Effects of Gravel on Water Retention Capability of Purple Gravelly Soils in a Hilly Area

By the experiments of water retention capability for the red-brown purple soils,grey-brown purple soils,and brown purple soils that were disturbed or undisturbed,the effects of gravel on water retention capabilities of purple gravelly soils in a hilly area were studied.Results showed that by considering gravel of undisturbed soils,the saturated water contents were reduced by 0.70%~10.70% and the field capacities,by 2.07%~4.33%.When the gravel content was less than 10%,it did not have an obvious relationship with the saturated water contents and field capacities of undisturbed soils.When the gravel content was more than 10%,the saturated water contents and field capacities increased with the decreased gravel content.At 0~30 kPa,the water-holding capacities and the a values of power functions for undisturbed and disturbed soils,the clay contents of undisturbed soils,and the specific water capacities of disturbed soils were all increased with the decreased gravel content.The specific water capacities of undisturbed soils decreased with the decreased gravel content.