Conventional Grouting Research Articles

State-of-the-art review and design of grouted duct connections for precast bridge columns

The use of prefabricated bridge columns in seismic regions is challenging since performance data on precast column connections is limited. A handful accelerated bridge construction (ABC) details to connect precast columns to adjoining members have been experimentally investigated, and some were found viable for seismic applications and field deployment. A connection consisting of ducts filled with conventional grout is the focus of the present study. In this connection type, precast column longitudinal bars are protruded out of the column and are inserted into grout-filled ducts matching the number and configuration of the column bars. A state-of-the-art review of the grouted duct connection studies and bridge component tests utilizing this connection type is presented. A preliminary design equation for duct connection filled with conventional grout is proposed based on the data collected from the literature. Subsequently, the validity of this equation is evaluated through pullout testing of 12 full-scale grouted-duct specimens. Finally, a refined design equation is proposed based on all available test data, and construction guidelines are developed to facilitate the use of grouted duct ABC column connections in high seismic regions. These design and construction guidelines were proposed to the American Association of State Highway and Transportation Officials (AASHTO) for possible adoption as national specifications.

Performance Evaluation of the Screw Nailed Walls in Tabriz Marl

Urban development and rapid extension of cities have been accompanied by considerable growth in excavation projects. Soil nail walls have been found to be an economical solution to many soil reinforcement and excavation support problems. To overcome some of the intrinsic problems with the conventional grout soil nails, screw soil nails were developed in recent years that provide several advantages over grouted soil nails. Tabriz marl outcrops at considerable parts of this city. Considering the rapid development of the Tabriz (as one of the biggest industrial cities of Iran), a large part of new urban areas and industrial zones will be located on marl soils. Therefore, it is necessary to evaluate the efficiency of the screw nailing method in Tabriz marl soils. In the present study, the performance of the walls reinforced by screw and grouted nails in different types of Tabriz marls was studied. For this purpose, a three-dimensional (3D) modeling is performed using the ABAQUS software. The results of the numerical analyses revealed that the failure zone of the screw and grout nailed walls is similar and consisting of parts entitled A and B. There is no significant difference between the characteristics of part B at both of the screw nailing and grout nailing methods. While, the A part of the failure zone and the maximum soil displacements in this part at the screw nailing method are smaller than those of the grout nailing method. At all types of the Tabriz marl, the lateral and vertical displacements of the reinforced walls by screw nails are smaller than those of grout nails, and in the case of yellow marl, the difference is considerable, while, at brown marl, it is negligible. The results of analyses show that the screw nail performs better than the pressurized cement grouted nail in terms of wall displacement. The efficiency of the screw nails increases in comparison to grouted nails by proceeding with the excavation process. At yellow marl because of lower elastic modulus value, the performance of the screw and grouted nails is more obvious than the other types of marl. The rate of increase in settlement values and maximum settlement of the soil for screw nailed walls are smaller than those of grout nailed walls. Also, the settlement profile of ground surface behind the wall is consisting of two parts, including critical and non-critical parts. The difference in the behavior of the screw and grouted nailed walls is obvious in the critical part of the soil behind the wall.

Evaluation of Injection capabilities of a biopolymer-based grout material

Injection grouting is one of the most common ground improvement practice to increase the strength and reduce the hydraulic conductivity of soils. Owing to the environmental concerns of conventional grout materials, such as cement-based or silicate-based materials, bio-inspired biogeotechnical approaches are considered to be new sustainable and environmentally friendly ground improvement methods. Biopolymers, which are excretory products from living organisms, have been shown to significantly reduce the hydraulic conductivity via pore-clogging and increase the strength of soils. To study the practical application of biopolymers for seepage and ground water control, in this study, we explored the injection capabilities of biopolymer-based grout materials in both linear aperture and particulate media (i.e., sand and glassbeads) considering different injection pressures, biopolymer concentrations, and flow channel geometries. The hydraulic conductivity control of a biopolymer-based grout material was evaluated after injection into sandy soil under confined boundary conditions. The results showed that the performance of xanthan gum injection was mainly affected by the injection pressure and pore geometry (e.g., porosity) inside the soil. Additionally, with an increase in the xanthan gum concentration, the injection efficiency diminished while the hydraulic conductivity reduction efficiency enhanced significantly. The results of this study provide the potential capabilities of injection grouting to be performed with biopolymer-based materials for field application.

