Soil friction angle

It is observed that with the increase in values of soil friction angle (f>) and soil-wall interface friction angle (<5), the passive resistance increases significantly and the stability of gravity walls reduces with the increase in values of horizontal and vertical seismic accelerations. 

TABLE 9.10 Typical Value of Pile-Soil Friction Angles 5 ... 

Influence of Soil Strength Properties The soil strength properties, soil friction angle, soil cohesion, c, can also influence on the... 

Here, 4> = peak soil friction angle, co = wall/slope face inclination taken as positive in a clockwise direction from the vertical, 8 = interface friction angle at the back of the wall (or back of the reinforced soil zone), p = backslope angle taken from horizontal, and 0 = seismic inertia angle given by ... 

A pressure dependence of the internal angle of friction is known to represent the quantification of the pore space dependence of internal friction [3], Such a dependence has also been observed in wall friction experiments for the bed friction angle [5, 13] of soil. So, we must assume 6 = 6(p) and pressure dependence of friction angle with pressure [3,5,13], the simplest parameterisation is linear and we choose... 

Relative designation (2) Unconfined compressive strength in kilonewtons per square meter (pounds per square inch) (3) Ratio of stiffness of grouted to ungrouted soil (4) Friction angle, 4>r in degrees (5)... 

Where, Oj = maximum stress O3 = minimum stress c = cohesive force (p= friction angle. When f>0, the material will suffer shear failure. Under the normal stress conditions, the tensile strength of soil is low, and hence it is able to determine whether the rock has suffered tensile failure in accordance with the tensile strength criteria (ct, > 0, ). The rock mechanical parameters used in this paper were listed in Table 1. 

For an NC clay or a sandy clay in the grormd, a relation between S, tive friction angle (( ) ) can be derived as follows Consider a soil element at A in Figure 8.37. The major and minor effective principal stresses at A can be given by and K, a vo/ respectively. K is the coefficient of earth pressure at rest. Let the soil element be subjected to an unconsolidated rmdrained (UU) triaxial test. The total and effective stress Mohr s circles for this test, at failure, are shown in Figure 8.38. A review of this figure shows that at failure the total major principal stress is Oj = -I- AOj the total minor principal stress... 

Since a granular soil will drain under static loading conditions, the measured friction angle can be used in Figure 10.44 to determine the factor NJ for use in Equation 10.61 with c = o. 

Table 1 shows the effect of soil fnction angle (4>) and soil-wall interface friction angle ( ) on critical failure surface which is governed by the critical angles of logarithmic spiral (6 ), the rupture plane with the groimd surface () and t / T ratio fortypical values of k = 0.l, k = 0.05, ff/A= 0.3, ii/77= 0.16 and /= 1.0. It can be found from Table 1 that for constant ratio of 6 / 4>... 

Note ko = — sin ) (where is soil effective angle of friction). 

Serial number Soil type Unit weight Cohesive strength Friction angle Modulus of compression Poisson s ratio Layer thickness... 

Soil Density (kg/m ) Cohesion (c) (kPa) friction angle ((p) n Young s modulus (MPa)... 

In our investigation we consider the friction angle (p and the cohesion c of the soil as random variables. All other quantities are taken as deterministic values. Based on the measurements pubhshed in Moormaim... 

The steepness of capping system slopes ranges from 4 1 (14°) to 2.5 1 (22°), and the interface friction angles between adjacent geosynthetics can be from 8° to The soil load, with the combination of low interface... 

Soil layer Gs(MPa) Relative density Density (kg/cm ) Friction angle tp... 

Soil layers Voids ratio, e Relative density, Unit weight, ya kN/m Friction angle, cp ... 

The required soil configuration consists of a dense supporting layer and a medium dense backfill. The material proposed for both layers is Leighton Buzzard (LB) sand BS 881-131, Fraction B Dso — 0.82 mm, Gg = 2.64 Mg/m, = 0.486, max = 0.78). This particular soil has been used extensively in experimental research at Bristol and a wide set of strength and stiffness data is available (detailed references in Bhattacharya et al. 2012). The empirical correlation between peak friction angle (p and relative density D, provided by the experimental work of Cavallaro et al. (2001) was used for a preliminary estimation of the soil strength properties. 

The designer decided to ask the investigation department to calculate the stability of the cut slope. The faulted mud was taken for soil test, and the results show that the internal friction angle and cohesion of... 

Based on field trials, indoor routine testing, engineering analogy and parameter inversion methods, we have determined that the soil s bulk density of the slope is about 19.76 kN/m the internal friction angle O) is about 30° and the cohesion (C) is about 14 kPa in a natural state. 

Second method is shear test (Vane Cone Shear Test, VCST), in-situ cohesion and friction angle are independently measured in half an hour. Figure 8 shows relationship between VCST and tri-axial compression test or simple shear test in several soil samples. Initial torque, which is the torque when vertical load is zero, correlates to cohesion by tri-axial test. Furthermore, trend angle of approximation line by VCST correlates to friction angle. 

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