碩士論文公告區

碩士論文公告區
年度：	96
姓名：	陳志瑋(Chih-wei Chen)
論文題目(中)：	粉土質砂土中摩擦型群錨之垂直受力行為
論文題目(英)：	Uplift Behavior of Frictional Anchor Groups in Silty Sand
摘要(中)：
	本研究利用數值分析與現場試驗的方式闡述粉土質砂土中摩擦型群錨之受力行為。數值分析的方式係經由現地採樣進行三軸試驗，利用SHASOVOD模式(A Continuous Strain Hardening Softening and Volumetric Dilatancy Model)，求取該模式所需之參數，再利用數值分析軟體FLAC3D進行摩擦型單錨與群錨之受力行為分析。此外，為驗證分析模式的適用性，本研究進行現地摩擦型單錨與群錨施工及拉拔試驗。於確認數值分析模式之可行性後，再進行不同條件下摩擦型單錨與群錨之參數研究。由三軸試驗結果中發現，粉土質砂土的剪力強度隨著圍壓與相對密度之增加而增加，且當軸差應力達到尖峰強度後，試體破壞面開始產生。此時剪力強度將迅速遞減到殘餘階段，最後趨於定值；試體之體積先產生壓縮，然後膨脹，最後亦趨於穩定。上述之應力-應變行為相當符合SHASOVOD模式的構架。由現地拉拔試驗之結果可發現，對直徑15cm，自由段10m，錨碇段15m的摩擦型單錨而言，當位移量達13cm時，極限拉拔力約為542kN；而由間距60cm之22排列式群錨試驗可得知，當平均位移量12.5cm時，極限拉拔力約為522kN。因此，群錨效應係數φ為95%。不論是單錨或群錨的荷重-位移關係或是極限拉拔力，數值分析皆可得到與現場試驗相近似的結果。由數值分析發現，對於22排列之群錨，水平間距Sh=2D(D：地錨直徑)時，群錨效應係數僅有75%~80%；但水平間距Sh大於6D後，群錨效應係數可達98%以上，甚至不受群錨效應的影響。覆土深度增加時群錨周圍土壤降伏區域隨覆土深度增加而增加，此時增加地錨的水平間距Sh能減少地錨拉拔力受群錨效應的影響。比較22與33排列群錨之群錨效應與水平間距之關係中發現，在相同的水平間距下33排列之群錨受群錨效應的影響比22排列群錨顯著。
摘要(英)：
	Both numerical analyses and field tests were accomplished to elucidate the anchorage behavior of frictional anchor groups in silty sand. A series of triaxial tests was performed on specimens taken from test site, based on the frame of constitutive model for the cohesionless soil named SHASOVOD (A continuous strain hardening- softening and volumetric dilatancy model), to obtained the parameters needed for the model. This study along with FLAC3D software to analyze behaviors of single anchors and anchor groups in silty sand. In addition, to verify the suitability of the numerical program, filed tests on a single shaft anchors and an anchor group arranged in 22 matrix form were conducted in silty sand. After the calibration, a succession of parameteric analyses was carried out to study the anchorage behaviors of single shaft anchors and anchor groups in silty sand. It was found from triaxial tests on silty sand, the shear strength increases as relative density and confining pressure increases. The failure plane occurs when the deviator stress reaches peak point. Hence, the shear strength decreases to residual state and tends to constant as axial strain increases. The volume decreases in the beginning, then dillates, and finally comes to the steady state. This stress-strain phenomenon meets the SHASOVOD model. It can be seen from field test results, the ultimate load of 542kN was estimated meanwhile the anchor head displacement reached 13cm for a single anchor with diameter of 15cm, free length of 10m, and fixed length of 15m; while the ultimate load of 522kN was measured with respect to the average of anchor head displacement of 12.5cm for a 22 anchor group with spacing of 60cm, efficiency of an anchor group was computed to be 95%. The load-displacement relations and ultimate loads calculated from numerical analyses were closed to those measured by field tests not only for the single anchor but also for the anchor group. When a 22 anchor group with spacing of 2D (D: anchor diameter), efficiency of the anchor group was calculated to be only 75%~ 80%. There is no interference when spacing was 6D, and the efficiency of an anchor group could more than 95%. The yielding zone of the anchor groups increase as overburden depth increase. The efficiency of anchor groups can be eliminated as the anchor spacing are increase horizontally. It can be found from the numerical results, the efficiency of 33 anchor group is greater than that of 2*2 anchor group.
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相關連結：	http://ethesys.lib.cyut.edu.tw/ETD-db/ETD-search-c/view_etd?URN=etd-0826108-113537

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