Ground Modification Research Articles

Application of surface wave method in assessment of ground modification with improvement columns

Surface wave testing is considered a promising method for assessing average property and actual area replacement ratio of ground modification with improvement columns, owing to its non-destructive nature and large sampling range. However, the surface wave method is essentially a 1-D method assuming horizontally-layered medium. What it measures in highly heterogeneous improved ground remains to be investigated. This study aimed at evaluating the feasibility of surface wave method in the heterogeneous ground with improved columns, and investigating the homogenization of shear wave velocity and the lateral sampling range. Field tests on a jet grouted construction site showed that the surface wave method worked well in such heterogeneous grounds and yielded a site-representative shear wave velocity profile regardless of the survey location. This is attributed to the survey condition where the wavelength is greater than the spacing of grout columns. 1-D analytical models and 2-D numerical simulations were conducted to investigate the quantitative relation between construction parameters and the percentage increase of shear wave velocity after ground improvement. A quantitative approach to estimate the area replacement ratio and overall quality of improvement columns by surface wave testing is proposed.

Advances in ground modification with chemical additives: From theory to practice

Abstract This keynote paper describes recent advances in chemical stabilization with a particular focus on applications related to transportation infrastructure. Chemical stabilization advances ranging from stabilization design guidelines with incorporation of fundamental soil chemistry principles to novel chemical additives for future stabilization are covered. This paper focuses on chemical treatments of shallow to moderate subgrade depths for supporting transportation pavement infrastructure. A background summary of stabilization methods along with modifications to the current design practices is presented. This section is followed by a comprehensive experimental program on chemical treatments of expansive subsoils. Both clay mineralogy influence and durability issues are fully addressed. Stabilization leachate studies and their implication in relation to real field performance are also addressed. The final outcome of this research is a more comprehensive stabilization methodology that addresses soil types and performance based testing methodologies. The last two sections cover a brief summary of new treatments of immense interest to addressing sustainable elements in ground improvement practices.

Deep Mixing Grows Up: The Evolution of Deep-Mixing Technology in the U.S. Market over the Last Decade

Over the last decade, deep mixing in the U.S. market has grown from being something of a mystery into a reliable ground modification technology that can be designed rationally, implemented with capable equipment, and verified with a full suite of QC/QA measures. This article provides a brief overview of deep-mixing technologies, the evolution of the technology during the last decade, key resources, and deep-mixing issues that would benefit from further research and development.

Geotechnical Aspects of Explosive Compaction

Explosive Compaction (EC) is the ground modification technique whereby the energy released from setting off explosives in subsoil inducing artificial earthquake effects, which compact the soil layers. The efficiency of EC predominantly depends on the soil profile, grain size distribution, initial status, and the intensity of energy applied to the soil. In this paper, in order to investigate the geotechnical aspects, which play an important role in performance of EC, a database has been compiled from thirteen-field tests or construction sites around the world, where EC has been successfully applied for modifying soil. This research focuses on evaluation of grain size distribution and initial stability status of deposits besides changes of soil penetration resistance due to EC. Results indicated suitable EC performance for unstable and liquefiable deposits having particle sizes ranging from gravel to silty sand with less than 40% silt content and less than 10% clay content. However, EC is most effective in fine-to-medium sands with a fine content less than 5% and hydraulically deposited with initial relative density ranging from 30% to 60%. Moreover, it has been observed that EC can be an effective method to improve the density, stability, and resistance of the target soils.

Effect of nano silica on the performance of cementitious grout for ground modification

Effect of nano silica on the performance of cementitious grout for ground modification

Development of an Innovative Bituminized Jute Paving Fabric (BJPF) Along with its Commercial Field Trials for Potential Application in the Field of Geotechnical Construction with an Eye Towards Global Concern

In the last quarter of the twentieth century, a new class of materials, Geosynthetics, emerged prospectively leading significant innovation in the design of geotechnical and geoenvironmental systems. Geotextiles have proven to be among the most versatile and techno-economically viable ground modification materials playing a significant role in modern pavement design and maintenance techniques. With the growing environmental concern across the globe, technologists, researchers have inclined towards the natural geotextile where Jute Geotextile (JGT) is one of the potential candidates. But, JGT has been restricted mainly as underlay in road construction. Hence, there is an urgent need to design and develop a precise innovative fabric as overlay on existing pavements and other emerging civil works to stay technically and economically competitive in the global market. Such a fabric will not only prove techno-economically viable but will also reduce the carbon foot-print generation to a large extent. This paper delineates the development of Grey Jute Paving Fabric (GJPF) followed by its bituminization with suitable type and grade of bitumen to develop Bituminized Jute Paving Fabric (BJPF). The BJPF will enhance the life of the overlay thereby reducing the cost of maintenance as well as serving as a partial substitute of bitumen mastic.

