Design Principle of Shallow Earth Tunnel

随着日本主要人口地区的扩张，有必要建设新的铁路系统。考虑到环境保护，特别是在商业和居住区，地下铁路的规划和建设变得越来越普遍。在地下铁路建设中，从建筑成本和维护成本的角度考虑，为了排水、通风和交通安全以及乘客的方便，最好将土覆盖层留得尽可能薄。由于日本的主要城市位于广阔的冲积平原，地下水位高，软土地基占主导地位，隧道应安全地建造，而不会损坏相邻或覆盖的建筑物，街道或公用设施。过去，这些城市隧道通常采用明挖法或盾构法施工。近年来，在桑迪地层中，越来越多地采用常规法代替盾构法施工，这在很大程度上降低了隧道工程的造价。隧道掌子面及周围地层的稳定性; 2.与地下水条件有关的问题;隧道开挖对邻近或上覆建筑物及公用设施的影响，为了解决这些问题，最重要的是了解隧道开挖过程中周围地层的实际行为，并建立一种尽可能准确地模拟其行为的分析方法。本文的研究正是为了弄清这些问题，为薄盖高埋深土质隧道的施工建立设计原则。

As a result of expansion of the major population regions in Japan, it has become necessary to construct new railway systems. It is becoming more common that underground railways are planned and constructed in consideration of the environment preservation especially in commercial and residential areas. In underground railway construction, it is better to leave the earth covering as thin as possible from the point of view of construction cost and maintenance cost for drainage, ventilation and traffic safety as well as the convenience of passengers. Since the major cities of Japan are located in wide alluvial plains where soft ground with a high groundwater table prevails, tunnel should be built safely without damaging adjacent or overlying buildings, streets or public utilities. In the past, these urban tunnels have usually been constructed by cut and cover method or shield method. In recent years, however, use of the conventional method has been increasingly implemented in sandy ground tunneling in lieu of the shield method and this has resulted in reduction of the tunneling cost to great extent.when tunneling through ground with a thin cover and high groundwater table, it is necessary to investigate the following problems carefully :1. the stability of tunnel face and surrounding ground,2. problems related to underground water conditions, and3. the effect of tunneling on adjacent or overlying structures and public utilities.To work out these problems, it is most important to understand the actual behavior of the surrounding ground during tunnel excavation and to establish an analytical method which can simulate the behavior as accurately as possible. This research has been carried out to make clear these problems and to establish the design principle for the construction of earth tunnels with thin cover and high groundwater table.