太陽能電誘滲透改良土中之樁基承載力研究

The Study for Pile Bearing Capacity in Clay with Solar Energy Electro-Osmotic Method

電滲改良土內正負極離子使混凝土模型樁的表面附著力成長增大，其附著方式與一般打擊式或埋入式基樁不同。本文以太陽能電誘滲透改良甚軟弱黏土，並提出電滲土之不排水剪力強度Su 評估模型樁承載力模式。電滲土內基樁之表面附著力之折減值á，隨著電極棒組增加而增大，且會超出Skempton（1959） 所提0.3~0.6 之範圍，但加多電極棒增加電滲土之模型樁附著力亦有其最大限度。靜力錐貫入試驗 （CPT） 的摩擦行為與模型樁在電滲土中之摩擦行為不相同，以CPT 之尖端抗力與表面摩擦力估算電滲土中之模型樁承載力與模型樁實作載重試驗之承載力，兩者相差很大。太陽能電誘滲透改良樁基入土深度內之甚軟弱黏土使其固結，可消除基樁表面負摩擦力，增加正向摩擦力。軟弱黏土反覆電滲下，停止電滲後土壤強度會降至電滲最高強度之1/3，但仍比電滲前大。

Owing to the existence of ions in soil treated by electro-osmosis, thesurface adhesion force of soil on concrete model piles increases. The typeof adhesion is not the same as on driven or buried piles. We introduceelectro-osmosis by solar energy to improve the strength of soft clay in thisstudy. The evaluation of bearing capacity of model piles is evaluated byusing undrained shear strength (Su) of the improved soil. The coefficientof adhesion, á on piles increases as the number of electrodes increases. Itwill exceed 0.3~0.6, which is the range Skempton (1959) proposed. Thiscoefficient is also limited if the number of electrodes exceeds a certainnumber. The friction behavior during a Cone Penetration Test (CPT) is different from the friction on model piles in electro-osmotically treated.The bearing capacity evaluated by CPT driving-shoe resistance and surfacefriction force on model piles in electro-osmotically treated soil is quitedifferent from the test result in the lab. Soft clay can be consolidated byelectro-osmosis. In the mean time, negative friction on pile surface can beeliminated while positive friction can be improved. After repeatedelectro-osmosis treatments on soft clay are terminated, the soil-bearingcapacity decreases by two third from its greatest strength. Nevertheless, itis stronger than soil not treated.