Highway Embankment Construction Research Articles

Field investigation of steel pipe pile under lateral loading in extensively soft soil

The construction of railway and highway embankments has a significant influence on the behavior of existing pile foundations, especially in the situation of high embankments and extensively soft soils, which are commonly encountered in coastal areas. A high embankment might produce large lateral movement and bending moment to the existing adjacent piles, which would cause the failure of the pile if the surcharge loading is not properly considered. A field test was designed and performed to investigate the effect of lateral surcharge loading on the existing adjacent pile in extensively soft soils. A 4 m high embankment was constructed in five lifts and was close to the existing adjacent steel pipe pile with a length of 35 m. The deformation of the pile and the soft soils, the excess pore water pressure, and lateral earth pressures were measured during the surcharge loading test. The test results showed that the lateral displacement of the steel pipe pile at the ground surface exceeded 229.9 mm and could not maintain constant due to the surcharge loading. The lateral displacement decreased along with the pile depth and was relatively small when the pile depth exceeded 10 m. Large lateral displacements were observed in the soft soils at different locations. The surcharge loading zone showed obvious downward displacements, while the soft soils close to the loading zone showed upward displacements. The excess pore water pressure changed regularly with the construction of the embankment, and its maximum value reached 53.6 kPa. The lateral earth pressures that acted on the pile continuously increased with the increase in the embankment height, which caused large deformation of the pile.

Performance of cement-stabilized weak subgrade for highway embankment construction in Southeast Nigeria

Soils with poor shear strength and high compressibility underlie the wetlands of southern Nigeria. They are susceptible to intolerable settlements and account for greater than 60% of the soils in the region. While requiring embankments for any infrastructure construction, these weak soils pose significant threat to the construction and service life of highway pavements in southeastern Nigeria. Therefore, this research investigates shear strength improvement of a highway embankment’s weak subgrade soil after mass stabilization of soil with 6 and 10% Portland cement. The factor of safety against shear failure of the embankment was analyzed for un-stabilized subgrade and then cement-stabilized subgrade. The analysis was carried out for embankment heights of 4, 5, 6 and 7 m using the limit equilibrium method. Thick soft clayey silt with Cu range of 9 to 15 kPa underlay the embankment, upon improvement, the Cu of 154 and 208 kPa was obtained for 6 and 10% stabilization respectively. The FoS for the embankment on Un-stabilized soil ranged from 0.88 for a 7 m embankment to 1.2 for a 4 m embankment. The FoS after mass stabilization of 1 to 5 m soil ranged between 1.77 and 5.22 for the different embankment heights. Stability was better improved as depth of mass stabilization and cement content increased. A linear relationship was observed to exist between the cement content, strength of the improved soils, stabilization depth and the factor of safety.

Appropriate Use of Lime in the Study of the Physicochemical Behaviour of Stabilised Lateritic Soil under Continuous Water Ingress

Lime stabilisation is one of the traditional methods of improving the engineering properties of lateritic soils for use as subgrade and foundation materials for the construction of road pavements and highway embankments. Understanding the mechanical performance of lime-stabilised lateritic subgrades in terms of their durability under continuous water ingress will improve environmental sustainability by conserving scarce natural resources and reducing the environmental impacts of repair and replacement of pavements. However, there are several conflicting reports on the durability of lime-stabilised soils subjected to continuous water ingress and harsh environmental conditions. Therefore, this paper evaluates the influence of leaching on the physicochemical behaviour and durability of lime-stabilised lateritic soil under continuous water ingress, simulating the typical experience in a tropical environment. Variations in the strength and durability of the lateritic soil at various lime contents (0, 2.5, 5, 7.5, 10, 15, and 20 wt.%) and soaking periods (3, 7, 14 and 28 days) were evaluated by performing the California bearing ratio tests before and after subjecting the lime-lateritic soil (LLS) samples to continuous leaching using two modified leaching cells. Furthermore, physicochemical analysis was performed to assess the variation of cation concentrations and changes in the physical properties of the pore fluid as the leaching time progressed from 3 to 28 days. The results show that the minimum strength reduction index of the soil corresponds to its lime stabilisation optimum (LSO). Electrical conductivity decreased monotonically and almost uniformly with an increase in leaching time, irrespective of lime content. So, too, was calcium concentration and to a lesser degree for pH and potassium concentration. Adverse changes in the physicochemical behaviour of the LLS samples occurred at lime contents below and slightly above the optimum lime content of the soil. Whereas permanent pozzolanic reactions occurred at lime contents above the LSO and thus resulted in a 45-fold increase in strength and durability. The results are significant for reducing the detrimental effect of the leaching-induced deterioration of flexible pavements founded on tropical floodplains.

