都市中維生管線眾多，為顧及景觀與街道空間視覺舒適，管線大多埋設於地下。常見地下管線之施工方法分為明挖及非明挖兩大類，近年來為降低施工對地面交通的衝擊，常採用推進之免開挖工法。為增加推進距離，減少中押裝置數量，常在地下推進作業中，灌入滑材以減低推管與土壤間之摩擦，並可避免推力過大導致管材破裂等問題。滑材材料通常為皂土液，有時亦摻入一些特殊混合料或油料。本研究針對推進工程中常用之滑材材料，即皂土及柔軟精，利用直接剪力試驗儀，以重模土壤及模擬管材進行直接剪力試驗及摩擦試驗，探討土壤之剪力強度性質及推管管壁與土壤間之摩擦性質，以推估推管與土壤間經由滑材輔助所減低摩擦力之效益。由實驗結果可知，滑材確可大幅降低推管管壁與土壤間之摩擦角，尤以皂土液最為顯著。此外，本研究考量地中應力之方向性，提出一計算推管推力之簡便公式，藉由此公式之估算，更明確証實加入滑材確可降低推管摩擦力，提高施工效率。Lots of lifelines are necessary and to be set in urban area. To keep the space and visual comfort of street, these lifelines are usually embedded underground. Two kinds of methods, i.e. open cut and trenchless method, are commonly used in the construction of underground pipelines. Recently, to avoid the impact of street transportation, jack method was used frequently as the trenchless method. Furthermore, to increase the pushing distance of pipe and to decrease the number of middle jack devices, some kinds of lubricating materials are injected onto the interface of pipe and soil. This may also avoid the rupture of pipes due to too large pushing force. Bentonite slurry is commonly used as lubricating material, but sometimes it may be mixed with oil or some other special materials. To investigate the effects of friction reduction of lubricating materials between pipe surface and soil, this research used remolded soil and pipe material and focused on the properties of bentonite and softener which are usually used as lubricating materials in JACK method, and performed a series of direct shear tests and direct friction tests by using direct shear apparatus. From the results of experiments, it is recognized that the lubricating materials can decrease the friction angle between pipe surface and soil apparently, especially for bentonite slurry. Furthermore, this research proposed a convenient formula to estimate the jacking force of pipe by considering the anisotropy of stress in subsoil layer. According to the calculating results with this formula, it is proved definitely that the friction between pipe surface and soil can be decreased apparently by adding lubricating materials.
