Cement mortar used for grouting while directional drilling and for reinforcing strata

The invention relates to the technical field of directional drilling construction of complex and instable strata like gravel-cobble, especially to a cement mortar used for grouting while directional drilling and for reinforcing strata. The cement mortar comprises, by mass, 91.5% of a mixture of water and cement, 0.5% of a wall protecting agent, 2% of a fluid loss agent, 2% of a filter cake improving agent, 2% of a viscosity reducer and 2% of a thixotropic agent, wherein the mass percents of the above-mentioned components sum to 100%, and a mass ratio of water to cement in the mixture of water and cement is 2: 1. The cement mortar is injected into strata during directional drilling; on the one hand, the cement mortar functions like common directional drilling slurry, and on the other hand, the cement mortar rapidly dehydrates and coagulates after entering into loose strata, exerting the effects of geological structure improvement and stratum reinforcement; thus, directional drilling crossing engineering of com