圖書典藏及影音數位平台

本地質探查報告為石門水庫阿姆坪防洪防淤工程可行性規劃之地質調查成果，地質調查評估係針對方案D-5路線，完成地表地質複核，地質鑽探12孔總深度1000公尺，現地及室內岩石試驗，地下水位量測7孔，地電阻影像剖面探測全線施作共4,200公尺，煤礦坑補充調查，路線工程地質及隧道特殊地質評估，繪製路線地質平面圖(1/10,000)、隧道沿線地質平剖面圖(1/5,000)、進出水口地質平剖面圖(1/1,000)、路線工程地質評估剖面圖。 計畫路線自阿姆坪以直線往#10及#11沉澱池，通過地層及構造由進水口往出水口包括桂竹林層、南莊層、南港層、石底層、新店斷層及卓蘭層，地質綜合評估成果摘要說明如下。 (一)進水口：位於一平坦之階地堆積層上，基盤為桂竹林層，岩石單壓強度約50kg/cm2，屬甚弱岩石，推估高程約在233~234公尺間，地層層面與洞口邊坡成順向坡，唯層理不發達，形成大規模平面破壞之可能性低，但由於岩石強度低，膠結不佳，邊坡降挖需留意邊坡穩定。階地外圍為傾斜之斜坡，與目前水庫之淤積面高程212約有23公尺之落差，引水管自平坦之階地上往水庫方向延伸，與此斜坡約略成平行，兩支引水管於高程上將會出現明顯落差。 (二)出水口：位於台4線省道下方，地層屬卓蘭層，岩性以砂岩夾頁岩為主，岩石單壓強度約50kg/cm2，屬甚弱岩石，部分岩體呈未膠結之鬆砂狀態。尾水渠道通過#10及#11沉澱池，此區段原為河階堆積層已移除作為容納水庫淤泥之空間，淤泥需進行固化處理。河階堆積層下方基盤為卓蘭層，高程約為105~107公尺，尾水渠道結構物基礎無法座落於岩盤面上，挑流工所在之岩盤岩石強度較低，為低至中耐久性，岩盤易受沖刷應進行保護。 (三) 本計畫隧道自里程0K-150至3K+675，全長約3,825公尺，最大覆蓋約為310公尺，通過湳仔溝溪覆蓋約為52公尺，可能遭遇工程地質問題及對策，整理如摘表1及摘圖一，並分別說明如下： 1、隧道於進洞後之150公尺，覆蓋厚度小於1D，通過桂竹林層岩性主要為膠結不佳之砂岩，岩體自持性差，隧道開挖可考慮採前進支撐及地盤改良等方法加以克服。 2、里程0+120~0+960通過南莊層，99BH-16(0K+450)鑽孔岩心至91公尺深均有鏽染情形，顯示此區域曾經歷地下水位返復的升降，目前水位約在地表下10公尺，水位甚高，地電阻影像剖面探查結果，亦顯示可能為含水層，有凝灰岩存在，似乎形成地下水變化之邊界，隧道通過0K+350~700區間需留意地下水問題，建議基設階段進行補充調查。 3、隧道里程0+960~1+800通過南港層，地電阻影像剖面探查顯示通過湳仔溝溪(1K+280~1K+370)可能為含水層，此區段最小覆蓋厚度僅52公尺，岩盤為堅實砂岩，透水度低，不致發生大量湧水。通過砂岩段有受壓水層，為水包型式。 4、隧道於里程1K+970~2k+130間通過石底層之4煤層，極可能遭遇有害性氣體地盤，隧道施工應加強隧道之通風排氣。未開採的煤層如同地層中之弱帶，煤層與鄰接岩層之間的抗剪強度極低，岩層容易沿著煤而發生滑動破壞。煤層本身之強度低、變形性高，隧道通過煤層上方時，則必須考慮沉陷量過大或不均勻沈陷的問題，建議於基設籍施工階段進行補充調查。 5、隧道於里程2+170~2+230通過新店斷層，由鑽孔中剪裂破碎夾泥之狀況，推估隧道通過剪裂破碎帶之長度為60公尺，擾動帶寬度則可能達120公尺，斷層泥未含膨脹性黏土。隧道通過新店斷層屬中度危害之斷層破碎帶，並伴隨高度擠壓問題，建議進行施工中前進探查確認，及固結灌漿方式克服。 6、里程2+230~3+675通過卓蘭層，屬於強度較低之B岩類，，另隧道出口處之99BH-12水平鑽孔於鑽探完成後孔口持續出水，地電阻影像剖面探查亦顯示3K+380~3K+530可能為含水層。由於卓蘭層膠結度不佳之性質，岩體自持性差，其可能之影響範圍建議進一步調查釐清，可考慮採前進支撐及地盤改良等方法加以克服。 7、隧道近出口處通過台4線省道下方，隧道上方之岩盤覆蓋僅1.5D，淺覆蓋長度約100 公尺，岩體自持性不佳，隧道開挖可考量採管冪工法配合地盤改良，以避免對交通造成影響。

This report is the result of geology explore with Shihmen Reservoir Amupin anti-silt project, geology estimate base on D-5 line. Geology explore finished 12 Boreholes and the total length was 1000 m, the terrain experiment and rock tests, 7 boreholes of the groundwater measurement, 4200 m of the RIP profile, addition explore of the coal mine location, tunnel geology estimate, Geological investigation of water entrance and exit already finished the tunnel geological plan and geological section(1/5000 and 1/10000), tunnel portal and local water conservancy project geological plan and section (1/1,000). In this project, tunnel passed through several strata as: the Shiti Formation, the Nankang Formation and the Cholan Formation. Main geological structure is the Hsintien Fault, the geology estimate as follows: 1、Tunnel inlet ： Tunnel inlet is located on an accumulative terrace and the based rock is the Kueichulin Formation. The rock Simple Compression Test is about 50kg/cm2. The elevation is about 233~234 meters. The stratification plane and tunnel portal side slope formed dip slope, but the stratification was not developed well and the possibility of large scale plane failure was less. Excavate under gentle slope needs to care the slope stability because the cement rock is weak and poor. The slope terrain is surrounded with the accumulative terrace and the elevation difference between terrace and reservoir silt plan was about 23 meters. The water pipes extend to reservoir way from terrace and parallel with slope. Two of the pipes will show obvious elevation difference. 