Field Experiment Research of the Polycystic Aeration Bolt: Model Design and Anchorage Mechanism

As a new type of bolt, the polycystic aeration bolt has a broad application prospect in soft soil area; however, its design and production are still in the stage of constant exploration and improvement. From the perspective of bolt material and engineering cost, the important components of the polycystic aeration bolt were analyzed by combination with the existing bolt models, and a new structural design scheme of a kind of polycystic aeration bolt which can be used in practical engineering was presented in this paper. Then, the stress and failure mode of this bolt were discussed, and the theoretical equation of the bearing capacity was derived by using the elastic‐plastic theory. In addition, the assembly and fabrication technology of this bolt in practical foundation pit engineering was described in detail. Finally, the field pull‐out test of the polycystic aeration bolt was carried out, and the test results were compared with those of the conventional grouting bolt, which indicated that this new bolt has a greater advantage in bearing capacity than the conventional grouting bolt, verifying the feasibility of the structural design scheme of the polycystic aeration bolt proposed in this paper.

Permeability and setting time of bio-mediated soil under various medium concentrations

The bio-clogging using bacteria can be an eco-friendly and sustainable alternative to conventional grouting methods for seepage control. However, it remains unclear to date how the dilute concentration of bacterium and medium during field installation can affect the setting time of bacterium and its correlation with permeability reduction. In this study, the setting time of bacterium and its effectiveness in permeability reduction were addressed through experimental and theoretical investigations. A series of sand column was cultivated using different concentrations of Leuconostoc mesenteroides and culture medium. The distribution and composition of the bacterial product (i.e. dextran) were observed by refractometer, scanning electron microscope (SEM), and energy dispersive X-ray spectroscopy (EDS). Soil permeability was recorded using a constant head test. The results revealed that bacterium was effective to produce dextran at the setting time of about 5 d after installation. This dextran can reduce the permeability of bio-mediated soil by two orders of magnitude, even without culture medium supply. In general, the dextran production decreased proportionally with increase of bacterium and medium concentration. However, at 50% bacterium and medium concentration by weight, it still has a significant influence on permeability reduction with similar setting time, compared to 100% concentration. • Bacteria became effective to produce dextran with setting time after 5 d of installation. • The bacteria and medium concentration seems to have little influence on the setting time. • Dextran can reduce the permeability of bio-mediated soil by two orders of magnitude, even without culture medium supply. • With 50% of bacteria and medium concentration, the dextran can be accumulated in soil macro-pores and thus remain effective to reduce permeability.

Study on Strength and Leaching Behavior of Biogeochemical Cemented Sand

Conventional ground improvement techniques involve densification of soil either by mechanical compaction or chemical grouting while others involve inclusion of reinforcements, etc. Many conventional grout materials were found posing a threat to environment due to their toxic nature and release of greenhouse gases. In this regard, research is initiated in developing more environmentally sustainable additives for soil improvement in which biological based alternatives are gaining momentum. In the present study, a noble technique Microbial Induced Calcite Precipitation (MICP) using Sporosarcina pasteurii was adopted to modify the properties of sand and improve its efficiency by supplementing with Cellulomonas flavigena. The mineralogy of treated specimens was studied using X-Ray Diffraction and Scanning Electron Microscope analyses. The leachability of precipitated calcite was studied under constant flowing conditions and the material was found to be stable. The Unconfined Compressive Strength (UCS) and elastic modulii of the treated specimens were found to be in the range of 266–343 kPa and 14–35 MPa respectively. The angle of internal friction found from Direct Shear Test on treated specimens was observed to be a little lower compared to virgin specimens. The permeability of treated specimen showed a reduction in magnitude by one order approximately.

