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Gao Z.-Y.,China Communications Construction Company Ltd. | Gao Z.-Y.,Key Laboratory of Port Geotechnical Engineering of the Ministry of Communication | Gao Z.-Y.,Key Laboratory of Port Geotechnical Engineering of Tianjin | Hou J.-F.,China Communications Construction Company Ltd. | And 5 more authors.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2013

It is suggested that the zero hydrostatic pressure level (or plane) should be defined as the groundwater level (or plane). Six factors for the groundwater measurement are analyzed. At the same time, the necessary and sufficient conditions for the decrease and increase of groundwater level are also shown. By analyzing the vacuum preloading mechanism and system of forces, necessary and sufficient conditions for change of groundwater level and field test results of groundwater level, the fact of the soils that are still saturated after improvement, and field data indicate that there are no lowering of the groundwater and preloading. It is illuminated that the groundwater level does not owing to ground improvement by vacuum preloading. A new type of rod instrument is put forward to measure the groundwater level. It is a direct method to measure the groundwater level, which eliminates the effects of incorrect vacuum degree and internal tube leaking as measured by means of the double pipe method. So this new instrument is reliable to measure the groundwater level. Source


Liang A.-H.,China Communications Construction Company Ltd. | Liang A.-H.,Key Laboratory of Port Geotechnical Engineering of the Ministry of Communication | Liang A.-H.,Key Laboratory of Port Geotechnical Engineering of Tianjin | Liu J.-J.,China offshore Oil Engineering Co. | And 6 more authors.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2013

A new vacuum preloading technology for ultra soft soils with footed-in filter tubes is verified through field tests. Compared with the construction technology reinforcement effect and engineering cost of the conventional vacuum preloading technology for surface-layer of ultra soft soils, the new technology is characterized by simple construction technology, low cost and good reinforcement effect. The technology is worthy of being widely spread. Smaller distance of drainage plates (0.4~0.6 m) in newly reclaimed ground can effectively improve the reinforcement effect and reduce consolidation time. The technology has successfully solved the problem that ultra soft foundation has large settlement but low strength increase after reinforcement. Source


Hou J.-F.,China Communications Construction Company Ltd. | Hou J.-F.,Key Laboratory of Port Geotechnical Engineering of the Ministry of Communication | Hou J.-F.,Key Laboratory of Port Geotechnical Engineering of Tianjin | Yu Z.-F.,China Communications Construction Company Ltd. | And 8 more authors.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2013

The artificial island outside of a sea is composed of steel cofferdam and sand filling in the island. The steel cofferdam inserts the impermeable soil layer. The soft clay ground of artificial island is treated by surcharge preloading with PVDs. In order to know the settlement of soft clay ground with steel cofferdam, the numerical analysis is adopted. The results of numerical analysis are compared with the field monitoring data. Through back analysis of the calculated and monitoring data curves, the parameters are modified, and more reliable results are achieved. From the results, the steel cofferdam restrains the lateral deformation of soft clay ground. The failure plane of soft clay ground is hard to form. The settlement velocity is farther greater than that defined in the relative code. So the settlement velocity rule of the relative code should be broken for such special structure. At the same time, the residual settlement is calculated by means of the numerical analysis method, and its value is 9 cm. The consolidation settlement is completed two years later after the project completion. The calculated results may provide reference for the period of its use. Source


Kou X.-Q.,China Communications Construction Company Ltd. | Kou X.-Q.,Key Laboratory of Port Geotechnical Engineering of the Ministry of Communication | Kou X.-Q.,Key Laboratory of Port Geotechnical Engineering of Tianjin | Liu A.-M.,China Communications Construction Company Ltd. | And 8 more authors.
15th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, ARC 2015: New Innovations and Sustainability | Year: 2015

With the development of the marine traffic engineering in China, it is needed to develop the construction method of artificial island in open sea. An artificial inland of 97962 m2 was built in a cross sea bridge project in southeast sea of China. The seawater depth at low tide at the location is 10 m depth and the seawater level at low tide is considered as standard level. The thickness of 6 m seabed mud (-10 m to -16m from standard level) was replaced by sand first. The steel cylinders were inserted into the impermeable soil layer (-40 m) and then the seawater were pumped. The PVDs was inserted from -8 m up to -33 m and the sand was added up to +4m to improve the soft ground by dewatering preloading. The settlements at three typical sections, east section of the island which has deepest burial depth of tunnel (section 1), central section of the island (section 2) and west section of the island which has thickest soft clay layer (section 3), were measured during stage the soft ground improvement. The 3D finite difference method was used to simulate the construction process of the fast-constructed artificial island. The fluid-mechanical interaction method and equivalent hydraulic conductivity is used to predict the degree of consolidation. The settlement curves predicted by numerical method are compared well with the measured results in the field up to 150 days. The numerical results show that the long-term settlements (2400 days) of sections 1, 2 and 3 reach to 2.74 m, 2.91 m and 2.80 m, respectively. The residual settlements after two years of finishing the tunnel construction (1550 days) are 1 cm, 12 cm and 10 cm, respectively. The settlement rate and final settlement of artificial island calculated by the present method using one-dimensional consolidation theory are smaller than the measurement values in the field and the values predicted by numerical simulation. So the predicted settlement results by present method need to be modified according to field data, and numerical simulation method should be used to predict the long-term settlement. Source

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