Loose Ash Fills Reinforced With the High Confined Encased Stone Columns: Experimental and Numerical Investigation

The use of industrial waste (ash) in large-scale earthworks for civil engineering applications such as construction of highway embankments, the rise of ash dykes, the filling low-lying areas, fillings of buildings, solves the problem of waste disposal besides in addition to the conservation of the natural soils. It is has a low density, low consolidation, lower potential for bearing and higher settlement. To use these areas for construction purposes, it is necessary to reinforce them at deeper depths. The present study uses highly confined stone columns to investigate the strengthening of ash fills. A total of six cases are investigated, including slope reinforced with an encased stone column. Model tests were conducted with pond ash at 40% relative density with a circular footing on untreated and treated ash fills. The enhanced cases include ordinary stone columns,vertically encased columns with geotextile, vertically encased columns with geogrid, highly confined vertically encased columns with both geotextile and geogrids (HC-1) and highly encased columns with both vertical encased geotextile and horizontal geogrid (HC-2) layers. The parametric study includes an examination of load-settlement behavior, load-carrying ratio, settlement reduction ratio, and stiffness factor, modulus of subgrade reaction and post-failure behavior of slopes reinforced with encased stone columns. In all cases, the high confined encased system yields better results. In each case, the stone column failure pattern of was observed at a distance range of 1–3 times the stone column diameter. Post-failure behavior indicates that for steep slopes where massive slip failures are expected, highly confined encased stone columns can be useful. Results are validated by the numerical modelling analysis of Plaxis.

Time-dependent field performance of PHC pile-cap-beam-supported embankment over soft marine clay

Routine capped rigid piles have been widely utilized to improve soft marine clay foundation for rapid construction of highway embankments and still exposed the problem of insufficient horizontal bearing capacity. An innovative composite system of pile-cap-beam (PCB) was presented in this study. Field measurements including pressures acting on the pile and soil surface, excess pore water pressures, settlements, lateral displacements and strains of ground beams were reported and discussed. The results elucidated that the response of ground beams subjected to embankment loading is closely related to the location of embankment corresponding to respective fill level. The beam between caps is prone to mid-span deflection at locations closer to the shoulder, which contributes to load transfer to the piles. The composite PCB system performed better in regard to reducing lateral displacements, total and differential settlements between the pile and surrounding soil, with a decrease of 57.1, 44.8 and 79.9%, respectively. The measured lateral displacement-settlement ratio suggested that the use of composite PCB system was remarkably effective in enhancing the stability of embankment. Moreover, feasibility of strain-based FBG sensors installed in the steel bar of ground beams was validated and limitations of the PCB system was also discussed in this study.

Batch leaching testing of stabilized dredged bottom-sea sediments

This study aims to define the long-term leaching of metals from structural fills composed of quarry byproduct-amended marine-dredged material under the influence of pH and to study the geochemical behavior of the species likely to form. Compaction and shear tests, image analysis, and pHstat and toxicity characteristic leaching procedure tests were undertaken to study the metal leaching behavior of raw dredged sediments and their blends prepared with three different quarry fines. Geochemical analysis was conducted to determine the predominant oxidation states from the analyzed metals, the aqueous concentrations of metal species, and the dominant leaching control mechanisms in the leachates. The quarry fine-amended dredged sediments satisfied the local compaction specifications for highway embankment construction while the raw sediments did not. The effective friction angle of the blends was also higher than that of raw sediments due to differences in soil structure and shape parameters. Leaching of As during the pHstat leaching tests followed an amphoteric pattern for raw sediments and a cationic pattern for the blends. Al, Cu, Fe, Ni, and Zn concentrations leached from the blends were below the EPA water quality limits at near-neutral pH. The concentrations of all metals released during the batch leach tests from the treated dredged materials are below the water quality limits under varying pH conditions. Geochemical modeling results indicated that release of all elements except arsenic from the treated dredged sediments was controlled by the dissolution and precipitation of oxide, hydroxide, and carbonate solids containing the elements.

