Study Of Treatment On Coastal Liquefiable Ground Using Cross Vibration Wing ResonanceMethod

Liquefiable foundation treatment is an integral part of the foundation treatment. Under the long-term sedimentation of Yellow River and Yangtze river, large amounts of liquefiable foundations can be found in the coastal areas, which is mostly conposed of silt powder sand and marine soft clay. The traditional method of treating the liquefiable foundation is less effective. Thus, an effective liquefied foundation treatment method has become the study focus.With the found provided by the national natural science fund project (41372308) and jiangsu province traffic scientific research project (2010 y28) finance plan, this study presents a research that using the latest developed cross vibration wing resonance method to treat the liquefiable foundations in the costal areas. Based on the construction of Huai Yan highway (Dafeng port section), the liquefiable foundation treatment was studied. The typical marine liquefiable section is selected as a test section, the in-situ field tests and laboratory tests are included to investigate the treatment of cross wing vibration resonance method. Meanwhile, pore pressure monitoring is also carried out to record the variation of pore water pressure during the construction. The reinforcement mechanism of the cross wings vibration resonance method is concluded from the aforementioned studies and the following conclusions can be obtained from this paper:(1) By conducting the in-situ standard penetration test and particle analysis of the disturbed soil, according to the related standard, it is determined that the test site has a big risk of liquefaction. The complicated soil particle composition indicates that both the liquefiable layer and unliquefible soft clay layer exsit in the site. CPTU test is included to further investigate the soil distribution in the site. Results show that apart from the wide distribution of silt and silty sand layer, there is an obvious weak interlayer in the depth of 2 to 3 m,8 to 9.5 m,12.5 to 14 m with the main components are clay and silty clay, which is a typical marine liquefiable foundation.(2) Results from the CPTU experiment directly reflect the enhance of soil strength and liquefaction elimination. Meanwhile, the seismic test also shows that the soil treated by cross wing resonance resonance method have a sharp increase in its compactness. Results from the standard penetration test with the corresponding standard specification indicate that after the cross wing vibration resonance treatment, the tested site becomes basically unliquefiable. Moreover, the strength of the soil and the engineering characteristics of the soil have sharp increase up to 2 times., and compared before and after the construction of the concrete numerical value, more detail to show the wings cross resonance resonance method of The reinforcement effect and mechanism are further studied by the in-situ undisturbed soil collection and laboratory experiments targeting on the soil before and after the treatment. The results form the soil particle analysis also illustrates that this method is very effective in reshaping the soil structure when dealing with complex engineering geological conditions, such as the a clay interlayer is found in liquefiable foundation.(3)Single-point pore pressure monitoring shows that pre-liquefaction happens during the treatment process. The excess pore water pressure reaches its highest value when the vibration rod reaches the corresponding depth. It is also found that pore pressure lowers down quickly after the treament. Multi-point pore pressure monitoring shows the existence of the pile-group effect. The compactness of soil is further improved due to the pile-group effect. Longer single-point vibration time can increase the effectiveness of the cross vibration wing resonance method. Significant settlement of the site is obseved when the the construction of group points and the average settlement depth is about 0.6 m. By analyzing the pore water pressure caused by the vibration, further investigation into the reinforcement mechanisim of the cross vibration wing resonance method is carried out. The pore pressure ratio is used to determine the liquefaction which is an direct parameter to reflect the pre-liquefaction happens during the construction.