Preservation of earthen relic sites against salt damages by using a sand layer

Salt damage is one of the main problems facing the preservation of earthen sites in heritage museums. The use of salt-inhibiting materials on the surface of earthen sites to prevent damages could cause secondary damage. A method of placing a sand layer as a water and salt barrier was introduced and evaluated based on the law of unsaturated soil water and salt transport. The method involves placing a sand layer on the lower layer of the earthen site to inhibit the migration of water and salt from the deep soil to the surface of the earthen site. Experiments and numerical simulations were conducted to study the long-term effect and efficiency of water and salt barrier of sand layers with different particle sizes. The results show that the sand layer could successfully block the continuous upwards transport of water. The salt was shown to stagnate at the boundary between the bottom of the sand layer and the experimental soil. According to the simulation results, the water and salt barrier effect of the sand layer is proportional to the particle size of the sand layer. The sand layer with particle sizes much larger than the experimental soil has a durable water and salt barrier effect. These results are important for understanding the mechanism of salt damage to earthen sites and for the sustainable preservation of relics against salt damage in a soil environment.