Grouting Technique Research Articles

Investigation on jet grouting support strategy for controlling time‐dependent deformation in the roadway

AbstractThe efficiency of coal mining is seriously affected by roadway stability, as large time‐dependent deformation of roadway frequently occurs and needs to be maintained several times during its service life. Such rheological deformation was common in soft coal mass at Huaibei coalfield in China. To address this issue, in this study, the time‐dependent deformation of the soft coal roadway was analyzed and a new Jet Grouting (JG) technique was presented for controlling deformation. The time‐dependent deformation of the soft coal roadway was numerically simulated and validated. Based on the field test results and the verified model, a JG support model was established to examine its effect on roadway deformation. The JG support system can reduce the horizontal and vertical displacement of the roadway effectively and constrain the time‐dependent deformation of coal mass. The deformation rate and stabilization time of roadway decreased significantly by comparison with conventional support. This work presented a promising JG support scheme for controlling the time‐dependent deformation in the roadway in deep underground mine, which can greatly promote the JG design and application.

Field study of the effect of jet grouting parameters on strength based on tensile and unconfined compressive strength

The improvement of the mechanical soil characteristics of jet grouting technique is very attractive. The jet grouted soil cement columns in soft is a complicated issue because it depends on a number of factors such as, soil nature, mixture, influence among soil and grouting materials, jetting force of nozzle, jet grouting and water flow rate, rotation and lifting speed. This paper discusses the estimation of shear strength parameters of soil-cement column (soilcrete) in soft clayey soil based on the relationships between the unconfined compressive and split tensile strength for the soilcrete and the effect of the jet grouting and water pressure in the values of cohesion and internal friction. For this reason, theoretical and field work models have been developed. The relation between split tensile and unconfined compressive strength results were used to draw a Mohr’s circle and failure enveloped to define the shear strength parameters of soilcrete. According to that, the results indicate that the resistance of the jet grout columns increases by increasing the nominal resistance of the grouting material (cement), water and jet grouting pressure. The shear resistance variables are increased by increasing the unconfined compressive and tensile strength of the jetting column. The value of the unconfined compressive strength ranges from (2.78-5.52 MPa). While the internal friction angle varies from 38° to 44°. On the other hand, the tensile strength is increased by increasing the unconfined compressive strength and ranges from (0.66-1.02 MPa).

Compression resistance of repaired structural concrete elements after core extraction

Abstract Core sampling for testing is considered a reliable method to provide information on structural materials and is one of the most implemented techniques in the evaluation of concrete elements. However, core drilling results in a decrease in cross section that can compromise structural mechanical strength even if the extracted section is repaired. Norm NBR 7680-1 recommends dry pack as a repair method but also allows the use of other techniques as long as its effectiveness is proven. This work evaluated the resistance of repaired structural prototypes after core drilling sampling. Concrete blocks with 20 MPa resistance were produced from which cores of 100 mm, 75 mm and 50 mm in diameter were extracted. The blocks were repaired with 20 MPa concrete, grout and dry pack techniques. The reconstitution with concrete showed poorest performance, while dry pack led to strengths even higher when compared to reference values.

EVALUATION OF SEMI-FLEXIBLE PAVEMENT PERFORMANCE

This study aims at characterization and design new special type of asphalt mixture havinglower asphalt content and higher rutting resistance to be used in paving surface layers atheavy loads areas. To achieve this objective, grouting technique of permeable open gradedasphalt mixtures was used. Such type of pavement is called as a semi-flexible pavement (SFP)or grouted macadam (GM). Different compaction efforts were used to achieve the requiredpercent of connected air voids between the bitumen coated aggregates. Crushed silicalimestone, crushed sand, and filler were used to prepare highly permeable asphalt mixtures.Asphalt contents of these mixes were determined theoretically and It was ostensibly examinedby the laboratory. Marshall molds representing open graded mixtures were prepared andgrouted using a grout composed of ordinary Portland cement (OPC) as well as a mixture ofsome concrete additives with different ratios. Choosing the suitable grout mixture dependedon the flow time, flexural and compressive strengths for lab-produced grout prisms.Measuring Marshall stability, Marshall flow, and indirect tensile strength test were conductedon grouted asphalt mixes to identify their properties. The same tests were conducted oncrushed silica limestone open graded mix of 2C gradation (Egyptian Standards for Roads) forcomparison purposes. Analyzing the study results, positive effect of grouting open gradedmixes was concluded using a mixture of OPC, fine sand, silica fume and superplasticizer. Therequired bitumen content for surface layers was decreased by percent between 27% to 37%compared with traditional dense asphalt mixtures. The resistance of rutting for grouted mixeswas increased through increasing stability and indirect tensile strength by about 3 times andmore compared with traditional open asphalt mixtures.

