半渗透边界下非饱和土砂井地基固结特性

CONSOLIDATION CHARACTERISTICS OF DRAINAGE WELL FOUNDATION IN UNSATURATED SOILS WITH SEMI-PERMEABLE BOUNDARY

以往的非饱和土砂井地基研究中未考虑砂井的涂抹作用,均按理想砂井进行研究。然而在实际工程中,施工的扰动会导致砂井内壁附近的土体渗透性减弱,从而影响地基的固结。针对这种情况,本文以均布荷载作用下非饱和土砂井地基为模型,考虑涂抹作用,并将其形成的边界假设为半渗透边界;引入Bessel函数,根据超孔隙压力的耦合控制方程推导了半渗透边界条件下非饱和土砂井地基在Laplace变换域内的固结半解析解,并且采用Crump方法进行Laplace逆变换,得到了时间域内的解;将该砂井地基模型退化为理想砂井模型,与现有文献结果对比,验证了本文研究方法的可靠性。最后通过算例来考察半渗透系数对非饱和土砂井地基固结特性的影响。研究表明,半渗透系数对砂井地基的固结有着重要的影响,且半渗透系数越大,超孔隙压力消散越快。

Former researches of unsaturated drainage well foundations always treated the foundations with ideal radial boundaries,but did not consider the smearing effect.The construction disturbance can affect the speed of consolidation by decreasing the soil permeability near the inside of a drainage well foundation.In this case,the smearing effect is illustrated with the semi-permeable boundary and is included in a new modeling of drainage well foundation in unsaturated soils.By introducing Bessel functions,analytical solutions with respect to excess pore pressures are achieved in the Laplace domain according to the governing equations.Secondly,by utilizing the Crump’s method,the inverse Laplace transform to obtain semi-analytical solutions to excess pore pressures in the time domain is performed.It is shown that the present solutions are in good agreement with the previous solutions in the literature and more reliable.Finally,parametric studies are conducted by the variations of excess pore pressures at different ratios of air-water permeability coefficient and the radius.Results indicate that the semi-permeability coefficients have significant influence on the consolidation,and excess pore pressures dissipate faster with the increase of semi-permeability coefficient.