高含冰量冻土路基融化固结规律研究

Study of thawing and consolidation law of ice-rich embankment

为了研究高含冰量冻土路基的融化固结规律,在线性大变形融化固结理论的基础上引入非线性本构关系,并运用分段插值法实现了孔隙比与压缩模量之间的非线性关系,完善了三维大变形融化固结数值模拟方法。在此基础上结合青藏公路实测数据验证了其合理性。研究结果表明,采用非线性应力-应变关系的大变形融化固结理论能够显著提高高含冰量冻土路基的沉降计算精度,并能够进一步合理描述热学场和力学场的相互叠加影响。冻土融化固结度受有效融化固结时间以及特征排水长度等因素的影响呈现出完全不同于融土路基的发展规律,即在路基运营初期其融化固结度上升,随着时间发展,其固结度在达到峰值后持续降低,这主要是由于融化深度持续增大后所引起的特征排水长度的增加和有效融化固结时间的缩短所造成的。因此,在计算高含冰量冻土路基稳定性设计指标时,应采用非线性应力-应变关系来进一步提高融化深度、沉降以及固结度等指标的计算精度。

In order to study the law of thaw consolidation for high ice content permafrost embankment,a nonlinear constitutive relationship was incorporated into the original linear large strain thaw consolidation theory and a piecewise interpolation function was used to implement the nonlinear relationship between compression modulus and void ratio.Numerical simulation method of thaw consolidation was further modified.Validity of this work was verified by the monitored data of Qinghai-Tibet highway.The analysis results shown that the thaw consolidation calculation accuracy of high ice content embankment can be notably improved by the modified thaw consolidation theory and numerical simulation method.Further analysis indicated that the interactive effects between thermal and mechanical field can be further reasonably described by the nonlinear stress-strain relationship.The thawing consolidation degree of frozen soil is affected by effective thawing consolidation time and characteristic drainage length,which is completely different from the development law of thawing roadbed.The thaw consolidation degree increases in the early stage of roadbed operation,while with the development of time,the degree of consolidation decreases continuously after reaching the peak value.This is mainly due to the increase of characteristic drainage length and the shortening of effective melting and consolidation time caused by the continuous increase of melting depth.Therefore,the nonlinear constitutive relationship must be employed to calculate the stability design parameters,such as thaw depth,settlement and consolidation degree when the high ice content permafrost embankment was involved.