At present, many studies have been carried out on the fatigue mechanical properties of conventional rocks, but there are few studies on the mechanical properties of rocks after water rock interaction. The aim is to better study the fatigue mechanical characteristics of sandstone after dry wet cycle and the research object we take was sandstone samples after a certain number of drying and wetting cycles. The WAW-2000 electro-hydraulic servo pressure system was used to carry out uniaxial fatigue cyclic loading and unloading tests with different amplitudes and different upper limit stresses. The test found that: when the sample is damaged under fatigue load, the stress-strain curve shows a sharp downward trend and a sudden instability failure occurred in the sample.With the increase of the upper limit stress and amplitude, the life of the sample decreases gradually which also conforms to the change of power function. Then the relationship between fatigue life and stress is obtained. The fatigue stress-strain curve is characterized by sparse-dense-sparse. With the increase of cycle time, the axial strain of the sample shows an inverted “S” shape. The strain change can be divided into three stages: initial stage, constant velocity stage and acceleration stage.

The subject of this paper is a new procedure applied for more precise determination of material fatigue characteristics. The proposed approach is based on a special definition of the strain energy density parameter used for material fatigue property descriptions and, in the consequence, on the new algorithm of the fatigue machine control in the feedback loop. On the basis of fatigue tests under uniaxial tension-compression with the strain energy density parameter control it was proved that the fatigue characteristics in energy approach (Wa - N1) determined directly from the tests and indirectly from the Manson-Coffin relation (E,, - Nj) with the strain control for material showing cyclic stability are similar. However, for material cyclic hardening these characteristics differ significantly in high cycle fatigue regime.