Research On The Meso-corrosion Test And Treatment Of Salt Dissolution Disease Of Chaerhan Rock Salt Roadbed

The Qinhai Tibet Railway K720+500-K752+680section passes through the Qarhan Saline Lake, the subgrade of the railway in Saline Lake area directly built up by the salt formations with saturated brine, up to more than30km, which is called "Highest Salt Bridge". It is the first attempt to filling roadbed with rock salt in our country, and became a pioneering work in the history of railway construction. The main component of rock salt is sodium chloride, which has significant characteristics such as soluble in water,moisture absorption etc. It would cause salt soluble phenomena when encountering fresh water or low salinity brine, caused subgrade dissolution damage and even influence the safety of railway traffic.Qarhan area has many poor engineering properties such as collapsible, corrosive etc. In recent years, under the influence of abnormal climate in saline lake area, the surface of Dabsan Lake and some other lakes near the railway expands rapidly, low salinity lake water seepage and flood to Saline Lake subgrade. Moreover,due to over exploitation of potash fertilizer, brine water level began to decline, providing channel to the low salinity brine across the railway subgrade. Resulting in the subgrade engineering disease, such as the salt soluble Saline Lake subgrade slope surface cracking, embankment slope collapse etc, thereby directly affect the stability of the rock salt roadbed. This paper made a series of local and laboratory tests to counter Qarhan rock salt subgrade disease, analyze the different salinity brine impact on subgrade of salt dissolution, summarizes the subgrade dissolution mechanism and influence factors. With the help of computer tomography (CT), the internat meso-structure change of rock salt under dissolution were analyzed by scanning. At the meso-scopic level analyzes the influence of different salinity brine to rock salt dissolution,studies on the research of the rock salt structure internal micro cracks derivative and repairing. Based on micro data of CT number put forward the damage parameter, qualitative analysis the internal materials immigrate to repair and dissolution damage. Provide experiment basis for controlling the rock salt subgrade dissolution disease. On this basis, geological radar detection and digging exploration were applied on charhan rock salt subgrade, focused on the changes of brine salinity and the settlement deformation of subgrade, and using ADINA finite element element software to simulate the effect of the lake water on both sides of the subgrade. According to the different levels of subgrade salt dissolution damage, the roadbed disease prevention measures was put forward, such as setting several gravity drainage wells, evaporation pool, as well as on the both sides of the subgrade buried water stop plate and bored grouting on the existing dissolution pores, so that achieve the purpose of blocking brain on both sides, thus realize the comprehensive treatment of subgrade salt soluble disease in Charhan salt Lake area, provide a guarantee for the long-term stability of railway subgrade in Saline Lake area.