Conventional Grouting Research Articles

Revamp of the eco-friendly grouting materials by mixing basalt fiber for earthen sites conservation: Compressive performance and constitutive models

Reinforcement techniques, including anchorage and sealing with grout, are frequently employed to protect earthen sites and minimize the impact of fissures, the effectiveness of these approaches relies heavily on the mechanical properties of grout. To enhance the strength and ductility of the conventional grout, an eco-friendly composite grouting material mixture basalt fibers of varying lengths and contents is prepared. The DIC-based UCS tests were conducted to evaluate its compressive performance. Constitutive models of the basalt fiber-reinforced grout, including elastic perfectly-plastic (EPP) and median nonlinear (MNL) constitutive models, were established respectively based on the equal energy rule and cross-sectional data analysis for simplification application and precision evaluation purposes. The results show that the mixture of basalt fibers resulted in a distinct semi-brittle failure mode for the grout, with a significant increase in its compressive strength, ductility, compressive fracture energy, and residual bearing capacity. However, the elastic modulus will be lower when the fibers are relatively longer. Considering the differences in the relations between performance parameters and fiber content, and length, the highest compressive strength was reached at the fiber length of 6 mm and the content of 0.2 wt%, while maximum ductility was achieved at 18 mm and 0.4 wt%. The fracture energy exhibits an approximate positive correlation with fiber content. In addition, the EPP and MNL constitutive models can effectively characterize the compressive mechanical behavior of semi-brittle materials to satisfy different requirements on the precision of engineering analysis. This study contributes valuable insights into the development of high-ductility grouting materials of earthen sites, and the establishment of constitutive models for semi-brittle materials.

Research on new magnetic epoxy resin composite slurry materials and localization grouting diffusion mechanism

A significant number of steep cracks are frequently encountered in underground engineering, posing a threat to operation. The high-pressure grouting method is a commonly utilized repair technique. Nevertheless, conventional grout is prone to displacement due to its weight, making it challenging to ensure adequate filling of the cracks. Therefore, this study aims to develop a grouting material with targeted displacement and anchoring properties. Firstly, an optimal magnetic slurry composition was determined through an orthogonal test. Subsequently, XRD and SEM were used to analyze the impact of the magnetic field on the composition distribution, internal pore structure, and transient viscosity of the slurry. Afterwards, a model for localized grout diffusion under magnetic was established. The results show that the application of a magnetic field caused the slurry to compact due to magnetic forces, reducing its porosity. Moreover, the dynamic viscosity of the slurry increased exponentially with rising magnetic induction intensity. Notably, a 40.5% increase in the diffusion area was observed when the magnetic field intensity rose from 2500 to 4500 GS. The error between the measured and theoretical values of the magnetic slurry diffusion model was only 8.91%, indicating the model's accuracy in describing the slurry diffusion process under magnetic field influence.

Influence of Sustainable Grout Material on the Moisture Damage of Semi-flexible Pavement

Semi-flexible pavement (SFP), also known as grouted pavement, is a type of pavement structure consisting of a porous asphalt skeleton with air voids between 25 and 35% injected with cementitious grout materials. The special skeleton of SFP provided enhanced durability and resilience, making it a promising option for the construction of road surfaces in high-traffic areas and severe conditions. The main aim of the current research is to investigate the rutting behavior and moisture resilience of SFP-containing sustainable grout using ceramic waste powder (CWP). This research introduced the use of CWP as a replacement for conventional grout (cement) in SFP for the first time. CWP partially replaced cement at ratios of 15, 20, 30, 40, and 50% of the cement weight. Indirect Tensile Strength (ITS) and Hamburg Wheel Tracking Tests (HWTT) were used to evaluate the performance of SFP to reduce the detrimental effect of moisture. The grout modified with CWP shows excellent results in the ITS and Tensile Strength Ratio (TSR), and all modified SFP mixtures give higher values in these tests compared with Control Mix (CM). In the HWTT, the minimum rut depth of the modified SFP was 2.8 mm and 3.10 mm. Compared to CM, rutting decreased by 73%–76% for CWP mixes with 20% and 30% replacement. This indicates the high fluidity of CWP, which enabled it to penetrate all voids in the porous pavement (PA) and form a dense microstructure due to its excellent pozzolanic interaction, making it a strong structure capable of bearing rutting.