Stability Control of Staged Filling Construction on Soft Subsoil Using Hyperbolic Settlement Prediction Method: A Case Study of a Tidal Flat in China

An improved method, which combines in situ measured settlement data, hyperbolic method, and deep lateral displacement rate, is presented in this study to predict the consolidation and stability of the ground, which can be used in conducting staged filling construction on soft subsoil. A case history of a highway embankment construction in a tidal flat with thick mucky clay is studied in Xia Pu, China. Preloading with the prefabricated vertical drain method is adopted to accelerate the consolidation of a subgrade. The field behavior of soft ground under filling load is observed through in situ monitoring sensors in four typical sections. The final ground settlement in each stage is determined using the field monitoring data based on the hyperbolic settlement prediction method. For each stage of graded filling load, the ground settlement with a strain consolidation degree of 95% is defined as the standard settlement, and the corresponding settlement time is set as the standard settlement time. The preloading period is estimated according to the standard settlement time. The deep lateral displacement rate of the ground is monitored to control the stability of the foundation and recommended to guide the embankment construction. Results indicate that the presented method can predict the preloading time of graded filling, reduce the frequency of observation, and ensure the consolidation and stability of the ground.

Stabilization of Expansive Soil Using Eko Soil Enzyme For Highway Embankment

Expansive soils are problematic due to their poor shear strength, bearing capacity, permeability, and high compressibility. In this paper, investigation was carried out on the effects of stabilizing a soil having poor geotechnical properties with Eko Soil (ES) enzyme to find its application for use as highway embankment construction. The ES was found best agent as a stabilizer to improve the Atterbergs’ Limit and hence plasticity index (PI) of expansive soil (C) as well as the unconfined compressive Strength (UCS) and California Bearing Ratio (CBR) of the same. Laboratory tests were performed with different percentages of ES, ranging from 1% to 6%. After satisfying result of PI, compaction test have performed on expansive soil with all combinations and found their respective optimum moisture content (OMC) and maximum dry densities (MDD). The OMC in each combination were used to prepared UCS and CBR samples and tested after 7, 28, 45 and 90 days curing. The Atterberg’s limit, OMC, MDD, UCS and CBR of ES stabilized Expansive Soil found more reliable at 4% ES and 28 days curing period. The values of CBR and UCS get an enhancement of 347% and 334% respectively.

Failures in transport infrastructure embankments

To ensure that road and rail transport networks remain operational, both highway and railway embankments require continual maintenance and renewal to mitigate against ongoing deterioration and repair any sections damaged by realised failures. This paper provides a review of recent developments in the understanding of highway and railway embankment degradation and failure. Failures due to pore water pressure increase, seasonal shrink-swell deformation and progressive failure are considered. The material composition and construction of highway and railway embankments differ, which influences the dominant type and timing of embankment failure. There is evidence for highway embankment failures induced by pore water pressure increase, but not seasonal deformation and progressive failure. Some railway embankments are susceptible to pore water pressure increase, seasonal shrink-swell deformation and progressive failure due to the age and nature of the dumped clay fill used in their construction. The approaches used to measure and explore embankment failure mechanisms are compared and discussed. Field observations have been used to understand pore water pressure increase and seasonal shrink-swell deformation in embankments, while the investigation of progressive embankment failure has mainly utilised physical and numerical modelling approaches. Further field and laboratory investigation is required before the rigorous analysis of embankment failure can be routinely undertaken. However, progress is being made to empirically identify and evaluate the various risk factors affecting transport infrastructure embankment failure.

