含有孔洞之地盤受壓時，其沉陷行為包括受壓時產生瞬間沉陷、土壤之壓密沉陷及孔洞變形時產生之徑向變形導致垂直沉陷，這三種行為在沉陷過程中彼此有其相關性。故研究中利用台北粉土質黏土重模製作含孔洞試體，進行壓密試驗，以模擬於軟弱地盤中孔洞開挖後之沉陷行為。試驗分析將視孔洞為試體一部分，進行壓密性質分析，並討論孔洞對沉陷量之影響。 經由試驗結果顯示，含孔洞土壤所包含孔洞直徑愈大，壓縮指數CC愈大，但增加變化量並不明顯。此外，土壤之在較小預壓力情況下，含不同孔洞直徑土壤之體積壓縮係數mv變化較大；在較大預壓力情況下，土壤顆粒已開始慢慢變緊密，因此含不同孔洞直徑土壤之體積壓縮係數mv變化較小。在沉陷量分析結果發現，含孔洞土壤之沉陷量將隨著孔洞直徑增加而變大，孔洞直徑對土壤沉陷量之影響主要受制於土體預壓力，亦即預壓力愈大土壤之勁度愈強，土壤中之孔洞對沉陷量影響愈小。另一方面，孔洞在試體瞬間沉陷過程中變形較明顯，在壓密沉陷過程中變形較小。 When a cavernous ground was compressed, the settlement of the ground consisted of the immediate settlement, consolidation and vertical displacement due to the deformation of the caves. In this research, the Taipei-Basin silty clay was used to fabricate the remolded soil samples with cavities, and the odometer test was conducted to simulate the displacement behavior of the weak soil layer after excavation. Assuming that the cavity was a new material of the soil sample, the test results could be analyzed. From the results of the tests, it was revealed that the compression index (Cc) tends to increase with the cavity diameter in the soil sample. The variation of the values of the coefficient of volume change (mv) was large in the initial loading stages. With increasing loading stress, this variation decreased to a smaller range. It was also found that the settlement of the soil was affected by the stiffness of the sample and the diameter of the cavity. With larger preconsolidation pressure, the soil was stiffer and the effects of the cavity diameter became less. The deformation of the cavity was obvious when the immediate settlement occurred, but became unapparent during the consolidation progress.
