Study On Bearing Capacity Of Cement Fly Ash Mixed Pile Composite Foundation

Fly ash is an industrial solid waste produced after coal burning.It is a kind of light porous loose body with complex composition.Improper treatment will cause environmental damage and ecological pollution.At present,the utilization technology of fly ash as admixture in the field of civil engineering and building materials industry has been quite mature and promoted to the whole country,but the fly ash accumulated in a large number of power plants as admixture is obviously not suitable for the requirements of economic benefits.Taking it as a foundation material and using it as an artificial stratum on the original basis can not only maximize the utilization of resources,but also realize the consumption and utilization of fly ash in situ.The fly ash stratum has insufficient bearing capacity,strong permeability,large porosity ratio and low shear strength,so that strengthening measures should be taken to ensure the safety of the building if the fly ash stratum is to be constructed.In recent years,the study on the characteristics of soil-cement mixed pile composite foundation has brought a new idea for the treatment of fly ash foundation.In order to reveal the bearing characteristics of Cement-fly ash mixing pile(CFMP)composite foundation,laboratory model test research on CFMP composite foundation is carried out,and the main research results are as follows:(1)With the increase of cement content,the compressive strength of the test block increases gradually,and the increase of compressive strength of the test block is the largest at 15% cement content;Field tests show that the bearing capacity of single pile composite foundation and the vertical bearing capacity of single pile under the optimal ratio meet the design requirements.(2)The bearing capacity of CFMP composite foundation is 220% of that of unreinforced fly ash foundation.The lateral friction of cement-fly ash mixing pile under vertical load of composite foundation has an obvious peak value,and the peak value is located in the middle of the pile.The softening of lateral friction occurs with the increase of load.When pile tip load reaches 800 N,the effect of pile tip bearing layer becomes prominent,and pile tip resistance ratio enters a rapidly rising period.(3)The cumulative settlement under different load ratios has "threshold effect",which can be divided into decay type and failure type.When the peak value of cyclic load is close to the ultimate bearing capacity,the dynamic failure of pile foundation will be caused.The settlement of cyclic load can be predicted by static load displacement.Under cyclic loading,the proportion of pile side sharing upper load decreases continuously,and the fatigue degradation of side friction occurs.The degradation can be alleviated by reducing the moisture content of fly ash and taking waterproof measures in construction.(4)The horizontal critical load and lateral deformation control ability of CFMP composite foundation are significantly higher than those of fly ash foundation under the same conditions.The analysis of horizontal resistance and soil pressure shows that the horizontal bearing capacity of composite foundation is greatly affected by the upper fly ash stratum.The displacement curve is calculated by m method and p-y curve method,and compared with the measured data,it can be seen that the p-y curve method is closer to the measured value.(5)Cyclic loading will reduce the horizontal deformation modulus of fly ash formation,and then cause the weakening of pile-fly ash system.When the cyclic load amplitude reaches the horizontal critical state,the pile-fly ash system is destroyed and enters the loading limit state,and the service performance of CFMP composite foundation is affected.Figure 51 Table 6 Reference 117...