Grout Holes Research Articles

Study on Deformation and Control Measures of Columnar Jointed Basalt for Baihetan Super-High Arch Dam Foundation

The Baihetan super-high arch dam is constructed under complicated geological conditions, including large-scale columnar jointed basalt with closely spaced joints and multiple interlayer and intralayer shear belts at the lower part of dam base. Due to large excavation depth and scale at the dam base, unloading deformation and relaxation of columnar jointed basalt and shear belts were revealed by field investigation, in situ testing, monitoring, and numerical simulations. It was found that the relaxation depth of columnar jointed basalt was related to geostress, rock mass quality, and gently dipping shear belts. The time effect of unloading relaxation is also obvious in the columnar jointed basalt. In terms of unloading deformation control, comprehensive reinforcement measures and proper construction sequence at the dam base were proposed, including reservation of a 5-m-thick rock mass layer as the protective layer, consolidation grouting on the protective layer, preinstallation of mortar anchors through consolidation grouting hole, excavation of protective layers with controlled blasting in small benches, timely anchorage by prestressed cables upon exposure of foundation surface, and additional consolidation grouting for shallow foundation rock mass under concrete cover weight. With the comprehensive reinforcement measures at the dam base, the relaxation depth of columnar jointed basalt was small and shear deformation of shear belts was effectively controlled. Thus, the proposed reinforcement measures were proven to be proper and effective, which could meet the requirements of dam base and provide some reference for similar hydropower projects.

Construction of Fluid - solid Coupling Model with Improved Richards - BP & Its Engineering Application

In order to study the slurry diffusion law during grouting, Richards unsaturated-saturated model was introduced, the definition of the grouting model is clear, the Richards model control equation was established, And the BP neural network was introduced, the improved fluid-solid coupling model was constructed, Through the use of saturated - unsaturated seepage flow model, As well as the overflow boundary iterative solution of the mixed boundary conditions, the free surface is calculated. Engineering practice for an example, with the aid of multi - field coupling analysis software, the diffusion law of slurry was simulated numerically. The results show that the slurry diffusion rule is affected by grouting material, initial pressure and other factors. When the slurry starts, it flows in the cracks along the upper side of the grouting hole, when the pressure gradient is reduced to the critical pressure, that is, to the lower side of the flow, when the slurry diffusion stability, and ultimately its shape like an 8. The slurry is spread evenly from the overall point of view, from the grouting mouth toward the surrounding evenly spread, it gradually reaches saturation by non-saturation, and it is not a purely saturated flow, when the slurry spread and reach a saturated state, the diffusion time is the engineering grouting time.

Rock Grouting in Copenhagen Limestone – The Cityringen Experience

Extensive rock grouting has been carried out during the construction phase of the Cityringen Metro Project. The main goal of the rock grouting has been to reduce the permeability in the rock by filling joints, cracks and fissures, in order to minimize the groundwater inflow during excavation of caverns, pump sumps and TBM break in/out through the stations/shafts. Both horizontal and vertical grouting has been performed above and below the water table, with unique challenges and advantages/disadvantages. The grouting has been performed as up-stage, where the grout hole is drilled to full depth and then grouted from the bottom and up in stages using a pneumatic packer. The split-spacing method has been used to expand the grouting pattern if needed after primary grouting campaign has been finished and tested. The article describes, through case histories, the achieved results, challenges and limits of the applied methods, including future recommendations. The rock characteristics of the Copenhagen limestone, in regards to the performed rock grouting, are also discussed.

A study on the improvements of geotechnical properties of in-situ soils by grouting

This paper discusses improvements of compressibility, permeability, static and liquefaction strengths of in-situ soils by grouting. Both field testing and laboratory evaluation of the on-site samples were conducted. The improvement of soils was influenced by two main factors, i.e., the grout materials and the injection mechanisms introduced by the field grouting. On-site grout mapping revealed the major mechanism was fracturing accompanied with some permeation at deeper zones of sandy soils, where long-gel time suspension grout and solution grout were applied. The study found the compressibility and swelling potential of CL soils at a 0.5 m distance to grout hole could be reduced by 25% and 50%, respectively, due to the grouting. The effect on hydraulic conductivity of the CL soils appeared insignificant. The grouting slightly improved the cohesion of the CL soils by 10~15 kPa, and the friction angle appeared unaffected. The grouting had also improved the cohesion of the on-site SM soils by 10~90 kPa, while influences on the friction angle of soils were uncertain. Liquefaction resistances could be enhanced for the sandy soils within a 2~3 m extent to the grout hole. Average improvements of 40% and 20% on the liquefaction resistance were achievable for the sandy soils for earthquake magnitudes of 6 and ≥ 7.5, respectively, by the grouting.