Utilization of controlled low strength material (CLSM) as a novel grout for geothermal systems: Laboratory and field experiments

Over the past decade, controlled low-strength material (CLSM) has been used extensively as fill material in flowable fills, structural fills, and void fills. However, owing to its good flowability and low shrinkage, CLSM can be considered a heat transfer medium as long as it has sufficiently high thermal conductivity. The main purpose of this study is to evaluate the use of controlled low strength material (CLSM) as a novel grout for geothermal systems by both laboratory and field experiments. Laboratory tests were performed first on various CLSM mixtures to evaluate their performance on general characteristics coupled with thermal conductivity, and the construction cost analysis. As a laboratory test result, all CLSM mixtures satisfied aspects of the abovementioned properties. In addition, in order to prove the proficiency of CLSM based-grout for geothermal systems, a large-scale test was also conducted to verify the workability and heat exchange rate of CLSM based-grout in the field with five boreholes and two control buildings. The workability of CLSM-based grout from the field tests was in the acceptable requirements reported in ACI 229R, (1999). In addition, the heat exchange rate of the proposed CLSM from the field test was found to be better than that of silicate sand and bentonite (i.e., conventional grouts). In conclusion, good workability and sufficient heat exchange rate obtained from the field test strongly reinforced the feasible use of the proposed CLSM as a thermal grout for geothermal systems.

Environmental impacts of chemical and microbial grouting.

Climate change is considered the major environmental challenge for the world. Cement and lime production is a highly energy-consuming, heavily polluting process, and the CO2 emissions are very substantial. Alkaline environment, high temperature, and long processing time lead the researchers to work on alternative soil improvements. Microbially induced calcite precipitation (MICP) has been introduced as a technique for modification of geotechnical properties of sand. The main purpose of the present study was to focus on the efficiency and environmental impact of conventional and microbial grouting. Samples were treated with three chemical stabilizers, namely Portland cement, lime, and cement and lime. The stabilizers were injected with flow gravity and constant head which are almost the same as microbial grouting. Then, the results of conventional grouting were compared with the results of biocement samples which were gathered from previous studies to discuss the efficiency and environmental impacts. The results for treated samples were discussed and compared based on 1 m3 of soil and a final target of 700 kPa. It was found that in order to obtain the same compressive strength, the cost and calcium carbonate consumption of the cement injection method were 2.5 times more than those of the microbial method. Biocementation has some advantages over existing technologies, such as less calcium usage in the same unconfined compressive strength (UCS).

Performance of hollow bar micropiles using green grout incorporating treated oil sand waste

Implementing waste materials in construction applications represents an effective solution for many waste management problems. This study presents an innovative solution for application of treated oil sands waste (TOSW) in grout mixtures used for micropiles construction. Effects of employing these grout mixtures on micropiles cross-section, surface interface properties and axial behaviour were investigated. The results showed an enhancement in the grout body diameter for micropiles installed using the developed grout, while maintaining the micropile surface properties. Micropiles installed using grout incorporating a high percentage of the TOSW (up to 30%) exhibited the same axial behaviour as that of micropile installed using conventional grout. Therefore, incorporating TOSW in micropile applications has high potential for producing cost efficient micropiles along with providing a green oil sands waste management solution.

A three-dimensional numerical investigation of a novel shallow bore ground heat exchanger integrated with phase change material

The heat transfer performance of an innovative design of ground heat exchanger, called underground thermal battery (UTB), was investigated in this paper. The UTB is designed to be installed in a shallow subsurface of the ground (less than 20 ft or 6 m below the grade), which is much shallower than the vertical bores (deeper than 200 ft or 60 m) required for installing conventional vertical bore ground heat exchangers (VBGHE). The UTB consists of a water-filled tank that also contains a phase change material (PCM), which impart the UTB a large thermal storage capacity. A three-dimensional (3D) numerical model has been developed to evaluate the performance of the UTB and to compare it with a conventional VBGHE. The simulation results indicated that a UTB can better regulate the entering water temperature of a ground source heat pump (GSHP) for more efficient operation than a conventional VBGHE under short-term high thermal load conditions. In addition, the UTB can make more effective use of PCMs compared with using PCMs to replace the conventional grouting material in a VBGHE.

