兰州交通大学博文学院毕业设计（论文）
倒灌。此外，在泄水孔入口附近应用易渗的粗颗粒材料做反滤层，并在泄水孔入口下方铺设粘土夯实层，防止积水渗入地基不利于墙的稳定性。泄水孔的布置应错开呈梅花桩式，以免在某一个面上形成软弱层，影响挡土墙的稳定性。
（3）排水沟。主要用途在于引水，将路基范围内的各种水源水流引至桥涵或路基范围内的指定地点。采用梯形截面，25cm厚5号浆砌片石加固，并设15cm厚砂砾垫层。
2．5．3沉降缝和伸缩缝的设置：为避免地基不均匀沉降引起墙身开裂，需按墙高和地基性质的变异，设置沉降缝，同时，为了减少圬工砌体因收缩硬化和温度化作用而产生裂缝，需设置伸缩缝。挡土墙的沉降缝和伸缩缝设置在一起，每隔10m设置一道，缝宽3cm，自墙顶做至基底，缝内宜用沥青麻絮、沥青竹绒或涂以沥青的木板等具有弹性材料，沿墙的内、外、顶三侧填塞，填塞的深度为20cm.公路挡土墙是路基防护工程的重
要组成部分。在山区公路中，挡土墙的应用更为广泛。挡土墙设计时，应进行详细地调查、勘测，确定构造物的形式与尺寸，运用合适的理论计算土压力，并进行稳定性和截面强度方面的验算，采取合理、可行的措施，以保证挡土墙的安全性。扶壁式挡土墙结构是在重力式挡土墙的基础上因地制宜发展而来的，实际工程中，可采取联合的结构形式，其计算方法基本相同。对于多地震带的地区，只要在地基应力允许的条件下，应尽量扩大抗滑计算值。
结束语
随着毕业日子的到来，毕业设计也接近了尾声。经过几个月的奋战我的毕业设计终于完成了。在没有做毕业设计以前觉得毕业设计只是对这几年来所学知识的单纯总结，但是通过这次做毕业设计发现自己的看法有点太片面。毕业设计不仅是对前面所学知识的一种检验，而且也是对自己能力的一种提高。通过这次毕业设计使我明白了自己原来知识还比较欠缺，自己要学习的东西还太多。通过这次毕业设计，我才明白学习是一个长期积累的过程，在以后的工作、生活中都应该不断的学习，努力提高自己知识和综合素质。
在这次毕业设计中也使我们的同学关系更进一步了，同学之间互相帮助，有什么不懂的大家在一起商量，听听不同的看法对我们更好的理解知识，所以在这里非常感谢帮助我的同学。
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兰州交通大学博文学院毕业设计（论文）
总之，不管学会的还是学不会的的确觉得困难比较多，真是万事开头难，不知道如何入手。最后终于做完了有种如释重负的感觉。此外，还得出一个结论：知识必须通过应用才能实现其价值！有些东西以为学会了，但真正到用的时候才发现是两回事，所以我认为只有到真正会用的时候才是真的学会了。
致谢
在此要感谢我的指导老师米海珍和乔雄对我悉心的指导，感谢老师给我的帮助。在设计过程中，我通过查阅大量有关资料，与同学交流经验和自学，并向老师请教等方式，使自己学到了不少知识，也经历了不少艰辛，但收获同样巨大。在整个设计中我懂得了许多东西，也培养了我独立工作的能力，树立了对自己工作能力的信心，相信会对今后的学习工作生活有非常重要的影响。而且大大提高了动手的能力，使我充分体会到了在创造过程中探索的艰难和成功时的喜悦。虽然这个设计做的也不太好，但是在设计过程中所学到的东西是这次毕业设计的最大收获和财富，使我终身受益。
设计参考文献
[1]
中华人民共和国国家标准，《建筑边坡工程技术规范》（GB50330—2002），人民
交通出版社，北京，2002；
[2] [3] [4] [5] [6] [7] [8]
陈忠达，《公路挡土墙设计》，人民交通出版社，北京，1999； 赵树德，《土力学》，高等教育出版社，北京，2002； 池淑兰，《路基及支挡结构》，中国铁道出版社，北京，2002； 邓学均，《路基路面工程》，人民交通出版社，北京，2002； 冯忠居，《基础工程》，人民交通出版社，北京，2002； 《基础工程分析与设计》， 中国建筑工业出版社；
朱彦鹏，《混凝土结构设计原理》，重庆大学出版社，重庆，2002；
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兰州交通大学博文学院毕业设计（论文）
[9]
张雨化，朱照宏，《道路勘测设计》，人民交通出版社，北京，1997；
[10] 中华人民共和国国家标准，《公路工程技术标准》（JTG B01-2003）人民交通出
版社，北京，2004；
[11] 其他与设计相关的资料等。
附：英文翻译
LIMIT ANALYSIS OF SOIL SLOPES SUBJECTED TO PORE-WATER PRESSURES
By J.Kim R.salgado, assoicite member, ASCE ,and H.S., member,ASCE
ABSTRACT: the limit-equilibrium method is commonly, used for slope stability analysis. However, it is well known that the solution obtained from the limit-equilibrium method is not rigorous, because neither static nor kinematic admissibility conditions are satisfied. Limit analysis takes advantage of the lower-and upper-bound theorem of plasticity to provide relatively simple but rigorous bounds on the true solution. In this paper, three nodded linear triangular finite elements are used to construct both statically admissible stress fields for lower-bound analysis and kinematically admissible velocity fields for upper-bound analysis. By assuming linear variation of nodal and elemental variables the determination of the best lower-and upper-bound solution maybe set up as a linear programming problem with constraints based on the satisfaction of static and kinematic admissibility. The effects of pro-water pressure are considered and incorporated into the finite-element formulations so that effective stress analysis of saturated slope may be done. Results obtained from limit analysis of simple slopes with different ground-water patterns are compared with those obtained from the limit-equilibrium method. INTRODUCTION