Experimental and theoretical analysis of single-jet column and concrete column using double-jet grouting technique applied at Al-Rashdia site

Abstract Progress in jet grouting technology has been focused on the cutting-edge observer of jets, which aims to generate large columns of jet grouting and increase the activity of construction sites. Since jet grouting techniques vary from conventional grouting methods to modern techniques, they can be used in a variety of soil types and their application areas are expanding quickly. So, grouting methods have become very popular methods for subsoil strengthening. This article includes finding the physical and mechanical properties of the soil of the AL-Rashdia site, using a single-jet grouting machine and a steel model to test concrete piles and jet piles, and a double-jet grouting machine to compare the results obtained from laboratory model of one-dimensional jet grouting column pile with those of a one-dimensional concrete pile. The comparison showed that the settlement of the jet pile was smaller than that of the concrete pile and the bearing load was higher with jet columns giving a high bearing capacity comparable with the concrete pile. Shen’s method is more adequate to find the ultimate bearing load and the settlement for this load. Also, the ultimate pile ratio was 115.63% for the jet column, and the ultimate pile ratio for the concrete column was 123.49%. The compressive strength of the core sample of jet columns was large which improved the bearing capacity of the foundation.

Harnessing the synergy of grout and adhesive: Numerical prediction of load capacity in hybrid composite joints

This study examines grouted joints for offshore wind turbine systems, where gaps between steel pipes are filled with grout, relying on adhesion, friction and compression struts formed by shear keys. Concerns about the limited load carrying capacity of large diameter grouted joints in offshore structures have prompted investigation. Whilst adhesive bonds are recognized for load transfer in structural steel, the complete replacement of grouting with bonding alone is proving impractical for large gaps in offshore structures, posing challenges in terms of cost and handling. To address these challenges, the study presents an innovative hybrid grouted joint for steel structures that combines grout and adhesive layers. This novel approach replaces traditional large shear keys with distributed micro-shear keys — small granules embedded in the grout material. Under axial loading, the hybrid joint demonstrates robust performance, with a maximum nominal shear stress on the inner pipe of 30.1 MPa and consistent load capacity across tests. Average shear strength is in line with, and occasionally exceeds, expectations. Notably, the hybrid joint shows resilience in different configurations and maintains a low coefficient of variation of 5.5%, indicating consistent performance. When the influence of the adhesive material on the hybrid joint is examined, the effect on the joint stiffness is minimal, despite variations in adhesive stiffness. Sikadur 370, which has a higher modulus of elasticity than DuploTEC, shows similar deformation curves in the elastic region, emphasizing the robustness of the joint. Differences in the maximum loads are attributed to the thickness of the adhesive layer and the lower modulus of DuploTEC, resulting in different shear strengths. The proposed hybrid joint offers a promising solution to improve the performance of conventional grouts and adhesives in offshore structures. The study also formulates a failure criterion, performs numerical stress analysis, and models the effect of geometric dimensions, eccentricity, and misalignment on load capacity. The methodology’s accuracy in predicting load capacity, supported by numerical analysis and large-scale joint simulations, contributes to a comprehensive understanding of hybrid joint performance in engineering applications.

Multiphase flow coupling analysis of shield synchronous grouting filling law with time-dependent viscosity

Owing to the non-visual characteristics of the shield synchronous grouting engineering, the law of grout filling in the shield tail gap remains obscure. There is a current deficiency in effective three-dimensional filling and diffusion models. Building upon a large-diameter, eight-hole shield tunneling grouting project in Hangzhou, this study aims to construct a holistic three-dimensional model of grout filling in the shield tail gap. Employing COMSOL Multiphysics and grounded on the two-phase Navier–Stokes equations, this study simulated the filling of grouting fluid in the shield tail gap. Utilizing the Brookfield DV3T rheometer, the study ascertained the time-dependent expression of grout viscosity and systematically analyzed the impacts of time-dependent grout viscosity, density, and injection pressure on the filling diffusion morphology, pressure field, velocity field, and the buoyancy experienced by the segmental lining. The results indicate that the injection pressure is positively correlated with the circumferential pressure field of the segmental lining, though the influence on the ring's total buoyancy is minimal. The rate of grout viscosity development significantly affects the overall diffusion morphology: conventional grout tends to be underfilled at the top of the shield tail gap while rapid-setting grout is more likely to be underfilled at the bottom. The grout density is positively correlated with the grout displacement speed and the total buoyancy of the segmental lining. In light of these insights, utilizing low-density, rapid-setting grout under high-pressure grouting for shield tail filling can ensure adequate filling rates while mitigating the adverse effects of segment buoyancy.

