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排序方式: 共有316条查询结果,搜索用时 31 毫秒
21.
提出颗粒型砂介质在压实过程中的两种特征:孔隙填充状态和颗粒滑动状态;针对孔隙填充状态的力学行为特征,提出相对体积改变量(压实量)作为表征此状态的特征参量,研究了瞬时压缩模量与压实量的函数关系;针对型砂的颗粒滑动状态,提出具有强化效应的Mohr-Coulomb屈服条件,推导描述颗粒屈服滑动状态的增量本构方程、以及三轴压实过程条件下的状态本构方程,最后,就不同侧向压力下的三轴压缩试验、带模样的型砂压实试验的大量试验数据进行处理和验证。 相似文献
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23.
《中国化学》2017,35(11):1701-1705
The development of asphalt‐based UV blocking materials is important to extend the alphalt lifespan in road construction. In this work, we put forward that the fabrication of host‐guest system can be an effective way to obtain UV blocking materials. Firstly, a new anionic Schiff base, N ,N' ‐bis(salicylidine)‐4,4'‐diaminostilbene‐2,2'‐disulfonic acid (SDSD ), has been synthesized, which was intercalated into Zn‐Al‐LDH by anion‐exchange method. FT‐IR and XRD illustrate the layered organic–inorganic composite, Zn‐Al‐SDSD‐LDH , has been successfully synthesized with high crystallinity. Laser particle size analyzer, SEM and TEM show that particle size distributions of Zn‐Al‐SDSD‐LDH is in the range 100–500 nm. UV –vis absorption spectra show that Zn‐Al‐SDSD‐LDH has better UV absorption than the pristine Zn‐Al‐LDH and SDSD . Furthermore, the mixture of asphalt and 3 wt% Zn‐Al‐SDSD‐LDH presents enhanced UV blocking property relative to the pristine asphalt after irradiating by UV spray accelerated weathering test. Therefore, this work not only develops a new type of host‐guest Zn‐Al‐SDSD‐ LDH , but also confirms it can be an effective asphalt UV blocking material for practical application. 相似文献
24.
我国北方地区的土石坝和水池的防渗沥青混凝土面板,常出现低温裂缝。因此,对沥青混凝土在低温条件下的温度应力疲劳进行实验研究很有必要.本项研究研制了适用于沥青混凝土低温低周大变形的弯曲疲劳试验机,进行了沥青混凝土在不同低温下的疲劳破坏性能试验。对试验结果用粘弹性理论和推广的应变区分法(SRP)和应变能区分法(SEP)进行了分析,首次得出了沥青混凝土的疲劳寿命与弯曲应力、应变和应变能的关系,并试用于实际工程的予测. 相似文献
25.
地表温度对颗粒跃移轨迹的影响 总被引:2,自引:0,他引:2
为了研究由地表温度变化引起的向上的垂向气流对沙粒跃移运动的影响,本文给出了考虑近地表温度变化和水平来流风场作用下的沙粒的跃移运动。在定量给出不同时刻的近地表温度和垂向风速的基础上,计算了由于太阳辐射所引起的近地表层垂向气流对沙粒跃移运动的影响,发现:垂向风速在午后可达到1.5m/s并使得沙粒跃移轨迹的最大高度和长度分别增加55.56%和73.68%;同时,与不考虑温度效应的情况不同的是,沙粒跃移轨道最大高度将随粒径变化。 相似文献
26.
The probability distributions of sand particles' lift-off and incident velocities in a wind-blown sand flux play very important
roles in the simulation of the wind-blown sand movement. In this paper, the vertical and the horizontal speeds of sand particles
located at 1.0 mm above a sand-bed in a wind-blown sand flux are observed with the aid of Phase Doppler Anemometry (PDA) in
a wind tunnel. Based on the experimental data, the probability distributions of not only the vertical lift-off speed but also
the lift-off velocity as well as its horizontal component and the incident velocity as well as its vertical and horizontal
components can be obtained by the equal distance histogram method. It is found, according to the results of the χ2-test for these probability distributions, that the probability density functions (pdf's) of the sand particles' lift-off
and incident velocities as well as their vertical components are described by the Gamma density function with different peak
values and shapes and the downwind incident and lift-off horizontal speeds, respectively, can be described by the lognormal
and the Gamma density functions. These pdf's depend on not only the sand particle diameter but also the wind speed.
The project supported by the National Natural Science Foundation of China (10532040) and the Hundred Talents Project, the
Knowledge Innovation Project of Chinese Academy of Sciences (KZCX2-304). The English text was polished by Keren Wang. 相似文献
27.
将沥青混合料看作由粗骨料和沥青砂组成的两相复合材料,根据给定的级配生成凸多面体骨料,然后利用随机投放算法建立沥青混合料试样的三维随机模型.采用广义Maxwell模型刻画沥青砂的本构行为,其参数通过单轴蠕变实验获得.在对三维随机模型的有效性进行验证之后,采用参数化建模方法建立包含不同骨料分布、含量和级配的沥青混合料有限元模型,通过数值模拟研究骨料分布、含量和级配对沥青混合料蠕变行为的影响.结果表明:骨料分布对沥青混合料力学性质的影响较小;沥青混合料瞬时弹性模量随骨料含量的增加呈近似线性增大,而且弹性模量与骨料含量之间的关系曲线处于Paul上下边界内;在计算考虑的粒径范围内,骨料平均粒径越小,沥青混合料抵抗变形的能力越强. 相似文献
28.
29.
通过高速摄影系统对电火花气泡与不同沙粒底面间的相互作用进行了实验研究,并改变气泡与沙粒底面之间的距离.实验结果表明:气泡在与沙粒底面的相互作用中会产生两种明显不同的现象,即形成与近刚性壁面类似的气泡射流以及“蘑菇状”气泡,“蘑菇状”气泡撕裂形成两个气泡,随后产生两个反方向的沿轴线方向的射流.沙粒底面边界具有刚性与弹性两种特征.另外,随着气泡与沙粒底面之间的距离d的增大,气泡脉动周期先增大然后减小,存在气泡脉动周期峰值.对于不同的沙粒底面边界,出现气泡脉动周期峰值的距离d随着沙底粒径的增大而越小. 相似文献
30.
To predict correctly the rut depths in asphalt pavements, a new nonlinear viscoelastic-elastoplastic constitutive model of
permanent deformation in asphalt pavements is presented. The model combines a generalized Maxwell model with an elastoplastic
one. Then from the creep theory, the linear and nonlinear constitutive equations of the generalized Maxwell model are obtained.
From the nonlinear finite element method for the rutting of the asphalt pavement, the rut depths of 4 asphalt-aggregate mixtures
are obtained. And the results are compared with the ones from the finite element method by SHRP and the experiments by SWK/UN.
The results in this paper are better than the ones by SHRP, and agree with the ones of the experiment by SWK/UN. This shows
that the nonlinear viscoelastic-elastoplastic constitutive model, which is presented in this paper for the rutting of the
asphalt pavement, is effective. The properties, such as nonlinear elasticity, plasticity, viscoelasticity and nonlinear viscoelasticity,
which affect the rutting of an asphalt pavement, can be shown in the model. And the characteristics of the permanent deformation
of the asphalt pavement can be presented entirely in the model. 相似文献