Shear box test

Figure 6, Design of Emboss Patterns for Shear Box Test...

Fig. 1. (a) Shear box test for powder adhesion and friction (b) plot of shear force versus load for a fine powder... 

The first ever equation used to describe adhesion between solids was devised by Coulomb in 1773 to explain the movement of soils under load. In a shear box test (Fig. la), a powder is loaded with a normal force N, and sheared with a force F. In general, the plot of F versns N (Fig. 1(b) does not pass throngh the origin but is displaced by an amount A on the horizontal axis. This displacement A represents the adhesive force pulling the particles into contact by Dispersion forces or other molecular attractions. Conlomb s eqnation describing this behavionr may be written as... 

Discussion of strength of soils as a one-dimensional concept seems to be beyond the realms of possibility. However, we can build up a model of strength of soils - using again our framework of critical state soil mechanics - from inspection of data from shear box tests. The use of this device as a source of data on strength and deformation of soils may seem eccentric. 

Fig. 3.21a. Shear stress as a function of horizontal displacement measured in the shear box test at various normal pressures (10, 20, 50, 100, 200, 300 kN/m ). The bottom diagram shows the static friction stress (maximum of the shear stress-displacement curve) as a function of normal pressure (strength or failure envelope). Shear-stress vs. displacement curves wiA sliding friction nearly eqirivalent to static friction are typical for embossed stractures in combination with a clay-mineral liner. Source of data is (Bliimel and Bmnunermarm 1994)...

Table 6.1. Collection of friction parameters from shear box tests (adhesion and friction angle) ...

Variation in friction parameters No substantial additional variation in friction parameters beyond test repeatability Shear-box testing of 30 cm-30 cm specimens in accordance with GDA E3-8... 

Texturing adhesion for applied texturing Behaviour in shear-box test No peel-off or removal of texturing Shear-box testing under compressive loads typical of landfills in accordance withGDAE 3-8... 

The effective shear strength can be tested in the laboratory by means of different test procedures such as a the direct shear test, simple shear test and the triaxial test. Normally testing is performed on saturated material. For every test setup, a clear distinction must be made between testing the material under drained or undrained conditions. From this point of view triaxial tests, type CU (Consolidated Undrained) or CD (Consohdated Drained) allow for a better control of the drainage conditions and porewater pressures than for instance shear box tests. For further elaboration on these types of tests, reference is made to textbooks on Soil Mechanics and laboratory testing (Head, 2006). 

Fill for use behind earth-retaining structures shall have a minimum internal friction angle of 33 degrees when compacted. The corresponding degree of compaction of the fill material shall be tested in a laboratory (triaxial or shear box tests). 

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