Ground response and grout distribution by field soil grouting

Generally, grout extent and ground deformation are of great concern in soil grouting practice. In this paper, the ground behaviour, injection mechanism and grout distribution relating to field grouting in soils are discussed. It is found that the mechanisms of injection comply with generally accepted groutability requirements based on particle size ratio, where suspension grouts fracture clayey soils and solution grout permeates sandy soils. Ground heaving is affected by the sealing effect of grouts in upper soil layers. This study shows ground heave increases with the depth of grouting. The final heave volume reaches about 22% of the total grout injected. Lateral ground expansion is influenced by the hydraulic fracturing of grouts. Hydraulic fractures, which are nearly vertically formed in soils, produce lateral movements of the ground. The final lateral expansion of the ground, within 1 m radial zone of the grout hole, is approximately 12% of the total grout injected. A three-dimensional grout distribution is postulated based on the mapped grout traces in soils. The observed vertical grout fractures, with apertures of less than 15 mm and lateral extents of 1~4 m, confirm that the site soil strata are normally consolidated.

Grouting to remove piles from a tunnelling machine cutter-head

This paper provides a summary report on measures taken to remove embedded steel ‘H' pile obstacles from the cutter head of an advancing tunnel-boring machine. The piles were part of the soil-mixing retaining wall built for the cut-and-cover tunnel construction of a Taiwan high-speed rail tunnel and a Taiwan railways administration tunnel, which were directly above the mass rapid transit tunnel that was to be constructed. The collision zone between the boring machine and piles was below groundwater level and was approximately 23 m below the ground surface in a silty sand layer. To remove the piles safely from the cutter head, horizontal grouting from two adjacent work pits was conducted for waterproofing and solidification purposes. By controlling the amount of soil being flushed out during the grout hole drilling first, and also the pressure used for grouting later, the measured tunnel settlement resulting from grouting was negligible. Because of the favourable watertightness of the grouted zone and the dewatering influence of a nearby construction site, pile removal was conducted under particularly dry working conditions. In total, 12 piles were identified in the collision zone and were successfully removed from the cutter head by hand tools.

A New Method for Optimal Locating of Boreholes in Rock Consolidation Works

ABSTRACT Zhang, J. and Lu, Z., 2015. A New method for optimal locating of boreholes in rock consolidation works. With respect to the design and construction of grouting and drainage works, the conventional method is to locate the grout hole and drainage hole in the direction perpendicular to the natural rock or excavation surface. The anisotropy of structural planes in leaking water or grout has been neglected in the design of the works. Investigation data about rock fissures are studied to find out the distribution law of structural planes and know how to best locate boreholes with respect to structural planes in order to get an optimum effect of grouting and drainage. A new method is put forward for locating grout holes and bore holes. The practice from the Houhe Reservoir shows the inclined borehole less than 75° has an obvious efficiency, and among the boreholes within the angle range of 65 to 75, the optimum locations have an average efficiency of 2.11.

