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1.
为了指导旧路加铺工程合理设计,对加铺结构在交通荷载作用下的受力状态进行了分析。基于路面力学弹性层状体系理论,建立了旧路加铺路面的轴对称有限元模型。主要考虑交通荷载作用,分析了沥青加铺层层底拉应力、剪应力和旧水泥路面层底的拉应力等指标。考虑加铺层和应力吸收层模量的影响对路面结构的力学响应进行了分析计算。为了快速计算材料力学性能对路面结构受力的影响,基于数值计算结果给出一个路表弯沉和沥青加铺层底拉应力的简易计算公式。结果表明:在车辆轴载作用下,增设应力吸收层会减小路表弯沉、沥青层底拉应力、新旧层间的剪应力和水泥层底拉应力各项指标,对于改善路面结构受力状态有积极影响;随着沥青面层模量的增加,路表弯沉、沥青层底剪应力和水泥层底拉应力都趋于减小,但是沥青层底拉应力会增大。由此建议在旧水泥路面加铺沥青面层设计时,应适当选用高模量的沥青混凝土材料,可以缓解路面新旧层之间的剪切脱层破坏,进而延长旧路改造路面的服役寿命。  相似文献   

2.
行车荷载及路面结构对车辙影响的有限元分析   总被引:10,自引:0,他引:10  
基于车辙的产生机理,采用实测轮胎接地压力,对柔性基层和半刚性路面结构内的剪应力进行三维有限元分析,结果表明,相同荷载条件下两种路面结构所受的剪应力有较大差异,水平力对剪应力亦有较大的影响;基层模量、面层厚度、面层模量对沥青层内的剪应力影响均比较显著.因此,为防治车辙,应该在路面设计时对路面结构组合类型的抗车辙能力进行充分的考虑,并严格控制超载.  相似文献   

3.
运用通用有限元软件ABAQUS及其二次开发平台,建立考虑路面材料非线性疲劳损伤的沥青路面结构数值计算模型,分析沥青路面结构在车辆荷载反复作用下路面结构损伤的空间分布、演化规律以及路面结构内部水平正应力的空间分布与演化规律。研究结果表明:路面结构损伤主要分布在双轮中心线下靠近基层与底基层层底的区域,随着荷载作用次数增加,基层层底与底基层层底损伤度均增加,且增加幅度逐渐增大;双轮中心线下靠近基层与底基层层底区域,考虑损伤的路面结构相比无损路面结构,层底水平拉应力均有所减小,且随荷载作用次数增加,水平拉应力逐渐减小,减小的幅度逐渐增大。研究结果可用于路面维修养护中路面破坏区域及程度的判断,以及路面设计研究中设计指标的确定。  相似文献   

4.
为快速分析水泥混凝土路面结构响应特性,将路面结构简化为Winkler地基上的双层欧拉直梁,基于Euler-Bernoulli梁理论和状态空间方法,提出了一种考虑层间界面剪切滑移效应的水泥混凝土路面结构力学响应的解析计算方法.通过与有限元数值计算的结果对比,验证了该解析计算方法的正确性,并揭示了不同路面结构长度与层间剪切刚度影响下水泥混凝土路面结构变形响应的变化规律,以及荷载大小对界面处剪切力集度的影响规律.结果表明:计算时选用不同的路面结构长度对变形响应具有显著影响,建议长度不宜小于10 m;层间界面的剪切滑移效应会显著地影响水泥混凝土路面结构的竖直位移与弯曲变形,且该影响会随着荷载的增加而愈加显著,层间界面的接触效应不容忽略;增大层间剪切刚度能够有效地减小荷载对水泥混凝土路面结构变形响应的影响.  相似文献   

5.
基于全过程时程分析方法,采用实用的动力稳定性判定准则,分析了在三种简单荷载作用下短程线型单层球面网壳结构动力稳定性能。阶跃荷载作用下考虑了初始几何缺陷和阻尼的影响,并对比了阶跃荷载与静力荷载作用下稳定临界值;简谐荷载作用下对比了共振区和非共振区的动力稳定性能;三角形荷载作用下考虑了不同持时的影响。通过不同参数变化对单层网壳结构动力性能的影响分析,得出了一些有意义的结论。  相似文献   

6.
为了探讨车辆随机动荷载对道路破坏的影响,基于二自由度1/4车辆振动模型,采用MATLAB/SIMULINK软件模拟得到车辆对路面作用的动荷载,采用ANSYS/APDL二次开发技术建立半刚性沥青路面三维有限元分析模型并实现随机动载加载,计算分析了路面在车辆随机动载作用下的动态响应规律,并与移动恒载计算结果进行比较。研究结果表明:随机动载与移动恒载作用下路面固定位置处的应力时程变化规律相似,而路面各层的应力极值波动情况明显不同,相对于固定位置处节点应力时程分析,路面各层的应力极值分布可以较好地反映车辆荷载的随机特征;随机荷载下路面各层的应力极值波动频率与所施加的动荷载波动频率相似,而且随着路面深度的增加,应力波动效应降低;随机荷载下路面应力响应数值大于移动恒载值,且随着路面不平度的增加应力响应数值变大,即在良好路面上随机荷载应力响应与移动恒载数值比较接近。  相似文献   

