Abstract:

A large amount of waste sand is produced in shield tunneling and it is of great importance to study the recycling use of the waste sand in backfilling grouting. In the paper, the waste sand produced in the construction of Weisanlu Rivercrossing Tunnel in Nanjing is classified into three grades with 1.652, 1.096 and 0.773 fineness modulus respectively, backfilling grouts with different water/binder ratios are prepared by using the mentioned waste sand, the influence of the fineness modulus of the sand on the basic properties of the backfilling grout is studied, and suggestion is made on the application of the waste sand in the backfilling grout. Conclusions drawn are as follows: 1) The higher the fineness modulus of the sand, the larger the fluidity, consistency, bleeding rate, volume shrinkage rate and setting time of the grout, and the lower the strength of the grout; 2) Grout prepared with the waste sand of 0.75~1.08 fineness modulus and having 0.9 water/binder ratio can be directly used for backfilling; 3) The following two waste sand recycling use schemes can be adopted for Weisanlu Rivercrossing Tunnel in Nanjing: A) The sand in the original mixing proportion is replaced by the waste sand screened by 1.25 mm sieve, with 75% replacement ratio, and the water/binder ratio is adjusted as 0.85; B) The sand in the original mixing proportion is replaced by the waste sand screened by 1.25 mm sieve, with 50% replacement ratio, and the water/binder ratio is adjusted as 0.9. 

Key words: waste sand, slurry shield, backfilling grouting, fineness modulus, Weisanlu Rivercrossing Tunnel in Nanjing