The Optimization for Grouting Hole of Concrete-Filled Steel Tubular Stent

The Optimization for Grouting Hole of Concrete-Filled Steel Tubular Stent

Quality control of double fluid jet grouting below groundwater table: Case history

A jet grout block created by overlapping columns aimed to convert the saturated silty sand soils into a safe space for breaking down four underground parking uplift piles along the tunnel alignment. Since the grouting platform was located on the mat foundation in the basement of underground parking and was under the groundwater table, a series of dewatering wells were installed before the 177 columns were constructed to prevent intrusion of the groundwater flowing upward from sandy soil to basement through grouting hole during wash boring and grouting stages from happening. Several quality control measures were undertaken prior to quality assurance testing. Two measurements of spoil return and spoil flow rate for each column were implemented. From a back analysis from the mean values of spoil density and spoil flow rate, the column diameter was estimated at around 1.56m, slightly smaller than the design diameter by 2.5%. In addition, a control chart with upper and lower control limits, established from a large dataset of flow rate of spoil return, was a means to recognize the likelihood of sand boiling and to serve as an early warning indicator of abnormal conditions for the jet grouting works below the groundwater table. As the mean spoil density of the infill column was larger than perimeter column, an optimal grouting sequence for clusters was suggested in this paper. The jet grout block exposed during the breakdown process of the piles showed safe working conditions as required and a shield machine then passed through as planned.

Consolidation grouting using horizontal directional drilling technology in the Praga district of Warsaw prior to TBM tunnelling

AbstractThe central section of the Warsaw 2nd Metro Line required preventive measures to protect buildings located in the Praga district above the tunnel alignment. The sections passing below buildings with EPB machines were certainly one of the most critical points. It was decided to carry out ground treatment in order to consolidate the subsoil around the tunnels. For this purpose grouting holes up to 261 m long were drilled by HDD following the tunnel path. Tunnelling did not affect the structures located above the ground, which always remained under close supervision with the use of specialist and multithreaded monitoring.

Time-Variant Flexural Reliability of Posttensioned, Segmental Concrete Bridges Exposed to Corrosive Environments

Posttensioned (PT) bridges are used on major thoroughfares because they are economical structures for traversing long spans. Special inspections of these bridges have revealed corrosion of the strands at void locations in the tendons. The integrity of these strands has significant influence on the safety of these bridges. Inspections indicate that many ducts (parts of the tendon that is supposed to protect strands from exposure to aggressive environments) are cracked and many grout holes and vents are opened, allowing direct ingress of moisture and chlorides. This paper presents a framework for assessing the flexural reliability of PT bridges exposed to various environmental conditions. The moment capacity of a PT girder is formulated using probabilistic models for the tension capacity of corroding PT strands exposed to various void and environmental conditions. Using Monte Carlo simulations, the flexural reliability of an example PT bridge is assessed. The research indicates that the flexural reliability index reaches a value below the recommended value within a relatively short period of time when moisture and chlorides infiltrate the tendons. These findings emphasize the critical need for new inspection, assessment, and repair methods for these bridge types.

Consolidation Grouting Quality Assessment using Artificial Neural Network (ANN)

Nowadays, grouting plays a vital role in dam foundation. The purpose of the grouting with pressure is to fill the joints, discontinuities, void distance and cavities in the rock masses to consolidate and caulk the rock masses for reducing seepage and uplift pressure in the dam foundation and related structures. Cheraghvays dam is located at 17 km away from the west of the Saqqez in Kurdistan province of Iran. In the Cheraghvays dam, the grout holes were arranged at 2 m intervals and with 10.5 m final depth. There are three grout sections (0–2.5, 2.5–5.5, 5.5–10.5 m) inside each grout hole and the grout process was conducted from the bottom to the top. Finally, the controlling holes are used to perform Lugeon test and to check the grouting quality of the dam foundation. Checking the operations in all areas of the foundation causes cost and time consuming. In this paper, experimental variogram and their mathematical model are calculated by geostatistics methods. To assess consolidation grouting quality, secondary permeability was predicted by artificial neural network (ANN) and the linear regression method. For this aim, datasets of 68 blocks which include first permeability, cement take and secondary permeability have been collected. The obtained results have indicated that ANN can predict secondary permeability in Cheraghvays dam foundation better than the linear regression method. So, ANN can be used in consolidation grouting quality assessment.

