In-situ testing instrument and testing method for permeability coefficient of permeable pavement system

The invention discloses an in-situ testing instrument and testing method for a permeability coefficient of a permeable pavement system and belongs to the technical field of civil engineering. The in-situ testing instrument comprises the pavement system, a basic pipe fitting, a measuring pipe fitting and a water supply system, wherein the basic pipe fitting is vertically mounted in the pavement system, and the bottom end of the measuring pipe fitting is matched and connected with the top end of the basic pipe fitting; the water supply system comprises a water outlet pipe used for supplying water to the measuring pipe fitting, and a valve and a flowmeter are arranged on the water outlet pipe. The testing method comprises steps as follows: water is supplied to the measuring pipe fitting, so that the water reaches an overflow port and is prevented from being overflown, and the seepage flow is acquired through the flowmeter; and the seepage coefficient is acquired by dividing the seepage flow by the discharge area of the basic pipe fitting. In-situ measurement on the pavement is realized, the change of the permeability coefficient of the same location on the permeable pavement can be monitored for years, and a basis is provided for optimization design of the permeable pavement and selection of maintenance methods and opportunities.