基于地下水劈裂的基坑突涌破坏机理研究与颗粒流数值模拟
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摘要
深基坑工程中防治底部承压水突涌的问题逐渐成为一个非常严峻的课题。承压水问题处理难度大,并且处理不当可能造成极其严重的工程危害。因此,如何准确判断含承压水基坑的抗突涌稳定已越来越引起工程上的重视。目前已有的基坑抗突涌稳定计算理论主要有以下几种:压力平衡理论、均质连续梁、板分析法、带预应力均质连续梁、板分析法、均质连续体法、统计预测法等等,这些方法从不同角度研究基坑突涌破坏的机理,但是均存在一些不足或缺陷,对基坑突涌破坏的过程和破坏机理都没有深入认识。
我们可以发现基坑突涌破坏和土石坝粘土心墙劈裂这两个不同工程领域现象的发生机理非常相似:都是存在高水压作用,都是在粘土层(弱透水层)产生渗漏通道,都是张拉破坏,两者发生都具有突然性,裂缝扩展过程与水力劈裂伸展的现象也非常相似,二者在发生机理、发生条件及计算方法方面应该存在共通之处。本文即借鉴土石坝粘土心墙的水力劈裂理论来解释基坑突涌破坏机理。
为了观测基坑突涌破坏过程并验证突涌破坏机理,本文利用适用于研究粒状集合体的破裂和破裂发展问题、以及颗粒的流动(大位移)问题的微/细观力学程序颗粒流PFC(Particle Flow Code)建立数值模型。通过一系列参数分析和试验,最终实现模拟基坑突涌的全过程。
Protecting from Bottom piping in deep foundation pit engineering has been gradually a very severe subject. It is difficult to solve the problem connected with confined water, and it might cause great damage to the project if the solution is not proper. Hence, how to estimate exactly the stability of anti-bottom-piping of foundation pit under the confined water becomes more and more important. The existing calculation theories of stability of anti-piping for foundation pit are summarized as followed: simple balance of the water pressure and the soil’s weight, considering the shearing and cementation strength of soil, considering the stiffness of the pit, overall consideration of the stiffness and the strength of the pit and statistics and anticipation based on neural network model. These methods have studied the mechanism of piping in different views, but all of them have some drawbacks and have not acquired a clear and deeply acknowledge to the mechanism of piping.
We can find that the bottom piping of foundation pit and the hydraulic fracturing of clay core in fill dam, which are two different engineering fields’phenomenon, is very similar in their mechanism. They both have the existence of high water pressure; have formed leak path in clay pan (low permeable layer) and broken due to tension. They both happen abruptly and the phenomenon of crack progressing and hydraulic fracture extension is exactly similar. Therefore there must be some common properties in their occurrence mechanism and condition and calculation method. In this paper, we are attempting to use the hydraulic fracture theory in fill dam engineering for reference to explain the mechanism of piping in foundation pit.
To observe the failure process of piping and verify the mechanism, we will use PFC (Particle Flow Code), which is suitable for studying problem with flow (large deformation) and fracture, to build numerical model. We will eventually achieve the simulation of the entire process of piping via a series of parameter analysis and test.
我们可以发现基坑突涌破坏和土石坝粘土心墙劈裂这两个不同工程领域现象的发生机理非常相似:都是存在高水压作用,都是在粘土层(弱透水层)产生渗漏通道,都是张拉破坏,两者发生都具有突然性,裂缝扩展过程与水力劈裂伸展的现象也非常相似,二者在发生机理、发生条件及计算方法方面应该存在共通之处。本文即借鉴土石坝粘土心墙的水力劈裂理论来解释基坑突涌破坏机理。
为了观测基坑突涌破坏过程并验证突涌破坏机理,本文利用适用于研究粒状集合体的破裂和破裂发展问题、以及颗粒的流动(大位移)问题的微/细观力学程序颗粒流PFC(Particle Flow Code)建立数值模型。通过一系列参数分析和试验,最终实现模拟基坑突涌的全过程。
Protecting from Bottom piping in deep foundation pit engineering has been gradually a very severe subject. It is difficult to solve the problem connected with confined water, and it might cause great damage to the project if the solution is not proper. Hence, how to estimate exactly the stability of anti-bottom-piping of foundation pit under the confined water becomes more and more important. The existing calculation theories of stability of anti-piping for foundation pit are summarized as followed: simple balance of the water pressure and the soil’s weight, considering the shearing and cementation strength of soil, considering the stiffness of the pit, overall consideration of the stiffness and the strength of the pit and statistics and anticipation based on neural network model. These methods have studied the mechanism of piping in different views, but all of them have some drawbacks and have not acquired a clear and deeply acknowledge to the mechanism of piping.
