Calculation Of Foundation Settlement Based On Pore Pressure Static Cone Penetration Technology

Excessive settlement of the foundation will often cause serious damage to the roadbed and pavement,threatening the normal operation and service life of the highway.Therefore,scientific calculation and prediction of foundation settlement is of great significance.The key to reducing settlement calculation errors is to obtain sufficiently accurate soil physical and mechanical parameters.However,the traditional indoor test method to obtain soil parameters has large errors due to sample disturbance and different test conditions from actual conditions.Therefore,Using in-situ testing technology to calculate the soil parameters,combined with a reasonable settlement calculation method to estimate the settlement of the foundation has huge technical and economic benefits.For this reason,this article relied on a certain expressway project in Hunan,took the foundation soil of the expressway to establish a model groove of size 120cm X 40cm × 85cm,and conducts pore pressure static cone penetration test and pore pressure dissipation test on the remolded foundation soil.The pore pressure penetration parameters of the remolded foundation soil and the variation law of pore pressure dissipation under consolidation pressure.Indoor consolidation test,unconfined compression test,and permeability test were performed on soil under different pressures.Through linear fitting method,the compressive modulus of each pressure section of the foundation soil was established Es25-50,Es50-100,Es100-200,Es200-300,compression index Cc,rebound index Cs and cone tip resistance qc,modified cone tip resistance qt,net cone tip resistance qn;fitting to obtain the total estimated undrained shear strength Cu of the foundation soil The cone-point cone coefficient Nk,the effective cone-point cone coefficient Nke,and the pore pressure cone coefficient NΔu were 33.35,25.25,and 4.71 respectively.Among them,the Cu is calculated by using the pore pressure cone coefficient with the smallest error;Comparing the permeability coefficient of the foundation soil with the results of the indoor permeability test,it is concluded that the empirical formula method is more suitable for estimating the permeability coefficient of the foundation soil;the logk-e relational expression of the permeability coefficient of the foundation soil changing with the void ratio was established.The four monitoring points of K52+450 and K44+990 two typical replacement foundations were monitored for settlement,and it was concluded that the curve change was roughly divided into three stages,the rapid growth stage of settlement in the initial stage of filling,the steady growth stage of settlement in the middle of filling stage,After filling,the settlement tends to be gentle;the uneven settlement of the foundations of the two sections is smaller,and the embankment is better filled.Using ABAQUS finite element to perform fluid-solid coupling calculation and analysis on the settlement of the expressway foundation,it is concluded that the foundation settlement calculated by the measured pore pressure penetration parameter qt of the engineering site foundation soil has high reliability;the foundation settlement was in the process of embankment filling The resulting pore water pressure changes had a clear correlation with embankment filling;the maximum horizontal displacements of the foundation appeared at the corners of the subgrade slope,and the maximum horizontal displacements of the two sections were 4.558cm and 3.956cm respectively;the settlements of the two sections in one year after construction was respectively 210.9mm and 190.4mm,the settlement after 15 years was 211.3mm and 190.6mm respectively,and the settlement after construction was 21.1mm and 19.3mm respectively.