低黏性砂土張力強度之驗證

Verification of Tensile Strength of Lightly Cemented Sand

李文淵(Wun-Yuan Lee)

指導教授 ： 葛宇甯

國立臺灣大學/工學院/土木工程學研究所/碩士(2014年)

https://doi.org/10.6342/NTU.2014.02889

摘要

在過去學者的研究當中，有許多方法可以決定土壤的張力強度，依據是否可直接量測拉力與否，可分為直接法與間接法。直接法主要是以直接拉力試驗 ( direct tensile test ) 為主，且可再分為水平或垂直施加拉力；而間接法常採用的方法有，例如 ： 劈裂試驗 ( split tensile test ) 、無圍壓縮貫入試驗 ( unconfined penetration test ) 或稱為雙貫入棒試驗 ( double punch test )。
本研究以複合驗證法求取低黏性砂土的張力強度，採用高嶺土與越南石英砂土混合之複合土壤 SC，分別進行兩大部分試驗，第一部份試驗，選定土樣 SC (S-石英砂 80% 與 C-高嶺土 20%) 為試驗土樣，主要為土壤張力強度間接法之相關試驗，分別依序進行 ： 直接剪力試驗、無圍壓縮試驗與無圍壓縮貫入試驗；第二部份試驗，選定土樣 SC (S-石英砂 80% 與 C-高嶺土 20%) 為試驗土樣，主要為土壤張力強度直接法試驗及壓力平板試驗。
在不同含水量下，直接張力試驗之有效張力強度的相對偏差很小，故含水量並不會影響不飽和土壤之有效張力強度，且由 Lu et al. (2006、2010) 所提出的的不飽和土壤有效應力架構計算直接張力試驗之有效張力強度，其值在含水量 w = 9%、11% 時相當接近，代表直接張力試驗有很高之準確性。

關鍵字

不飽和土壤 ； 吸應力 ； 基質吸力 ； 張力強度 ； 無圍壓縮貫入試驗

並列摘要

There are many methods of determining the tensile strength of soil. Depending on whether the specimen can be directly pulled in tension, it can be categorized into direct and indirect methods. In the direct methods, the specimen can be horizontally or vertically loaded. In the indirect methods, the split tensile test and the unconfined penetration test (double punch test) are often used.
In this study, compacted clayed sandy specimens (with 80% of sand and 20% of caly by weight) were prepared for a series of the tests. The first part of tests is related to the indirect test of soil tensile strength, including direct shear test, unconfined compression test, and unconfined penetration test. The second part of tests is related to the direct test of soil tensile strength, including direct tension test and pressure plate test.
The direct tension test of the effective stress varies slightly at different water contents, indicating the effective tensile strength of unsaturated soil was unaffected by the water contents. The direct tension test of the effective stress is quite close when the water content is at 9 and 11 percent, which suggests that the direct tension test be quite accurate in determining the tensile strength of lightly cemented sand.

並列關鍵字

unsaturated soil ； suction stress ； matrix suction ； tensile strength ； unconfined penetration test

參考文獻

44. 何冠德 (2013)，『低黏性砂土張力強度之探討』，碩士論文，國立台灣大學土木工程學系。

1. ASTM D2166-06, “Standard Test Method for Unconfined Compressive Strength of Cohesive Soil, ” ASTM International, West Conshohocken, PA, USA.

5. ASTM D4253-00, “Standard Test Methods for Maximum Index Density and Unit Weight of Soils Using a Vibratory Table, ” ASTM International, West Conshohocken, PA, USA.

6. ASTM D4254-00, “Standard Test Methods for Minimum Index Density and Unit Weight of Soils and Calculation of Relative Density,” ASTM International, West Conshohocken, PA, USA.

7. ASTM D4318-05, “Standard Test Methods for Liquid Limit, Plastic Limit, and Plasticity Index of Soils,” ASTM International, West Conshohocken, PA, USA.