Assessment of grouting applicability in type C Tehran alluvium

Abstract

With the increase in the construction of underground railway lines and other underground spaces in Iran and the necessity of tunnelling through loose formations, it is essential to study the groutability of alluvial soils which are present in most of the urban regions. In the present study, a laboratory investigation was conducted on several soil mixtures, the distribution of which was in accordance with type C Tehran alluvium as the hosting material for many parts of the Tehran subway system. Cylindrical specimens of these materials with 50 and 70% compaction were prepared. As a first step, grouting with different water/cement (w/c) ratios and various pressures was applied to the test specimens. Based on the aggregations of soil and cement, grout w/c ratio, fine grain percentage in the soil, grouting pressure and compaction percentage, the groutability of the samples was assessed in terms of their various weights before and after grouting and a numerical criterion was derived for the groutability of the type C Tehran alluvium. In addition, after determining the 28 d strength of the grouted specimens and making comparisons with the witness samples, a relation was derived to estimate the strength of successfully grouted cylindrical specimens.