Utilization of marine dredged soil in controlled low-strength material used as a thermal grout in geothermal systems

Abstract To date, controlled low-strength material (CLSM) has been used widely as fill material in flowable fills, structural fills, and void fills. However, owing to its good flowability and low shrinkage, CLSM can be considered a heat transfer medium as long as it has sufficiently high thermal conductivity. In this study, a newly developed CLSM, a blend of natural sand, marine dredged soil (MDS), and binders, was investigated and evaluated for the feasibility of it being used in geothermal systems. In addition to its general properties (flowability, fresh density, and unconfined compressive strength), thermal conductivity (i.e., heat transfer capacity), bleeding rate (i.e., involving volume compensation for boreholes), and environmental impacts (i.e., involving the potential risk of water pollution) were broadly investigated in this study. A bleeding-rate-based volume compensation concept is described for an actual large-scale geothermal system to evaluate total cost. All of the prepared CLSM mixtures performed well in terms of general and environmental characteristics. Moreover, the thermal conductivity of the developed CLSM-based grout was much higher than that of conventional grouts (i.e., bentonite and silicate sand). More importantly, an outstandingly positive effect of MDS was discovered: a sufficient addition of MDS to CLSM-based grout can lead to a considerable decrease in bleeding rate; hence, to only a small volume compensation of required boreholes. Ultimately, the total cost for geothermal construction can be reduced.

Development and Field Test of New Environmentally Friendly Water-Rich Sand Grout Material

The water-rich sand layer is a common source for underground engineering disasters. Considering the poor performance, high cost, and serious environmental pollution of conventional grouting materials, based on the requirements of environmental grouting treatment, a new type of environmental water-rich sand grouting material was proposed, which was mainly based on fly ash and cement and supplemented by water glass. The performance of the slurry was studied. The parameters such as the initial set time, the ratio of stone, and the compressive strength of the material under different water contents and fly ash contents were determined by experiments. The new grouting material was obtained with rapid setting, early strength, high ratio of stone formation, and strength, which were less affected by water content. The successful application of the new environmental grouting material in the Qingdao Metro not only ensures the safety of the project but also meets the requirements of environmental protection. It also verifies the scientificity of the material and will be useful for the innovation of the water-rich sand grouting material.

Experimental analysis of enhanced cement-sand-based geothermal grouting materials

Nowadays, Ground Source Heat Pumps (GSHP) are achieving significant efficiencies, mostly because of the development of their electromechanical components. However, concepts such as the technical performance of the grouting materials deserve more profound analysis, as becoming essential in areas where good potential thermal performance of the GSHP and serious risks of groundwater contamination exist. In this paper, several fluid mortars with enhanced characteristics have been evaluated. Results show improved mechanical and thermal properties compared to conventional grouting materials. Likewise, mortars exhibited good performance after being subjected to durability treatment. For now, the cost of some mortars may constitute a barrier.

Utilization of by-product in controlled low-strength material for geothermal systems: Engineering performances, environmental impact, and cost analysis

This paper evaluates the feasibility of by-product-based controlled low-strength material (CLSM) as a grout for geothermal systems. Quartz-based mine tailings and pond ash were adopted as filler and fine aggregates, respectively. Settlement, compressive strength, and thermal conductivity, required for grout for geothermal systems were investigated and the leaching behavior of toxic elements from the CLSM was evaluated. In addition, a cost analysis for actual construction sites of the geothermal system was conducted using a design program. The high-workable CLSM with tailings and pond ash satisfied the strength specified in the ACI 229R and its thermal conductivity was higher than that of conventional grout, i.e., bentonite-sand mixture. The CLSM made only with tailings satisfied the ‘Treatment Standard for Hazardous Wastes’ in the Code of Federal Regulations of US governments (40 CFR 268.40), whereas that with both tailings and pond ash did not. The total construction costs of the geothermal system reduced up to 20.8% when utilizing the by-product-based CLSM compared with conventional grout.

