【導(dǎo)讀】設(shè)計或科學研究的綜合訓(xùn)練，是前面各個教學環(huán)節(jié)的繼續(xù)、深化和拓展，是培養(yǎng)我們綜合素質(zhì)和工程實踐能力的重要階段。理論、基本理論和基本技能，分析和解決實際問題的能力。問題和解決問題，并可以繼續(xù)學習到一些新的專業(yè)知識，有所創(chuàng)新。失穩(wěn)的一種構(gòu)造物。在路基工程中，擋土墻可用以穩(wěn)定路堤和路塹邊坡，方、滑坡等路基病害。在山區(qū)公路中，擋土墻的應(yīng)用更為廣泛。為避免大量挖方及降低邊坡高度的路塹地段；可能產(chǎn)生塌方、滑坡的不良地質(zhì)地段；為節(jié)約用地、減少拆遷或少占農(nóng)田的地段。在考慮擋土墻的設(shè)計方案時，應(yīng)與其他方案進行技術(shù)經(jīng)濟比較。重力式擋土墻一般由塊石或混凝土材料砌筑。重力式擋土墻是靠墻。墻體內(nèi)設(shè)置鋼筋以承受拉應(yīng)力，故墻身截面較小。于缺乏石料的地區(qū)或地基承載力較差的地段。與重力式擋土墻相比，具有結(jié)構(gòu)輕、柔性大、工程量少、造。體穩(wěn)定和土的摩阻力大于由土自重和荷載產(chǎn)生的土壓力。擋土墻形式有重力式擋土墻和扶壁式擋土墻兩種。

　　

【正文】 ete 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 plexity of the putations. 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. 畢 業(yè) 設(shè) 計 第 42 頁 共 55 頁 Stability problem of natural slopes, or cut slopes are monly encountered in civil engineering projects. Solutions may be based on the slipline method, the limitequilibrium method, or limit analysis. The limitequilibrium method has gained wide acceptance in practice due to its simplicity. Most limitequilibrium 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 staticequilibrium 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 limitequilibrium method, efforts have focused on how to reduce the indeterminacy of the problem mainly by making assumptions on interslice forces. However, no solution based on the limitequilibrium method, not even the so called “rigorous” solutions can be regarded as rigorous in a strict mechanical sense. In limitequilibrium, 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 patibility condition and prefailure constitutive relationship. Limit analysis takes advantage of the upperand lowerbound 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 lowerbound solution is in equilibrium with 畢 業(yè) 設(shè) 計 第 43 頁 共 55 頁 imposed loads at every point in the soil mass, while the velocity field associated with an upperbound solution is patible with imposed displacements. In simple terms, under lowerbound 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 lowerbound solution and the lowest possible upperbound 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 upperbound method. This is due to the fact that the construction of proper statically admissible stress fields for finding lowerbound solutions is a difficult task. Most previous work was based on total stresses. For effective stress analysis, it is necessary to calculate porewater pressures. In the limitequilibrium method, porewater pressures are estimated from groundwater conditions simulated by defining a phreatic surface, and possibly a flow , or by a porewater pressure ratio. Similar methods can be used to specify porewater pressure for limit analysis. The effects of porewater pressure have been considered in some studies focusing on calculation of upperbound solutions to the slope stability problem. Miller and Hamilton examined two types of failure mechanism: (1) 畢 業(yè) 設(shè) 計 第 44 頁 共 55 頁 rigid body rotation。 and (2) a bination of rigid rotation and continuous deformation. Porewater 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 porewater pressures were considered as internal forces and had the effect of reducing internal energy dissipation for a given collapse mechanism, has been disputed. Porewater pressures may also be regarded as external force. In a study by Michalowski, rigid body rotation along a logspiral failure surface was assumed, and porewater pressure was calculated using the porewater pressure ratio ru=u/ǐz, where u=porewater pressure, ǐ=total unit weight of soil, and z=depth of the point below the soil surface. It was showed that the porewater pressure has no influence on the analysis when the internal friction angle is equal to zero, which 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 porewater pressure on upperbound analysis of slopes, the writers are not aware of any lowerbound 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 porewater pressures. The objectives of this paper are (1) present a finiteelement formulation in 畢 業(yè) 設(shè) 計 第 45 頁 共 55 頁 terms of effective stresses for limit analysis of soil slopes subjected to porewater pressures。 and (2) to check the accuracy of Bishop’s simplified method for slope stability analysis by paring Bishop’s solution with lowerand upperbound solution. The present study is an extension of previous research, where Bishop’s simplified limitequilibrium solutions are pared with lowerand upperbund solutions for simple slopes without considering the effect of porewater pressure. In the present paper, the effect of porewater pressure is considered in both lowerand upperbound limit analysis under planestrain conditions. Porewater pressures are accounted for by making modi