基于强度折减法的靠崖式黄土窑洞稳定性分析
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摘要
靠崖式黄土窑洞是西北黄土高原典型的传统民居形式,合理保护黄土窑洞具有重要的政治意义和生态意义。基于ABAQUS有限元分析软件,分别建立了靠崖式黄土窑洞的平面模型和三维模型,并通过强度折减法对既有窑洞的安全性进行分析,得出了既有窑洞的安全系数和塑性区发展规律。窑洞的平面模型分析表明:其仅能发生洞室的失稳破坏,塑性区自窑腿根部呈"U"型向上扩展,经综合判断其安全系数为2. 40;三维窑洞模型分析表明:其可能出现洞室失稳和边坡失稳两种破坏情况,因窑洞模型的跨高比较小,窑洞在因拱券坍塌而失稳破坏前即因边坡失稳而破坏,塑性区仍起源自窑腿根部,但其后沿纵向从坡脚向坡顶发展,经综合判断其安全系数为2. 00。窑洞的安全系数取决于洞室安全系数和所在边坡安全系数的较小值。以有限元数值分析的收敛性作为判定结构失稳的依据得到的安全系数较大;而通过塑性区贯通和关键结点位移突变得到的安全系数则更为合理且具有较高的一致性。建议在黄土窑洞稳定性分析中,综合采用潜在滑动面塑性区贯通和关键结点位移突变作为失稳判据。
Loess cave dwelling by cliff is a typical traditional residence form in the northwest loess plateau. It is of great political and ecological significance to protect the loess cave properly. Based on the finite element analysis software ABAQUS,the plane model and three-dimensional model were established respectively. Then,the safety of the existing cave was analyzed by the method of shear strength reduction FEM. The safety factor and the plastic zone development regularity of the existing cave were obtained. The results showed that the sole instability failure of the caverns occurred in the plane model of the cave. The plastic zone extended upwards from the root of the cave with the"U"type,and the safety factor was 2. 40 by comprehensive judgment. There may be two damage conditions in the three-dimensional model,of which were the instability of the caverns and the instability of the slope. Because that the height of the cave was relatively small,the failure occurred in slope before the arch collapsed. The plastic zone originated from the root of cave,and then developed from the foot of the hill to the top of the hill along the longitudinal direction. The safety coefficient was 2. 00 from the perspective of comprehensive judgment. The safety factor of the cave depended on the smaller value between the safety coefficient of the cavern and that of the slope. The safety factor was larger by taking the convergence of finite element numerical analysis as the basis for determining the instability of the structure. The safety factor determined by the transfixion of the plastic zone and the displacement of the key joint was more reasonable and had a higher consistency. It was suggested that the transfixion of the plastic zone and the displacement of the key joints of the potential sliding surface should be taken as the judgment basis for instability.
Loess cave dwelling by cliff is a typical traditional residence form in the northwest loess plateau. It is of great political and ecological significance to protect the loess cave properly. Based on the finite element analysis software ABAQUS,the plane model and three-dimensional model were established respectively. Then,the safety of the existing cave was analyzed by the method of shear strength reduction FEM. The safety factor and the plastic zone development regularity of the existing cave were obtained. The results showed that the sole instability failure of the caverns occurred in the plane model of the cave. The plastic zone extended upwards from the root of the cave with the"U"type,and the safety factor was 2. 40 by comprehensive judgment. There may be two damage conditions in the three-dimensional model,of which were the instability of the caverns and the instability of the slope. Because that the height of the cave was relatively small,the failure occurred in slope before the arch collapsed. The plastic zone originated from the root of cave,and then developed from the foot of the hill to the top of the hill along the longitudinal direction. The safety coefficient was 2. 00 from the perspective of comprehensive judgment. The safety factor of the cave depended on the smaller value between the safety coefficient of the cavern and that of the slope. The safety factor was larger by taking the convergence of finite element numerical analysis as the basis for determining the instability of the structure. The safety factor determined by the transfixion of the plastic zone and the displacement of the key joint was more reasonable and had a higher consistency. It was suggested that the transfixion of the plastic zone and the displacement of the key joints of the potential sliding surface should be taken as the judgment basis for instability.
引文
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[3]郑颖人,邱陈瑜,张红,等.关于土体隧洞围岩稳定性分析方法的探索[J].岩石力学与工程学报,2008,27(10):1968-1980.
[4]郑颖人,肖强,叶海林,等.地震隧洞稳定性分析探讨[J].岩石力学与工程学报,2010,29(6):1081-1088.
[5]郑颖人,赵尚毅.有限元强度折减法在土坡与岩坡中的应用[J].岩石力学与工程学报,2004,23(19):3381-3388.
[6] ZIENKIEWICZ O C,HUMPHESON C,LEWIS R W. Associated and Non-Associated Visco-Plasticity and Plasticity in Soil Mechanics[J]. Geotechnique,1975,25(4):671-689.
[7]李垠,程丹,苏凯.基于有限元强度折减法的边坡失稳判据统一性研究[J].大地测量与地球动力学,2016,36(1):69-74.
[8]侯继尧.中国窑洞[M].郑州:河南科学技术出版社,1999.
[9]王徽.窑洞地坑院营造技艺[M].合肥:安徽科学技术出版社,2013.
[10]陈莉粉.黄土地区窑洞建筑中结构稳定性的研究[D].西安:西安科技大学,2012.
[11]陈孟乔,刘建坤,肖军华.砂土中盾构隧道开挖面失稳土体三维形状分析[J].岩土力学,2013,34(4):961-966.
[12]费康,张建伟. ABAQUS在岩土工程中的应用[M].北京:中国水利水电出版社,2010.