Consolidation Theory and Application of Double-Layered Foundation for Fiber-Reinforced Solidified Lightweight Soil

Firstly, based on one-dimensional Terzaghi consolidation theory, we derived and established the analytical solution of excess pore water pressure and average consolidation degree of double-layered foundation, which can reflect the effect of fiber reinforcement. Meanwhile, the one-dimensional consolidation test of a double-layered foundation was carried out by means of a modified WG-type (product series code) consolidation instrument. The accuracy of the theoretical solution was verified by designing different consolidation parameters of the basalt fiber-reinforced solidified lightweight soil (BF-SLS) layer. Secondly, our findings suggest that the settlement rate of the double-layered foundation decreased with the increase in thickness, compression modulus and fiber mixing ratio of the BF-SLS layer. Nevertheless, the average pore pressure dissipation rate changed in the opposite trend. Both increased with increasing permeability coefficient of the BF-SLS layer. Within the thickness ratio range of 0 to 1/2 between the upper and lower layers, the thickness of the BF-SLS layer significantly influenced the consolidation process of the double-layer foundation. At equivalent Tv levels, the difference in consolidation degree exceeded 60%. Finally, a comparison of various simplified methods for calculating the average consolidation degree of double-layer foundations reveals that neither the weighted consolidation coefficient method nor the average index method yields results that are in good agreement with theoretical solutions. The difference between Us (defined by sedimentation) and Up (defined by pore pressure) cannot be distinguished. This research can further refine the consolidation theory of “upper hard and lower soft” double-layer foundations.