Zhengzhou, China
Zhengzhou, China

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Han Y.,Zhengzhou Rail Transit Co. | Zhu W.,Hohai University | Liu Q.,Hohai University | Zhong X.,China Railway Shisiju Group Corporation
Geotechnical Special Publication | Year: 2010

The application of cemented mortar in tail void grouting of shield tunnel construction is becoming increasingly popular. However, the effect of mix ratios on cemented mortar performance is not well understood, and grout engineering properties cannot meet the demand of shield tunnel construction. Pumping difficulty and pipe blockage were occurred during backfill grouting process, and large stratum settlement was induced while shield passed. Determination method of mix proportioning for desired grout engineering properties is unreasonable, mix proportioning cannot be adjusted quickly with shield construction conditions change. Orthogonal experimental design method is used to study on grout engineering properties. The qualitative and quantitative relationships between mix ratios and grout engineering properties were obtained by variance analysis and regression analysis of experimental results respectively. Finally, mix ratios were calculated for desired grout engineering properties by goal programming method, and the rationality of goal programming results was examined by trial. Experimental analysis results show that the influence of water-binder ratio on all grout engineering properties is mostly obvious, and water-binder ratio is key impact factor. Bleeding rate and segregation degree reduce with the increasing of bentonite-water ratio, so bentonite is beneficial to increase the physical stability of cemented mortar. Grout volume shrinkage is mainly induced by drainage consolidation, so grout shrinkage rate decrease with the enhancing of mortar water retention ability and the decreasing of binder-sand ratio. Cemented hydration products were dispersed by the defloccu lating action of water-reducing retarder to prolong the setting time of mortar and decrease the early age strength of mortar. It was illustrated that combinatior of orthogonal experimental design, regression analysis and goal programming is an effective method to determine mix proportioning quickly that is suitable to shield construction environments.

Si H.-Y.,Beijing Jiaotong University | Si H.-Y.,Zhengzhou Rail Transit Co. | Chang H.-T.,Zhengzhou Rail Transit Co. | Chang H.-T.,Tongji University | And 3 more authors.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2011

The consolidation time in the centrifugal model tests is 1/n2 of that in the prototype, thus the long-term settlement of deep soft clay ground can be simulated within short time. Based on the principles of centrifugal model tests, different test schemes are designed and centrifugal model tests are employed to study the improvement mechanism of D-M method. The tests results show that the D-M method is feasible to improve deep soft clay ground. Compared with the deep mixing, the D-M method is beneficial to reduce the differential settlement and the cost of ground treatment. At the same time, the method has better treatment effect than PVD in post-construction settlement and differential settlement.

Zhou J.,Tongji University | Guo J.-J.,Tongji University | Zhang Z.,Zhengzhou Rail Transit Co. | Jia M.-C.,Tongji University
Yantu Lixue/Rock and Soil Mechanics | Year: 2010

A model test of single pile static load has been carried out through visualization model box. Considering some influence factors, such as the different diameters of piles and different soil compactnesses, the settlement mode of single pile, the behaviour of skin friction resistance and pile-tip resistance with penetration are researched. Through screen and image-processing technology, the change rule of porosity in pile tip and pile-surrounding soil is researched too, through exploitation the process of planar particle flow code, simulation the pile-tip resistance and the change rule of porosity in pile tip and pile-surrounding soil. The results show that the simulation using method of particle flow code can preferably simulate the process of static load of single pile and post the mechanisms of macro-scale and meso-scale of static load of single pile.

Li F.,Zhengzhou Rail Transit Co. | Li F.,Zhengzhou University | Guo Y.,Zhengzhou University | Shi G.,Zhengzhou University | Qian H.,Zhengzhou University
Advanced Materials Research | Year: 2011

This paper presents a theoretically study on the time-dependent characteristic of soil-nail axial force in the whole construction process of foundation pit. Firstly, the time-varying performance of axial forces of soil nails is analyzed according to the measured lateral deformation curves of pile-anchor and soil-nail composite supporting deep foundation pit. Then combined with a soil rheological model, a time-dependent formula of soil nail axial force is put forward, and the simulated results are compared to the back-analyzed ones. Finally, a formula to predict the time-dependent axial force of soil nail in the whole construction process of foundation pit is established and an example is investigated to validate the method. © (2011) Trans Tech Publications.

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