A Study on Methods for Judgment of Effectiveness of Grouting by Chemical Injections

在桑迪土层中进行化学灌浆工艺设计，必须根据被加固土的特性确定最适宜的灌浆条件。为了找到理想的注浆条件，必须了解土壤条件和注浆条件如何定量和定性地影响土壤的固结。本实验着重研究了凝胶时间、注入速率、上覆压力和土壤相对密度四个变量对化学浆液生长的影响。本研究采用克砂6号、克砂7号和天然河砂制备了高、直径分别为30 cm的圆柱形砂样，通过200个室内试验，得出了上述结果。采用两种不同的化学路线来缩短反应时间（5秒）和长凝胶时间对于松散状态（Dr=35%）和致密状态（70%）的试样，上覆压力从49 kN/m^2变化到245.2kN/m^2。试验结果表明，当成胶时间较短、注入速度较低时，易发生劈裂灌浆。然而，当凝胶时间较长时，渗透灌浆倾向于发生而不考虑其他变量，并且在这种情况下，灌浆导致固结砂的近球形形式，这被认为是灌浆的理想条件。对于凝胶时间短的浆液，当注入速率较低时，容易发生水力压裂，在这种情况下，得到不规则形状的固结砂。当上覆压力高时，可以获得类似于渗透灌浆的球形。然而，应注意的是，当上覆压力高时，固结土的体积减少约15%至20%的估计体积。

In order to design chemical grouting process in sandy soil layrs, it is necessary to determine the most suitable grouting conditions depending on the characteristics of soils to be stabilized. For the purpose of finding ideal grouting conditions, one must know how soil conditions and injection conditions will affect the consolidation of soils quantitatively and qualitatively. This experiment focuses on the effect of four different variables, namely gel time, injection rate, overburden pressure and relative density of soils, on the growth of chemical grouts. The results presented in this study were drawn from 200 laboratory trials of cylindrical sand specimen whose height and diameter were held constant at 30cm respectively, which were prepared by Keisa No.6, No.7 and natural river sand. Two different types of chemical routs were used to get short get time (5 seconds) and long gel time (5 minutes) and injection rate was changed from 500cc/min to 2000cc/min. The overburden pressure was varied from 49kN/m^2 to 245.2kN/m^2 for the specimens of loose state (Dr=35%) an dense state (70% ).The results of this experiment indicate that fracture grouting tends to occur when the gel time is short and injection rate is relatively slow. However permeation grouting tends to occur irrespective of other variables when the gel time is long and in this condition the grout results in nearly spherical form of consolidated sand which is said to be a desired condition of grouting. For the cases of short gel time grouts, hykraulic fracturing tended to occur when the injection rate low and in this case irregular form of consolidated sand was obtained. When the overburden pressure is high, it is possible to obtain a spherical shape similar to permeation grouting. However it should be noted that when the overburden pressure is high, the volume of the consolidated soil is decreased about 15% to 20% of the estimated volume.