Abstract
Full-face water-rich gravel stratum is a large challenge during tunnel excavation with earth pressure balance shields (EPBs) because of accidents such as water spewing from the screw conveyor and ground collapse. Slurry and polymer have been used as conditioning agents to avoid such problems and thus ensure a successful tunneling. However, limited improvement of sandy gravel was achieved when traditional soil conditioner were applied. This study proposes a new conditioner (modified slurry) consisting of bentonite slurry, viscosity modifier, sodium silicate and polymer, which will enhance the properties of sand gravel stratum. Low reaction time, high apparent viscosity, good plastic behavior and low permeability were employed for investigating the optimum ratio of the ingredients. The proposed modified slurry has a good performance in conditioning sandy gravel soils and can be the reference for EPBs’ excavation in highly permeable, non-adhesive coarse-grained soil stratum.
Highlights
Since Beijing, Chengdu and other cities that are vigorously developing the metro are rich in sandy pebble stratum, a new soil conditioner for highly permeable sandy gravel to prevent water spewing has become a key technology problem to be solved in underground tunnel construction and in the application of earth pressure balance shields (EPBs) in
To ensure a successful tunneling by EPBs in a water-rich sandy gravel stratum, this study proposed a new soil conditioner that is capable of effectively improving the plasticity and impermeability of sand and gravel
In order to find a slurry additive material and a better ratio decrease to reduce the permeability of the slurry-soil mixture, a large number of experiments show that the permeability of mixing system is decreased with the sodium silicate solution or polymers solution is added into the traditional slurry-ammonium chloride mixing system
Summary
The traditional slurry is commonly the aqueous solution of sodium bentonite with. 10–18 wt%. Ammonium chloride, sodium silicate and high molecular polymers were mixed into the traditional slurry to modify and improve it, in which ammonium chloride was the viscosity modifier to adjust the reaction time. Sci. 2021, 11, 2109 the mixed solution of ammonium chloride and high polymers. The sodium bentonite (Henan Zhongyuan Mining Company, Henan Province, China) chemical components and physical characteristics are shown in Tables 1 and 2. The ammonium chloride was analytically pure (>99%), the sodium silicate solution (Shandong Dongyue Group, Shandong Province, China) had a Baume Degree of 40, and the content was 34 wt%. In the process of polymer solution preparation, it should be noted that the weighed reagent was slowly added into the 50–60 ◦ C distilled water and the solution was stirred at 2000 r/min for more than 30 min until the solution was clear.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