Evaluation of the grouting in the sandy ground using bio injection material

This study was intended to evaluate the improved strength of the ground by applying the bio grouting method to a loose sandy ground. The injection material was prepared in the form of cement-like powder, with the bio injection material produced by microbial reactions. The grouting test was conducted under the conditions similar to the field where the bio injection material can be applied. In addition, the injection materials (cement and sodium silicate No. 3) used for Labile Waterglass (LW) method and the conventional grouting methodwere prepared through a two-solution one-step process. The injection into the specimens was done at a pressure of 150 kPa and then, with a bender element, their moduliof elasticity were measured on the 7th, 14th, 21st and 28th curingdays to analyze their strengths according to the duration of curing. It was confirmed that in all injection materials the moduli of elasticity increased over time. In particular, when 30% of the bio injection material was added to 100% cement, the modulus of elasticity tended to increase by about 15%. This confirmed that the applicability became higher when the bio injection material was used in place of the conventional sodium silicate.

Property transformation of a modified sulfoaluminate grouting material under pressure circulation for a water-sealed underground oil cavern

Water-sealed underground oil caverns are quite different from conventional underground projects because of the harsher conditions. For one of the largest such caverns in China, conventional grouting materials could not meet the project standard. Therefore, the authors invented a new grouting material based on sulfoaluminate cement (SAC) and studied its properties under pressure circulation. During circulation, the time to the hydration exothermic peak time was reduced, and the peak temperature increased with the pressure. The compressive strength decreased during circulation and with the circulation time. These results were important for grouting during the project.

고수압 해저터널에 급속 인공동결공법 적용시 간극수의 염분 농도가 동결속도에 미치는 영향 평가: 실내 동결챔버시험 위주로

고수압 조건의 해저터널 공사에 기존의 그라우팅 공법은 제한을 받게 되어 굴착작업이 어려울 수 있으나, 인공동결공법을 적용할 경우 신속한 차수 및 지반보강 효과를 얻을 수 있다. 인공동결공법을 적용할 경우, 동결 조건에 따라 동결토의 거동이 크게 변화하므로 기존의 연구 사례를 바탕으로 해저지반 등 특수한 조건에서 동결토의 역학적 거동을 예측하는 것에는 한계가 있다. 또한, 인공동결공법의 설계를 위해서는 동결체 형성에 필요한 소요시간 및 동결범위를 산정해야 하며, 해저지반의 경우 간극수 내 염분의 영향을 반영해야 한다. 본 논문에서는 동결토의 열적 특성을 파악하기 위해 인조규사 시료에 대한 실내 열전도도 측정시험과 동결챔버시험을 수행하였다. 동결토와 비동결 포화토 간극수의 염도를 조절하여 동결 과정과 염분에 따른 유효 열전도도를 비정상 열선법을 적용하여 측정하였다. 인조규사 간극수의 염도에 의한 동결특성 변화를 파악하기 위해 동결챔버를 설계 및 제작하였고 이를 통하여 동결 조건을 변화시키며 동결챔버시험을 수행하였다. 동결 조건에 따른 시료내 온도 변화를 분석하고 이를 통해 동결 조건이 사질토의 열전달 특성에 미치는 영향을 평가하였다. 비동결 포화토의 경우는 간극수가 담수(염도 0%)인 조건과 염수(염도 3.5%)인 조건 모두 유효 열전도도가 유사하게 평가되었으나, 동결토의 경우는 간극수가 염수인 조건이 보다 큰 유효 열전도도를 보였다. 이는 동결챔버시험에서 간극수가 염수인 조건이 담수인 조건보다 동결속도가 더 빠른 결과와 일치한다. It is extremely difficult to apply conventional grouting methods to subsea tunnelling construction in the high water pressure condition. In such a condition, the rapid artificial freezing method can be an alternative to grouting to form a watertight zone around freezing pipes. For a proper design of the artificial freezing method, the influence of salinity on the freezing process has to be considered. However, there are few domestic tunnel construction that adopted the artificial freezing method, and influential factors on the freezing of the soil are not clearly identified. In this paper, a series of laboratory experiments were performed to identify the physical characteristics of frozen soil. Thermal conductivity of the frozen and unfrozen soil samples was measured through the thermal sensor adopting transient hot-wire method. Moreover, a lab-scale freezing chamber was devised to simulate freezing process of silica sand with consideration of the salinity of pore-water. The temperature in the silica sand sample was measured during the freezing process to evaluate the effect of pore-water salinity on the frozen rate that is one of the key parameters in designing the artificial freezing method in subsea tunnelling. In case of unfrozen soil, the soil samples saturated with fresh water (salinity of 0%) and brine water (salinity of 3.5%) showed a similar value of thermal conductivity. However, the frozen soil sample saturated with brine water led to the thermal conductivity notably higher than that of fresh water, which corresponds to the fact that the freezing rate of brine water was greater than that of fresh water in the freezing chamber test.

