The chemical grouting improvement is one of the typical countermeasures against liquefaction during an earthquake. The quality of the improved ground is usually identified by the uniaxial compressive strength. However, the sample disturbance is likely to occur during sampling because the target strength of the improvement body is relatively low. Therefore, it is very difficult to grasp a characteristic change before and after the improvement. In this study, we focused on the change in electric resistivity in addition to the uniaxial compressive strength as a quality identification. The effectiveness of quality identification using electric resistivity was confirmed by metal barrel model experiments and a field test.

The chemical grouting methods have been widely used as liquefaction mitigation methods. However, the injection loss due to the leak of chemical liquid from the drilling hole and the injection inhibition due to the borehole wall failure have been often observed. In this study, we developed a new chemical grouting method to overcome these problems. A developed chemical grouting method has two unique technical features. One is the packer which is made up of cloth and rubber. The other is a special sealing material which protects the borehole wall during drilling and is fluidized during the chemical injection. From the trial in-situ injection tests results, it was found that 1) the leak of chemical liquid from the drilling hole has not been observed, and 2) a wide range of chemical grouting has been achieved by about 30% of the injection pressure compared to the conventional Double-Pipe Double-Packer method.

This study presents an evaluation of feasibility of using a new phosphate-based binder, named KMP, to solidify/stabilize mixed zinc (Zn) and chloride (Cl) contaminated soil collected from an abandoned industrial electroplating company site. The solidified/stabilized soils cured at 1, 3, 7, and 28 days were subjected to various tests including unconfined compression, soil pH and leachability. The analyses of Zn speciation, X-ray diffraction, and SEM-Mapping were performed to investigate immobilization mechanisms of Zn and Cl in the solidified/stabilized soils. The test results showed that the unconfined compressive strength of the soils solidified/stabilized with 6% KMP was significantly improved, and the leached Zn and Cl concentrations were well below their corresponding remediation goals. The addition of the KMP binder to the contaminated soil transformed large amounts of extractable Zn to stable chemical species. The XRD and SEM-Mapping results indicated the formation of phosphate-bearing precipitates containing Zn and Cl were the predominant mechanisms of immobilizing Zn and Cl with KMP binder.

The bearing capacity of bored piles is significantly improved and the dispersion of bearing capacity is reduced obviously by employing the method of grouting. However, there is still a lack of systematic research on the calculation and analysis of the reliability index of post-grouting pile. In this paper, the static load test data of 152 non-grouted bored piles and 113 post-grouted bored piles are collected. The influence of factors such as safety factor K, types of load effect combination, and the pile diameter are taken into account. Then, the approximate probability method based on the first-order second-moment method (JC method) and Monte Carlo method is employed to analyze the reliability indexes of post-grouted bored piles and non-grouted ones.

The strength of cement-stabilised soil mixed using the jet grouting method is generally evaluated by the unconfined compressive strength of core samples after 28 days of curing. If the 28-day in situ strength of the soil‒cement mixture does not meet the design criteria, disposal of the deficient mixtures and reworking of the soil improvement are required, that may affect the construction period and cost. If the 28-day in situ strength can be predicted after a few days of mixing work, additional jet grouting work can be effectively performed if necessary, thereby reducing the impact on the construction schedule. In this study, laboratory tests were performed to estimate the 28-day strength of soil‒cement mixture specimens using accelerated curing at high temperature for a few days. The effects of accelerated curing and mixture conditions on the strength properties of the soil‒cement mixture specimens were investigated and the results validated the applicability of the high-temperature accelerated curing method for the evaluation of the 28-day strength.

This paper presents results of Piezocone Penetration Tests (CPTu) in a sand during the flight of a geotechnical centrifuge at an acceleration of 50 g. Two rates of penetration were used and its effect on penetration resistance was interpreted. Calibration of the CPTu was performed to predict the internal friction angle of the sand using cavity expansion theory and compared with results obtained from laboratory triaxial tests. It is found that penetration rate has strong but different effects on tip resistance and sleeve friction. However, the internal friction angles predicted by cavity expansion theory are approximately identical using a friction ratio to include both the tip resistance and sleeve friction response. It indicates a minor effect of the predicting rate on the soil strength prediction. Further study is needed to clarify the mechanism.