Research On Thawing Settlement Controll Of Artificially Frozen Soils By Artificial Thawing

Artificial Ground Freezing method is superior to other ground treatment methods because it is well suit for almost all kinds of layers and has less impact on environment, since it is firstly applied in England. However, frost heave and thawing settlement exert bad influence on surroundings so that the method is not adopted in projects which need high environment protection requirement. In order to reduce the influence of thawing settlement on environment, the method of grouting and compensation, the theory of which is artificial thawing with grouting to control thawing settlement, is applied generally in projects. It is a pity that there is always no suitable formula for calculating thawing settlements controlled by grouting in respect that applicability of the traditional formula is limited resulting in not well guiding construction.The mechanism of thawing settlement of frozen soils and displacement grouting is introduced in the dissertation. What's followed, the basic principal that settlement of frozen soils is controlled by displacement grouting is presented. Stochastic medium theory is also introduced to combine with analyzing thawing settlement. The truth of the stochastic medium theory and its applicability in displacement of ground by excavation of elements is presented. At the same time, the formula for analyzing thawing settlement controlled by ground surface displacement owing to displacement grouting is established by combining stochastic medium theory with the mechanism of displacement grouting. And then, the formula is solved by Legendre - Gauss quadrature method.The practical parameters and the measured data of Restoration Project of Line 4 of Shanghai metro are joined in the above-mentioned formula. In succession, the displacement brought by thawing settlement and displacement grouting are calculated and furtherly analyzed. The results show that the parameters, i.e. distance between the axis of tunnel and ground surface, major influencing radius, index of thawing settlement, the range of grouting, grouting amount and so on, affect greatly the ultimate ground displacements. Index of thawing settlement and grouting amount respectively denote possible volume deformation of their own which result in corresponding displacement of ground. On the side, the requisite parameters for grouting in practical projects can be reckoned by the above-mentioned formula after the thawing settlement is calculated with parameters and the measured data.In conclusion, thawing settlement and grouting amount can be effectively speculated by stochastic medium theory. Comparing results with the measured data in project, construction of aritificial thawing with grouting can be well guided by the formula.