Seismic performance of innovative prefabricated reinforced recycled concrete shear walls

In this study, the seismic performance of innovative prefabricated recycled concrete shear walls has been investigated. Unlike the conventional grouting sleeve connections, the "button-head bars" grouting connections to connect the walls have been proposed. Four shear wall specimens with different construction types (two semi-prefabricated, one fully-prefabricated, and one cast-in-place) were tested under low-cyclic loading. The fully-prefabricated wall was connected to the foundation only using the proposed button-head bars; while for the semi-prefabricated walls, the two cast-in-place concealed columns were arranged at both edges of the wall. The failure modes, hysteretic behavior, skeleton curves, strength, ductility, stiffness and degradation process, energy dissipation, and strain characteristics were investigated. The influence of axial force ratio and construction type on the seismic performance of the shear walls was analyzed. The results showed that the seismic performance of semi-prefabricated shear walls and cast-in-place shear walls was similar. The shear slip for the cast-in-place, semi-prefabricated, and fully-prefabricated shear walls was 0.3 mm, 0.32 mm, and 0.78 mm, respectively. The cast-in-place concealed columns could effectively limit horizontal shear slip. An increase in the axial force ratio significantly enhanced the strength and energy dissipation capacity of semi-prefabricated specimens. The ultimate strength according to different design codes was calculated, with the Chinese GB-50010 design code providing the most accurate prediction of the strength of prefabricated shear walls.

Development of a novel cement-based grout with enhanced thermal and sealing performance for borehole heat exchangers

Filling a borehole with proper grout is important for maintaining the safety and performance of borehole heat exchangers (BHEs). The current grouts have problems of large shrinkage and low thermal conductivity, which may restrain BHE efficiency and pose safety risks. To address this, this study explores solutions to enhance the thermal and sealing performance of cement-based grout, specifically for BHE applications. A novel grout, composed of ordinary Portland cement (OPC)-calcium sulfoaluminate (CSA) cement-gypsum ternary system and graphite, was developed and thoroughly examined. The developed grout exhibited good flowability and volumetric stability, meeting the required compressive strength in one day. It displayed high thermal conductivity, ranging from 1.606 to 2.504 W/mK at oven-dry conditions and 2.173 to 3.532 W/mK at saturated conditions. At last, numerical modeling was conducted to compare the thermal performance of boreholes using the novel grout developed in this study and a conventional grout. Numerical models prove that using developed grout can improve the thermal performance of boreholes and decrease the borehole resistance, thus lessening the required borehole length, further reducing the costs and carbon emissions of borehole construction. Overall, the developed grouts showcased enhanced thermal and sealing performance. They can be applied in BHE systems not only to enhance operational efficiency and safety, but also to reduce costs and carbon footprints.

Preparation of the geopolymer grouting material by coal-based solid wastes for the aquiclude key strata and its application

The application of grouting to repair cracks in the key strata of the aquiclude is an effective measure to safeguard the overlying aquifer during underground coal mining. However, conventional grouting materials are expensive and can induce serious environmental pollution. In this study, a cost-effective geopolymer grouting repair material was prepared by using coal gangue, fly ash, bentonite, and other additives. The response surface methodology was employed to design the compressive strength and seepage strength tests on the cemented body, and the microstructure of the cemented body was also explored. The results show that when the ratio of coal gangue to fly ash to bentonite is 23:22:5 and the NaOH content is 4 %, the optimal performance of the grouting material is achieved, with a compressive strength of 10.11 MPa and a seepage strength of 2.38 MPa at the curing age of 28 d. The compressive strength and seepage strength of the grouting material are significantly improved by the network structure formed by the cross-linking of ettringite generated from the hydration of the material and the gel of sodium silicate hydrate.

