时,坡面风沙更容易起动,风沙起动速率随着坡度的变陡而变小.在坡度一定时,风沙起动风速受到风向的影响很大,起动风速随风力与水平面垂线夹角的增大而增大.与平面相比,当风力与水平面垂线夹角小于90°时,坡面风沙起动流速比平面为小.在当风力与水平面垂线夹角大于90°时,起动风速比平面为大.当坡面为平面时,风沙起动公式与平面拜格诺起动公式完全一致.     

Stress intensity factors and crack deviation conditions in a brittle anisotropic solid

For arbitrary anisotropy in the linear manifold of singular solutions generating square-root singularities of the crack tip stress, a special basis is introduced that possesses the same properties as in the isotropic case and provides simple integral representations for the attributes of the energy fracture criterion, in particular, the conditions of crack deviation from a straight path. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 46, No. 3, pp. 98–107, May–June, 2005.     

刚性元方法和块状岩体稳定性分析

本文提出的刚性元方法是一种数值分析方法,它将变形体离散为一些刚性块体(剐性元)和块体之间的可变形薄层(节理元)的组合体,在各种载荷条件下求出块体的运动以及薄层的变形和应力分布。本文联合岩石系统的失稳准则来使用刚性元方法,成功地研究了块状岩体的稳定性问题。计算实例表明,本文提出的方法可以正确地反映块状岩体的失稳机制,是一种合理和可行的岩体稳定性分析手段。