Performance evaluation of stabilised soil–slag mixes as highway construction material

This paper presents an investigation on effective utilisation of steel slag, a by-product from the steel industry, as construction material in highway pavement layers so that the industrial wastes can be used and disposed properly with reduction in environmental impact as well as the demand for natural construction materials can be minimised. Steel slag was mechanically stabilised with locally available Powai soil (silty soil with intermediate plasticity) of ranges from 20 to 70% by weight, considering the utilisation in embankments and road pavement layer constructions. The mix as 30% slag and 70% soil provided the optimum strength based on the California bearing ratio (CBR) value and unconfined compressive strength (UCS).The optimum slag–soil mix was chemically stabilised using ordinary Portland cement and nanomaterial (amorphous nanosilica) in different percentage ranges, 4–10% for only cement, 2–6% for only nanomaterial, and for the mixture of cement with nanomaterial, it was always 4% cement with varying nano-percentages from 2 to 6%. From the experimental analyses, it was observed that cement-stabilised optimum slag–soil mixes and cement with nanosilica-stabilised mixes satisfied the material specifications for the construction of pavement layers. It was also observed that steel slag–soil mixes acquired good strength, drainage and plasticity characteristics to act as a potential material for highway embankment construction.

Model studies on fly ash slopes reinforced with planar steel grids

Fly ash, waste by-product from coal industries, is being used extensively in construction of highway and railway embankments. This paper describes the effectiveness of steel grid reinforcement in the form of planar mattress along with jute geotextile at facia throughout the slope and with fly ash as backfill material. The models were subjected to loading in the form of uniform and strip loading by means of rigid steel plates as footings. Series of laboratory model tests were carried out on homogeneous unreinforced and reinforced fly ash slopes with slope angle 60° on rigid base to check the efficacy of reinforcement in improving the load carrying capacity and stability of slope. For fly ash slope on rigid base, length of the reinforcement was varied from 0.7H to 0.2H (H = Height of the slope). The steel reinforcement having grid thickness of 1.2 mm with square openings of 15 mm was laid along the width of the slope in continuous form as well as with coverage ratios (Cr) of 0.5 and 0.6. All the tests were conducted by applying both uniformly distributed load (UDL) and strip loading until failure. Based on the experimental results, for all types of reinforcement cases, slope with continuous grid of length 0.7H supports maximum for strip loading before failure as compared to UDL. The variation in length of the reinforcement showed significant effect on the settlement of the backfill.

Multi-scale laboratory evaluation of the physical, mechanical, and microstructural properties of soft highway subgrade soil stabilized with calcium carbide residue

Calcium carbide residue (CCR) is an industrial by-product, stockpiles of which are rapidly accumulating worldwide. Highway embankment construction has been identified as an avenue to consume huge quantities of CCR as an economical, less energy intensive, and environmentally friendly chemical additive for soil stabilization. Previous studies have investigated the mechanical behavior of soils stabilized by CCR or blends of CCR with other additives; however, interpretation of the macroscale geomechanical behavior of CCR-stabilized soft soils from a systematically microstructural observation and analysis is relatively unknown. This paper presents a multi-scale laboratory investigation on the physical, mechanical, and microstructural properties of CCR-stabilized clayey soils with comparison to quicklime-stabilized soils. Several series of tests were conducted to examine the Atterberg limits, particle-size distribution, compaction characteristics, unconfined compressive strength, California Bearing Ratio, and resilient modulus of the CCR-stabilized clayey soils. The influences of binder content, curing time, and initial compaction state on the physical and mechanical properties of treated soils are interpreted with the aids of physicochemical and microstructural observations including soil pH, soil mineralogy obtained from X-ray diffraction and thermogravimetric analysis, and pore-size distribution obtained from mercury intrusion porosimetry. Soil particle flocculation and agglomeration at the early stage and pozzolanic reactions during the entire curing time, which originate from the finer particle size, greater specific surface area, and higher pH value of CCR, are the controlling mechanisms for the superior mechanical performance of CCR-stabilized soils. The outcomes of this research will contribute to the usage of CCR as a sustainable and alternative stabilizer to quicklime in highway embankment applications.

Effect of L/D Ratio of UCC Specimen on Shear Strength of Clay Soil

The role of Geotechnical engineering application in land reclamation, construction of highway, railway and canal embankments require a very large quantity of soil of desirable properties. It is often difficult to obtain good quality soil for the above applications from the nearby quarries. In such a situation, the locally available problematic soils (having low shear strength high compressibility and swelling nature) after stabilizing the same with the addition of admixtures such asuse of sand, lime, cement etc. for the improvement of problematic soils is costly because of their high demand in other civil engineering applications. To overcome the difficulties experienced with problematic soils in geotechnical applications on one side and safe disposal of solid wastes on the other side, an attempt is made in this study to explore the possibilities of utilizing to improve the engineering behaviour of problematic soils. In this study an attempt is made to know the index properties, compaction and unconfined compressive strength, may be used to improve the strength properties in four different types of problematic soil which have high swelling and high compressible nature. It can be concluded the as the L/D ratio decreases the unconfined compressive strength increases.

