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101.
顶板浅部裂隙通道演化规律与分布特征 总被引：2，自引：0，他引：2
为得出顶板裂隙通道的演化过程和空间分布特征,以岩体力学和煤岩全应力-应变过程中瓦斯流动变化规律为理论基础,采用深部位移自动监测仪和裂隙通道巡回摄录仪,进行理论分析和现场测试研究,得出了瓦斯裂隙通道形成判据和分布特征。结果表明:煤岩分层成为瓦斯裂隙通道边界需要满足其变形小于下分层或大于上分层,同时其稳定跨距大于顶板悬露距离,据此判别出试验矿区顶板浅部主干裂隙通道位于顶板上方1.5,5.0 m处;随工作面推进,顶板裂隙通道经历原生裂隙通道主导阶段、裂隙通道产生、扩张、成熟和闭合阶段的演化过程,重新压实区至工作面前方原岩应力区距离与工作面日推进速度的比值为裂隙通道的演化周期,试验矿区演化周期为11～14 d。 相似文献
102.
《International Journal of Pavement Engineering》2012,13(4):229-240
This paper documents and discusses an investigation into the time–temperature superposition principle as it relates to ductile failure in asphalt. Seven binders of approximately the same low and intermediate temperature and varying high temperature Superpave® grades were tested in a dynamic shear rheometer (DSR) and double-edge-notched tension test to determine their rheological and failure energy master curves. Master curves typically permit the prediction of rheological properties at very long or short timescales from measurements at higher or lower test temperatures over more accessible testing timescales. It has been suggested in the Strategic Highway Research Program final report A-369 that rheological shift factors obtained from a DSR experiment can be used to predict failure master curves from experimentally accessible data at various temperatures. The findings of this study suggest that this substitution is not generally accurate. For straight asphalt binders the difference can be relatively small but for more highly modified materials serious errors would be introduced. 相似文献
103.
《International Journal of Pavement Engineering》2012,13(2):152-165
The present study is focused on using warm mix asphalt (WMA) technology in stone matrix asphalt mixtures and investigated in detail on the moisture sensitivity of these mixtures using three different types of WMA technologies. The experimental design involved three sources of aggregates (A, B and C) and three WMA technologies using additives Asphamin®, Sasobit® and Evotherm® technology. Test results indicated that 13 mixtures failed to meet the minimum tensile strength ratio requirement of 85%, and all mixtures tested met the minimum wet indirect tensile strength (ITS) value of 448 kPa (65 psi) as per SCDOT specifications. Statistical analysis showed that there was significant difference in the wet ITS values between aggregate A (micaceous granite) and granite (C) for all the mixtures studied. Statistical analysis showed that except for two mixtures, there were no significant differences in the wet ITS values of WMA mixtures amongst four types of mixtures under identical conditions. The mixtures containing over 15% rubber (by weight of virgin binder) produced similar resistance to moisture susceptibility compared with mixtures made with PG 76-22+fibres. 相似文献
104.
《International Journal of Pavement Engineering》2012,13(1):13-23
This paper reports on how temperature and loading rate affect the low-temperature yield properties of two asphalts (California Valley and Bow River sources), straight and modified with 5% by weight of four commonly used commercial polymers (styrene–butadiene diblock, triblock and radial and ethylene–vinyl acetate copolymers). The Bow River asphalt was also tested with the addition of mineral filler. Both the source of the bitumen as well as the nature of the additive and the presence of filler were found to have a significant influence on how the yield stress changes with temperature and loading time. Only one homogeneous, California Valley binder modified with SBS triblock copolymer, provided a typical Eyring plot with a constant activation energy of 42 kJ/mol and activation volume of 3.7 nm3. Other systems showed atypical behavior in that the activation parameters changed rapidly with both temperature and rate of loading. 相似文献
105.
《International Journal of Pavement Engineering》2012,13(3):339-348
AbstractThe 7, 28, 60 and 90 day mechanical properties of CSCRA were experimentally tested, including unconfined compressive strength (UCS), resilient modulus, splitting strength and flexural-tensile strength. According to the test results, the strength growth equations and relation models of mechanical indexes are established innovative. The strength criteria of cement-stabilised recycled concrete aggregate (CSRCA) against fatigue failure was proposed based on load response of pavement, mechanical and fatigue properties of CSRCA as well as Miner’s theory of fatigue accumulation. Results showed that when the curing age was smaller than 60 days, the UCS and resilient modulus of CSRCA showed a V-shaped variation with the increase of recycled concrete aggregate (RCA) dosage, and decreased with the increasing of RCA content when the curing age was 90 days. Splitting strength and flexural-tensile strength of CSRCA increased slightly with the increase of RCA dosage. A fatigue equation of CSRCA was established, which reflected that the fatigue life of CSRCA increased slightly with the increase of RCA dosage. The strength growth equations could represent strength growth characteristics of CSRCA accurately. The UCS and splitting strength criteria of CSRCA against fatigue failure were proposed, which were correlated with pavement structure and layer, material properties and service life. It realised the goal of structure-material integrated control of CSRCA base or sub-base fracture. 相似文献
106.
