台灣西部海岸線地下水長期受到養殖業、農業、工業等用途大量的開採，產生嚴重的區域地層下陷，將危及生命財產及公共運輸安全，根據東西向快速道路台78線道路與高鐵交會處附近之地表測量資料，顯示此區域每年的地表沉陷量以2008年的沉陷量最大，每年沉陷量約7.5cm至9.3cm左右。在2015/01至2015/05期間降雨量減少並碰上全台大缺水，土庫區宏崙站的地下水位亦是降至近十年來之最低點，和2013與2014年同期之地下水位差距達2公尺。因此，使得每年沉陷量由2014年的4.1cm至5.1cm左右提升至6.3cm。
本研究顯示利用單向度壓密試驗公式分析台78線公路路堤與高鐵墩柱各階段施工程序對地層下陷之影響，台78線公路路堤主要影響在地表下40公尺內，高鐵墩柱之影響主要在地表下40-300公尺內。交會處之高鐵墩柱的差異沉陷，從2003至2014/03之監測結果，在P7/512和P7/513之差異沉陷為36.7mm，P7/514和P7/515之差異沉陷量結果為30.4mm，而模擬分析結果，在P7/512和P7/513之差異沉陷為40.9mm，P7/514和P7/515之差異沉陷量結果為27.7mm，結果相當接近。
為探討交會處因地下水位變化引致地層下陷的問題，在考慮不受高鐵或台78線道路的影響下，以交會處測沉磁環監測站STA9監測結果作為模擬比較的對象。利用現地監測資料，運用逆解析法取得土層的壓縮指數Cc與回脹指數Cs，再以2014/06/24至2015/03/01的地下水位變動進行模擬地層分析，並針對2013/09/04至2016/02/20期間地表下300公尺內地層的總沉陷量進行模擬分析，分析結果為69mm，而實際量測的總沉陷量為78mm，模擬結果顯示地下水位的升降確實影響地層的沉陷量。

Groundwater of Taiwan western coastline has been massively exploited by aquaculture, agriculture, industry and other users, thus results in serious regional subsidence. This has jeopardized the human lives and safety of both property and public transport. According to ground surface measurement data nearby the intersection of 台78線公路(East-West Expressway 78) and Taiwan High-Speed Rail (THSR), the maximum annual ground subsidence happened in 2008, and the average ground subsidence with variety from 7.5cm to 9.3cm per year have been displayed. Reduced rainfall and water shortages for whole country between January 2015 and May 2015, have caused underground water level of the Hong-Lun Station fell to the decade low level; in addition, the difference of underground water level reached up to 2 meter between 2013 and 2014. Thus, the current annual ground subsidence amount is increasing up to 6.3cm from previous 4.1~5.1cm in 2014.
According to the STA9 magnet extensometer monitoring data nearby the intersection of Provincial Highway 78 and Taiwan high-speed rail (THSR). We found out the main reason for ground subsidence is consolidation settlement in deep stratum caused by lifting of underground water level. The one-way compaction test was applied to find out the influence to ground subsidence for both embankment construction of Provincial Highway 78 and pier construction of THSR during various stages . It displays that embankment of Provincial Highway 78 mainly affects the area within 40 meters depth and pier construction of THSR mainly affects the area within 40-300 meters depth below the surface.
The followings are survey results for differential settlement at this area
(the intersection of Provincial Highway 78 and THSR) from 2003 to 2014/03 :
The differential settlement is 36.7mm between P7 / 512 and P7 / 513
The differential settlement is 30.4mm between P7 / 514 and P7 / 515.
The followings are the different settlement based on simulation result:
The differential settlement is 40.9mm between P7 / 512 and P7 / 513 ;
The differential settlement is 27.7mm between P7 / 514 and P7 / 515
which are close to actual survey monitoring results.
To explore the subsidence problem due to the variation of underground water level , without considering the construction influence of THSR or Provincial Highway 78, we apply the monitoring data from STA9 magnet extensometer as the comparative object of this simulation task.
We use existing ground survey data, utilize inverse analysis method then we obtain soil compression index Cc, soil rebound index Cs, and then undergo the simulation analysis based on variation underground water table during 2014/06/24 and 2015/03/01. We also undergo the simulation based on total settlement result within 300m below ground level from 2013/09/04 to 2016/02/20 04. The analysis result is 69mm and the actual ground surveyed settlement is 78mm. The simulation result shows that lifting groundwater level does affect the stratum settlement amount.