2、Tunnel outlet： Tunnel outlet is located under Tai No.4 Line province way and the laccolith is the Cholan formation. The lithology is sandstone interbedded with some shale which is weak and poor and the rock Simple Compression Test is about 50kg/cm2. The tailrace tunnel which was accumulative terrace but now already remove and use to hold silt of reservoir passes through #10 and #11 settle poor. The base of accumulative terrace is the Cholan Formation. The elevation is about 105-107 meters and the tailrace tunnel foundation could not be located on the base rock plan. It is need to discrete consideration the water erosion to affect to weak laccolith. 3、Tunnel： The tunnel started from mileage 0K-150 to 3K+675 and the maximum overburden range was about 310 meters. The overburden in Nantzugo River though area was about 52 meters. Possible engineering geology problem and situation as table A-1, descriptions as following: 1、About 150 meters later at tunnel inlet, the overburden range is less than 1D. The laccolith passed though area is weak cementation sandstone of the Kueichulin Formation. To avoid tunnel failure and collapse suffering, excavation processing could consider to forward support and ground stabilization methods. 2、The area of mileage 0+120~0+960 passed though the Nanchuang Formation. The borehole of No. 99BH-16(0K+450) showed rust traces at 91 meters depth from the ground surface. It revealed the ground water in this area have seen many times of fluctuation. The ground water level now is about 12 meter depth from ground surface and high position. The RIP result also showed it could be an aquifer. It needs to be careful of mine water problem in mileage 0K+350~700 area of the tunnel. 3、The area of mileage 0+960~1+800 passed though the Nankang Formation and Nantzugo river area (1K+280~1K+370) might be an aquifer showed by RIP result. The minimum overburden range of this area was just about 52 meters and the laccolith was sandstone. 4、The area of mileage 1K+970~2k+170 passed though four coal beds of the Shiti Formation. Tunnel excavation has much possibility to encounter gases ground base. Airway gears and ventilation system are very important. The coal beds had much lower shear strength in strata and liked a weak plan of rock and slide failure is easy to occur. The coal bed had low strength and high deformability. The settlement increases too much and unequal settlement problem is need to be consider. 5、The area of mileage 2K+170~2k+230 passed though the Hsintien fault. The fault zone length is about 60 meters and the width is about 120 meters by fault gouge observation in borehole. This area might occur high squeering problem. 6、The area of mileage 2+230~3+675 area passed though the Cholan Formation and belong to type B rock which is weak. The horizontal borehole of No. 99BH-12 at the outlet continued inflow after install finished and mileage 3K+380~3K+530 might be an aquifer showed by RIP result. Poorly cementation and weakly strength of the rock in the Cholan formation might to be scour out by ground water when tunnel excavation processing, it might cause collapse or base scour suffering. Forward support and ground stabilization methods could be consider in tunnel excavation. 7、The side of tunnel outlet passed though the underground area of Tai No.4 Line province way. The range of the overburden upper the tunnel was just 1.5D and the length of shallow overburden area was about 100 meters. Tunnel excavation could adopt pipe roof method and ground stabilization to overcome.