Stability Control for the Rheological Roadway by a Novel High-Efficiency Jet Grouting Technique in Deep Underground Coal Mines

In maintaining the efficiency of coal mining, the stability of roadway plays a significant role, as it is closely related to the production of coal and the safety of personnel. In deep underground coal mines, the rheological deformation of roadway normally occurs, which affects its service life. To address this problem, in this paper, a novel high-efficiency Jet Grouting (JG) technique was presented, and its control effect on roadway stability was investigated. A creep test of a coal specimen in a laboratory scale was performed, and its creep behavior was revealed. The rheology of the coal mass surrounding the roadway was further analyzed according to the field-monitoring results of roadway deformation. A time-dependent numerical model with a Burger-creep visco-plastic model (CVISC) was established and validated by comparing the calculated displacement with in-situ measurement. The JG technique was tested in the field, and its applicability and practicability were confirmed. According to the validated model and field test results of JG, a numerical model with CVISC by JG support was established to analyze the effect of JG on the roadway. The results showed that the JG support can effectively reduce roadway deformation, optimize stress conditions, and reduce the extent of the plastic zone around the roadway. The rheological properties of the soft coal roadway were constrained and long-term stability was ensured. This pioneering work can guide the application of JG for the stability control of roadways and promote the sustainability of coal mining efficiently.

Experimental and numerical investigation on a novel support system for controlling roadway deformation in underground coal mines

AbstractRoadway stability in extremely soft coal mass is a typical challenge in deep underground mines, as the most widely adopted support structure such as rock bolting, compound support system normally fails. This paper proposed a novel prereinforcement method for coal roadway, that is, jet grouting (JG) technique, to improve the quality of surrounding soft coal mass and form a stable support structure namely jet grouted coalcrete. The field and laboratory tests were conducted for evaluating the applicability of JG and the mechanical parameters of coalcrete. A numerical model was verified by comparing the calculated results with field measurements. According to the confirmed model, three typical JG support schemes were performed to assess the roadway stability after JG. The results showed that the proposed JG schemes can reduce the deformation and failure zone of the roadway and optimize the stress states around the roadway. The mechanism related to these advantages was investigated. This study provides a promising idea for supporting soft coal roadway in deep underground coal mines, which can promote the JG application in the field.

Remediation of Damaged Shield Tunnel Using Grouting Technique: Serviceability Improvements and Prevention of Potential Risks

AbstractShield tunnel damage induced by excessive and differential tunnel displacement has become a major threat to the operational safety of urban subways in China. Grouting offers an effective wa...

Experimental Assessment of Geopolymer Grouts for Stone Masonry Strengthening

Grout injection is a useful repair and strengthening technique to intervene in old masonry buildings. Until now, a very limited amount of work has been reported on the potential of geopolymers for consolidation of old stone masonry walls. In the last decades there has been several research initiatives focus on the development of materials involving a higher volume of supplementary cementitious materials that substitute the traditional binders. Geopolymers that were developed as a part of these efforts, can not only reduce the dependence on traditional binders, but also potentially present materials with less environmental impacts and improved performance. This study investigates the fresh and hardened properties of grouts composed of natural hydraulic lime (NHL) and geopolymer. The experiments were conducted using a geopolymer made of fly ash, sodium hydroxide and water. The effects of the replacement of NHL by the fly ash-based geopolymer (at the dosages of 0, 20, 50, 80 and 100%) on the rheological parameters, stability, water absorption, compressive strength and durability were investigated. The results showed that the geopolymer-based grout has several advantages regarding the mechanical strength, durability and fresh stability, but the improvement of their rheological performances proved to be a challenging task. Overall, the findings of this study will be useful in assessing the design of grouts incorporating alternative binders and consequently contribute to the improvement of the grouting technique.

