COLLAPSE CHARACTERISTIC OF LOESS UNDER STATIC LOADING AND DYNAMIC PENETROMETER TESTS

Loess has various particular properties. One of them is its collapsibility when inundated with water. Collapse deformation occurs on a large scale, at a great speed. A rapid degradation of mechanical characteristics takes place when loess is wetted at constant stress.After a brief review of various criteria which were utilized for identifying collapse soils and are based on laboratory tests, a new simple methods were proposed to evaluate in situ loess collapsibility with help of dynamic penetrometer tests and static loading tests. The method consists in carrying out penetrometer tests with a portable dynamic penetrometer of variable energy in natural and saturated conditions as a first step, a compressibility test (static loading test) is then performed after the cone penetrometer tests.The paper presents the procedure of in situ penetrometer testing and static loading testing. With the data measured in Central Loess Plateau in China, a detailed analysis of correlation between loess cone resistance q dnat  in natural conditions, q dsat  in saturated conditions, the index of collapsibility  s measured in laboratory and compressibility curve parameters (penetrometer limit pressure p pf , penetrometer creep pressure p pl  and penetrometer modulus E pn ) was taken. The results permit to state that the method proposed is suitable to characterize in situ loess collapsibility.