華梵大學位於一順向坡，在北台灣的西部麓山帶大崙山地區中是被視為不穩定的邊坡。此邊坡岩性主要由砂岩和頁岩的夾層，砂岩厚度由薄層到塊狀且與中新世的頁岩互層。本研究利用從鑽孔資料得到的崩積層厚度進行內插，並使用surfer軟體獲得其內插結果。結果顯示岩屑在移動方向為西南向的坡腳處堆積。由於受構造活動的影響，特別是根據前人的調查，穿過本研究之研究區域的兩條局部斷層為改變地層之走向的重要角色。為了詳細分析該邊坡的地質結構，本研究使用多項式曲面擬合來建立 3D 地質模型，該模型能利用從鑽孔中得到的資料來迴歸出層面的走向，此過程是基於計算通過指準層高程的迴歸面。結果表明，迴歸面的方向與露頭的測量結果一致。此外，也製作了數個剖面圖來使本研究所建立之3D 地質模型更加完整。最後，再比較地表和地下監測數據以完善 3D 地質模型。此地質模型將對邊坡破壞之現象具有重大貢獻，並可作為減少災害的指導方針。

The slope at Huafan University is recorded as a dip slope that has been proposed to be possibly unstable in the Dalun Mountain of Western Foothills in northern Taiwan. The lithology is mainly composed of intercalation of sandstone and shale, and the thickness of the sandstone varies from thin to massive interbedded with shale of the Miocene age. By interpolating the thickness of colluvium as the cover material derived from the borehole data and analyzing the contouring of the interpolation result in the surfer software, it is revealed that debris accumulates at the slope foot toward the southwest in the direction of movement. Because of the influences of tectonic activities, especially, according to previous investigations, two local faults that pass through the study area play an important role in changing the strata’s orientation. For a detailed analysis of the subsurface geological structure of this slope, this study focuses on the development of a 3D geological model by using a polynomial surface fitting which is aimed to compute the regressive orientation of the bedding plane derived from the borehole data. Based on calculating the regression plane passing through the elevations of the geologic interface (key bed), the results show that the regression plane's direction is consistent with the measurement of outcrops. Moreover, several cross-sectional profiles are made to visualize and clarify the 3D geological model. Finally, surface and subsurface monitoring data are compared to refine the 3D geological model. The geological model will contribute significantly to the phenomenon of slope failure and can be guidelines to minimize disasters.

[1]. Bamisaiye, O.A., 2018. Subsurface mapping: selection of best interpolation method for borehole data analysis. Spatial Information Research, 26(3), pp.261-269.
[2]. Bates, R. L., and Jackson, J.A., 1987. Glossary of Geology: American Geological Institute. Alexandria, Virginia, pp.788.
[3]. Caumon, G., Collon-Drouaillet, P. L. C. D., De Veslud, C. L. C., Viseur, S., & Sausse, J., 2009. Surface-based 3D modeling of geological structures. Mathematical Geosciences, 41(8), pp. 927-945.
[4]. Chen, R.F., Chang, K.J., Angelier, J., Chan, Y.C., Deffontaines, B., Lee, C.T., Lin, M.L., 2006. Topographical changes revealed by high-resolution airborne LiDAR data: the 1999 Tsaoling landslide induced by the Chi–Chi earthquake. Engineering geology, 88 (3–4), pp. 160-172.
[5]. Chorley, R.J. and Haggett, P., 1965. Trend-surface mapping in geographical research. Transactions of the Institute of British Geographers, pp.47-67.
[6]. Golden software, llc, 2016. Surfer 16. Golden software, llc, Po box 281, Golden, CO 80402-0281 USA.
[7]. Goodman, R.E., 1989. Introduction to Rock Mechanics. New York: Wiley, Vol.2.
[8]. Hoek, E., and Bray, J. D., 1981. Rock slope engineering. CRC Press.
[9]. Huang, J.S., Jeng, C.J., 2004. A supplementary geological survey and analysis of the Dalun area around the Huafan University (in Chinese). J. Art Design Huafan University., 1, pp. 59-70.
[10]. Huang, C.Y., Wu, W.Y., Chang, C.P., Tsao, S., Yuan, P.B., Lin, C.W., Xia, K.Y., 1997. Tectonic evolution of accretionary prism in the arc-continent collision terrane of Taiwan. Tectonophysics 281, pp. 31-51. http://dx.doi.org/10.1016/S0040-1951(97) 00157-1.