Stability of the pipe-liner system with a grouting void surrounded by the saturated soil

The rehabilitation of the deteriorated pipe is most commonly undertaken by installing a thin-walled close-fitting cured-in-place pipe (CIPP) polymer liner. The lining procedure results in a small shrinkage gap between the liner and its surrounding pipe. Such a small gap is expected to be eliminated by the grouting technique. However, a small crown grouting void is inevitable between the liner and its host pipe due to the bubbles in the grout and the gravity effect. This grouting void may result in different buckling behavior from the perfectly-confined liner. Therefore, this paper studies the confined liner with a grouting void under water pressure. Firstly, the analytical solutions are derived to predict the buckling pressure of the confined liner with a grouting void. Then, a two-dimensional (2D) simulated model is developed to trace the buckling and post-buckling pressure-displacement equilibrium path, from which the maximum pressure (critical buckling pressure) is obtained. After that, the numerical buckling pressure is compared and shows excellent agreement with the analytical solution, as well as other available experimental data. Finally, the parametric study indicates that the grouting void reduces the pressure capacity dramatically and should be avoided in engineering applications.

Theoretical and numerical analyses of the structural stability of the pipe-grout-liner system with a crown void subjected to external pressure

The thin-walled polymer liner is widely used to rehabilitate the deteriorated underground pipe. Although the liner is installed close-fitting in the lining procedure, an annular shrinkage gap is inevitable between the liner and the pipe. The grouting technique is commonly employed to eliminate the small gap and often results in a small crown void between the liner and the pipe. Therefore, a pipe-grout-liner system generates. This paper focuses on the structural stability of the pipe-grout-liner system with a crown void subjected to external pressure. It is found that the radially-inward out-of-roundness imperfection results in a single-lobe deformation and the radially-outward out-of-roundness imperfection results in a double-lobe deformation, respectively. The critical buckling pressure is derived and obtained theoretically, and then verified by developing a two-dimensional finite element model. The numerical result shows very close agreement with the analytical solution and other closed-form expressions for both single-lobe and double-lobe cases, respectively. Finally, the effect of the crown void is examined. It is found that the system with a small crown void can sustain the same buckling pressure as the perfectly-confined liner without void. However, a significant reduction of the critical buckling pressure was observed when the crown void is larger than the small size level.

Überlegungen zu Gebirgsinjektionen für den Tunnelbau im gestörten Gebirgsverband mittels Manschettenrohren

AbstractGrouting into an open borehole is a process that has been well described academically. Numerous grouting techniques and grouting criteria are available for various applications and combinations of rock mass/ground. Tube á manchette (TAM) or sleeve port grouting systems have until now mostly been used in specialized civil engineering work in soft ground. In order to be able to carry out grouting successfully in faulted rocks, cased drilling is necessary in order to maintain the stability of the borehole for the insertion of the sleeve pipe. Under these premises, fundamental considerations for successful TAM grouting in faulted rocks are presented. The rheological properties of the grout used, the form and size of the injection opening and the strength and thickness of the sheathing compound significantly influence the penetration into the surrounding rock mass. Increased effective pressure is necessary in order to break through the sheathing compound and also to overcome friction losses during the grouting process. The necessity of high effective pressure and the emergence of the grout at the sleeve ports can, in contrast to an open borehole, increase the risk of jacking the ground in the course of grouting and this has to be carefully taken into account and investigated in advance. The interaction of effective grouting pressures and friction losses of the grouting system and their effect on the grouting process in faulted rock are described through the formulation of a general grouting criteria for TAM grouting.

Determination of Young's modulus of jet grouted coalcretes using an intelligent model

The coalcrete, a new supporting material produced by jet grouting (JG) technique was firstly studied for improving soft coal mass to support roadways in Guobei coal mine, China. Young's modulus is an essential indicator to evaluate the deformation-resisting ability of coalcretes. In this study, for determining Young's modulus of coalcretes efficiently, an intelligent technique was proposed using the support vector machine (SVM) and beetle antennae search (BAS). The hyper-parameters of SVM were firstly tuned by BAS, and then the SVM-BAS model with optimum hyper-parameters was employed to model the non-linear relationship between the inputs (coal content, water content, cement content, and curing time) and output (Young's modulus). By combining these variables, 360 coalcrete samples in total were prepared and tested for establishing the dataset. The results show that BAS is more reliable and efficient than the trial–and–error tuning method. Moreover, by comparison with other baseline models such as back-propagation neural network (BPNN), logistic regression (LR) and multiple linear regression (MLR), the optimized SVM-BAS model is more reliable, accurate and less time consuming for predicting Young's modulus of coalcretes. Besides, by conducting sensitivity analysis (SA), the importance of different input variables was determined. This pioneering work provides guidelines for predicting Young's modulus of coalcretes and designing proper JG parameters in engineering applications.