Control of rock jacking considering spread of grout and grouting pressure

This paper describes a theoretical approach for monitoring fracture dilatancy (or “jacking”) during grouting. From this, a methodology to optimize the grout pumping pressure has been developed, based on the required penetration length (i.e. the distance that the grout spreads from the grout hole into the network of fractures within the rock mass). Empirical rules are put forward to prevent the damage that may result from uncontrolled deformation (Jacking) of the fractures, by limiting either pumping pressure or the injected grout volume, or by a combination of both. The state of the fractures and the spread of the grout when these limits are reached are discussed. The theoretical approach, which is referred to here as the Real Time Grouting Control Method, enables the estimation of grout penetration length or “spread” in real time. This gives an opportunity to monitor fracture dilation as it happens and, for the purpose of this paper, the allowable limits of elastic deformation and jacking have been estimated based on the grout spread. Two case histories are analyzed, for which the physical reaction of the fracture deformation with time and grout spread are determined from the recorded pressure and flow. By comparing the observed physical reaction with the theories for jacking presented here, the Real Time Grouting Control Method has been validated, and it is shown that this theoretical approach is superior to commonly used empirical methods, in that it allows the optimization of the pumping pressure to achieve a given penetration length in the shortest time and with an acceptable fracture dilatancy. This approach is a major step forward in customizing grouting works.

Analysis on Sealing Method and Sealing Materials of Gas Drainage Borehole

With the increase of gas drainage volume and gas drainage requirement of coal seam in China, more and more attention to gas drainage effect of coal seam is paid. The gas flow law and borehole sealing mechanism are briefly described, the borehole sealing technologies of different materials are analyzed and the requirements are obtained as follows: 1Sealing materials shall have permeability. 2Sealing materials shall have expansion. 3The strength and hardness of sealing material can not be too high. 4Sealing materials are compact; sealing materials shall have certain strength. 5Sealing materials can be obtained easily and their price shall be low. 6Sealing process is simple and is constructed easily. Finally, the high polymer foam sealing technology, the mechanical elastic sealing technology, borehole packer sealing technology, the new pressure grouting hole sealing technology, yellow clay borehole sealing technology and rubber ring (or capsule)-sealing fluid sealing technology are briefly analyzed, the advantages and disadvantages of the borehole sealing method and the sealing materials used in coal mines in China are summed up. The results can provides the reference for selection of borehole sealing methods and sealing materials of gas drainage in coal mines.

The Application of Pressure Grouting Technology in Foundation Treatment of Clarifiers

Basing on diffusion radius formula of pressure grouting which was deduced by the Darcy's law in groundwater dynamics and connecting with engineering example, this article introduces the construction parameters and analyzes results of pressure grouting. Several methods including Re-grouting, coring method and SPT were used in the effect detection, it turns out that the slurry owns a consolidation and filling effect around the grouting holes when it is injected into soil. This effect can reduce the porosity and moisture content of soil, then the foundation bearing capacity is improved and the settlement can be reduced. Practice has proved the feasibility of pressure grouting in repairing soft foundation of important buildings, so it is a valuable reference to foundation reinforcement under similar conditions.

Numerical Simulation and Optimization of Hole Spacing for Cement Grouting in Rocks

The fine fissures of V-diabase were the main stratigraphic that affected the effectiveness of foundation grout curtain in Dagang Mountain Hydropower Station. Thus, specialized in situ grouting tests were conducted to determine reasonable hole spacing and other parameters. Considering time variation of the rheological parameters of grout, variation of grouting pressure gradient, and evolution law of the fracture opening, numerical simulations were performed on the diffusion process of cement grouting in the fissures of the rock mass. The distribution of permeability after grouting was obtained on the basis of analysis results, and the grouting hole spacing was discussed based on the reliability analysis. A probability of optimization along with a finer optimization precision as 0.1 m could be adopted when compared with the accuracy of 0.5 m that is commonly used. The results could provide a useful reference for choosing reasonable grouting hole spacing in similar projects.

The Calculation of Grouting Diffusion Radius on Based Bingham Fluid for Chunnel That Passes through Fractured Rock Mass

To conduct pro-grouting design and make the prediction of the result of grouting about the chunnel that passes through fractured rock mass, the essay adopts following theoretical formula to calculate the fractured rock mass grouting diffusion radius: Wittke and Wallner Formula、Lombadi Formula and Huang Chunhua Formula. Finally through the analysis of calculation results can conclude: (I) The diffusion radius of the slurry can meet the design requirements under the condition of 3-4 Mpa designed grouting pressure、5 cm grouting holes’ radius and 1800-3600s grouting time. (II) The calculation result of Huang Chunhua Formula is almost the same as Wittke and Wallner Formula and Lombadi Formula, but the margin of grouting diffusion radius’ change as grouting time and grouting pressure growing are different, it’s more close to the real situation.(III) The calculation of these theoretical formula only consider the breadth of fractured rock without considering the variation of its thickness and direction. So all of the calculation results of these formula are generally bigger than the standard.

