DEFORMABILITY AND STRENGTH CHARACTERISTICS OF THE SAND DUNES OF KARAKALPAKSTAN BASED ON TRIAXIAL TEST RESULTS

This paper presents the results of an experimental study of how the initial density of dune sand from the vicinity of Nukus, Karakalpakstan, affects its deformability and strength. Air-dry specimens were tested in a triaxial compression apparatus (stabilometer) using a consolidated-drained scheme with strain-controlled loading, at confining pressures of 100, 200 and 300 kPa and initial void ratios of 0.53, 0.65, 0.80 and 1.0. The dependences of deviator stress on vertical strain are nonlinear and convex toward the stress axis, and the volumetric strain changes only marginally during deviatoric loading. As the void ratio decreases from 1.0 to 0.53, the internal friction angle increases from about 38.7° to 42.3°, the cohesion from about 30 to 43 kPa, and the deformation modulus (at 100 kPa) from about 35 to 48 MPa; each parameter is described by a power function of the void ratio with R2 of 0.94–0.99. These dependences can be used in the design of sand cushions under shallow foundations in Nukus, provided they are applied within the tested range of stresses and densities.