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141.
针对钻井过程中钻遇的盐层段井眼蠕变缩径问题,利用弹塑性力学理论,蠕变本构方程采用Heard蠕变方程,在平面应变和均匀地应力假设下,推导出控制井眼收缩的钻井液密度新公式,该公式与前人推导的公式不同。通过理论分析,指出产生差异的根本原因在于蠕变应力差(极坐标下表示的径向应力与切向应力之差)公式的推导上,用有限元法计算结果对理论公式进行检验,证明是可行的。对文中的力学模型采用有限元法建模、求解,利用求解结果对各应力差公式进行验证,得出:根据文中公式计算结果与有限元法计算结果完全一致,而据前人公式计算结果偏离有限元计算值较大,从而间接证明了该钻井液密度新公式的推导更严密,更准确。 相似文献
142.
143.
Pipe piles can be classified as either closed- or open-ended piles. In the present paper, the load capacity of both closed- and open-ended piles is related to cone penetration resistance qc through an experimental program using calibration chamber model pile load tests and field pile load tests. A total of 36 calibration chamber pile load tests and two full-scale field pile load tests were analyzed. All the test piles were instrumented for separate measurement of each component of pile load capacity. Based on the test results, the normalized base resistance qb/qc was obtained as a function of the relative density DR for closed-ended piles, and of both the relative density DR and the incremental filling ratio (IFR) for open-ended piles. A relationship between the IFR and the relative density DR is proposed as a function of the pile diameter and driving depth. The relationship between IFR and DR allows the estimation of IFR and thus of the pile load capacity of open-ended piles at the design stage, before pile driving operations. 相似文献
144.
土石坝无粘性粗粒料填筑标准和质量评价探讨 总被引:2,自引:0,他引:2
土石坝无粘性粗粒料填筑标准往往根据经验确定,而施工质量主要是通过碾压参数控制,理论依据不足。最大干密度和已建工程实践证明表面振动器法最大干密度与实际填筑干密度基本相等,可以直接指导设计和施工,据此提出了设计和施工控制标准;从砂砾石料、堆石料等无粘性粗粒料的特性探讨了填筑标准的适用范围,利用干密度与<5 mm粒径含量关系和填筑干密度,可以准确及时地对照填筑标准作出填筑质量评价结果。 相似文献
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146.
1,3,5‐Triglyceratetriazine [first tier (G1)] and tri(1,3,5‐triglycerate) triazine [second tier (G2)] dendrimers were prepared with 1,3,5‐trichlorotriazine and sodium glycerate in a 1 : 3 mass ratio in an ethanolic medium.G1 and G2 were amorphous, white, solid substances. Their structures were elucidated with IR, 1H‐NMR, and 13C‐NMR, and their thermal stability was studied with thermogravimetric analysis. The activation energy was calculated with the Freeman–Carroll model. Densities, viscosities, and surface tensions for 0.01–0.08 mol/kg aqueous solutions increased at 0.01 mol/kg for sodium glycerate, 1,3,5‐trichlorotriazine, 1,3,5‐triazine triglycerate chloride, G1, and G2. These values were measured at 298.15 K. The apparent molal volume, reduced viscosity, and inherent viscosity were calculated from the densities and viscosities, respectively. The data were regressed for the limiting densities, limiting apparent molal volumes, intrinsic viscosities, limiting inherent viscosities, and limiting surface tensions for solute–solvent interactions. The positive limiting apparent molal volume values were noted in the order of G2 > 1,3,5‐triazine triglycerate chloride > G1 > 1,3,5‐trichlorotriazine > sodium glycerate, with weaker hydrophilic intermolecular interactions of G2. The higher intrinsic viscosity and limiting inherent viscosity values for G2 implied stronger G2–H2O hydrophilic interactions, and the higher limiting apparent molal volume of G2 indicated slightly higher dynamic conformational changes in comparison with G1, with stronger structural activities. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
147.
Bamboo strips treated with caustic solutions of different concentrations, e.g., 5%, 10%, 15%, 20%, 25%, and 50%, were subjected to mechanical testing giving stresses on tensile strength, percent elongation at break, flexural strength, flexural modulus, and toughness. The change in average density was ?15%, and the weight loss value shows a maximum of 21.94% at 50% alkali treatment. The mechanical properties of bamboo strips increase steadily with increasing concentration of caustic soda, showing a comparable increased value at 15 and 20%, and then exhibiting a gradual fall. The percent elongation at break corroborates these observations showing a continuous decreasing trend. The properties under investigation exhibit a clear transition in between 15 and 20% alkali concentration. The morphology of strips was studied by scanning electron microscope and polarizing light microscope. The crystal structure of both untreated and treated strips was compared by XRD analysis. In both cases, the breakdown of the crystal structures of the cellulose fibers and the recrystallization or reorientation of the degraded chains that are devoid of hemicellulose are quite apparent. However, at a very high concentration (to the extent of 25%) the breakdown of structure predominates much more over the reorientation or recrystallization. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
148.
149.
粉末粒度对粉末制品的性能具有重要的影响,而这些影响主要通过改善材料的密度来达到。该文根据模拟粉末堆积模型,确定相对合理的粒度组成,并通过试验予以验证。 相似文献
150.