Strengthening treatment and analysis for the left bank abutment of Jin Ping Arch Dam

AbstractThe Jin Ping arch dam foundation exhibits large differences in the stiffness between left and right bank due to a fault in the valley and unloading, relaxation and rock crushing effects in the left abutment. An extremely complex engineering problem appears by achieving mechanical balance for the dam body. To reinforce the left dam foundation concrete pads refilling faults, huge concrete piles and consolidation grouting together with grout and drainage curtains are investigated and executed. The numerical results show that these reinforcement measures for the excavated dam foundation improved significantly the rock mass deformability and its stability.A suitable excavation sequence for reinforcement tunnels and caverns is studied and the stability of these tunnels is analysed. The influence of consolidation grouting on the slope stability is investigated by varying spacing and number of active grouting holes. During the construction of the reinforcement tunnels the vibrations induced by blasting are simulated and measured. For different distances between tunnels and slope to tunnels respectively, the maximum quantity of explosives for single drives is studied.

Treatment of Seepage through Vendarasankulum Twin Reservoir in Eastern Sri Lanka - Cost Comparison of Alternative Techniques

The purpose of this study is to select a more effective technique from ‘upstream cutoff’ and ‘grouting treatment’ for the control of seepage through the Vendarasankulum reservoir. Using engineering judgment, empirical and theoretical knowledge, trapezoidal cross sectional dimensions of layers of different soil materials were determined. For example, the cross section at 490m (from left); SC layer on the U/S side slope has widths, 3m and 12m at bund top and bottom respectively; clay layer in the core has widths 12 m and 3 m at the top and bottom respectively. The effective fetch (1.72 km) and thereby the maximum wave height (0.84m) were computed in order to extract values for thicknesses of riprap (0.45 m) and bedding layer (0.30m). Grouting treatment involves clay-cement grouting in the overburden and 6m deep cement grouting in the rock, requiring a total of 296 grout holes. While the estimated cost of construction of the upstream cutoff is SLR 30.3 million, the same for grouting treatment is SLR 11.3 million, indicating the former option would cost 168 percent more. Therefore, grouting treatment is more economical and sufficient, although upstream cutoff could offer better seepage control.

The application of low frequency longitudinal guided wave mode for the inspection of multi-hole steel floral pipes

Shed-pipe grouting technology, an effective advanced supporting method, is often used in the excavation of soft strata. Steel floral pipes are one of the key load-carrying components of shed-pipe grouting supporting structures. Guided waves are a very attractive methodology to inspect multi-hole steel floral pipes as they offer long range inspection capability, mode and frequency tuning, and cost effectiveness. In this contribution, preliminary experiments are described for the inspection of steel floral pipes using a low frequency longitudinal guided wave mode, L(0,2). The relation between the number of grouting holes and the peak-to-peak amplitude of the first end-reflected signal was obtained. The effect of the grouting holes in steel floral pipes on the propagation velocity of the L(0,2) mode at 30 kHz was analyzed. Experimental results indicate that the typical grouting holes in steel floral pipe have no significant effect on the propagation of this mode. As a result, low frequency longitudinal guided wave modes have potential for the non-destructive long range inspection of multi-hole steel floral pipes. Furthermore, the propagation velocity of the investigated L(0,2) mode at 30 kHz decreases linearly with the increase of the number of grouting holes in a steel floral pipe. It is also noticeable that the effect of the grouting holes cumulates along with the increase in the number of grouting holes and subsequent increase in reflection times of longitudinal guided waves in the steel floral pipe. The application potential of the low frequency longitudinal guided wave technique for the inspection of embedded steel floral pipes is discussed.