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71.
针对皖中地区高速公路建设中遇到的膨胀土问题,选取合六叶高速公路典型土样开展了系统的承载比(CBR)特性试验研究,并在此基础上探讨了膨胀土作为路基填料的适用性。研究表明:(1)起始含水量对膨胀土CBR值影响显著,CBR最大值对应的含水量高于最佳含水量,且击实功越大,二者差值也越大;(2)CBR膨胀量随起始含水量增大而减小,起始含水量越低,CBR膨胀量就越大,路基的水稳性就越差;(3)当击实功较大时,膨胀土的最佳含水量较小,适合填筑的可变含水量范围较宽,建议现场施工控制采用重型击实标准;(4)在重型击实条件下,将弱膨胀土起始含水量控制在比最优含水量大2%4%范围内,能同时满足压实度和CBR值要求以用于填筑下路堤,中膨胀土作为路基填料时必须经过改性处理。研究结果对于在膨胀土地区进行公路建设具有参考意义。 相似文献
72.
Masayuki Koike Toru Kaji Prathuang Usaborisut Tomohiro Takigawa Akira Yoda Shozo Takahashi 《Journal of Terramechanics》2002,39(3):127-141
To investigate the soil compactibility during the cyclic loading, three different kinds of paddy field soils were prepared so as to clarify interrelationships among stress amplitude ratio, bulk density, soil water content and pore water pressure. The presetting values of specimen include the soil water content(percent dry basis) and bulk density of 25% d.b. and 1.1 Mg/m3 respectively. The relation between the number of cyclic loading and axial strain exhibited an asymptotically increasing trend, converging toward a specific value for each experimental condition. Possible effect caused by elastic–plastic characteristics could be recognized, when axial strain for 0.5 Hz excitation becomes greater than the one of 1.0 Hz under same stress amplitude ratio. When the stress amplitude ratio took 0.1, the absolute value of axial strain of 0.5 Hz was greater than the one of 1.0 Hz, whereas its decreasing trend was recognized in the sequence of silt, clay and silty sand. The qualitative relations between pore water pressure and number of cyclic loading were also examined to scrutinize the effect of effective water pressure to the soil compactibility. 相似文献
73.
Analysis model to simulate the cracked pipe buried in soil 总被引:1,自引:0,他引:1
This paper describes the use of the finite element method to simulate crack propagation in a pipeline in the presence of soil
backfill. Since typical values for soil modulus are known, a spring element can be used to simulate the effects of backfilled
soil on crack propagation. This consists of the relationship between the soil property and the stiffness of the spring element,
and the effect of backfill depth on the crack propagation in the pipes. By equating crack driving force,G, in the presence of soil, to the dynamic fracture toughness of the pipeline material, a theoretical predictive capability
is obtained for the first time for the gas transmission and distribution pipelines. Numerical calculations have also been
carried out for the cracked pipe with backfill and without backfill. 相似文献
74.
75.
循环载荷下砂质土的本构模型 总被引:6,自引:0,他引:6
提出了一个描述砂质土循环载荷条件下主要特性的本构模型,并且采用不同围压下多种加载途径的土力学实验确定了模型中的待定材料常数,由本构模型的增量工数值积分计算所得到的理论曲线与不同应力路径下实验曲线十分接近,经实验验证这种本构模型能广泛地应用土工问题的弹-塑性有限元分析中。 相似文献
76.
Viscoelastic behavior, phase morphology and flow conditions relationships in polymer/rubber blends have been investigated. The importance of such correlations is illustrated on polymethylmethacrylate (PMMA)/rubber blends subjected to different flow conditions both under small and large deformations. In small-amplitude oscillatory shear (the morphology does not change during the flow) the elastic modulus G of the concentrated blends shows a secondary plateau, G
p
, in the low frequency region. This solid-like behavior appears for rubber particle contents beyond the percolation threshold concentration (15%). Morphological observations revealed that for concentrations higher than 15%, the particles are dispersed in a three-dimensional network-type structure.In capillary flow it was found that the network-type structure was destroyed and replaced by an alignment of particles in the flow direction. This morphological modification resulted in a decrease in both viscosity and post-extrusion swell of the blends. Morphological observations revealed that the ordered structure in the flow direction was concentrated only in the skin region of the extrudate, where the shear stress is higher than the secondary plateau, G
p
. A simple kinetic mechanism is proposed to explain the observed morphology.Similarly, steady shear measurements performed in the cone-and-plate geometry revealed alignment of particles in the flow direction for shear stress values higher than Gp.Presented in part at the Symposium Recent Developments in Structured Continua Montréal (Canada) 26–28 May 1993 and at the 45th Canadian Chemical Engineering Conference, Quebec, October 15–18 (1995) 相似文献
77.
GUAN Linbo 《力学与实践》1979,42(5):622
对地基土沉降计算的课程内容提出改革思路,从讨论土体固结度的角度展开,进而引出最终沉降量的计算,最终引出不同的试验方法和压缩性指标。新的教学思路将土力学固结沉降的基本理论与实践应用进行合理的区隔,既能保证基本理论的纯粹性、合理性,也不回避实践中土体复杂 性质对理论进一步发展和丰富所提出的挑战。 相似文献
78.
79.
爆炸荷载作用下钢筋混凝土梁的动力响应及破坏形态分析 总被引:15,自引:0,他引:15
对基于Timoshenko梁理论建立的非线性动力有限元法作了改进。根据压区理论得到混凝土的平均剪应力和平均剪应变关系,建立了能反映箍筋的抗剪作用的材料模型;此外,对结构在爆炸荷载作用下可能出现的各种响应现象进行了描述,以准确地预测梁破坏时不同位置截面上钢筋和混凝土的受力、变形及破坏情况。应用改进的材料模型,对爆炸荷载作用下的五个钢筋混凝土试验梁的动力响应和破坏形态进行了数值模拟,结果表明,该数值方法能较好地模拟钢筋混凝土梁的弯曲、弯剪和剪切等破坏形态。 相似文献
80.
准饱和土体中圆形衬砌对弹性波的散射 总被引:1,自引:0,他引:1
采用Vardoulakis和Beskos提出的准饱和土体的波动控制方程,根据Helmholtz矢量分解定理,得到了准饱和土中P1波(快压缩波)、P2波(慢压缩波)和S波(剪切波)的波数的势函数表达式.将准饱和土体和圆形衬砌视为各向同性的均质体,运用波函数展开法将入射波、散射波和折射波的势函数展开成Fourier-Bessel函数的级数形式,根据准饱和土体与衬砌边界处应力和位移连续及衬砌内完全自由的边界条件,得到了平面P1波入射下,准饱和土体内深埋圆形衬砌的散射系数和折射系数的理论解,通过数值计算分析了饱和度对准饱和土体和衬砌的DSCF(动应力集中因子)及准饱和土体的PPCF(孔压集中因子)的影响规律,结果表明:准饱和土体的DSCF随着饱和度的增大而减小,衬砌的DSCF基本不受饱和度的影响,而准饱和土体的PPCF则随着饱和度的增大而增大. 相似文献