裂隙岩体冲击韧性及破坏模式实验

为研究裂隙对岩体冲击韧性及破坏模式的影响规律,以及裂隙岩体在高应变率下的动态破坏特征,采用摆锤式冲击实验机对裂隙及完整岩体进行了不同冲击速度、不同裂隙条件下的冲击实验。实验结果表明,对长度相同的完整试件而言,试件直径越大,即试件体积越大,试件破碎就越充分,断面也越不规整;试件中的裂隙长度越长,试件破坏时的吸收功就越小,冲击韧性也越小,试件吸收功和冲击韧性随裂隙长度的增加而减小;试件裂隙角度越大,试件破坏断面就越不规整,试件破坏后的块度也越不均匀,试件吸收功和冲击韧性随裂隙倾角的增大而减小。     

Cracked asphalt pavement under traffic loading – A 3D finite element analysis

An asphalt pavement containing a transverse top-down crack is investigated under traffic loading using 3D finite element analysis. The stress intensity factors (SIFs) and the T-stress are calculated for different distances between the crack and the vehicle wheels. It is found that all the three Modes (I, II and III) are present in the crack deformation. The signs and magnitudes of K_I, K_II, K_III and T are significantly dependent on the location of the vehicle wheels with respect to the crack plane. The magnitude of T-stress is considerable, if compared to the stress intensity factors, when one of the wheels is very close to the crack plane.     

裂纹转子识别中Wigner-Ville分布与小波变换的比较

建立基于简单铰链裂纹模型的裂纹转子瞬态响应的动力学模型,得到裂纹转子与无裂纹转子的数值仿真解,比较裂纹转子与无裂纹转子Wigner-Ville分布和小波变换时频特性的不同。数值仿真进一步对比研究Wigner-Ville分布和小波变换对刚度变化的敏感性,并讨论质量偏心和质量偏心角对Wigner-Ville时频特性与小波时频特性的影响,为工程实际中裂纹转子的识别提供依据。     

深层—超深层古老烃源岩滞留烃及其裂解气资源评价

我国高-过成熟海相天然气主要成因类型为原油裂解气,滞留烃是原油裂解气的重要来源,对其进行定量研究意义重大。为此,结合正演(实验模拟)和反演(地质剖面解剖)两种方法,求取了我国重点盆地不同类型、不同丰度、不同演化阶段的滞留烃量,建立了5种类型烃源岩(腐泥型、偏腐泥混合型、偏腐殖混合型、腐殖型、煤型)的滞留烃演化模型。结果表明:腐泥型、偏腐泥混合型优质烃源岩在低成熟阶段的排烃效率低于20%,在主生油阶段的排烃效率介于20%~50%,在高成熟阶段的排烃效率介于50%~80%,而相应阶段偏腐殖混合型和腐殖型烃源岩的排烃效率则要低约10%。基于该演化模型,初步计算了四川盆地海相烃源岩中高成熟阶段-现今滞留烃资源分布和裂解排气量:该盆地下寒武统筇竹寺组滞留烃在高演化阶段裂解排出的气态烃总量达230.4×10~(12)m~3,震旦系陡山沱组烃源岩滞留烃裂解气的排出量为12.3×10~(12)m~3,均显示出很好的天然气成藏潜力;进而指出,四川盆地筇竹寺组烃源岩滞留烃裂解气的有利区主要包括高石梯-磨溪、资阳、威远地区,有利分布面积达4.3×10~4 km~2。     

乙烯废碱液的苛化法再生工艺研究

采用苛化法对乙烯裂解废碱液进行处理，Na2CO3的苛化转化率在80％以上(平衡反应液的苛化率在90％以上)；废碱液的反复再生和利用对碱液的吸收性能无显著影响，再生碱液可满足吸收裂解气中CO2等酸性气的要求。     

用等离子体促进渣─金属液间的反应

分析了等离子体的冶金属性，简要报导了用等离子体强化钒在渣铁间的还原，及在等离子体条件下用V2O5代替钒铁对钢液进行还原合金化的研究结果，提出直接在钢包内进行还原合金化的可能性及前景．     

The stress field in a [0°/90°] laminated composite plate containing a finite line crack

This paper deals with the construction of an asymptotic solution for the stress field in a laminated composite plate, with [0/90] stacking sequence. The plate contains through the thickness a line crack of length 2c and its perimeter boundaries are sufficiently far away from the crack so that no edge effects are present. The stress field is derived explicitly, and includes a correction factor to account for the laminate effects in the third dimension. The stress _zz is a maximum at an angle of 3° (see Figure 3). The stress field may now be used to bridge the gap between macro and micro mechanics and to derive a series of fracture criteria, at the micro and macro level, which ultimately will provide us with a better understanding of the formation of the damaged zone ahead of the crack tip. For example, the stress field is used to derive one such approximate fracture criterion for mode I loading and for a self similar type of fracture, similar to that of Griffith. This criterion shows how the periodic length of the material lay-up microstructure effects the fracturing characteristics of the material system. Comparison with some experimental observations for two different material systems shows a fairly good agreement which substantiates the predicted influence.     

THE FATIGUE BEHAVIOUR OF CRACKED CONCRETE

Abstract— Cracks are among the most common flaws in civil engineering structures and, considering the cyclic nature of the variable loading patterns, it is evident that the evaluation of the structure safety factor should consider the stability of cracks when fatigue loading occurs.
In the present paper, the behaviour of cracked concrete subjected to cyclic loading is experimentally investigated by means of direct tension tests. In particular, the experiments concern cycles that stay below the critical concrete softening curve.
The results show that, depending on the maximum load, damage could occur and that the cyclic envelope curve is very close to the monotonic quasi-static curve. On the basis of the experimental results, an empirical model for subcritical crack growth for cracked concrete under low-cycle fatigue loading is proposed.     

Modelling fatigue crack propagation of a cracked metallic member reinforced by composite patches

The concept of fracture for material elements at front of a crack for fatigue crack propagation was extended to the fatigue crack propagation of a cracked metallic member reinforced with a composite patch in this paper. From static mechanics and linear elastic fracture mechanics, force transfer on a cracked member through a composite patch was analyzed and a formula connecting the stress intensity factor with crack length was obtained. Thereafter, a fracture model for fatigue crack propagation of a repaired cracked metallic member was proposed. A new expression for the fatigue crack propagation rate has thus been derived. The expression was verified objectively by the test data. It is in good agreement with the test results.     

Interactive Effects of Fly Ash and CNI on Corrosion of Reinforced High-Performance Concrete

The interactive effects of fly ash and CNI in corrosion of reinforced concrete were investigated. A 3⁴ full factorial design was developed considering water to cement ratio, fly ash percent, CNI and cracked condition as factors. The response factors were the weight loss calculated from Linear Polarization Resistance measurements and the pit depth of the steel bars embedded in concrete. Small-scale concrete slabs containing steel reinforcement with a cover depth of 20 mm were cast for this purpose. The slabs were subjected to a simulated marine environment with two cycles of wetting and drying per day during one year; after the exposure, the slabs were broken, the bars were cleaned and the pith depth measured by using SEM. Under the studied conditions, it was found that CNI alone does not provide corrosion protection of the steel reinforcement even for uncracked silica fume concrete in a 0.45 w/c ratio; however, the combination of CNI and fly ash can be useful to overcome this problem. The results indicate that low w/c ratio concrete in its crack state creates conditions suitable for the development of pitting corrosion.