EVALUATION OF CBR USING GEOSYNTHETICS IN SOIL LAYERS

In urban areas, the service life of pavement on weaker soil subgrade affected severely due to their high compressibility and plasticity behaviour. These soils possess less strength, CBR value and have high affinity to moisture content. Also the seasonal changes affects the soil properties adversely. Stabilization techniques using geo-synthetic materials for improving properties of these types of soft subgrades. To increase the sub grade soil strength and to reduce the thickness of flexible pavement, Geosynthetics are increasingly used in wide variety of civil engineering applications. Geo- synthetics are the cost-effective ground modification materials which acts as a reinforcement and also increases the stability and bearing capacity of soil. Many researchers recommends the use of geo-synthetic material performs good results in soil stabilization. From this view, Evaluation has been made on poorly graded sand with the inclusion of go-grid, geo-textile and geo-composite materials between soil layers in different proportions. The CBR and shear parameters are determined for different combinations of subgrade thickness. The geo-engineering properties such as Atterberg limits, grain size distribution, compaction characteristics, and CBR value of poorly graded sand were evaluated and reported. To get the maximum California bearing ratio (CBR), the present study is put forward to understand the strength change in the soil with the addition of geo-synthetic materials. Such a study would be helpful in material selection based on site condition and strength gain along with economy.

Study on Ground Motion Intensities and Modification for Seismic Analysis of Reinforced Concrete Frames

The selection of input ground motion for seismic analysis of the structure is a complicated task, especially when nonlinear dynamic analysis is utilized. A decision has to be made regarding the intensity measure better to represent the potential damage of the ground motion. This paper presents a lot of analysis to deal with the problem. A set of nonlinear dynamic analyses were conducted on reinforced concrete buildings widely present in China. Input ground motions contain uncertainty and variability comes from both natural recordings and synthetic data. First, a set of natural recordings is considered. Second, two ground motion modification schemes are used in this study: magnitude scaling and spectrum matching. Third, a set of ground motion is synthesized. The peak value of displacement has been selected as the response parameter better able to represent the structural damage level. Nonlinear dynamic analyses of reinforced concrete buildings simulated by OpenSEES are carried out to evaluate the correlation coefficients of displacement response and the chosen ground motion parameters. Findings from the investigation indicate that the Housner intensity is the more effective intensity measure for selecting the seismic input. The synthesized ground motion fit with code spectrum shows good performance as a design input motion. Considering ground motion modification, spectrum matching is generally more stable in response prediction than scaling.

In-Situ Stabilization of Soil Slopes Using Nailed or Anchored Geosynthetics

The incidence of soil slope instability is, and has been, a natural hazard of major proportions and is ongoing to this day. While stabilization can be afforded by excavation and reconstruction, oftentimes structures and utilities are involved requiring in situ stabilization methods. This paper is focused accordingly. The method uses soil nails or soil anchors connected to a geosynthetic surface covering which is tensioned thereby stabilizing the encapsulated soil and providing tensile reinforcement. The paper is subdivided as follows: (i) introduction and theoretical background, (ii) required theoretical modifications, (iii) basics of soil nailing and anchors along with surface geosynthetics effects, (iv) implementation of the technique, (v) current activities by manufacturers, suppliers and ground modification companies, and (vi) summary and conclusions.

A REVIEW ON JUTE GEOTEXTILE – PART 1

Geotextiles have proven to be the most versatile and cost effective ground modification materials. Their use has extended rapidly into nearly all areas of civil, geotechnical, environmental, coastal and hydraulic engineering. They form the major component of the field of Geosynthetics, the others being geogrids, geomembranes and geocomposites. One of the growing alternatives in today’s context, with respect to growing environmental concern and carbon foot print generation, is the emergence of technical textiles made out of natural fibres which includes geotextile products for geotechnical applications, agrotextile products as well as other such relevant areas. Jute geotextile (JGT) can certainly be considered as a potential aspirant replacing majority of today’s popular synthetic products which are posing severe threats to our environment thereby adversely affecting the eco-congruity. For sustainable socioeconomic development, applications and usable area of jute geotextile are in increasing trend. There is a wide scope for innovative and prospective use of jute geotextile followed by the design and engineering of the products, oriented as per the end-user requirements for different geotechnical applications. This will open up newer avenues for Jute, not only as a technical textile, but for the entire Jute Sector as it is environment friendly and its application is effective for protecting environmental degradation. Therefore, keeping in mind about the potential candidature of jute geotextile this paper has substantiated a detailed review on jute geotextile-its designing and manufacturing along with its characteristic features, end-use specific applications, advantages and eventually its techno-economic viability.

