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991.
992.
高钙粉煤灰加固促淤地基机理和性状试验研究 总被引:6,自引:0,他引:6
结合高钙粉煤灰与上海浦东国际机场工期促淤软土拌和后加固土体的室内外试验,指出高钙粉煤灰足加固促淤软土地基的一种新型材料。基于在不同掺灰量、不同游离氧化钙含量和添加不同激发剂情形下拌和灰土的室内物理力学性能试验,探讨了高钙粉煤灰加固促淤软土的固化机理和工程特性,加固后土体在无侧限抗压强度、变形、渗透特性以及抗液化能力等方面均有明显改善,指出灰土强度与掺灰量、土体改性激发剂的品种和数量以及养护龄期有关,高钙灰与土体拌和后自膨胀特性下降为12%,消除了高钙灰的体积不稳定问题。现场进行粉喷桩加固软土地基试验表明,复合软土地基的极限承载力达到240kPa以上,可以替代水泥土搅拌桩,桩间土体强度和变形也得到改善。加固场地地下水质分析表明,高钙灰加固促淤软土地基不会影响地下水质和环境。 相似文献
993.
丹霞地貌发育几个重要问题的定量测算 总被引:9,自引:1,他引:8
论述了用河流阶地冲积层相当于古河流平水期水面的样品年龄及该采样点至今日河流平水期水面的相对高度求得地壳上升速度,再由地壳上升速度及丹霞地貌的相对高度求得地貌年龄,由地貌年龄及陡崖谷地上缘的宽度求得岩壁后退速度,由地貌年龄及被蚀去的地貌体积求得侵蚀速度,这是地貌学由定性描述向定量研究的一次尝试. 相似文献
994.
995.
柔性基础下复合地基下卧层沉降特性的数值分析 总被引:15,自引:3,他引:12
采用复合本构有限元和传统有限元两种计算模型,通过不同桩土模量比和置换率条件下复合地基、双层地基、人工均质地基下卧层沉降与天然地基相应计算结果的比较,系统地研究了复合地基下卧层的沉降特性,并在此基础上建立了相应的计算方法。 相似文献
996.
997.
998.
CFG桩复合地基沉降计算探讨 总被引:8,自引:0,他引:8
CFG桩(水泥粉煤灰碎石桩)复合地基是新近发展起来的一项地基处理技术,具有承载力提高幅度大,地基沉降小,适用范围广,造价低,施工方便等特点。阐述了CFG桩复合地基加固机理及沉降模式,详细讨论了其沉降计算,包括它的计算厚度、影响因素、压缩模量选取及附加压力计算等。提出按变形控制理论进行变形计算有其优点,但仍有很多工作要做。 相似文献
999.
Modelling of the retreat process of composite riverbank in the Jingjiang Reach using the improved BSTEM 下载免费PDF全文
Bank retreat in the Jingjiang Reach is closely related not only to the near‐bank intensity of fluvial erosion but also to the composition and mechanical properties of bank soils. Therefore, it is necessary to correctly simulate bank retreat to determine the characteristics of fluvial processes in the Jingjiang Reach. The current version of bank stability and toe erosion model (5.4) was improved to predict riverbank retreat, by inputting a dynamic water table, and calculating the approximation of the distribution of dynamic pore water pressure in the soil near the river bank face, and considering the depositional form of the failed blocks, which is assumedly based on a triangular distribution, with the slope approximately equalling the stable submerged bank slope and half of collapsed volume deposited in the bank‐toe region. The degrees of riverbank stability at Jing34 were calculated using the improved bank stability and toe erosion model. The results indicate the following trends: (a) the degrees of riverbank stability were high during the dry season and the rising stage, which led to minimal bank failure, and (b) the stability degrees were low during the flood season and the recession stage, with the events of bank collapse occurring frequently, which belonged to a stage of intensive bank erosion. Considering the effects of bank‐toe erosion, water table lag, and the depositional form of the collapsed bank soil, the bank‐retreat process was simulated at the right riverbank of Jing34. The model‐predicted results exhibit close agreement with the measured data, including the total bank‐retreat width and the collapsed bank profile. A sensitivity analysis was conducted to determine the quantitative effects of toe erosion and water table lag on the degree of bank stability. The calculated results for toe erosion indicate that the amount of toe erosion was largest during the flood season, which was a primary reason for bank failure. The influence of water table lag on the degree of stability demonstrates that water table lag was an important cause of bank failure during the recession stage. 相似文献
1000.
An analytical model for vapor‐phase volatile organic compound diffusion through landfill composite covers 下载免费PDF全文
Haijian Xie Huaxiang Yan Hywel R. Thomas Shijin Feng Qihua Ran Peixiong Chen 《国际地质力学数值与分析法杂志》2016,40(13):1827-1843
One‐dimensional mathematical models for vapor‐phase volatile organic compound (VOC) diffusion through composite cover barriers are presented. An analytical solution to the model was obtained by the method of separation of variables. The results obtained by the proposed solution agree well with those obtained by a numerical analysis. Based on the proposed analytical model, the VOC breakthrough curves of five different composite covers are compared. The effects of degree of saturation of geosynthetic clay liner (GCL) or compacted clay liner (CCL) on VOC migration in the composite covers are then presented. Results show that the composite cover barriers provide much better diffusion barriers for VOC than the single CCL. The top surface steady‐state flux for a composite barrier, consisting of a 1.5 mm geomembrane (GM) and a 20 cm CCL, can be 8.3 times lower than that for a 30 cm CCL. The surface steady‐state flux for the case with (1.5 mm GM + 6 mm GCL) was found to be 2.3 times lower than that for the case with (1.5 mm GM + 20 cm CCL). The degree of saturation Sr of the CCL has a great influence on VOC migration in composite covers when Sr is larger than 0.5. The steady‐state flux at the surface of GM for the case with Sr = 0.7 can be 1.8 times lower than that for the case with Sr = 0.2. The proposed analytical model is relatively simple and can be used for verification of complicated numerical models, analysis of experimental data and performance assessment of composite cover barriers. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献