膨脹儀試驗在粉砂中之標定

Abstract

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。膨脹儀試驗（dilatometer test, DMT）是一種在歐美廣泛使用的現場試驗方法。然而就像其他的現場試驗一樣，膨脹儀試驗的結果多靠經驗公式來分析。現有的經驗公式多來自歐美，根據在級配均勻之乾凈砂土中所做之標度試驗推導得來。台灣西海岸的砂土，包括雲林麥寮，含粉土（silt）量相當高。實驗結果顯示此種砂土具有高壓縮性與破碎性，而膨脹性不高的特性。含細顆粒之砂土與級配均勻之乾凈砂土在工程性質上有相當大的差異，因此將來自歐美的DMT經驗公式應用於台灣西海岸的砂土之可靠性很有疑問。 本研究是一系列關於雲林麥寮粉土細砂工程性質研究的延續。現有完成的部份包括麥寮砂基本物理與力學性質之決定與圓錐貫入試驗之標定。本研究以麥寮砂中DMT結果之標定為重心。計畫之主要目的是確認現有DMT經驗公式對雲林麥寮粉土細砂之適用性，或提出新的經驗的方法來解釋在含細顆料砂土中DMT之結果。考慮細顆粒含量、相對密度和改變側向土壓力等因素，在標度槽系統中進行一系列的DMT標度試驗。本論文敘述研究之背景、目的、進行步驟、DMT標度試驗之程序與試驗結果資料。對於在粉砂中DMT結果進行分析，提供建議並討論。

Because of the lack of cohesion, it is very difficult to obtain undisturbed samples for sand. In situ tests are often used to determine the engineering properties for sand. The Marchetti flat dilatometer test (DMT) is a popular in situ test method in Europe and Northern America. As in many other types of in situ test methods, the interpretation of DMT data is mostly empirical. The majority of the available empirical rules came from Europe or Northern America, and are based on tests in uniformly graded, clean sand. The sand on the West Coast of Taiwan, including in Mai Liao, Yuen Lin, contains significant amounts of silt. Experiments have indicated that this type of sand is compressible and crushable, and has a less tendency to dilate. The differences between a uniformly graded clean sand and a silty sand can be significant. Hence, to directly adopt the empirical DMT interpretation rules developed in the West, to the sand on the West Coast of Taiwan may be undesirable. This research is part of an effort to establish the engineering characteristics for the Mai Liao silty and (MLS) that typifies the sand deposit on the West Coast of Taiwan. A series of experiments have been carried out to establish the basic physical and engineering properties of MLS. Existing experiments include calibration of cone penetration tests in MLS. This research project concentrates on DMT. The main objective of this research project is to evaluate the feasibility of the existing empirical DMT interpretation methods, and to establish new interpretation methods when necessary. Considering the effects of high fines content, relative density and lateral earth pressure, a series of DMT calibration tests have been conducted. The thesis describes the background of this research, its objectives, approach, procedures of the DMT calibration tests and their results.