Strength Characteristics and Solidification Carbonization Mechanism of Mgo Based Shield Tunneling Centrifugal Waste Silt

In response to the problem of the accumulation of waste silt produced by slurry shield tunneling, which is difficult to directly utilize, MgO carbonization acceleration technology is adopted. Carbonization modification equipment is used to test the water content (w) and unconfined compression strength (UCS) of waste silt produced by slurry shield tunneling under different soil curing agent content (as), curing time (T), and carbonization time (t). The strength characteristics of the process of MgO solidification carbonization shield tunneling centrifugal waste silt were clarified. The micro mechanism was revealed and its engineering usability was also explored. The results show that MgO cooperated with carbonization acceleration technology can improve the properties of waste silt, with a maximum decrease of 9.3∼31.7 % and UCS can be increased to a maximum of 776.8 kPa. The maximum UCS of MgO solidified carbonized silt was higher than that of CaO solidified carbonized silt at various contents. Under the condition of T=7d, by comparing UCS, it was concluded that MgO carbonated solidified silt is more suitable for building foundation filling. And as =7 % while t=1 h modified silt can meet the strength requirement of 180 kPa under the condition of small MgO content. An improved three-phase model diagram of MgO solidification carbonation process based on water conversion research has been proposed for centrifugal high liquid limit silt in slurry shield tunneling. It can be divided into three stages: solidification reinforcement, carbonation reinforcement, and carbonation deepening, with strength growth mainly concentrated in the solidification reinforcement stage. During the solidification process, the hydration product Mg(OH)₂ and the reaction products MSH and MAH from the pozzolanic reaction are gradually transferred into various carbonization products, These products agglomerated and bonded with each other to form a whole, enhancing the bonding strength between particles and improving the strength of the silt. During the carbonization process, it is necessary to avoid the strength reduction caused by too long carbonization time.