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題 名 | 砂土中圓錐貫入標定試驗結果對擴孔理論值之修正=Modified Theoretical q[93dd] Values by CPT Calibration Chamber Tests |
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作 者 | 許懷後; 黃安斌; | 書刊名 | 臺灣公共工程學刊 |
卷 期 | 2:1 民95.06 |
頁 次 | 頁71-77 |
分類號 | 441.12 |
關鍵詞 | 圓錐貫入試驗; 標定槽試驗; 邊界效應; Cone penetration tests; Calibration chamber tests; Boundary effects; |
語 文 | 中文(Chinese) |
中文摘要 | 由於缺乏凝聚力,砂土的非擾動性試樣很難取得。為量測砂土的工程性質,現場試驗是常用的方法。圓錐貫入試驗(Cone Penetration Test, CPT)是一種廣泛使用的現場試驗方法,然而就像其他的現場試驗一樣,圓錐貫入試驗的結果多靠經驗公式來分析。經驗公式大多根據試驗室中的標定試驗結果,經由一些理論的推導而來。標定試驗的重要缺陷是它的邊界效應。傳統標定槽中的試體其橫向邊界狀態可以是固定應力或為零變形。這兩種邊界狀態都無法模擬介於此兩者之間的現地情況,因此現有經驗公式之可靠性極為有限。學者曾提出以修正因子的方法來抵消邊界效應,但修正因子的正確性與邊界影響之機制至今都尚未得到證實。Salgado(1993)依據擴孔理論所提出之錐尖阻抗(q[93dd])理論值,與橫向邊界狀態為固定應力時(B1 Condition)之CPT標定試驗q[93dd]值有接近之結果,然而對於無限邊界之狀態,仍無法證實其理論值之正確性。為改進傳統標定槽邊界效應的缺點,交通大學已研發完成一套能夠模擬現地狀況的標定槽系統,並在模擬現地的狀況下進行了一系列的砂土圓錐貫入試驗。本研究根據模擬現地狀況的圓錐貫入標定試驗結果,與Salgado(1993)之理論值進行分析比較,結果顯示在無限邊界之狀態下,Salgado之q[93dd]預測值皆較實際量測值為高,其範圍介於97%至223%之間;在B1之狀態下,Salgado之q[93dd]預測值接近實際量測值,其範圍介於71%至93%之間,然而此相近之結果是邊界效應所導致。 |
英文摘要 | Due to lack of cohesion, it is difficult to obtain undisturbed samples for sand. In-situ testing is often used to determine the engineering properties for sands. The cone penetration test (CPT) is a popular in-situ test method. However, as for many other in-situ test methods, we rely on empirical equations to interpret CPT data. A Significant part of these empirical equations came from laboratory chamber calibration tests with limited theoretical basis. An important drawback of the calibration chamber is its boundary effects. The lateral boundary of the sand specimen in a calibration chamber is either stress controlled or rigid. Neither of these two boundary conditions can truly duplicate the field conditions which lies somewhere in between. Hence, the validity of these empirical equations are questionable. Salgado (1993) used cavity expansion theory to derive q[93dd] under stress-controlled boundary conditions and compared with calibration chamber data. Results show that q[93dd] values agree within ±30%. However, this prediction method under free field condition has not been verified. A new chamber system that is capable of simulating field conditions ahs been developed. A series of CPT has been performed in this chamber system. The main objectives of this research are to compare the q[93dd] values based on the calibration chamber data (q[93dd],□) and the Salgado's cavity expansion theory (q[93dd],[92b8]). Results show that q[93dd],[92b8] is overestimated under free field condition, the range of q[93dd],[92b8]/q[93dd],□ is between 97% to 223%. The q[93dd],[92b8] is well estimated under B1 condition, q[93dd],[92b8]/q[93dd],□ is between 71% to 93%. Nonetheless, these q[93dd] values under B1 condition resulted from boundary effects. |
本系統中英文摘要資訊取自各篇刊載內容。