MEASUREMENTS OF THE BEARING CAPACITY OF TWO-LAYER SYSTEMS

The paper deals with measurements of the subgrade bearing capacity and of the subgrade improved by a layer of different materials. There are described the plate bearing tests on two-layer systems, constructed as models on silty soil subgrade. The materials of the improving layer were: sand and gravel, sand and gravel with geotechnical fabrics, sand and gravel with fibres, crushed stone (quarry and waste material), crushed stone with geotechnical fabric and with fibres. The static loading tests were made by rigid circular plates with area of 0,1 and 0,4 M2 and with double tyred wheel. The dynamic loading test was made by a falling weight deflectometer. Using the deflection values from measurements the e-modulus was calculated for elastic halfspace. A great difference in deflections and calculated e-modulus according to various method was estimated. The bearing capacity of the crushed stone (quarry waste material) layer was generally 1,6 times higher than the sand and gravel one. The significance of geotechnical fabrics under the layer of material is greater on subgrade with lower bearing capacity. Thin layer of sand and gravel on fabric is not effective. The additional load on surface has a great significance for measured deflection by static and dynamic load test. (a) (TRRL)