Abstract:The fundamental features of shallow -hidden karst subsidence is groundwater going up and down frequently and lots of soil hole and limestone cave existing in shallow stata, which is hidden danger to railway safety. Clay hardening grouts is overwhelmingly superior to others when it is applied for consolidation on shallow-hidden karst roadbed in Louzhan Railway Line by stuff and horizontal curtain grouting, for example, its lower construction cost, simple and practical technology, good property in intercepting groundwater and anti-seismic capability. By testing, clay hardening grouts optimum prescription is made up of 20-45% clay, 10-30% cement, 3-5% water glass, 1-3% special hardening agent and viscosity of mud is above 30s. Shallow-hidden Karst roadbed has been consolidated by stuff and horizontal curtain grouting in Luozhan Railway Line, depth of which is about 5 meters. The outcome of several inspection measurements show a good quality of grouting consolidation construction has been achieved.