土木工程专业英语原文及翻译精选.docx

土木工程专业英语原文及翻译 土木工程专业英语原文 及翻译 文档编制序号：[KKIDT-LLE0828-LLETD298-POI08] 08 级土木(1) 班课程考试试卷 考试科目专业英语 考试时间 学生姓名 所在院系土木学院 任课教师 徐州工程学院印制 Stability of Slopes Introduction Translational slips tend to occur where the adjacent stratum is at a relatively shallow depth below the surface of the slope:the failure surface tends to be plane and roughly parallel to the slips usually occur where the adjacent stratum is at greater depth，the failure surface consisting of curved and plane sections． In practice, limiting equilibrium methods are used in the analysis of slope stability. It is considered that failure is on the point of occurring along an assumed or a known failure surface．The shear strength required to maintain a condition of limiting equilibrium is compared with the available shear strength of the soil，giving the average factor of safety along the failure surface．The problem is considered in two dimensions，conditions of plane strain being assumed．It has been shown that a two-dimensional analysis gives a conservative result for a failure on a three-dimensional(dish-shaped) surface． Analysis for the Case of φu =0 This analysis, in terms of total stress，covers the case of a fully saturated clay under undrained conditions, . For the condition immediately after construction．Only moment equilibrium is considered in the analysis．In section, the potential failure surface is assumed to be a circular arc. A trial failure surface(centre O，radius r and length L a where F is the factor of safety with respect to shear strength．Equating moments about O： Therefore The moments of any additional forces must be taken into account．In the event of a tension crack developing ，as shown in ，the arc length L a is shortened and a hydrostatic force will act normal to the crack if the crack fills with water．It is necessary to analyze the slope for a number of trial failure surfaces in order that the minimum factor of safety can be determined． Based on the principle of geometric similarity，Taylor[]published stability coefficients for the analysis of homogeneous slopes in terms of total stress．For a slope of height H the stability coefficient (N s) for the failure surface along which the factor of safety is a minimum is For the case ofφu =0，values of N ss depends on the slope angleβand the depth factor D，where DH is the depth to a firm stratum． Gibson and Morgenstern [] published stability coefficients for slopes in normally consolidated clays in which the undrained strength c u(φu =0) varies linearly with depth．Example A 45°slope is excavated to a depth of 8 m in a deep layer of saturated clay of unit weight 19 kN ／m3:the relevant shear strength parameters are c u =65 kN／m2 andφu In the cross-sectional area ABCD is 70 m2. Weight of soil mass=70×19=1330kN／m The centroid of ABCD is m from O．The angle AOC is °and radius OC is m．The arc length ABC is calculated as ．The factor of safety is given by： This is the factor of safety for the trial failure surface selected and is not necessarily the minimum factor of safety． The minimum factor of safety can be estimated by using Equation . From ，β=45°and assuming that D is large，the value of N s 9.3 The Method of Slices αand the height, measured on the centre-1ine,is h. The factor of safety is defined as the ratio of the available shear strength(τf)to the shear strength(τm) which must be mobilized to maintain a condition of limiting equilibrium, . The factor of safety is taken to be the same for each slice，implying that there must be mutual support between slices，. forces must act between the slices． The forces (per unit dimension normal to the section) acting on a slice are： total weight of the slice，W=γb h (γsat where appropriate)． total normal force on the base，N (equal to σl)．In general this force has two components，the effective normal force N'(equal toσ'l ) and the boundary water force U(equal to ul )，where u is the pore water pressure at the centre of the base and l is the length of the base． shear force on the base，T=τm l. total normal forces on the sides, E1 and E2. shear forces on the sides，X1 and X2. Any external forces must also be included in the analysis． The problem is statically indeterminate and in order to obtain a solution assumptions must be made regarding the interslice forces E and X：the resulting solution for factor of safety is not exact． Considering moments about O，the sum of the moments of the shear forces T on the failure arc AC must equal the moment of the weight of the soil mass ABCD．For any slice the lever arm of W is rsinα, therefore ∑Tr=∑Wr sinα Now, For an analysis in terms of effective stress， Or where L a is the arc length AC．Equation is exact but approximations are intr。