Study on hydrodynamic diffusion law of the swelling particle slurry in karst pipeline

The swelling particle grouting material has demonstrated remarkable plugging effectiveness in high-pressure and large-flow burst water within karst pipelines. Currently, current research on the rheological model, flow computation theory, and plugging mechanism of this material is lacking. The conventional grouting slurry diffusion process, using the liquid-liquid two-phase flow method, fails to accurately simulate high solubility slurry and particle swelling. To address these limitations, this study established a precise constitutive model to describe the swelling particle slurry diffusion process in dynamic water. Additionally, a coupling calculation method was proposed to analyze the spatiotemporal heterogeneity of viscosity during slurry diffusion by considering the migration of slurry and the changes in viscosity. To investigate the interaction between particle swelling and flow field changes, a Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) coupling model was developed for the diffusion of swelling particle slurry. It is demonstrated that slurry viscosity increases exponentially within the diffusion front as the particle swelling rate rises, and the drag force exhibits an intriguing behavior of initially increasing and then decreasing as the slurry flows through the pipeline. Furthermore, the CFD-DEM coupling model proved to be more accurate in describing viscosity distribution and diffusion distance compared to the finite element solution. The primary objective of this paper is to reveal the plugging mechanism and provide theoretical support for the engineering application of the swelling particle grouting material.

Mechanical behaviour of fiber-reinforced grout in rock bolt reinforcement

Grouted rock bolts subject to axial loading in the field exhibit various failure modes, among which the most predominant one is the bolt-grout interface failure. Thus, mechanical characterization of the grout is essential for understanding its performance in ground support. To date, few studies have been conducted to characterize the mechanical behaviour of fiber-reinforced grout (FRG) in rock bolt reinforcement. Here we experimentally studied the mechanical behaviour of FRG under uniaxial compression, indirect tension, and direct shear loading conditions. We also conducted a series of pullout tests of rebar bolt encapsulated with different grouts including conventional cementitious grout and FRG. FRG was developed using 15% silica fume (SF) replacement of cement (by weight) and steel fiber to achieve high-strength and crack-resistance to overcome drawbacks of the conventional grout. Two types of steel fibers including straight and wavy steel fibers were further added to enhance the grout quality. The effect of fiber shape and fiber volume proportion on the grout mechanical properties were examined. Our experimental results showed that the addition of SF and steel fiber by 1.5% fiber volume proportion could lead to the highest compressive, tensile, and shear strengths of the grout. The minimum volume of fiber that could improve the mechanical properties of grout was found at 0.5%. The scanning electron microscopy (SEM) analysis demonstrated that steel fibers act as an excellent bridge to prevent the cracks from propagating at the interfacial region and hence to aid in maintaining the integrity of the cementitious grout. Our laboratory pullout tests further confirmed that FRG could prevent the cylindrical grout annulus from radial crack and hence improve the rebar's load carrying capacity. Therefore, FRG has a potential to be utilized in civil and mining applications where high-strength and crack-resistance support is required.

Case Study on the Method of Rock Mass Overburden Consolidation Grouting for Dam Foundation

Conventional grouting methods present challenges in achieving effective surface rock grouting and avoiding interference with concrete grouting and construction processes. The proposed approach includes reserving rock overburden, controlling grouting pressure and concentration, using a segmented grouting method, and selecting appropriate materials to develop a key method for consolidation grouting. This method not only overcomes the problems associated with the conventional consolidation grouting method but also effectively protects the thin layer of breccia lava in the Baihetan Dam foundation and solves the problem of unloading and relaxation of columnar jointed basalt caused by exposed consolidation grouting. The results show that the post grouting inspection hole permeability qualification rate is 99.3%, with the proportion of high-speed measuring points of various rock types ranging from 91.8% to 93.3%, and the proportion of low-speed measuring points ranging from 2.0% to 2.9%. The drop rate of the grout take of sequence I and sequence II is between 30%–60%, except for some dam sections. These results indicate that the proposed method for consolidation grouting meets the design requirements. The findings have significant implications for the design and construction of consolidation grouting in similar projects.

Seismic performance of a new precast concrete frame joint with a built-in disc spring

A new, precast concrete frame beam-column connection is designed in this research. The connection adopts the assembly mode of the precast column and seam area jointly to maintain the integrity of the joint area and increase the assembly efficiency. Based on the conventional grouting sleeve connection, a disc spring device is constructed on the beam end to improve the ductility of the joint. Ten connecting specimens were tested under low cyclic loads, including two monolithic connections, four ordinary precast connections, and four new precast connections. The test parameters included the joint type and axial pressure ratio, and the difference in the seismic performance was determined by evaluating the failure mode, hysteresis characteristics, stiffness degradation, energy dissipation, and shear deformation of the joint area. Compared to monolithic connections, conventional precast connections display similar hysteresis characteristics. Although their ductility is slightly lower, their bearing capacity is higher. Compared with the previous two connections, the new connection with the built-in disc spring device has superior seismic performance. The axial pressure ratio is a significant aspect in determining the failure mode of the precast connection, and the specimen exhibits less shear damage at a larger axial pressure ratio.

