Rapid Setting Effect (RSE)

Introduction

RSE is a modified high polymer that forms a gel-like substance soluble in water, produced by blending multiple covalently bonded polymer compounds.

Application

Modification of sand gravel and muck soil、prevent gushing.

Advantages

1.To enhance RSE’s debris-carrying performance, certain colloidal groups are introduced into the molecular chain of RSE, modifying it to reduce the curling and contraction caused by electrostatic attraction on the polymer chain.

2.To improve RSE's anti-gushing performance, a small amount of hydrophobic groups are incorporated into the main structure of the RSE polymer chain, which undergoes hydrophobic modification to the originally hydrophilic polymer. The hydrophobic association enhances the polymer's bridging adsorption and viscosity. These hydrophobic groups give RSE unique rheological properties, as they allow polyacrylamide to form associations both within and between molecular chains, rapidly creating a network structure that strengthens the anti-gushing performance.

Principle

Based on the characteristics of shield tunneling, the Rapid Setting Effect (RSE) must possess three essential functions: preventing gushing, carrying debris, and reducing friction.

Due to the high water pressure at the tunnel face and the high permeability of the excavated spoil, water cannot be effectively blocked. The screw conveyor cannot mix the excavated muck with groundwater to transport it to the belt conveyor. High-pressure water passes through the excavation chamber and screw conveyor, causing gushing. When RSE is mixed with water, it rapidly forms a network structure that binds the groundwater and excavated spoil in the excavation chamber. This process reduces the spoil's permeability while "trapping" the groundwater between the soil particles, forming a soil plug that blocks incoming water, thus dynamically preventing gushing during shield tunneling.

Large-diameter cobbles and gravel tend to accumulate between the cutterhead and the excavation face or at the bottom of the excavation chamber, causing discharge blockages. This accumulation clogs the spoil discharge channel, preventing the normal discharge of spoil. As a result, spoil cannot be promptly and smoothly discharged from the excavation chamber,aggravating the accumulation, which creates a vicious cycle. RSE enhances viscosity by forming a spatial network structure in water through its molecular chains. Unlike ordinary polymers, RSE does not lose viscosity when spoil temperatures are high; instead, its molecular chains further dissolve and extend. This helps to overcome the decreased debris-carrying capacity that occurs with ordinary polymers at high spoil temperatures.

The friction and compression between the cutterhead and the excavation face cause varying degrees of tool wear, which progresses through three stages: initial wear, normal wear, and rapid wear. While soft ground such as silt, clay, and loam causes minimal wear on cutting tools, sandy soil, gravel, and hard rock significantly increase wear. The viscous lubricating liquid formed by the reaction between RSE and water effectively reduces the friction coefficient. The electrostatic repulsion between the positively charged viscous lubricating liquid and the spoil particles further reduces the friction coefficient, offering enhanced lubrication.

Specification

liquid, 200 KG per drum

The Rapid Setting Effect (RSE) is used to manage gushing incidents in shield tunneling

As shown in the diagram: in water-rich strata without cohesive soil or with low cohesive soil content, water at the tunnel face quickly carries away fine to medium particles (fine particle spoil or bentonite used for improvement). This creates a water flow channel between the tunnel face and the screw conveyor, making it difficult for the screw conveyor to form a soil plug effect, leading to gushing. As large particles of spoil continue to accumulate at the bottom of the excavation chamber, the screw conveyor and cutterhead can easily become jammed.

By using the Rapid Setting Effect (RSE) combined with sodium bentonite (to increase the mud content in the spoil) and adding it to the excavation chamber in a specific ratio, the RSE, sodium bentonite, and spoil bind tightly together. This prevents the formation of a water flow channel between the water and the screw conveyor, effectively resolving the gushing problem and allowing for continuous shield tunneling.