Study On Evaluation Method Of Compaction Quality For Earth-rock Composite Foundation Based On Additive Mass Method

Based on the science technology project of department of transpot of JiangXi province,named Study on Evaluation of Compaction Quality with High Filled Subgrade Based on Combined Test Using CT Technology and Additive Mass Method,and graduate education innovation foundation project of Chongqing Jiaotong University,named Study on Evaluation of Compaction Quality with Earth-rock Composite Foundation Based on Additive Mass Method,this paper was finished.By establishing the physical model of earth-rock composite foundation and testing,the applicability and influencing factors were studied with additive mass method applied to test of earth-rock composite foundation.Based on the density inversion theory,the density of earth-rock composite foundation was calculated,and so as to the comparative analysis of various density inversion methods.In addition,the evaluation method of compaction quality for earth-rock composite foundation based on additive mass method was put forward,and its application effect and reliability verification could be obtained by evaluation of compaction quality for the model foundation and practical foundation.The main research contents and results were as follows:(1)Taking the diffrences between undamped linear elastic model and prototype of earth-rock composite foundation into consideration,the effects of damp on model were analyzed by calculating the vibration damp and the linear approximation of model was analyzed by analyzing the relationship between force and deformation.The result shows that there is little difference between the undamped natural frequency of model and the damp natural frequency of prototype under the condition of vibration;based on the prominent relationship between the measured vibration natural frequency and the additive mass,the model can reflect the linear elasticity characteristic markedly.(2)The rigidity and vibration mass of earth-rock composite model foundation were detected with additive mass method.The detection effects of various additive mass in loading and steps in loading were studied by model test with additive mass method.The result shows that the more total additive mass in loading is able to lead to the better correlation between the2?-and(35)m on average while not as to single test point;besides,the change of the total additive mass can’t lead to the responsible change of the rigidity and vibration mass of model foundation,the rigidity and vibration mass of model foundation were with the regularity of the same increase or decrease along withthe change of total additive mass;more steps in loading can lead to lower volatility of correlation coefficient among the test points as well as smaller rigidity and vibration mass of model foundation.(3)Based on the theory of density inversion,the foundation density was calculated with various density inversion methods.Comparing with the model,performance and error in inversion,the influence of the various inversion methods on density inversion of earth-rock composite foundation were analyzed.The result shows that both the rigidity correlation method and the volume correlation method can reach the goal of density inversion calculation,however,the volume correlation is superior to the rigidity correlation on regression performance and error volatility,thus lead to the density values calculated by volume correlation method were more fit with that mearsured by pit method which is considered to be the most accurate method;compared with correlation method,BP neural network method was more intuitive,more simple and with more accurate and representative results because of the smaller inversion error.(4)The evaluation method of compaction quality for earth-rock composite foundation based on additive mass method was put forward.The application effect of this method was studied by calculating and evaluating the compaction quality for the model of earth-rock composite foundation as well as the reliability verification was accomplished further by the application to the practical engineering.The result shows that the application results based on this method were in accordance with that based on pit method,showing there was high accuracy and reliability with this evaluation method.