7.
轴载与速度对半刚性沥青路面动力响应的影响   总被引:5,自引:2,他引:3  
为了研究实际车辆荷载下半刚性基层沥青路面动力响应的规律,在修筑的试验路段上,以重型运输车辆为加载设备,通过检测运动车辆下面层底部的纵向动应变和横向动应变,分析车辆轴载和速度对路面结构动态响应的影响.研究结果表明:不论是横向应变还是纵向应变,均既有拉应变状态,又有压应变状态;随着车辆行驶速度的提高,各应变分量都基本呈下降趋势,但在车辆行驶速度超过40 km/h后,变化明显减小;动应变与轴载基本呈线性关系;进行路面结构动态设计时,不但要考虑面层底部拉应变的作用,而且要考虑压应变的作用;在疲劳寿命试验时,应考虑应变比的影响,应变比不仅与速度有关,还与轴载有关.  相似文献   

8.
为了研究沥青路面结构在车辆荷载作用下的疲劳损伤演化特性并分析其形变规律,运用通用有限元软件ABAQUS及其二次开发平台,建立考虑路面材料疲劳损伤的沥青路面结构数值计算模型,分析沥青路面结构在车辆荷载反复作用下路面结构损伤和水平正应变的空间分布与演化规律,以及路表弯沉随荷载作用的演变规律.结果表明:路面结构损伤主要分布在双轮中心线下靠近层底的区域,基层层底与底基层层底损伤度随荷载作用均增加,但增加幅度逐渐减小;路面结构层内水平正应变在荷载作用下,靠近层底位置拉应变逐渐增大,但增加幅度逐渐减小,中性轴上移;路表弯沉在荷载作用下逐渐增大,但增加幅度逐渐减小.研究结果可为沥青路面结构设计、养护维修及长期性能预测提供理论支撑.  相似文献   

9.
为了研究动荷载作用下纤维沥青路面的响应,基于弹性理论,应用有限元方法分析单周期动荷载作用下,不同的荷载作用时间、路面体阻尼比、土基模量和加载方式对不同纤维沥青路面结构的路表最大弯沉的影响规律.对于不同纤维沥青路面结构:不同荷载作用时间下,路面的动静态弯沉差值基本接近;随着路面体阻尼比的逐渐增加,路面的动态弯沉逐渐减小,但减小率和到达最大动弯沉对应的时间基本接近;随着土基模量的逐渐增加,路面的动态弯沉逐渐减小,但减小率基本接近;半矩形波荷载比半正弦荷载作用下的路面动态弯沉大,而弯沉差值基本接近.分析表明,在单周期动荷载作用下,纤维的加入提高了路面的整体抗变形能力,但对路面的动态弯沉影响规律基本相同.  相似文献   

10.
目的分析在两种不同行驶位置的移动荷载作用下,不同下封层沥青路面力学性能的差异.方法笔者对4种不同下封层的沥青路面进行室内模拟试验,获得不同下封层下基面层间的连接状况参数.在此基础上建立移动荷载作用下不同基面层连接状况的沥青路面结构有限元分析模型.结果基面层连接状态越好,移动荷载作用下所产生的应力越小;荷载位于路面中间所产生的竖向剪应力和基层层底拉应力比荷载位于路面两侧时大;在不同基面层间接触状态下,荷载位于路面两侧的竖向剪应力的差异性大于荷载位于路面中间,荷载位于路面两侧的基层层底拉应力的差异性稍小于荷载位于路面中间.结论与在路中央行车相比,在路两侧行车对路面的不利影响更小.下封层的连接效果越强,荷载对路面结构的不良影响越小,故推荐使用橡胶沥青封层.  相似文献   

11.
Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.  相似文献   

12.
何延凌 《科技信息》2008,(4):258-258
Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women's language from these perspectives: pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women's language, more attention should be paid to language use in social context. What's more, the linguistic phenomena in a speaking community can be understood more thoroughly.  相似文献   

13.
There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.  相似文献   

14.
理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。  相似文献   

15.
The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3~4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰~ -7.8‰, PDB) and matrix dolomites (-6.6‰~ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084~0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078~0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.  相似文献   

16.
As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.  相似文献   

17.
王慧 《科技信息》2008,(10):240-240
Wuthering Heights, Emily Bronte's only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.  相似文献   

18.
The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.  相似文献   

19.
In the 19th century the society was controlled by men, and women were just appendants of them, they had not any rights and freedom. But Jane was an exception, she showed some characteristics of early feminist. Jane showed her characteristics of feminism in three aspects: rebellion, equality, and independence. These characteristics were helpful to her success, and feminism is the only way out for women of that time.  相似文献   

20.
1 Rise of studies on climate change's effects on biodiversity
Until the 1980s, climate change and biodiversity were studied as two independent disciplines for more than a century. In 1992, the Ecological Society of America's annual report named climate change, biodiversity, and the sustainable ecological system as the three major global environmental issues of the twenty-first century [1].  相似文献   

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