Rheology of Natural Hydraulic Lime Grouts for Conservation of Stone Masonry—Influence of Compositional and Processing Parameters

This review provides an overview of the recent progress in the field of the rheology of grouts for historic masonry consolidation. During the last two decades, significant research has been devoted on the grouting technique for stone masonry consolidation but most results are scattered by scientific papers, congress communications, and thesis. This paper compiles and briefly demonstrates the effect of several intrinsic and extrinsic parameters, such as admixtures, additions, pressure, temperature, and measuring instrumentation, on the rheological performance of natural hydraulic lime-based grouts.

Roof collapse mechanisms for a shallow tunnel in two-layer rock strata incorporating the influence of groundwater

Abstract It is inevitable that adverse conditions such as layered strata, groundwater, and ground overload will be encountered during the excavation of shallow tunnels. However, analytical theories on shallow tunnel stability are not well investigated while taking above factors into consideration together. In this paper, a shallow tunnel in two-layer rock strata is taken as an example. The influences of the groundwater table, ground overload, supporting force, etc., are considered. The corresponding kinematically admissible velocity fields for roof collapse under two cases are established. The analytical solutions of the curvilinear equations for failure of the roof surrounding rock masses and the critical burial depth of the shallow tunnel in Case I and Case II are obtained, respectively, based on upper bound theorem and variational principle. In addition, the influencing regularities of the roof collapse mechanisms under differing mechanical parameters are analyzed. It was found that the roof collapse range increases when the groundwater table drops or the supporting force, rock empirical parameter A, compressive strength, or tensile strength increase. Conversely, the roof collapse range decreases when the thickness of the upper stratum, pore water pressure coefficient, ground overload, rock empirical parameter B, or unit weight increase. The collapse range indicates the safety state of the tunnel roof. The larger the range is, the more external force power is required to generate collapse and the safer the roof is. Practically, it is efficient to improve the roof stability of the shallow tunnel by increasing the supporting force or employing the grouting technique to increase rock empirical parameter A and other strength parameters.

Water Inrush from Pregrouting Fractures Induced by Mining Activities and Its Engineering Control Method Optimization

Water inrush accidents during coal mining still occur after reinforcement of fissured water bearing strata underlying coal seams through grouting, which seriously troubles field technicians. In order to further prevent the water inrush, especially the water inrush after grouting reinforcement, the grouting technique needs to be improved. Experimental design, theoretical analysis, and numerical simulation have been carried out in sequence. On the microscale level, the relationship between strains and water flow rate was analyzed through laboratory experiments; on the macroscale level, the propagation mechanism of grouting cracks resulting from the rock strata deformation during coal production was analyzed with rock beam theory, and then a new model of casing pipes preventing water inrush by controlling deformation of the floor rock strata is proposed. The laboratory test results show that the response of the radial strain and the water flow rate to mining operation is consistent and positively correlated and verify that it is feasible to reduce water inrush disaster by controlling deformation of the rock strata. The deformation governing equation of the casing pipes is deduced theoretically. At last, the numerical calculation was done to prove the effectiveness of controlling the floor rock strata deformation by the casing pipe group, which indicated that the displacement of the monitoring points after grouting is smaller than that before grouting practice. It is practicable to realize grouting technique optimization by the innovative adoption of the grouting casing pipes in the future.

Effects of grout injection techniques in pressure grouted soil nail system

The use of pressure grouting techniques in the soil reinforcement system is frequent as it has many advantages over gravity grouting. Pressure grouting can be injected by pressure and volume (flow) controlled techniques. A preliminary study was conducted for a newly developed pressure grouted soil-nail system, where a latex membrane was used as a liner around the grouting outlet to form a Tube a Manchette (TAM) for direct injection of grout into sand. In addition, a grout bag was formed with the membrane to prevent the grout injection into the sand for simulating a compaction grouting. In the investigation, a newly developed volume controlled injection system was used to inject the cement grout into the sand or grout bag for a specified flow rate and the interaction of injected grouted with the soil mass (i.e., soil stress state) was monitored by the installed total earth pressure cell around the grout outlets. From the investigation, it was found that the injected grout volume was much less for the soil-nail (TAM) than that with a grout bag around for a certain flow rate. In addition, the preliminary results indicated that the pullout capacity of the pressure grouted soil-nail controlled by the injected grout volume (grout bulb).

