Grouting serves as an effective method for mitigating geotechnical disasters in subsea tunnels. However, current theories and designs, primarily based on terrestrial tunnel contexts, seldom address the long-term effects of seawater ion erosion on reinforcement. An improved sand permeation grouting simulation test system was employed to examine the mechanical property evolution of sand layer grouting reinforcement under seawater erosion utilizing various grout types. The mechanical properties of grouting reinforcement, under varying curing conditions, were analyzed using a uniaxial compression test, permeability test, and scanning electron microscope (SEM) test. Test results indicate that seawater curing conditions initially enhance the strength and impermeability of grouting reinforcement; however, prolonged curing diminishes these mechanical benefits. The onset of this process occurs significantly sooner in cement-sodium silicate grout (28–56 days) compared to cement grout (56d to 90d). For the cement grouting reinforcement, the deformation modulus increases over time, albeit at a decreasing rate. The deformation modulus of cement-sodium silicate grouting reinforcement follows an increase-decrease-increase pattern, correlating with the volume ratio over time. The decline in mechanical properties of grouting reinforcement during the test's mid to late stages under seawater conditions results from the interplay between erosive ions, which inhibit mechanical growth and accelerate deterioration.
To study the penetration mechanism of cement-based slurry in intersected fractures during grouting and the related pressure distribution, we have used two different variants of cement, namely, basic cement slurry and fast-setting cement slurry. The influence of a retarder, time-varying viscosity, fracture width and location of injection hole is also considered. A finite element software is used to implement two and three-dimensional numerical models for grouting of intersected fractures in hydrostatic conditions. Results show that there are significant differences in the diffusion morphology and pressure distribution depending on the considered cement slurry. Retarder can effectively slow down the rising rate of injection pressure and extend the diffusion distance of grout. The influence of the branch fracture is more important when basic cement slurry is considered, indicating that the change of grout pressure is correlated with the slurry viscosity. The faster the viscosity increases, the less evident is the effect.
Abstract Taking the TBM water inrush accident in An-Xue section of Qingdao Metro Line 1 as the engineering background, the research is carried out from two aspects of TBM water inrush emergency measures and grouting reinforcement treatment technology, which can ensure the strength of stratum reinforcement and water shutoff, and at the same time prevent the slurry from damaging the cutter head. For different areas, the grouting construction technology is proposed. After the reinforcement, the water stopping effect is obvious, the water inrush point has no water flow out, the hole drilling effect is good, the core removal rate is 75%∼85%, and the strength meets TBM excavation requirements.
Permeation grouting is widely used in grouting engineering because of its low grouting pressure and minor disturbance to the stratum. However, influenced by the complex properties of sand layer and slurry, an accurate prediction of the groutability of the sand layer remains to be a hard work. In this paper, the permeability of sand layer is studied based on a self‐designed permeation grouting test device, which considers the different sand particle size, relative density of sand layer, slurry water‐cement ratio, and clay content. The influencing factors of sand layer groutability are analyzed, and the different parameters that affect the grouting of sand layer are evaluated, thus proposing a new approach to predict the groutability of sand layer. Results show that the sand particle size and slurry water‐cement ratio are positively related to the groutability of sand layer, and the relative density and clay content of sand layer are negatively correlated with the groutability of sand layer. The proposed alternative empirical formula to estimate the groutability of sand layer will help predict the groutability of sand layer with a higher degree of accuracy, which can provide a certain reference for engineering.
Through the pre-grouting engineering practice of F1 fault fracture zone in People's Hall Station of Qingdao Metro Line 4, the research on the pre-grouting Strengthening Technology of shallow and large section metro tunnel through fault fracture zone is carried out, and the effective means to control the crossing fault fracture zone of the shallow and large section metro tunnel are explored. The results show that it is an effective method to treat the collapse of fault fracture zone by using the combined grouting method of first detection and grouting, and the combination of surface grouting and tunnel grouting in the shallow and large section metro tunnel. For the fault fracture zone near the sea, in order to prevent the continuous erosion of seawater ions to fault fracture zone and station structure, the cement-water glass and sulpho-aluminate cement materials can be considered on both sides of the station, and ordinary portland cement and sulpho-aluminate cement can be used in the middle of the station to ensure the safety and stability of the station, which also could reduce the cost of construction as much as possible.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)