分析結果獲得無論是外包或層狀加勁，當樁徑愈小或加勁材勁度愈大，加勁材所提供之圍束應力愈大，柱體可承受之軸向壓力也愈大，對柱體腫脹之抑制效果愈佳。一般加勁材勁度的情況下(100-1000 kPa)，層狀加勁所提供的軸向承載壓力優於外包形式；但若採用極高勁度加勁材(5000 kPa)，且於較大的軸應變下，則外包加勁形式可提供較大的軸向壓力。此外，層狀加勁之加勁材與砂土間的界面摩擦角，也將明顯影響加勁礫石樁的軸向承載壓力。 The purpose of this study is to compare the mechanical behavior of encased and laminated granular columns using a numerical method. The numerical analysis is performed using the finite difference program FLAC. An axial symmetrical model is used based on elastic-plastic constitutive model with non-associated flow rule. Numerical analysis results are verified via laboratory triaxial tests on encased/laminated sand columns. The reinforcement stiffness, strength and diameter of the granular column in the field influence reinforced columns response is also studied. Based on the same amount of reinforcement, the axial bearing capacity is compared for the both reinforced types.
Parametric studies on the column diameter, an increase in the reinforcement stiffness or a decrease in the column diameter might obtain greater axial bearing pressure and inhibit column bulging due to increase of confining pressure in the soil mass for the both of type reinforced columns. The bearing capability for a laminated reinforced column is greater than an encased column as same amount of reinforcement under general reinforcement stiffness (100-1000 kPa). However, the encased column might cause higher capability as using the high-stiffness (5000 kPa) reinforcement under larger axial strain. The interfacial friction angle may cause slippage to occur early for laminated reinforced columns. Therefore, a reinforced column with lower interfacial friction angle achieves lower strength.