水利署網頁(2016), http://epaper.wra.gov.tw/Article_Detail.aspx?s=1C0D10A505218988
杜富麗、歐陽湘(1995)，"地陷預測模式COMPAC 之應用研究"，地層下陷研討會(IV) 論文集。
林志憲(2004)，"雲林地區高鐵沿線之地層下陷檢討"，台灣公路工程，第31卷，第6期，pp.29-40。
柳志錫(2004)，"複雜含水地層之抽水沈陷行為"，交通大學土木工程學系博士論文，新竹。
高速鐵路工程局網頁(2014), http://newsletter.hsr.gov.tw/article/index/id/94
洪偉嘉(2009)，"應用多重感應器監測雲林地區三維變形"，交通大學土木工程學系博士論文，新竹。
洪明瑞、鍾明松、朱振宏、洪兆慶、李旭加、張惠文(1997)，"因抽水導致地層下陷之簡易預測法"，第七屆大地工程研討會論文集，pp.875-882。
徐享崑、鄭昌奇、童慶斌、游忠信、陳均源、趙子澤、許澤善(1997)，"沖積扇地層下陷之預測方法"，第二屆地下水資源及水質保護研討會論文集，pp. 235-246
耿慶志，薛仲修，龔誠山(1994)，"雲嘉平原及離島工業區地下水與地層下陷沉陷模式研究"，地下水資源及水質保護研討會，pp. 453-472。
財團法人工業技術研究院(2006)，"雲林地區地層下陷監測井及GPS固定站之規劃建置與觀測分析"，經濟部水利署。
財團法人成大研究發展基金會(2016)，"台78線快速公路與高速鐵路交會處減載工法成效評估研究期末報告"。
康家桂(2006)，"以時間序列預測麥寮地區地層下陷之研究"，交通大學土木工程學系碩士論文，新竹。
曹以松(1969)，"台北盆地過度抽取地下水引起之地層沉陷及其補救方法"，台灣水利，第17卷,第一期。
單信瑜、羅文俊、陳明城，(1999)，”台灣西部沿海砂質土壤變形對地層下陷之影響”，交通大學土木工程研究所。
楊秀隆，「深層含水地層之壓縮行為」，碩士論文，國立交通大學土木工程研究所，新竹 (2005)
經濟部中央地質調查所(2016)，"地質資料整合查詢系統"，http://gis.moeacgs.gov.tw。
萬鼎工程服務股份有限公司(2012)，"台78線路堤載重對高鐵結構沉陷之影響評估報告"，交通部公路總局第五處養護工程處委託計畫。
萬鼎工程服務股份有限公司(2013)，"台78線22k+700附近地層監測委託服務工作工程地質探查報告書"，交通部公路總局第五區養護工程處委託計畫。
賈儀平、陳鴻泉(1997)，"台西及麥寮地區地層下陷之研究"，第二屆地下水資源及水質保護研討會論文集，pp. 275-290。
劉志純、劉振宇、陳增壽、陳瑞昇(1997)，"抽水行為對雲林地區地層下陷之影響"，第二屆地下水資源及水質保護研討會論文集，pp.187-198。
賴典章、費立沅、江崇榮(2003)，"台灣地下水分區特性"，水文地質調查與運用研討會論文集，第1-24頁。
鍾明松、朱振宏、李旭如、洪兆慶、洪明瑞、張惠文、李顯智(1997)，"以地下水洩降量及土壤結構評估地層之沉陷行為"，經濟部水資源局八十五年度地下水觀測網暨地層下陷防治執行方案成果發表會，台北，pp.215-234。
譚志豪(2002)，"黏土壓縮與壓密行為之研究"，中央大學土木工程學系博士論文，中歷。
蘇苗彬、楊高明、陳育志(1997)，"地層下陷行為之逆算模擬與推測"，第二屆地下水資源及水質保護研討會論文集，pp. 291-304。
Buisman, A. S. K. (1936), “Results of long duration settlement tests”, Proc.1st Int. Conf. Soil Mech. Found. Eng., Cambridge, pp. 100-106.
Davis,E. H. and Booker J. R. (1973), “The effect of increasing strength with depth on the bearing capacity of clays”, Géotechnique, Vol. 23, Issue 4, pp. 551 –563.
Duncan, J. M. (1993)., “Limitations of Conventional Analysis of Consolidation Settlement”, Journal of Geotechnical Engineering,ASCE, Vol. 119, No. 9, pp. 1333-1359.
Gabrysch, R. K.(1969), “Land subsidence in the Houston-Galveston Region, Texas, in Tision”, Inter. Assoc. Sci. Hydrology, pub.88, pp43-54, 1969
Kumai, H., Sayama, M., Shibasaki, T.,Uno, K. (1969), “Land subsidnec in the Shiroishi Plain, Kyushu, Japan, in Land Subsidence”, Vol.2, Int. Assoc. Sci. Hydrology, pp645-657.
Lo, K. Y. (1961), “Secondary compression of clays”, J. Soil Mech. Found.Div., ASCE, Vol. 87, SM4, pp. 61-87.
Puzrin,A. M., Alonso,E. E., Pinyol,N. M.(2010), “Unexpected Excessive Settlements: Kansai International Airport, Japan”, Geomechanics of Failures, pp. 23-43,DOI 10.1007/978-90-481-3531-8_2.
Raymond, G. P. and Wahls, H. E. (1976), “Estimating 1-dimensionalconsolidation, including secondary compression, of clay loaded fromoverconsolidated to normally consolidated state”, Special Report 163,Transportation Research Board, Washington, D.C., pp. 17-23.
Terzaghi, K., Theoretical Soil Mechanics, Wiley, New York (1943).
Yamamoto, S. (1984), “Case History No. 9.10 Bangkok, Thailand, Guide to studies of land subsidence due to groundwater withdrawal, Unesco.