Effect of Rock-Sized Aggregates on Soil Compaction Results

In the construction of highway embankments, earth dams and many other engineering structures. It is recommended that three contractors must achieve a compacted field dry unit of 90%-95% of the maximum dry density. The values are often affected by varying percentages of large aggregate which consultants and contractors do not usually put into consideration. In this research work three methods of handling rock sized aggregates which include compacting the whole sample (method 1) compacting only samples passing through sieve No. 4 (4.75 mm) and (method 2) using rock correction equation. It is discovered that correction methods (methods 2 & 3) are consistent when percentage passing through sieve No. 4 is greater than 30. It is recommended that the average values of the correction methods be used rather than depending on only one correction method.

Numerical Modeling of Geotextile-Reinforced Embankments over Deep Cement Mixed Columns Incorporating Strain-Softening Behavior of Columns

Geotextile-reinforced embankments over deep cement mixed (DCM) columns are widely used for the construction of highway embankments over soft clay with low shear strength and high compressibility. Numerical modeling based on the finite element method (FEM) is widely used to investigate the behavior of these embankments during construction and serviceability, incorporating consolidation of the foundation soil over time. However, not much attention has been paid to the strain-softening behavior of DCM columns beyond yield, which is essential in ultimate limit-state computations to determine the stability of embankments during the failure of columns. This paper presents a constitutive model, which is an extension of the Mohr-Coulomb model, for the simulations of strain-softening behavior of cement admixed clays. The model is validated using triaxial test data found in the literature for cement admixed Singapore and Hong Kong marine clays and Ariake clay. A two-dimensional (2D) coupled mechanical and hydraulic numerical implementation of a geotextile-reinforced DCM column-supported (GRCS) embankment constructed over a very soft soil in Finland is carried out incorporating strain-softening behavior of DCM columns. Even though the isolated columns and overlapped column walls used in this embankment do not yield significantly under the service loads, the model simulations show good agreement with field data, confirming the capability of the 2D plane strain finite-element model in predicting the GRCS embankment behavior. Finally, the finite-element model with strain-softening DCM columns is used to investigate the progressive failure of a typical hypothetical GRCS embankment with isolated columns in a square pattern. Results clearly illustrate the bending failure mode caused by progressive softening of the DCM columns, including the plastic hinge development within the columns.

Investigation of Induced Trench Method Using a Full Scale Test Embankment

The construction of highway embankments in urban areas often interferes with existing underground facilities such as sewer lines and other buried conduits. In many instances, the extra loads imposed by embankment construction on buried conduits would be unacceptably high. Severe consequences of overstressing an underground utility conduit include damage and interruption of services for both the utility and highway. Typical alternatives considered to address this problem include: relocation of utility lines; embankment load reduction using lightweight fill; at-grade pile cap bridging; at-grade geogrids-reinforced bridging; and induced (imperfect) trenches. The relocation, lightweight fill and pile cap alternatives are usually cost prohibitive. A full-scale instrumented test embankment is constructed by Ontario Ministry of Transportation to study the effects of embankment construction on the underground utilities. The test embankment comprised four sections, which facilitated the evaluation of four configurations including the conventional backfill, induced trenching and two at-grade geogrid-reinforcing bridging with different spans. Each configuration consisted of a 3 m deep trench overlain by a 10 m wide, 10 m long and 6 m high embankment section. Earth load cells were installed to monitor stresses at the fill/ground interface and at depths of 1.5 and 3 m. The numerical models of the test embankment are generated using the finite difference program FLAC. This paper presents the results of stress measurements in the 3 m wide trench under embankment loads and the results of numerical varification analyses. The results showed that the use of induced trench method (ITM) resulted in substantial reduction in vertical stresses relative to positive projection method case. It was also observed that horizontal stresses increased when ITM is employed.

