Ground-penetrating Radar Detection Of Road Surface Water Content And Degree Of Compaction Applied Research,

Water content, the voids and the density of the pavement are important indexes. These indexes have important influence on qualities of road. Traditional method to evaluate road, such as bore and sampling, will not meet the demands, because they have many disadvantages such as low efficiency, low-precision, bad representation and destruction. Therefore, a new, rapid, high-precision, effective and nondestructive technology is required to meet the engineering demand.Ground Penetrating Radar (GPR) is developed recently and is a nondestructive technology for road detection in a few years. GPR works near the surface of the road and transmits electromagnetic (EM) wave to the pavement layers. When the electromagnetic wave propagates in the pavement layers, it will be reflected at the interface of two different kinds of medium. As we know, different medium have different dielectric constant. The reflected wave will be received by the receive antenna and transferred to digital data. We can analyze the data that saved by the computer of GPR to deduce the medium's property, situation, location and so on. Being a kind of nondestructive, untouched method, it has many advantages such as nondestructive, rapidness, simpleness and high precision, so it will have wide applications in the ways of examination, control and maintenance to road quality, especially for highway.But up to now, Ground Penetrating Radar (GPR) is mainly applied for road thickness detection and has still many jobs need to be completed. Moisture, the voids and the density of the pavement are expected for many operators in the road department. In order to promote the application of GPR to detect pavement quality as quickly as possible, in this paper some research works were zone. The mainly research results includes the following aspects:(1) Since the dielectric constants of pavement medium have important influence on radar detection results, dielectric properties of pavement layers materials are analyzed for the design of practical GPR system and field application.(2) Since central frequency of the antenna have important influence on depth and precision of detection results, frequency-dependence of dielectric constants of pavement medium are analyzed, and the range of central frequency are deduced using debye-model.(3) The principle of GPR to detect Moisture, the voids and the density of the pavement is analyzed and relevant formulae is educed.(4) Influence on reflected wave of the moisture of surface, base and subgrade andvoids of asphalt surface is analyzed and characteristic waves are simulated to offer reference to analyzing actual wave.(5) GPR tests were tried out in actual highway, then the practicability, rationality and accuracy are discussed in the bases of analyzing actual data. The results show that using GPR to survey pavement moisture and voids is an effective method.