The settlement calculation of postgrouting piles is complex and depends on the calculation method and parameters. Static load tests were conducted to compare the settlement characteristics of nongrouting and postgrouting piles, and three vital parameters in the layer-wise summation method were revised to predict the settlement of postgrouting piles. The elastic compression coefficient was deduced based on the Mindlin–Geddes method by considering the influence of the change in the pile side resistance distribution and end resistance ratio on the elastic compression after grouting. The relationship between the compression modulus and soil gravity stress and cone penetration resistance were established, respectively, using experimental data. The optimum value of the settlement empirical coefficient was determined using regional data. Finally, we used the postgrouting pile of the Wuqi–Dingbian expressway as a practical example. The results obtained from the layer-wise summation method after parametric optimization were close to the measured values. The results of this study provide reference data and guidance for the settlement calculation of postgrouting piles in this area.

The density of the sand is important factor for its engineering properties, There are many methods to evaluate the sand density, just the results may be differences, usually means, this is the test error of the different test methods. In fact, the reasons of the sand formation and buried conditions, sand particle shape and size, sand gradation, groundwater etc. are also the important factors for its engineering properties, but these factors are often ignored. Bearing pressure of confined water will change the distribution of the effective weight stress in soil and the abnormal phenomenon of sand density will appear. In the project, the cause analysis of sand density require attention. According to theoretical knowledge, to identify applicable conditions of the various evaluation methods and their advantages and shortcomings.

From the view of design, this paper have discussed some problems of design and application of deep cement mixing pile, and have analyesd the determination of single pile bearing capacity method, the checking of soft stratum, defects or errors existing in the calculation of cement mixing pile of composite foundation settlement, and have put forward some suggestions for improvement.

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