Stability and deformation problem in geotechnical engineering are boundary-value problem; differential equations must be solved for given boundary conditions. Solutions are found by solving differential equations derived from condition of equilibrium, compatibility, and the constitutive relation of the soil, subjected to boundary condition. Traditionally, in soil mechanics, the theory of elasticity is used to set up the differential equations for deformation problems, while the theory of plasticity is used for stability problems. To obtain solution for loadings ranging from small to sufficiently large to cause collapse of a portion of the soil mass, a complete elastoplastic analysis considering the mechanical behavior of the soil until failure may be thought of as a possible method. However, such an elastoplastic analysis is rarely used in practice due to the complexity of the computations. From a practical standpoint, the primary focus of a stability problem is on the failure condition of the soil mass. Thus, practical solutions can be found in a simpler manner by focusing on conditions at impending collapse.
Stability problem of natural slopes, or cut slopes are commonly encountered in civil engineering projects. Solutions may be based on the slip-line method, the limit-equilibrium
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兰州交通大学博文学院毕业设计（论文）
method, or limit analysis. The limit-equilibrium method has gained wide acceptance in practice due to its simplicity. Most limit-equilibrium method are based on the method of slices, in which a failure surface is assumed and the soil mass above the failure surface is divided into vertical slices. Global static-equilibrium conditions for assumed failure surface are examined, and a critical slip surface is searched, for which the factor of safety is minimized. In the development of the limit-equilibrium method, efforts have focused on how to reduce the indeterminacy of the problem mainly by making assumptions on inter-slice forces. However, no solution based on the limit-equilibrium method, not even the so called “rigorous” solutions can be regarded as rigorous in a strict mechanical sense. In limit-equilibrium, the equilibrium equations are not satisfied for every point in the soil mass. Additionally, the flow rule is not satisfied in typical assumed slip surface, nor are the compatibility condition and pre-failure constitutive relationship.