Roof filling control technology and application to mine roadway damage in small pit goaf

To recover coal resources that have been damaged by traditional mining methods and ensure stability of the lower roadway in a small pit goaf, the goaf area must be filled and reinforced. In this research, the 1202 working face of the Hanzui mine is considered as an example for classifying the roof of the mining tunnel under the small kiln destruction zone, the effect of the goaf on the roadway is determined based on the radio tunnel penetration method, a mechanical model to determine the roof filling control mechanism was established, and the duct foaming system and roof filling process were designed. The results show that the scope and degree of influence of the goaf on the mining lane are large, but safe tunneling can be ensured through the use of a steel shed and advanced grouting techniques. When the roof conditions are not similar, materials with different filling heights and filling strengths can be used to control the roof filling of the roadway. By combining field experience and laboratory tests, it was determined that a high-foaming material with a water-cement ratio of 1:0.6, a suitable high-foaming additive, and a water volume ratio of 1:30 is cost-efficient for filling and meets the filling strength requirements. Finally, the reliability of the proposed technology was verified by field experiments, which provide a reference for filling operations in similar mines.

Field study on post-grouting effects of cast-in-place bored piles in extra-thick fine sand layers

The post-pressure grouting technique has proven to be an effective method to enhance axial resistance. In this paper, field tests were conducted to investigate the performances of large-diameter cast-in-place bored piles for six combined side-and-tip grouting piles and two side-grouting piles in extra-thick fine sand layers. The load–displacement response, shaft resistance, and mobilization of unit base resistance were discussed. The field results indicate that compared with the piles before post-grouting both the shaft resistance and base resistance for the piles after post-grouting are significantly improved. The piles after post-grouting have higher load-bearing capacity. Meanwhile, the load-bearing capacity of combined-grouting piles is also greater than that of side-grouting piles. Additionally, the strengthening effect of the surrounding soil improvement due to side grouting on the base resistance can enhance the unit base resistance, and the unit shaft resistance can also be increased by the soil improvement at the pile tip due to tip grouting. Moreover, the distribution of the injected pressurized grout at the pile tip and side is detected by an electromagnetic wave computerized tomography (EWCT) technique. The results reveal that EWCT can detect the distribution pattern of the pile, injected grout and geotechnical interface and evaluate the diffusion range of the grout of the soil at the pile tip and side, which can be used to assess the grouting effect of grouted piles. Finally, an in situ standard penetration test is employed to evaluate the grouting effect of grouted pile by variation of the SPT N value before and after post-grouting. The research results have reference value and guiding significance for the design and effect detection of post-grouting piles.

Improving Shear Strength Parameters of Sandy Soil using Enzyme-Mediated Calcite Precipitation Technique

Several methods have been established for their various potential applications as soil improvement technique, and recently the application of grouting technique using biological process have been proposed. This study discussed the applicability of enzyme-mediated calcite precipitation (EMCP) in improving the shear strength parameters of sandy soil. In this study, soil specimens were prepared and treated with the grouting solutions composed of urea, calcium chloride, magnesium sulfate and enzyme of urease. Evolutions in the cohesion and internal friction angle of the improved soil were examined through the direct shear tests. The presence of the precipitated materials, comprising 4.1 percent of the soil mass of the treated sand, generated a cohesion of 53 kPa. However, contrary to the improvement of cohesion, the friction angle is relatively constant. It indicated that the application of the EMCP technique has no significant impact on the friction angle

Nondestructive Evaluation of Non-Strand Defects in Stay Cable Specimens

Stay cable systems are used extensively for the construction of long-span bridges owing to their inherent advantages. In most cable-stayed bridges the steel strands within the main tension elements (MTEs) are grouted to provide a corrosion protection system. However, there could be segregated grout, voids, and water accumulation/infiltration within these voids in the ducts due to poor quality of the grouting material and grouting techniques. These locations may act as initiators for the corrosion of steel strands within the ducts, which can have serious implications on the load carrying capacity and safety of cable-stayed bridges. In this investigation, several nondestructive evaluation (NDE) techniques are evaluated to determine their ability to detect grout defects within the anchorage regions, end caps, and MTEs of the stay cable system. Four stay cable specimen mock-ups with known grout defects and voids were fabricated. NDE methods that were part of this investigation included ground penetrating radar, infrared thermography, electrical capacitance tomography, impact echo, sounding, ultrasonic tomography, ultrasonic pulse velocity, low frequency ultrasound, visual testing, and borescope. While a few NDE methods could identify voids and water infiltration defects within the high-density polyethylene (HDPE) MTEs, it is evident that there is still a need for a method that is effective in detecting grout defects within the metal ducts embedded in the anchorage region and metal MTEs. Although visual testing and borescope methods are effective in identifying the defects, prior information about the location of the defects is generally required.