Experimental and numerical studies of loaded strip footing resting on reinforced fly ash slope

ABSTRACT: Being a waste material, fly ash can be used in large quantities in construction of highway and railway embankments. This paper presents a series of plane strain model tests carried out on both reinforced and unreinforced fly ash embankment slopes. Laboratory tests were conducted by varying parameters such as embedment ratio, length and number of reinforcement layers, and edge distance from slope crest. A numerical study using finite-element analysis (PLAXIS 2D, version 9.0) was also carried out to verify the model test results. The size of the numerical model was kept the same as that of the laboratory test model. The agreement between observed and computed results was found to be reasonably good. Based on numerical and experimental results, the critical values of the geogrid parameters for maximum reinforcing effects were established.

Model with artificial neural network to predict the relationship between the soil resistivity and dry density of compacted soil

This paper presents a technique to obtain the outcomes of soil dry density and optimum moisture contents with artificial neural network ANN for compacted soil monitoring through soil resistivity measurement in geotechnical engineering. The compacted soil monitoring through soil electrical resistivity shows the important role in the construction of highway embankments, earth dams and many other engineering structure. Generally, soil compaction is estimated through the determination of maximum dry density at optimum moisture contents in laboratory test. To estimate the soil compaction in conventional soil monitoring technique is time consuming and costly for the laboratory testing with a lot of samples of compacted soil. In this work, an ANN model is developed for predicting the relationship between dry density of compacted soil and soil electrical resistivity based on experimental data in soil profile. The regression analysis between the output and target values shows that the R2 values are 0.99 and 0.93 for the training and testing sets respectively for the implementation of ANN in soil profile. The significance of our research is to obtain an intelligent model for getting faster, cost-effective and consistent outcomes in soil compaction monitoring through electrical resistivity for a wide range of applications in geotechnical investigation.

Effect of Temperature on Shear Strength of Recycled Asphalt Shingles

The effect of seasonal variations in field temperature on the shear strength of recycled asphalt shingles (RAS) improved by mixing with bottom ash (BA) was evaluated for their use as structural fill material in highway embankments. Typical field temperatures ranging from 5°C to 35°C were induced to compacted mixtures of RAS:BA. An increase in temperature reduced the shear strength of compacted mixtures of RAS:BA, and therefore temperature effects should be taken into consideration in design. The friction angle of compacted RAS:BA mixtures, however, remained within the range suitable for stability of embankment fills. Thermal cycling induced thermal preloading to the mixtures containing RAS; this preloading in turn increased shear strength. From these results, to achieve optimum engineering behavior, construction of highway embankments made with granular materials containing RAS is recommended during warm seasons. The use of RAS in high-volume structural fill applications can contribute to more sustainable roadway infrastructure.

Evaluation of Leaching Protocols for Testing of High-Carbon Coal Fly Ash–Soil Mixtures

Beneficial reuse of coal combustion byproducts, e.g., in highway construction, requires an evaluation of metal leaching potential. Metal leaching from high-carbon fly ash in soil mixes typical of highway embankment construction was evaluated using different soil-fly ash mixtures and three common leaching tests: the water leach test (WLT), the Toxicity Characteristic Leaching Procedure (TCLP), and the column leach test (CLT). The effect of test methodology and pH on Cu, As, and Cr leaching was examined. TCLP concentrations for Cu and As exceeded those from WLTs in the majority of mixtures due to lower pH conditions, while Cr was higher in the WLT for alkaline fly ash mixtures. Maximum CLT concentrations were higher than TCLP and WLT concentrations for the majority of mixtures, but usually decreased rapidly, suggesting that leachate concentrations might initially exceed regulatory limits, but only for a short time. A comparison of leaching results is discussed as a framework for the development of a flexible, integrated leaching protocol incorporating elements of batch and column leach tests to provide more accurate, site-specific leaching predictions given time and cost constraints. DOI: 10.1061/(ASCE)EE .1943-7870.0000668. © 2013 American Society of Civil Engineers. CE Database subject headings: Fly ash; Chromium; Copper; Arsenic; Coal; Soils; Mixtures; Recycling. Author keywords: Leaching; Fly ash; Batch leach test; Column leach test; Chromium; Arsenic; Copper.