Những ngày này, phát triển kinh tế đòi hỏi chúng ta xây dựng các tòa nhà có quy mô lớn và cơ sở hạ tầng xã hội trong những khu vực có nền móng yếu như các khu vực ven biển và đầm lầy ven sông do sự sẵn có hạn chế của đất có nền tảng vững chắc. Như là một ví dụ ở Nhật Bản, đường băng thứ tư của sân bay Haneda đã chính thức được gọi là Tokyo Sân bay quốc tế đang được xây dựng như là một phần mở rộng của nó trong Tokyo bay ra khỏi cửa sông. | Foundation Improvement of the Deep Soil Layer Takashi TAKENAKA Water Research Co. Ltd. 1. Introduction These days economic development asks us to construct large-scale buildings and social infrastructures in the areas with weak foundation such as coastal areas and swamps along rivers due to the limited availability of land with solid foundation. As an example in Japan the fourth runway of Haneda airport officially called the Tokyo International Airport is under construction as part of its extension in the Tokyo bay off the estuary of the Tamagawa River. It is not reasonable for the foundation improvement of structures to apply the conventional method . replacement of weak soil layers by excavation in terms of costs as well as realistic issues of construction . under-water construction in case of the extension of the Haneda airport. Considering the above situation new technologies called Earth Drilling Method refer to Attachment-1 are widely applied to improve the weak foundation in Japan. This is a brief paper to introduce the Earth Drilling Method. 2. Characteristics of Earth Drilling Method As seen in Attaachment-1 there are several ways for the Earth Drilling Method of which we herein discuss the method to apply the drilling machine which has a function to inject soil hardening agent of which there are two types of powder and slurry at the same time. That is the drilling machine digs a hole by agitating soils and injects soil hardening agent to mix with agitated soils at the same time. After reaching to the necessary depth the drilling machine is pulled out by rotating the blade of drilling machine reverse. This reverse rotation of drilling machine acts as a compressor to consolidate the agitated soil mixed with the soil hardening agent. After drilling holes with an interval of 2 to 5 m to the longitudinal and horizontal directions making holes in the mesh form by the machine with the function to inject soil hardening agent the soil layers between holes .