Biogeochemical processes and geotechnical applications: progress, opportunities and challenges

Consideration of soil as a living ecosystem offers the potential for innovative and sustainable solutions to geotechnical problems. This is a new paradigm for many in geotechnical engineering. Realising the potential of this paradigm requires a multidisciplinary approach that embraces biology and geochemistry to develop techniques for beneficial ground modification. This paper assesses the progress, opportunities, and challenges in this emerging field. Biomediated geochemical processes, which consist of a geochemical reaction regulated by subsurface microbiology, currently being explored include mineral precipitation, gas generation, biofilm formation and biopolymer generation. For each of these processes, subsurface microbial processes are employed to create an environment conducive to the desired geochemical reactions among the minerals, organic matter, pore fluids, and gases that constitute soil. Geotechnical applications currently being explored include cementation of sands to enhance bearing capacity and liquefaction resistance, sequestration of carbon, soil erosion control, groundwater flow control, and remediation of soil and groundwater impacted by metals and radionuclides. Challenges in biomediated ground modification include upscaling processes from the laboratory to the field, in situ monitoring of reactions, reaction products and properties, developing integrated biogeochemical and geotechnical models, management of treatment by-products, establishing the durability and longevity/reversibility of the process, and education of engineers and researchers.

Influence of Ground Motion Spectral Shape on Nonlinear Responses of a 3-Storey RC Frame

Selection and modification of recorded earthquake ground motions is one of the most important issues for reliable seismic performance evaluation of the structure. In order to investigate the influence of ground motion spectral shape on nonlinear seismic response and to find the implication for ground motion selection and modification, a 3-storey RC planar frame is taken as case study in this paper. 15 ground motion records are chosen from PEER Ground Motion Database and Wenchuan Great Earthquake as dynamic analysis inputs.

Erosion Control Using Modified Soils

As a result of Hurricane Katrina, many sections of the flood protection systems in New Orleans were eroded due to plunging water, and sections of flood walls were determinately damaged. Therefore, mitigating this type of erosion and failure is necessary for counteracting similar catastrophic events. This study evaluated the method to mitigate erosion due to plunging water by strengthening the soil with ground modification. The Vetiver plant and Polyhedral Oligomeric Silsesquioxanes (POSS) were the two main ground modifiers used in this test. Test results showed that both POSS and the Vetiver were effective in reducing erosion. POSS showed good erosion resistance with good applicability to field soils; Vetiver showed higher resistance to erosion by plunging water, but required time to achieve a well established root/stem system.

Jet Grouting to Provide Scour Protection

The San Juan Creek Bridge near Antonio Parkway in Orange County, California, was slated for improvement as part of the widening of Ortega Highway (SR-74) into four lanes to relieve traffic congestion and accommodate planned growth in the region. To provide scour protection for the existing and new bridge piles, soilcrete (soil–cement) columns were constructed around the pile locations by using jet grouting, an in situ ground modification system. The Super Jet system of jet grouting was used. Headroom under the existing bridge was 10 ft. One hundred fifty-eight overlapping soilcrete columns were constructed around the planned piles. These columns were installed to the top of the San Juan Capistrano formation or to the designed scour depth. The specified minimum unconfined compressive strength (UCS) was 600 psi, and the required average strength was 750 psi. A test section was used to confirm the geometry and strength of the soilcrete columns. UCS tests were performed on wet grab samples and core samples. State-of-the-art quality control measures were implemented throughout the project. The design, construction, and quality control measures undertaken by the geotechnical contractor are discussed.

Artificial neural network models for predicting electrical resistivity of soils from their thermal resistivity

The knowledge of soil electrical and thermal resistivities is essential for several engineering projects such as laying of high voltage buried power cables, nuclear waste disposal, design of fluidized thermal beds, ground modification techniques etc. This necessitates precise determination of these resistivities, and relationship between them, which mainly depend on the soil type, its origin, compaction density and saturation. Such a relationship would also be helpful for determining one of these resistivities, if the other one is known. With this in view, efforts were made to develop artificial neural network (ANN) models that can be employed for estimating the soil electrical resistivity based on its soil thermal resistivity and the degree of saturation. To achieve this, measurements of electrical and thermal resistivities were carried out on different types soils compacted at different densities and moisture contents. These models were validated by comparing the predicted results vis-à-vis those obtained from experiments. The efficiency of these ANN models in predicting the soil electrical resistivity has been demonstrated, if its thermal resistivity is known. These ANN models are found to yield better results as compared to the generalized relationships proposed by the earlier researchers.