We can find that the bottom piping of foundation pit and the hydraulic fracturing of clay core in fill dam, which are two different engineering fields’phenomenon, is very similar in their mechanism. They both have the existence of high water pressure; have formed leak path in clay pan (low permeable layer) and broken due to tension. They both happen abruptly and the phenomenon of crack progressing and hydraulic fracture extension is exactly similar. Therefore there must be some common properties in their occurrence mechanism and condition and calculation method. In this paper, we are attempting to use the hydraulic fracture theory in fill dam engineering for reference to explain the mechanism of piping in foundation pit.
To observe the failure process of piping and verify the mechanism, we will use PFC (Particle Flow Code), which is suitable for studying problem with flow (large deformation) and fracture, to build numerical model. We will eventually achieve the simulation of the entire process of piping via a series of parameter analysis and test.
引文
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[3]叶琳昌,要重视基坑围护中的防水问题[J],中国建筑防水,2000,1:18-22
[4]刘国彬,王洪新,上海浅层粉砂地层承压水对基坑的危害及治理[J],岩土工程学报,2002,24(6):790-792
[5]朱雁飞,深基坑工程中承压水危害的综合治理方法(上)[J],上海建设科技,2008,4:16-19
[6]戴斌,王卫东,受承压水影响深基坑工程的若干技术措施探讨[J],岩土工程学报,2006,28(增):1659-1663
[7]郑刚,焦莹,深基坑工程设计理论及工程应用[M],北京:中国建筑工业出版社,2010,12:379-380
[8]夏明耀,曾进伦,地下工程设计施工手册[M],北京:中国建筑工业出版社,2002
[9]建筑基坑支护技术规程(JGJ120-99)[S],北京:中国建筑工业出版社,1999
[10]梁勇然,条形基坑的突涌分析[J].岩土工程学报,1996,18(1):75-79
[11]李建交,屠厚泽,关于矩形基坑中突涌问题的分析与探讨[J].地质科技情报,1998,17(3):91-94
[12]杜贵成,改进的条形基坑突涌判别式[J],辽宁工程技术大学学报,1998,17(5):507-510
[13]马石城,印长俊,邹银生,抗承压水基坑底板的厚度分析与计算[J],工程力学,2004,21(2):204-208
[14]谭松林,考虑土体强度的建筑基坑突涌问题分析[J],地球科学-中国地质大学学报,2002,27(2):209-212
[15]张云,梁勇然,基于BP神经网络的基坑突涌分析[J],工程勘察,2001,2:22-25
[16]丁春林,王东方,基于塑性破坏的承压水基坑突涌计算模型研究[J].工程力学,2007,24(11):126-131
[17]丁春林,软土地区弱透水层承压水基坑突涌计算模型研究[J],工程力学,2008,25(10):194-199
[18]吴林高,工程降水设计施工与基坑渗流理论[M],北京:人民交通出版社,2003
[19]《工程地质手册》编委会,工程地质手册[M],北京:中国建筑工业出版社,1992
[20]刘国彬,王卫东,基坑工程手册[M],北京:中国建筑工业出版社,2009
[21]陈仲颐,叶书麟主编,基础工程[M ],北京:中国建筑工业出版社,1997
[22]李超胜,何爽,刘珣,基坑抗突涌计算方法的对比分析[J],安全与环境工程,2008,15(3):110-113
[23]李琳,杨敏,张慧,承压水作用下圆形基坑底板突涌的临界厚度计算公式[J],勘察科学技术,2006,5:13-15