Seepage behavior and mechanical properties of two kinds of polyurethane/water glass in combined grouting experiment

Combined grouting with multiple materials can effectively block flowing water that cannot be blocked by conventional grouting methods. Firstly, foam grouting is used to reduce the fluidity of water, and then reinforcement grouting is employed to improve the grouting effect. The traditional cement grout cannot achieve the required foamability, setting rate, and injectability. Therefore, two kinds of polyurethane/water glass grouts have been used in combined grouting experiments. In this study, we combine foam and reinforcement polyurethane/water glass to examine the interaction performance of grout seepage. We develop a visible grouting facility, including a transparent chamber and a grouting pump. We monitor the grouting pressure during the test and use a charge-coupled device camera to capture the diffusion of both grouts in the granular media. After solidification of the grouts, the samples were cored and tested to obtain the uniaxial compressive strength (UCS), porosity, and density. Our results demonstrate that the reinforcement grouting pressure increased, as compared with the foam grouting pressure, because the foam grouting blocked water and pressure conduction. The reinforcement grout intruded into the foam grout, and the UCS was improved. The higher the grouting pressure at the corresponding location of the samples, the larger the total filling ratio. The larger the volume percentage of RPU/WG, the smaller the volume percentage of FPU/WG, the greater the strength and the greater the density of the samples. The empirical strength-equivalent porosity equation is also provided in this paper. We suggest that foam grouting shall be carried out outside the stress-bearing area first, and then reinforcement grouting shall be carried out inside the stress-bearing area. This study provides a reference for the theoretical development and field application of combined grouting.

Development of a dry mortar with nanosilica and different types of industrial waste for the application in borehole heat exchangers

A geothermal borehole is a heat exchanger between the soil and a heat transfer fluid. This fluid flows throw in the geothermal pipes, which has been inserted into borehole. Using a Ground Source Heat Pump (GSHP) systems, the fluid provides heating and cooling buildings.The space between the geothermal pipes and the ground is filled with a geothermal backfill. This geothermal fill must be having high thermal conductivity for facilitate the heat flow. In this way this fill is an important element in a Borehole Heat Exchanger as its choice can result in significant economic and energy savings during the geothermal installation’s lifetime. However, in general it has not received enough attention.The geothermal backfill materials formed by a mixture of cement, fine aggregate, sand and/or additions are known as geothermal grouts. The aggregated additives and the other materials aggregated confers to the geothermal backfill high thermal conductivity. This property is rejected in the conventional grouts used in buildings.On the other hand, the use of industrial waste or by-products in geothermal grouts is considered more sustainable, for it reduces landfill volume and the need of exploiting new mineral resources.This paper describes the development of a geothermal grout, named MG 7. MG-7 has improved thermal properties compared with conventional grouts. In this case, mining and by-products from surrounding companies have been used, following the principles of the circular economy.To determinate the geothermal grout properties different techniques and conventional equipment has been used. However, to calculate the thermal conductivity a specific device developed by the authors. Finally, it has been obtained a pre-dosed geothermal grout with a thermal conductivity of 2.01 ± 0.08 W/m∙K (K = 2), in which 30 % of the aggregates come from industrial waste, such as mine tailings, ladle furnace slag, fly ash and silica fume. It also contains 2 % of silica nanoparticles.

Experimental investigation on pneumatic pre-fracturing grouting in low-permeability soil

Effective injection of grout into low-permeability soil is difficult in the process of soil reinforcement. To address practical problems, this study proposes a pneumatic pre-fracturing grouting method comprising model experiments to analyze the initiation and propagation of fractures, earth pressure, soil displacement, and the characteristics of grouting consolidation. In the pneumatic fracturing experiment, the fractures exhibited larger effective radii under gradual pneumatic loading compared with those created due to instant loading, providing more initial channels for grout diffusion. Meanwhile, the higher the pneumatic pressure, the greater the residual height of the fractures after pneumatic fracturing, yielding a predominant condition for grout injection. Compared with conventional grouting, the effective injection amount, effective diffusion radius, and height of grout consolidation of pneumatic pre-fracturing grouting were much larger. The results prove the feasibility and superiority of pneumatic pre-fracturing grouting in low-permeability soils.