Design and construction of UHPC-filled duct connections for precast bridge columns in high seismic zones

One of the column connection types that has been recently emphasised for accelerated bridge construction (ABC) in high seismic zones is grout-filled duct connections. Experimental results have shown that the seismic behaviour of reinforced concrete columns connected to precast cap beams using this connection type is emulative of conventional columns. However, an alternative ABC connection is required to connect precast columns to shallow cap beams and footings due to insufficient anchorage length in those elements. Ultra-high-performance concrete (UHPC) was proposed in this study to be used instead of conventional grout in the connection to reduce the anchorage length. First, fourteen large-scale pullout tests were performed to investigate the bond strength of UHPC-filled duct connections. The test results showed that the incorporation of UHPC instead of normal grout as duct filler can reduce the bar embedment length by 50% or more. Second, design equations were developed based on the pullout test data to compute the bar development length in these connections. Subsequently, two half-scale precast bridge columns utilising this connection type at the column base were tested to verify the design equations. Full column plastic moment was developed in both specimens under cyclic loading with no UHPC-filled duct connection failure such as bar pullout even under 12% drift ratio cycles. Finally, a guideline was proposed based on the pullout and column test data for the design and construction of the UHPC-filled duct connections to facilitate field deployment.

Non-structural injection grouts with reduced water content: Changes induced by the partial substitution of water with alcohol

Conventional grouting – used to stabilise delaminated plaster – typically involves the use of water as suspension medium. Water can be dangerous when water-sensitive original materials are present and can cause the solubilisation of salts, leading to their re-crystallisation on drying. Ethyl alcohol is a less effective solvent for soluble salts and generally does not affect the original materials. This is the reason why it was used as a partial substitute for water in grout preparations in the present research. Three water–ethyl alcohol-based grouts were compared with the correspondent water-based grout. The working properties and performance characteristics of the injection grouts with reduced water content were measured to assess their suitability for use on historic plasters.

Aperture controlled grouting – benefits of the discrete fracture network approach

Fractured rocks, specifically sedimentary sequences, present a particular challenge for grouting, as major connected fractures that must be sealed will rarely be intersected by vertical groutholes. The aperture controlled grouting (ACG) method can be readily applied using discrete fracture network (DFN) analysis approaches to understand the pattern of fractures that need to be grouted. Aperture controlled grouting then utilises a combination of the principles of fracture grouting and grouting intensity number (GIN) grouting for practical and cost-effective grouting of tunnel, dam, shaft, or environmental restoration projects. This paper illustrates the application of DFN techniques for fracture assessment for grouting design and then compares the ACG approach to more conventional grouting approaches based on recent grouting experience.