Construction method of foundation pit support structure in existing building in karst area

The invention discloses a construction method of a foundation pit support structure in an existing building in a karst area, and belongs to the technical field of urban underground construction. The construction method of the foundation pit support structure in the existing building in the karst area comprises the steps that S101, the karst area in the building is surveyed; s201, karst pretreatment is conducted, the karst caves are divided into unfilled karst caves, partially filled karst caves and fully filled karst caves according to the size, the filling condition, the burial depth and the stratum condition of the caves according to the exploration result of S101, and filling and grouting are conducted on the ground caves; and S301, filling the hole body, judging the depth of the hole body and the stratum condition according to the survey result of the S101, and performing grouting by drilling and pipe burying. By means of the construction method of the foundation pit support structure in the existing buil