Under the influence of Wenchuan earthquake

it is more urgent to prevent and control debris flows in many provinces especially in Sichuan.The outbreak of debris flows has suddenness

now we give first place to its prevention.Compared to solid dams

the grille-dam with material saving and higher stability is used for debris flow disasters mitigation more and more widely.But there is no systematic method for grille-dam design.With reference to the theory for calculating the distance of comb-dam-piers we present a method to calculate the distance between two piers of grille-dam

and put forward a formula to calculate the distance of beams of grille-dam based on the existing experiment data.It changes the calculation situation

in which the distances on beams in different dams or in different parts of the dam are the same. Seeing that the distance between two piers is not large enough

taking the beam of grille-dam as a simply supported beam is not reasonable

we consider the beam to be a fixed beam and calculate the force caused by the big stone’s impact on the beam.The result from this mode is 3 times larger than that from simply supported beam mode.Finally

considering different situations of the dam after construction

detailed calculation condition for pier

beam and side dam of the grille-dam is presented

and on the basis of the design theory mentioned above

the design of control project of Lanni Gully debris flow is carried out.