[11]. Jeng, C.J., Hung, C.S., Shieh, C.Y., 2008. Case study of the application of in-situ geological mapping and 2D-resistivity image exploration for the slope in Huafan University (in Chinese). J. Art Design Huafan Univ., 4, pp. 166-180.
[12]. Jeng, C.J., Sue, D.Z., 2016. Characteristics of ground motion and threshold values for colluvium slope displacement induced by heavy rainfall: a case study in northern Taiwan. Natural Hazards and Earth System Sciences, 16(6), pp. 1309-1321.
[13]. Jeng, C.J., Yo, Y.Y., Zhong, K.L., 2017. Interpretation of slope displacement obtained from inclinometers and simulation of calibration tests. Natural Hazards, 87(2), pp. 623-657. https://doi.org/10.1007/s11069-017-2786-6.
[14]. Krumbein, W.C., 1963. Confidence intervals on low‐order polynomial trend surfaces. Journal of Geophysical Research, 68(20), pp. 5869-5878.
[15]. Lee, C., 2011. Dip-slope and Dip-slope Failures in Taiwan-a Review. AGU Fall Meeting Abstracts., Vol. 2011, pp. NH13E-1420.
[16]. Lee, C.C., Zeng, L.S., Hsieh, C.H., Yu, C.Y. and Hsieh, S.H., 2012. Determination of mechanisms and hydrogeological environments of Gangxianlane landslides using geoelectrical and geological data in central Taiwan. Environmental Earth Sciences, 66(6), pp. 1641-1651.
[17]. Lin, C.C., 2000. Explanatory Text of the Geological Map of Taiwan (in Chinese). Central Geological Survey of Taiwan, Hsintien, pp. 77. Sheet 32.
[18]. Lo, C.M., 2017. Evolution of deep-seated landslide at Putanpunas stream, Taiwan. Geomatics, Natural Hazards and Risk, 8(2), pp. 1204-1224. https://doi.org/10.1080/19475705.2017.1414079
[19]. Lo, C.M., Weng, M.C., Lin, M.L., Lee, S.M. and Lee, K.C., 2018. Landscape evolution characteristics of large-scale erosion and landslides at the Putanpunas Stream, Taiwan. Geomatics, Natural Hazards and Risk, 9(1), pp. 175-195.
[20]. Mei, S., 2009. Geologist-controlled trends versus computer-controlled trends: introducing a high-resolution approach to subsurface structural mapping using well-log data, trend surface analysis, and geospatial analysis. Canadian Journal of Earth Sciences, 46(5), pp. 309-329.
[21]. Noroozi, A. G., and Hajiannia, A., 2015. The effects of various factors on slope stability. International Journal of Science and Engineering Investigations, 4(46), pp. 44-48.
[22]. Sonnette, L., Lee, J. C., Horng, C. S., 2017. The arcuate fold-and-thrust belt of northern Taiwan: Results of a two-stage rotation revealed from a paleomagnetic study. Journal of Asian Earth Sciences, 147, pp. 284-309.
[23]. Suppe, J. O. H. N., 1980. A retrodeformable cross section of northern Taiwan. In Proceedings of the Geological Society of China, vol. 23, pp. 46-55.
[24]. Teng, L.S., 1990. Geotectonic evolution of late Cenozoic arc-continent collision in Taiwan. Tectonophysics, 183(1-4), pp. 57-76.
[25]. Tseng, C.H., Chan, Y.C., Jeng, C.J., Hsieh, Y.C., 2017. Slip monitoring of a dip-slope and runout simulation by the discrete element method: a case study at the Huafan University campus in northern Taiwan. Natural Hazards, 89 (3), pp. 1205-1225.
[26]. Tseng, C.H., Chan, Y.C., Jeng, C.J., Rau, R.J. and Hsieh, Y.C., 2021. Deformation of landslide revealed by long-term surficial monitoring: A case study of slow movement of a dip slope in northern Taiwan. Engineering Geology, 284, pp. 106020.
[27]. Tsou, C. Y., Feng, Z. Y., Chigira, M., 2011. Catastrophic landslide induced by typhoon Morakot, Shiaolin, Taiwan. Geomorphology, 127(3-4), pp. 166-178.
[28]. Varnes, D.J., 1978. Slope Movements And Types And Processes. Landslides Analysis and Control. Transportation Research Board Special Report, 176, pp. 11-33.
[29]. Zhang, F., Chen, W., Liu, G., Liang, S., Kang, C. and He, F., 2012. Relationships between landslide types and topographic attributes in a loess catchment, China. Journal of Mountain Science, 9(6), pp. 742-751.