|Abstract: ||摘要:隨著各項重要建設的推展,樁基礎的使用頻率也日益增加。以往基樁軸向承載力之檢測,大都採用耗費時間的靜載重試驗方式進行。為彌補傳統試驗方法之不足,於本研究中嘗試探討利用快速簡便的動態方法預測鋼筋混凝土基樁軸向承載力之可行性。 於本研究中之試驗部分,主要採用六根不同條件之鋼筋混凝土模型基樁分別打設於乾砂中,俟其穩定後對樁頭施加衝擊荷重,並同時記錄基樁受力、速度、位移等對應時間關係。試驗所得資料分別以美國Case方法及荷蘭TNO方法進行分析後,再與靜載重試驗及雙曲線模式預測靜態承載力之結果進行比較。此外,於研究中並引進Tsai & Liang發展的應力波理論解析解作為動態試驗結果比對之用,以探討理論分析結果及動態試驗結果間之差異性。 經由各項試驗及分析之結果,可歸納得到下列幾項結論:(1)進行動態試驗所得之各項對應關係,與應力波理論分析模式之結果非常接近。(2)動態方法預測基樁打設於氣乾砂土中軸向承載力之結果,一般而言,較靜載重試驗結果高。(3)預測基樁軸向承載力之動態方法中以Case方法較為可行,TNO方法之分析結果則存在較大的變異性。(4)進行大應變基樁動態試驗時,基樁重量與樁錘重量比值約為11左右可得到最小的誤差。(5)相同長度之模型基樁進行靜載重試驗時,其細長比(L/D)越小則試驗所得之靜態軸向承載力越大。(6) Tsai & Liang方法之理論分析結果與動態試驗結果間具有相當一致的現象。這種情形顯示,應力波理論之假設模式與基樁動態試驗之實際行為相類似。|
abstract:Pile foundations are frequently used on the increase in combination with the development of many important constructions. The static loading test is traditionary used to evaluate the axially bearing capacity of pile foundations. It is very expensive and time consuming. To supplement the defect of static loading test, this paper is to study of the axially bearing capacity of reinforced concrete model pile by means of a fast and simple dynamic method. The experimental investigation in this paper is to use six different conditions for the reinforced concrete model pile which are driven into dry sand. The relationship between force, velocity and displacement versus time are recorded when hammer impact pile top. The results obtained from experiment are analyzed by the Case and TNO methods and then compared with the results those of static loading test and statically bearing capacity predicted by the hyperbolic model. The results succeeded in getting the analytic solutions of one-dimensional wave theory are also compared with the results of dynamic test in order to study the difference between the theoretical and dynamic test results. Through the results of test and analysis, some important conclusions are described as follows: (1) The results of dynamic loading test is very approach to the results of analytic solution of stress wave theory. (2) Generally speaking, the axially bearing capacity obtained from dynamic loading test is higher than the static loading test ones. (3) The Case method is feasible for predicting the axially bearing capacity of reinforced concrete model pile driven into dry sand. The analytical result of the TNO method is of great variation. (4) For the dynamic loading test, one can get the minimum error when the ratio of pile weight to hummer weight is approach to 11. (5) In the case of same length of model pile for static loading test, the less slenderness ration L/D (L=pile length, D=pile diameter), the larger axially statical bearing capacity. (6) The analytic solutions come up to the results of dynamic loading test. This means that the assumption used in this paper is very much the same as the real behaviour of pile dynamic test.