Soil Improvement for Mitigation of Damage During the 1999 Kocaeli Earthquake

Ground modification has been used extensively to reduce earthquake damage at poor soil sites. Case history data are crucial for assessing the effectiveness of such mitigation. Following the 1999 Kocaeli Earthquake (Mw = 7.4), the authors investigated the performance of industrial/commercial facilities along Izmit Bay. The region is vital to Turkey's economy, generating about 10% of the nation's GDP. Soil conditions along the Bay consist of soft, weak soils that increase earthquake damage potential. Soil improvement is being increasingly used in the region as a cost-effective mitigation solution. Our study of four major facilities on improved ground showed the treatment to be effective in mitigating losses relative to facilities on unimproved ground.

Effect of preloading on the cyclic strength of reconstituted sand

The effect of preloading on the cyclic soil strength under level ground was investigated by cyclic direct-shear tests where horizontal shear stress oscillated about a zero mean value. Tests on reconstituted samples were performed on two different sands and at varying prestress ratios, densities and vertical stresses. Test results showed a marked increase of the cyclic soil strength with the prestress ratio. The effect is more pronounced for the looser specimens. Arelationship giving the increase of the cyclic strength of sands with the prestress ratio is proposed. This relationship predicted reasonably well the increase in cyclic soil strength measured in previous laboratory studies. The domain of validity of this equation and the manner in which it can be used for ground modification projects under earthquakes are discussed.On étudie ici l'effet du préchargement sur la résistance cyclique du sol en dessous de la surface à niveau au moyen d'essais cycliques de cisaillement direct où la contrainte de cisaillement oscillait autour d'une valeur moyenne nulle. Des tests, réalisés sur des échantillons reconstitués, ont étéeffectués sur deux types de sables et pour des rapports de précontrainte, densités et contraintes verticales variables. Les résultats ainsi obtenus montrent une augmentation significative de la résistance cyclique du sol avec le rapportde précontrainte. Ce phénoméne est encore plus marqué pour les échantillons les plus meubles. Il est proposé uneéquation donnant l'augmentation de la résistance cyclique des sables en fonction du rapport de prélcontrainte. Cetterelation a permis de prédire de maniére relativement satisfaisante l'augmentation de résistance cyclique du solmesurée dans des é tudes de laboratoire précédentes. Ondiscute ici également du domaine de validité de cette équation et de la façon dont elle peut être appliquée auxprojets d'amélioration des sols soumis à des tremblementsde terre.

Design and Monitoring of an Embankment on Controlled Modulus Columns

The controlled modulus columns (CMC) foundation is one technique of ground modification for support of light structures such as highway and railway embankments. In this technique, a specially designed auger, powered by equipment with large torque capacity and high static down thrust, displaces the soil laterally without vibration. During the auger extraction process, a column is developed by pressure grouting to achieve a predetermined stiffness ratio with the surrounding soil. Because of the combined effect of densification and reinforcement, the properties of soft soil are improved because of composite action. The design and monitoring of a column-supported embankment project are presented; 2,193 CMC columns were installed up to a depth of 12.5 m to control settlement. The main challenges were construction on soft ground and the need for an accelerated construction technology for timely delivery of the project. Various alternatives, stability analysis, design considerations, construction challenges, quality control, and monitoring system were evaluated.

Design and Monitoring of an Embankment on Controlled Modulus Columns

The controlled modulus columns (CMC) foundation is one technique of ground modification for support of light structures such as highway and railway embankments. In this technique, a specially designed auger, powered by equipment with large torque capacity and high static down thrust, displaces the soil laterally without vibration. During the auger extraction process, a column is developed by pressure grouting to achieve a predetermined stiffness ratio with the surrounding soil. Because of the combined effect of densification and reinforcement, the properties of soft soil are improved because of composite action. The design and monitoring of a column-supported embankment project are presented; 2,193 CMC columns were installed up to a depth of 12.5 m to control settlement. The main challenges were construction on soft ground and the need for an accelerated construction technology for timely delivery of the project. Various alternatives, stability analysis, design considerations, construction challenges, quality control, and monitoring system were evaluated.

Generalized relationship for determining soil electrical resistivity from its thermal resistivity

The knowledge of soil electrical and thermal resistivity finds its application in many of the real life engineering projects like laying of high voltage buried power cables, ground modification techniques etc. This necessitates determination of soil electrical resistivity and thermal resistivity and development of a relationship between them. However, as these resistivities mainly depend on the type of the soil (i.e. its physical composition) and its saturation, efforts have been made in this paper, to develop a generalized relationship to relate them. Validation of the relationship has been conducted vis-à-vis the results obtained from the laboratory experiments and those reported in literature.