Grouting technology and construction schemes of a tunnel in aeolian stratum: a case study of Shenmu No. 1 tunnel

The naturally formed aeolian sand dunes in northern Shaanxi exhibit unique engineering characteristics. Several challenges, such as the poor self-stabilization ability of the surrounding rock, difficultly in injecting grout, and insufficient construction experience, restrict the construction of road tunnels under this stratum. Therefore, in this study, a case study of the Shenmu No. 1 tunnel was conducted to investigate the engineering characteristics of aeolian sand tunnels, compare the grouting effects of commonly used grouting materials, and discuss the reinforcement effects of different construction schemes in aeolian sand tunnels. Based on a field grouting test, it was determined that it is difficult to inject ordinary cement grout into an aeolian sand layer. Furthermore, it was determined that superfine cement grout and modified sodium silicate grout can be injected, but the former exhibits a poor reinforcement effect. Additionally, results of numerical analysis indicated that an approach based on a concept of “horizontal jet grouting pile + benching partial excavation method with a temporary invert” is suitable for the construction of tunnels in aeolian sand in China.

Laboratory Study on the Effect of Water-Cement Ratio on Strength Characteristics of Jet Grouting Columns

Jet grouting is one of the most widely applied soil improvement techniques. It is suitable for most geotechnical problems, including improving bearing capacity, decreasing settlement, forming seals, and stabilizing slopes. One of the difficulties faced by designers is determining the strength and geometry of elements created using this method. Jet grouted soil-cement columns in soil are a complicated issue because they are dependent on a number of parameters such as soil type, grout and water flow rate, rotation and lifting speed of monitor, nozzle jetting force, and water to cement ratio of slurry. This paper discusses the effect of the water-cement ratio on the physical and mechanical characteristics of soilcrete. In the laboratory, sandy soil mixed with cement grout with water-cement ratio varies from (0.7:1 to 1.4:1). To evaluate the characteristics of soilcrete, 96 specimens were prepared in the laboratory and tested at different curing times. The results indicate that the Uniaxial Compressive Strength (UCS) of soilcrete decreases with increasing the (W/C) ratio of the grout, where the soilcrete strength of W/C ratio of 0.7 is higher about 237% of W/C ratio of 1.4 at 28-day; the evolution of the (UCS) is proportional to the logarithm of the curing time; the ratio between the modulus of elasticity (Etg50) to the maximum UCS varies from 113 to 175; when the water-cement ratio increases, the dry density of soilcrete decreases, as a result, the (USC) of soilcrete decreases.

Principles and Developments in Soil Grouting: a Historical Review

Grouting includes a range of processes that involve the injection of wet or dry materials into the ground to provide improved engineering properties. Common aims are to increase strength or stiffness or to reduce permeability within the mass of ground treated. The simplest process in concept is the permeation of the pore spaces with a fluid grout which then sets, and provides the desired properties. Jet grouting employs erosion and mixing using high energy jets, to attack a wide-ranging set of soils and applications. This paper, mainly, addresses permeation grouting for the improvement of soils, in terms of strengthening or reduction of permeability, and compensation grouting for the displacement of structures during subsurface exploration. The historical evolution of these two grouting processes is described leading up to present-day practice. Reference is made to grouting materials, methods of injection, equipment, limitations and verification for each type of grouting. The grouts used to make permeation grouting are mainly suspensions and chemical solutions. The suspensions penetrate well into soils with granulometry up to coarse sand. On the contrary, the chemical solutions penetrate satisfactorily in finer formations up to fine sands or coarse sludges. Because some chemical solutions are toxic or generally harmful to the environment and humans, an effort has been made internationally in recent years to replace them with inorganic fine-grained suspensions.

Application of Fluidized Bed Furnance Bottom Ash in Civil Engineering – A Review

For several years there has been widespread and open discussion about climate problems and human responsibility for the generated waste. The number of regulations has led to a search for applications for by-products of combustion. Moreover, the forecasted economic crisis additionally motivates to use every possible material to reduce the cost of manufacturing activities. Efficient waste management is a key element for Polish companies in their efforts to reduce their negative impact on the environment. Fluid combustion of fuels in the Polish power and heat industry still belongs to relatively new technologies. Despite the application of the most technologically advanced processing methods, bottom ashes from fluidized bed boilers are still reluctantly used. The author sees possibilities of using bottom ashes in geotechnical works. The aim of this review is to present the existing source papers relating to the use of bottom ashes in construction processes. A particular area of interest is the use of said ashes in jet-grouting (JG). The paper briefly refers to fluidized bed combustion technology as a source of combustion byproducts. The author pay special attention to the characteristics defining the characteristics of the ashes. The reader's attention will then be drawn to jet-grouting technology. References can be found to the methodology of general cement-soil testing. Due to the nature of the use of JG, the focus is particularly on their strength, water-permeability and frost resistance properties. Due to the need to determine the internal structure of the cement-ground, attention was also paid to the possibility of using X-ray computed tomography for soil cement testing.

A Practice for the Application of Waste in Road Asphalt Pavements in an Eco-Friendly Way

The integration of circular economy principles in the design of road pavements raises the problem of obtaining high-performance asphalt mixtures for reduction of waste and environmental pollution compared to traditional solutions. In this study, the base and binder layers of road asphalt pavements were prepared by using reclaimed asphalt pavement and construction and demolition waste as coarse aggregates, while jet grouting waste and fly ash served as fillers. A leaching test was performed for the marginal materials, after which the engineering performances of the designed asphalt mixtures were investigated through laboratory tests. A life cycle assessment methodology was applied to determine the life cycle impacts of one cubic meter of each asphalt solution. Next, a multi-criteria decision analysis (MCDA) was performed for the solutions suggested for the binder and base layers. Finally, a sensitivity analysis was conducted to identify the most suitable MCDA solutions by varying the weights for a total of 24 different weight configurations. The results of this work revealed that the solutions utilizing jet grouting waste (in particular, the hot asphalt mixture for the binder layer and cold asphalt mixture for the base layer) were preferred to other traditional and alternative solutions in most decision-making scenarios.