土木工程专业英语原文及翻译

发布时间：2024-01-28 13:22:39

徐 州 工 程 学 院
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08 级 土木(1 班课程考试试卷
徐州工程学院印制
Stability of Slopes 9.1 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 slope.Compound 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．
9.2 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, i.e. 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 La
where F is the factor of safety with respect to shear strength．Equating moments about O：
Therefore

(9.1
The moments of any additional forces must be taken into account．In the event of a tension crack
developing ，as shown in Fig.9.2，the arc length La 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[9.9]published stability coefficients for the analysis of homogeneous slopes in terms of total stress．For a slope of height H the stability coefficient (Ns for the failure surface along which the factor of safety is a minimum is
(9.2 For the case ofφu =0，values of Nss depends on the slope angleβand the depth factor D，where DH is the depth to a firm stratum．
Gibson and Morgenstern [9.3] published stability coefficients for slopes in normally consolidated clays in which the undrained strength cu(φu =0 varies linearly with depth．
Example 9.1 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 cu =65 kN／m2 andφu
In Fig.9.4, the cross-sectional area ABCD is 70 m2. Weight of soil mass=70×19=1330kN／m The centroid of ABCD is 4.5 m from O．The angle AOC is 89.5°and radius OC is 12.1 m．The arc length ABC is calculated as 18.9m．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 9.2. From Fig.9.3，β=45°and assuming that D is large，the value of Ns
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(τfto the shear strength(τm which must be mobilized to maintain a condition of limiting equilibrium, i.e. The factor of safety is taken to be the same for each slice，implying that there must be mutual support between slices，i.e. forces must act between the slices．
The forces (per unit dimension normal to the section acting on a slice are： 1.The total weight of the slice，W=γb h (γsat where appropriate． 2.The 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．
3.The shear force on the base，T=τml.

土木工程专业英语原文及翻译

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