Formation Mechanism of “Large-Area Sweating” Water Seepage from Deep Mine Sandstone Pores

The groundwater in nonkarst areas can be divided into two categories: pore water and fracture water. Unlike fracture seepage, sandstone pore seepage in deep mines manifests as a large area of “sweating,” rather than an area of local “spray,” and is difficult to plug via conventional grouting methods. This study focused on pore seepage in deep mine sandstone to improve the grouting effect. Taking the deep mine sandstone in the southwest Shandong coal field, where “large-area sweating” seepage occurs, as the study object, this study examined the pore structure, petrological characteristics, physical properties, and grain sizes of the sandstone by analyzing experimental data from thin sections and scanning electron microscopy samples. The formation mechanism of the “large-area sweating” seepage was then analyzed. The range of permeability in which “large-area sweating” seepage may occur in the sandstone was discussed. The results indicate that the process of “large-area sweating” seepage in deep mine sandstone can be divided into a matrix softening stage, a matrix erosion stage, and a “large-area sweating” water seepage formation stage. According to the case analysis on the “large-area sweating” seepage in the Tangkou coal mine of the Southwest Shandong coalfield, the lower limit of permeability of the “large-area sweating” sandstone is approximately 0.25 mD. Thus, this type of seepage can occur in deep mine sandstone with a permeability of greater than 0.25 mD and affect typical mining production. The results of this study provide information about the formation mechanism of “large-area sweating” water seepage from sandstone pores and can theoretically inform the development of a new permeation grouting technique.

Seepage Grouting Mechanism for Foundations in Goaf Sites considering Diffusion Paths

Grouting treatment is the main technology to reduce or eliminate the residual deformation and activation deformation of foundations in the goaf sites. Under the influences of the overburden of the mining, the distribution of grouting in goaf foundation is quite different from that of conventional grouting mechanism in porous media. In this paper, considering the time-dependent viscosity and diffusion path of the slurry, the conventional permeation diffusion mechanism of Bingham fluid is derived based on the seepage motion equation in porous media. The theoretical formula is modified according to the fracture distribution characteristics of caving zone and fault zone of the goaf foundation and the superposition effect of porous grouting. Combined with the laboratory test, the theoretical formulas for four working conditions ((i) only considering the time-dependent viscosity, (ii) considering the time-dependent viscosity and diffusion path, (iii) combining the fracture distribution characteristics of goaf foundation, and (iv) combining the fracture distribution characteristics and the superposition effect of porous grouting) are verified, respectively. The results of theoretical formula are used to compare with the design scheme of an engineering example. The research results have an important engineering significance for revealing the mechanism of seepage grouting in goaf foundation and designing the optimal spacing between grouting holes.

Novel masonry grout incorporating high volumes of industrial by-products: microstructure characteristics and pursuance of durability properties

One solution to the high cost and scarcity of building materials is to use alternative and sustainable materials. The study presented herein developed an eco-friendly masonry grout using high volumes of palm oil clinker powder to replace cement and palm oil clinker to replace coarse aggregate. Several batches of grouts with different amounts of these materials were made to determine the technical viability of the grout. Scanning Electronic Microscope (SEM), X-Rays Diffraction (XRD), Energy Dispersive X-Ray (EDX) and Thermogravimetric Analyzer (TGA) analyses were conducted to investigate the microstructure characteristics of the grout, and water absorption, initial rate of absorption, sulphate attack and electrical resistivity tests were conducted to determine its durability. Compressive strength tests were conducted at different curing ages and the drying shrinkage of the grout was monitored for 180 days. The results indicate that the new grout is as good as a conventional grout but with added sustainable and economic benefits. The new grout can be used in masonry construction and can be used to alleviate the inadequate supply of affordable housing.

Numerical and analytical study of a geo‐exchange borehole using conventional grout and bentonite‐based backfilling material

Numerical and analytical study of a geo‐exchange borehole using conventional grout and <scp>bentonite‐based</scp> backfilling material