《International Journal of Pavement Engineering》2012,13(11):1275-1284
ABSTRACTThere have been many fracture tests – the Thermal Stress Restrained Specimen Test, the Single-Edge Notched Beam test, the Semi-Circular bend test, the Indirect Tensile Test and the Disc-Shaped Compact Tension (DCT) test – developed to understand thermal cracking in asphalt pavement. Among these tests, the DCT test is the most recent test method developed that has gained significant interest. This paper includes a laboratory study to measure the effect of different mixture design parameters on the DCT test results. The parameters include per cent binder replacement from recycled asphalt pavement, binder modification, low-temperature binder grade, oxidative ageing and mix design traffic level. To investigate the significance on the factors controlled, ANOVA and multi-linear regression analyses are used to show that only a few factors can be considered significant in terms of their effects on DCT parameters, and the significance of those factors could not explain the range in DCT response variables. Some of the trends in change in the DCT test responses with mixture ageing and some other factors are also found to be illogical. This paper does not offer solutions, but highlights some of the challenges experienced when applying the DCT test to performance specifications. 相似文献
107.
水库正常运营后,库水位将按计划周期性的上升或下降,浸泡–风干循环作用将导致库岸边坡变幅带岩体性质逐渐劣化,进而影响库岸边坡的稳定性,基于此,设计了考虑水压力升、降变化的砂岩浸泡–风干循环作用试验,重点研究了砂岩试样的变形及破坏特征。研究结果表明：水压力升、降变化和浸泡–风干循环作用对岩样造成了不可逆的渐进性损伤,在循环作用过程中,砂岩试样的应力–应变曲线逐渐变缓,压密段长度逐渐变长,弹性变形段的斜率逐渐减小,弹性模量逐渐降低,屈服阶段也逐渐变长,试样达到峰值强度时对应的轴向应变逐渐变大,试样的剪切破坏角有逐渐变小的趋势。应力–应变曲线的变化显示岩样有明显的“变软”的趋势,而且,浸泡–风干循环次数越多,岩样的损伤越严重。研究成果对于把握库岸边坡库水消落带岩体变形、破坏规律具有较大的参考价值,为库岸边坡的长期稳定性分析提供了有益的依据。 相似文献
108.
《Advanced Composite Materials》2012,21(4):227-237
SiCP/Al–Fe–V–Si (Al–Fe–V–Si reinforced with SiC particles) composite prepared by spray deposition was densified by hot pressing and then rolled into sheets. Microstructure of the composite was observed, and fracture properties and fractographies of the composite at different tensile temperatures were investigated. The results show that uniform distribution of SiC particles and strong bonding between the particles and the matrix are obtained by rolling after hot pressing. It is found that fracture properties and fractographies of the composite are affected by the distribution and orientation of SiC particles. The composite is characterized by the fractographies of the composite varying with the elevation of temperature. Cracking of SiC particles is the dominant rupture mode because of the strong interface bonding with the tensile temperature below 300 °C. Debonding at SiC/Al matrix interfaces becomes the dominant rupture mode with tensile temperature above 300 °C, particles breakage reduces sharply as the tensile temperature is elevated, while tensile strength and elongation of the composite decreases rapidly as the tensile temperature increases. 相似文献
109.
《Advanced Composite Materials》2012,21(5-6):401-412
An analytical model of the push-out test was developed to predict the interfacial fracture toughness of fiber-reinforced matrix composites. Elastic deformation, thermal residual stress, Poisson effect, and energy dissipation due to interfacial friction are all accounted for in the model based on a fracture mechanics approach and a general solution was derived from the analysis. In addition, finite element analysis was performed to validate the analytical model. The results show that the predictions from the analytical model are in good agreement with the finite element results and experimental data on SiC-reinforced Timetal834 composites. The effects of residual stress, the friction stress ,and the debonding crack length on the interfacial fracture toughness were discussed for a better understanding of the interfacial phenomena in push-out test. The analytical model could be applied to other composite systems as well. 相似文献
110.
《Advanced Composite Materials》2012,21(3):165-174
Carbon/carbon composites (C/Cs) are widely used as thermal protection materials in aviation and aerospace field. Most of the fracture processes of C/Cs have been found to be profoundly affected by their interfacial properties. Specially arranged fiber bundle push-out test was utilized to determine the fiber bundle/matrix interface shear strength of one three-dimensionally reinforced C/Cs. In order to reveal the link between the interfacial properties and the failure behavior, the micromechanisms of damage initiation at the notch tip on the C/Cs was investigated in real-time during the flexural fracture tests through scanning election microscopy. Real-time fracture observation revealed that the damage was nucleated in the fiber bundle/matrix interfaces around the notch tip and the failure crack was successfully observed along the fiber bundle/matrix interface. Fiber yarns acted as an obstacle to crack propagation hence it was necessary to increase the load to propagate the crack through the next fiber yarn. 相似文献