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161.
文章通过相似模型试验,研究了钢纤维混凝土材料应用于隧道支护结构的力学行为。试验通过千斤顶逐级加载的方式,得到支护结构整个力学行为过程中与围岩之间的接触压力、变形发展规律及其裂后承载能力。通过与传统素混凝土支护结构相比,钢纤维混凝土具有良好的承载和变形能力,是一种理想的柔性支护材料。 相似文献
162.
基于Biot饱和多孔介质动力学理论,运用Laplace变换和波函数展开法,根据饱和土体与衬砌结构交界面的连续条件和衬砌结构内边界上的应力自由条件,得到饱和土中深埋圆柱形衬砌洞室对瞬态平面P波和SV波散射问题的解答,该解答可以退化成为饱和土中深埋圆柱形空穴或弹性夹塞物的情形,并很容易转换成为对稳态波散射的解.通过与已有的相关问题的解析解答进行对比,验证了该解答的正确性.同时利用Laplace逆变换的数值方法,给出了饱和土和衬砌中应力和位移场在时域内的数值解,通过算例,分析了衬砌厚度、刚度对衬砌内边界处应力集中因子的影响. 相似文献
163.
According to the mass conservation equation of solid phase, water transport, air migration and enthalpy balance equations in a deformable and unsaturated porous medium, and the mechanics model, a thermal‐hydro‐mechanical (THM) coupling mathematical model is developed in order to accurately predict the crack propagation of the compacted clay lining (CCL) in a landfill closure cover system. Numerical simulation analysis of the cracking and failure of the CCL in a landfill closure cover system under complex conditions (landfill gas pressure, variation of soil surface temperature, moisture loss of coverage soil, and uneven settlement of landfilled MSW (municipal solid waste)) is performed. The results show that the cracks are discovered firstly on the soil surface and then extend to the deeper cover system and became bigger. The cracks had broken through the closure cover system at 30 days. Over the depth range of 0.06 m, the change rate of settlement is found to be the highest because of the strong influence of temperature. The rise of temperature around the cracks is fast when the CCL is broken through by the cracks. There is a hollow area near the cracks over the depth range from 0.15 to 0.7 m, and the temperature stabilize at around 11°C without any obvious reduction. Under the condition of evaporation, the main crack in the CCL is similar to a pumping well, which causes more rapid moisture content reduction around the cracks. Vertical deformation increases linearly with depth in the process of deformation and cracking of CCL induced by uneven settlement of landfilled MSW. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
164.
Thousands of buildings were damaged by the devastating Chi‐Chi earthquake on September 21, 1999. Of all the public buildings, school buildings are the most vulnerable to earthquake damage, and the retrofitting of existing school buildings becomes a stringent issue. In addition to cost effectiveness, the impact of retrofitting methods on the functions of the school buildings needs to be considered. This paper therefore proposes the retrofitting of school buildings by adding sandwich columns onto partition brick walls. The sandwich column is divided into two parts and is added to the two sides of the partition brick wall held with pairs of U‐shaped bars. The retrofit does not require the removal of windows or doors in the longitudinal direction making the proposed method cost effective and minimizes the impact on the function of the school buildings. Five full‐scale specimens without and with retrofitting were designed and fabricated for testing based on the partition brick wall frames of the existing school buildings. The specimens were subjected to cyclic loading in the out‐of‐plane direction through a loading frame so that the columns deformed with double curvatures. The experimental results verified the feasibility of the proposed retrofit method. The data showed that the lateral strength of the retrofitted specimen doubled that which was not and that the residual strength of the retrofitted specimen was just as high as the ultimate strength of the specimen without retrofitting. The analytical results in lateral strength yielded conservative figures compared with experimental measurements. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
165.
166.
The interactions between perpendicularly crossing tunnels in the Sydney region are investigated using a full three-dimensional (3D) finite element analysis coupled with elasto-plastic material models. Special attention is paid to the effect of subsequent tunnelling on the support system, i.e. the shotcrete lining and rock bolts, of the existing tunnel. The results of the analysis show that in a region such as Sydney, with relatively high horizontal stresses, installation of the new tunnel causes the shotcrete lining of the existing tunnel to be in tension in the side facing towards the tunnel opening and in compression at the crown and invert. The pre-stressed rock bolts are usually tensioned more in the sections closest to the tunnel opening. For this particular study, if a new tunnel is driven perpendicularly beneath an existing tunnel, significant increases are induced in the bending moments in the shotcrete lining at the lateral sides of the existing tunnel and in the axial forces at its crown and invert. The increase in side bending moments causes further tensile cracking but the crown and invert stresses remain within the thresholds for both compressive failure and tensile cracking for shotcrete lining of typical concrete quality. Moreover, the driving of the new tunnel causes the tensile forces in the existing side rock bolts to increase and those in the existing crown rock bolts to decrease. In contrast, if the new tunnel is driven perpendicularly above the existing tunnel, compressive failure of the existing shotcrete lining is induced at the crown of the deeper tunnel for concrete of typical capacity and a significant tensile force increase of the existing rock bolts around the crown. It is concluded that in order to ensure the stability of the existing tunnel, local thickening is needed at the sides of the existing shotcrete lining if the shallow tunnel is installed first and local thickening is needed at the crown if the deep tunnel is installed first. 相似文献
167.
168.
Prediction of tunnel lining loads using correction factors 总被引:3,自引:0,他引:3
A design method for the prediction of lining loads should include the decrease of lining loads due to the stress release before lining installation and the increase of lining loads due to development of ground yielding. Schwartz and Einstein included both factors in their original closed form solutions in the form of a support delay factor λd and a yield factor λy respectively. The validity of the design method is reviewed by comparing the loads calculated using the methods with the field measurements obtained from several tunnels. The possible causes of the load discrepancy between measurements and predictions are presented.
Schwartz and Einstein's proposed method gives reasonable results for tunnels with short delay lengths. However, the method could not be used reliably for tunnels either with long delay lengths or with voids between the soil and TBM due to the difficulties finding the pre-support ground movements and therefore λd. 相似文献
169.
本文给出了地下圆形衬砌结构与地面上的半圆形凸起地形对垂直于地面入射的SH波散射问题的解答。方法是将求解区域分割成两部分。其一为包含半圆形凸起地形在内的圆形区域Ⅰ,其二为带有一个半圆形凹陷和一个圆形衬砌结构的弹性半空间Ⅱ,半圆形凹陷部分为其公共边界,在区域Ⅰ和Ⅱ中分别构造其位移解,然后再通过移动坐标,使其满足“公共边界”上的条件和地下衬砌的边界条件,建立起求解该问题的无穷代数方程组。最后,本文给出了算例,并讨论了数值结果,给出了圆形衬砌结构周边上的动应力集中系数变化规律。 相似文献
170.