| 姓名 | 江秀旭(Shiu-Shu Chiang) | 電子郵件信箱 | s8751404@yam.com | |
| 畢業系所 | 營建工程系碩士班(Department and Graduate Institute of Constrction Engineering) | |||
| 畢業學位 | 碩士(Master) | 畢業時期 | 91學年第2學期 | |
| 論文名稱(中) | 互層軟岩隧道破壞模式探討 | |||
| 論文名稱(英) | Failure Mechanisms of Tunnels in Weak Rock with Interlayered Structures | |||
| 檔案 |
請遵守中華民國著作權法之相關規定，切勿任意重製、散佈、改作、轉貼、播送，以免觸法。 |
論文使用權限 | 校內外完全公開 | |
| 論文語文/頁數 | 中文/155 | |||
| 摘要(中) | 摘要 台灣西部麓山帶主要構成岩相多為沉積岩層，大多屬地質年代相當年輕之互層岩體區，其普遍存在固結差、膠結不良、遇水極易軟化等特性，以致於在山坡地中施工之隧道工程，常遭遇嚴重之擠壓、抽心、滑動及剝落等災害，往往造成機具損傷、工期延宕與經費增加。針對互層軟岩隧道之工程災害，本論文以碧潭及木柵隧道案例，採用以分離元素法為主之UDEC程式分析，模擬其破壞之原因、過程及模式，並研究互層岩體層面位態、層面傾度、層面間隔及側向應力係數對隧道破壞之影響。 模擬分析所得之破壞模式與碧潭及木柵隧道現地破壞狀況相符，由模擬所得之破壞過程與模式，可得到下列結論：(1)隧道在互層軟岩中其破壞模式，以層間滑動、擠壓及挫屈居多；(2)由數值模擬狀況，隧道位於節理岩體區時，除垂直節理外，其破壞驅動模式，大都由節理位置較上層區破壞，帶動頂拱沉陷，然後引發位置較低區節理破壞，(3)側向應力係數K=1.5時之隧道頂拱擠壓量，小於K=0.33時之隧道頂拱擠壓量；相反的K=1.5時之隧道側向擠壓量，大於K = 0.33時之隧道側向擠壓量。(5)高覆蓋之互層岩體隧道開挖，其覆蓋層上方地表較少發生沉陷之狀況；而低覆蓋之隧道開挖，其破壞除隧道內擠壓外，大部分伴隨覆蓋層地表沉陷，其沉陷狀況視岩體強度而定。(6)高強度、高覆蓋岩體會因岩體自重之關係，使得隧道頂拱因岩體重力向內擠壓，而高強度低覆蓋之岩體，則無此現象，此即為何歐洲大陸其隧道擠壓一般都發生在高覆蓋情形下。(7)高覆蓋岩體、高傾角單組節理岩體，較不可能發生坍塌破壞形式，此乃因節理長度在滑移過程中，仍然會提供節理間之殘餘之摩擦力，即殘餘剪力強度存在，因此較不可能如低覆蓋岩體隧道完全坍塌之現象產生。(8)當岩體強度參數高時，高覆蓋之隧道節理傾角90o時，其因岩體自重會使得隧道頂拱內擠，且大部分此類岩體較穩定。(9)一般岩體節理間距愈大，破壞情況會較趨於穩定，但如岩體強度極低，其節理間距愈大破壞會愈明顯且快速。 | |||
| 摘要(英) | ABSTRACT Formations of interlayered sandstone and shale are common deposits in northern and western parts of Taiwan. Construction problems and failures, such as large deformations and sliding in slopes and tunnels, had occurred very often in these formations. Tunnels constructed in these formations along the Northern Second Highway around Taipei area in Taiwan had encountered some serious failures, including squeezing, block falling, sliding, buckling, and caving, during construction. Two of the tunnels that experienced squeezing failures and caused subsequent massive caving and sliding of rock formation from the roof are evaluated and analyzed to reveal the actual causes of failure in this study. Impacts of discontinuity orientation and spacing of interlayered sandstone and shale on the tunnel failure modes are also analyzed and discovered through a series of numerical experiments. Numerical analyses using distinct element method were used to simulate and to understand the causes and related mechanisms of these two failure cases. The interlayered soft rocks had steeply dipping angles, 60 and 80 degrees for each of the tunnels, and had low frictional resistance between the interface of sandstone and shale. The thickness of interlayered sandstone and shale varied from several centimeters to several meters. The tunnel axes were all paralleled to the strike of the bedding plane. It was found that the failure processes of these two tunnels were all initiated from the squeezing failure of one of the sidewalls and then led to massive block sliding failure falling out of the roof along the bedding plane. The thickness, width, and location of the interlayered formation and the depth of overburden also greatly affect the stability of the tunnel. Discontinuity orientation and spacing of interlayered sandstone and shale will have great impacts on the tunnel stability and on the dominated failure mode. Tunnel will become more unstable as the joint spacing decreased. The major failure mode of the tunnel is changing from block falling from the roof, then sidewall squeezing, and to flexural tensile buckling as the joint dip changed from 90 to less than 10 degrees. Results of the analyses can be used for future tunnel construction in these interlayered formations to mitigate the possibility of failure and for suggestion of tunnel reinforcement. | |||
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