The Experimental Study On Load-bearing Characteristics For Anti-pulling-out On Single Pile In Calcareous Sands

In recent years,the construction of pile foundation related to calcareous sand is changing rapidly,a large number of scholars around the world have focused on this area.Different regions have different regional experience and research status,and only regional research experience is not enough to provide a powerful and effective solution to the analysis and solution of the project's engineering problems.Therefore,on the basis of predecessors' experimental research,this paper will test the calcareous sand collected from the reef near the Nansha Islands in China.The main plan of the experiment is to build a model test system in the model tank to study the embedded in the calcareous sand.The uplift loading characteristics and deformation capacity of aluminum pipe piles and other relevant characteristics are compared,and the relevant test results are plotted as curves for comparison.The calcium granules were sieved to determine their related physical properties.The density of the calcareous sand in the pre-pile area before each uplift test was measured by the ring knife method and the irrigation method,which was helpful for the following data analysis.The uplift test used fixed pulleys,moving pulleys,data acquisition instruments,and I-beams that acted as counter-forces.Through manual operation to change the pile foundation buried depth and use to bury the pile foundation of calcareous sand have a certain water content,at the same time through tamping machine tamping change the relative density of calcareous sand.Compared with the previous experiments,the control of water content and relative density of calcareous sand is different from those of previous experiments.So in order to analyze the force of single pile uplifting in calcareous sand,the vertical drawing test of small size single pile model in the model trough is planned by changing the relative compactness of calcareous sand and burying depth of aluminum pipe pile according to the proportion scale of the full scale aluminum pipe pile.According to the recorded load of data acquisition instrument,the displacement and strain of the pile are calculated to draw the correlative curves of each test,and the relationship between the parameters of pile deformation,displacement,axial force,side friction and other characteristics such as the compactness of sand around pile foundation and embedded depth of pile is analyzed,the mechanism of pile-soil interaction in calcareous sand stratum is further explored.After comprehensive analysis,it can be seen that the greater the relative density and depth,the greater the maximum uplift force when the pile is pulled out,but the vertical displacement does not increase with the increase of density,and the pile excavation displacement is about 0.1 times the diameter of the pile.and the excavation displacement of the pile body cracks when the pile diameter is about 0.1 times the pile diameter.When the degree of compaction of the calcareous sand formation is relatively large,cracks and bulges occur in the soil near the upper part of the pile,and the soil in the lower part becomes dense.The friction resistance of the pile increases from the top to the bottom,and the reduction in the axial force shows an approximate decrease.The trend is particularly evident in the middle and lower part of the pile.When the density is small,the soil density in the middle and upper part of the pile is dense.The friction resistance of the pile increases from the top to the bottom and then decreases,and the axial force shows a rapid decrease.The trend of slowing down is often highlighted by the rapid decrease in the middle and upper part of the pile.Using the above conclusions,it can provide reference value for the stress analysis of various pile foundations constructed in the calcareous sand stratum,and it can help in the design and optimization.