Before tunnelling work on Tokyo-Nagoya Expressway, we made six horizontal borings as a geological survey, and good results were obtained.In this report we try to explain our boring technique, its efficiency, geological problems and some other considerations to be taken for the future. The three representative features of the horizontal boring are as follows:1. Continuously we can get necessary ... [Show full abstract] informations about the cross section of the proposed tunnel, such as distribution of rock properties, location of faults and cracking degree.2. We also continuously get the information about the condition of underground water.3. The geological survey will be done more economically and yet more precisely by adding the horizontal boring technique to the usual vertical boring method.