[24]李涛,王超,高承压水地层开挖基坑底板隆起稳定性分析[J],岩土工程学报,2009,31(8):1236-1341
[25]杨建民,郑刚,基坑降水中渗流破坏归类及抗突涌验算公式评价[J],岩土力学,2009,30(1):261-264
[26]张丙印,于玉贞,张建民,高土石坝的若干关键技术问题[A],第九届土力学及岩土工程学术会议论文集[C],北京:清华大学出版社,2003:163-186
[27]陈五一,赵颜辉,土石坝心墙水力劈裂计算方法研究[J],岩石力学与工程学报:2008,27(7):1380-1386
[28]黄文熙,对土石坝科研工作的几点看法[J],水利水电技术,1982,4:23-27
[29]Lo K Y, Kiny K. Hydraulic fracture in earth and rock-fill dams [J]. Canadian Geotechnical Journal, 1990, 27(4): 496-506
[30]Bjerrum L, Andersen K H. In-situ measurement of later pressures in clay [A]. Proceeding of 5th European Conference on Soil Mechanics and Foundation Engineering[C]. Madrid: 1972. 333-342
[31]Vaughan P R. The use of hydraulic fracturing tests to detect crack formation in embankment dam cores [R]. London: Department of Civil Engineering, Imperial College, 1971
[32]Independent Panel to Review cause of Teton dam failure [R]. U S. Bureau of Reclamation, 1976, 1-10
[33]Nobari E S, Lee K L, Duncan J M. Hydraulic fracturing in zoned earth and rock fill dams [ R ]. Berkeley: University of California, 1973
[34]章定文,刘松玉,土体中水力劈裂研究进展[J],水利水运工程学报,2006,2:71-78
[35]孙亚平,水力劈裂机理研究[D],北京:清华大学,1985
[36]张丙印,李娜,李全明等,土石坝水力劈裂发生机理及模型试验研究[J].岩土工程学报,2005,27(11):1277-1281
[37]王俊杰,朱俊高,堆石坝心墙抗水力劈裂性能研究[J],岩石力学与工程学报,2007,26(增1):2880-2885
[38]朱俊高,王俊杰,张辉,土石坝心墙水力劈裂机制研究[J],岩土力学,2007,28(3):487-493
[39]Alfaro M C, Wong R C K. Laboratory studies on fracturing of low-permeability soils [J]. Canadian Geotechnical Journal, 2001, 38: 303-315
[40]冯晓莹,栾茂田,徐泽平,黏土心墙坝水力劈裂发生机理及判别方法[J],北京工业大学学报,2009,35(4):470-475
[41]Murdoch L C. Hydraulic fracturing of soil during laboratory experiments Part 1, Methods and observations [J]. Geotechnique, 1993, 43(2): 255-265
[42]殷宗泽,朱俊高,袁俊平等,心墙堆石坝的水力劈裂分析[J],水利学报,2006,37(11):1348-1353
[43]Lawrence C M. Mechanical Analysis of idealized shallow hydraulic fracture [J]. Journal of Geotechnical and Geoenvironmental Engineering, ASCE, 2002, 128(6): 488-495
[44]袁大军,黄清飞,小泉淳等,水底盾构掘进泥水喷发现象研究[J],岩石力学和工程学报,2007,26(11):2296-2301
[45]袁大军,黄清飞,李兴高,盾构掘进黏土地层泥水劈裂伸展现象研究[J],岩土工程学报,2010,32(5):104-105
[46] Cundall P A. PFC2D User’s Manual (Version2.0) [R].Minnesota: Itasca Consulting Group Inc, 1999
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