Limit analysis takes advantage of the upper-and lower-bound theorems of plasticity theory to bound the rigorous solution to a stability problem from below and above. Limit analysis solutions are rigorous in the sense that the stress field associated with a lower-bound solution is in equilibrium with imposed loads at every point in the soil mass, while the velocity field associated with an upper-bound solution is compatible with imposed displacements. In simple terms, under lower-bound loadings, collapse is not in progress, but it may be imminent if the lower bound coincides with the true solution lies can be narrowed down by finding the highest possible lower-bound solution and the lowest possible upper-bound solution. For slope stability analysis, the solution is in terms of either a critical slope height or a collapse loading applied on some portion of the slope boundary, for given soil properties and/or given slope geometry. In the past, for slope stability applications, most research concentrated on the upper-bound method. This is due to the fact that the construction of proper statically admissible stress fields for finding lower-bound solutions is a difficult task. Most previous work was based on total stresses. For effective stress analysis, it is necessary to calculate pore-water pressures. In the limit-equilibrium method, pore-water pressures are estimated from ground-water conditions simulated by defining a phreatic surface, and possibly a flow net, or by a pore-water pressure ratio. Similar methods can be used to specify pore-water pressure for limit analysis.
The effects of pore-water pressure have been considered in some studies focusing on calculation of upper-bound solutions to the slope stability problem. Miller and Hamilton examined two types of failure mechanism: (1) rigid body rotation; and (2) a combination of rigid rotation and continuous deformation. Pore-water pressure was assumed to be hydrostatic beneath a parabolic free water surface. Although their calculations led to correct answers, the physical interpretation of their calculation of energy dissipation, where the pore-water pressures were considered as internal forces and had the effect of reducing internal energy dissipation for a given collapse mechanism, has been disputed. Pore-water pressures may also be regarded as external force. In a study by Michalowski, rigid body rotation along a log-spiral failure surface was assumed, and pore-water pressure was calculated using the pore-water pressure ratio ru=u/ǐz, where u=pore-water pressure, ǐ=total unit weight of soil, and z=depth of the point below the soil surface. It was showed that the pore-water pressure has no influence on the analysis when the internal friction angle is equal to zero, which
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兰州交通大学博文学院毕业设计（论文）
validates the use of total stress analysis with Φ=0. In another study, Michalowski followed the same approach, except for the use of failure surface with different shapes to incorporate the effect of pore-water pressure on upper-bound analysis of slopes, the writers are not aware of any lower-bound limit analysis done in term of effective stresses. This is probably due to the increased in constructing statically admissible stress fields accounting also for the pore-water pressures.
The objectives of this paper are (1) present a finite-element formulation in terms of effective stresses for limit analysis of soil slopes subjected to pore-water pressures; and (2) to check the accuracy of Bishop’s simplified method for slope stability analysis by comparing Bishop’s solution with lower-and upper-bound solution. The present study is an extension of previous research, where Bishop’s simplified limit-equilibrium solutions are compared with lower-and upper-bund solutions for simple slopes without considering the effect of pore-water pressure. In the present paper, the effect of pore-water pressure is considered in both lower-and upper-bound limit analysis under plane-strain conditions. Pore-water pressures are accounted for by making modifications to the numerical algorithm for lower-and upper-bound calculations using linear three-noded triangles developed by Sloan and Sloan and Kleeman. To model the stress field criterion, flow of linear equations in terms of nodal stresses and pore-water pressures, or velocities, the problem of finding optimum lower- and upper-bound solutions can be set up as a linear programming problem. Lower- and upper-bound collapse loadings are calculated for several simple slope configurations and groundwater patterns, and the solutions are presented in the form of chart.
LIMIT ANALYSIS WITH PORE-WATER PRESSURE Assumptions and Their implementation
Limit analysis uses an idealized yield criterion and stress-strain relation: soil is assumed to follow perfect plasticity with an associated flow rule. The assumption of perfect plasticity expresses the possible states of stress in the form
' F(?ij) = 0 (1)
''Where F(?ij) = yield function; and?ij = effective stress tensor.
Associated flow rule defines the plastic strain rate by assuming the yield function F to coincide with the plastic potential function G, from which the plastic strain rate ?ijp can be obtained though ?ijp???G?F?? （2） ''??ij??ij
where ?= nonnegative plastic multiplier rate that is positive only when plastic deformations occur.
Eq. (2) is often referred to as the normality condition, which states that the direction of plastic strain rate is perpendicular to the yield surface. Perfect plasticity with an associated with very large displacements are of concern. In addition, theoretical studies show that the
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