Earthfill Embankment Research Articles

The applicability of microbially induced calcite precipitation (MICP) for internal erosion control in gravel–sand mixtures

Seepage-induced internal erosion in earth-filled embankment dams has been attracting the attention of civil engineering researchers and practitioners for decades. Microbially induced carbonate precipitation (MICP), owing to its proved performance in soil enhancement and permeability control, can potentially be used for internal erosion control. This paper examines the applicability of MICP for internal erosion control in gravel–sand mixtures using a large one-dimensional column test apparatus which incorporates the implementation of MICP. Visual observations, erosion characteristics and hydro-mechanical behaviours of non-MICP and MICP treated gravel–sand mixtures were investigated through a series of constant-pressure erosion tests. Test results confirm that MICP treatment can reduce the cumulative erosion weight, erosion rate and axial strain relative to non-MICP soil. The magnitudes of hydraulic conductivity for all tested samples before the erosion process fall into a range from 5·5 × 10−5to 8·0 × 10−3 m/s. After the erosion process, non-MICP soils and MICP treated soils with low cementation concentrations experience a significant increase in hydraulic conductivity. Furthermore, a hydro-mechanical coupling analysis was conducted and different erosion modes were identified for low and high concentrations of cementation solution. Fundamentally, the efficiency of internal erosion reduction is controlled by the calcium carbonate precipitation content within the tested soils. Higher precipitation content can facilitate the formation of larger clusters of cemented sand particles, thus reducing the likelihood of erosion.

Breaching of Bridge Abutments and Scour at Exposed Abutment Columns

AbstractOur note presents laboratory findings on the breaching of the earthfill embankments of bridge abutments at river crossings and the consequent scour at exposed abutment columns, the structur...

Assessment of long-term coordinate time series using hydrostatic-season-time model for rock-fill embankment dam

The safety control of dams is based on monitoring activities and modelling of registered observations. The statistical hydrostatic-season-time model was originally developed and proposed for analyzing of monitoring data on concrete dams. In some later works, the model was implemented for earth-fill embankment dams. The model admits a simultaneous estimation of hydrostatic load, temperature influences and irreversible deformations. In our study, we analyze long-term coordinate time series of a geodetic point on the crest of a rock-fill embankment dam. Coordinate time series are result of an adjustment of the observations in a permanent geodetic network for different epochs. An optimal model is defined using a multiple linear regression by combined process of exclusion and inclusion of individual parameters. In the process, different statistical parameters are observed. The analyses confirmed that not all parameters are significant. The most interesting and important conclusion of computations can be stated as follows: after inclusion of significant coefficients of the hydrostatic load and long-term trend, the residual time series still expose underlying periodicities. They can be removed by inclusion of at least one parameter of the seasonal term, where the temperature influences (i.e. air, water and soil) are modelled. The influences of the temperature on the dam are not significant in any direction, but the inclusion of the parameters improves the statistical performance of the used model. Copyright © 2016 John Wiley & Sons, Ltd.

Development of Louth flood alleviation scheme outline design

The market town of Louth (in Lincolnshire), on the River Lud, has suffered from flooding on many occasions, most recently in 2007. Atkins was commissioned to conduct a feasibility study into the potential for a flood defence scheme. This paper begins once the preferred option of two online flood storage areas had been identified; the brief from this point was to develop their outline design. Atkins worked closely with a contractor to develop a cost estimate for the works and to ensure buildability was considered. The two dams are designed as homogenous earth fill embankments, with heights of circa 6 m, and retaining a combined volume of 213 000 m3 (during a flood event); both storage areas fall under the requirements of the Reservoirs Act 1975. As in many cases, these reservoirs present particular challenges; designed to be empty for the majority of their life, they are required to meet the needs of a variety of stakeholders. The design was further complicated by the risk of unexploded ordnance and burrowing animals. This paper presents the outline design under three sections: the location, embankments and control structures. For each section the paper discusses the alternatives considered, the selection process and the adopted design.

An adaptive methodology for risk classification of small homogeneous earthfill embankment dams integrating climate change projections

This paper presents the application of the advanced probabilistic slope stability model with precipitation effects developed to assess the performance of small homogeneous earthfill embankment dam slopes, when exposed to future seasonal precipitation scenarios. Here, the UK's latest probabilistic climate model known as UKCP09 is applied. To reflect the critical conditions conducive to slope failure, a benchmark has been developed to identify the change, if any, in the risk classification of the slope's performance level due to precipitation. Thus, enabling the reassessment of the dam's risk classification, as categorised by the Flood and Water Management Act 2010. Such an approach could therefore be well placed to support and enhance the decision-making process, its impact on the public, especially in relation to future climate effects.

Safety inspections and seismic behavior of embankment dams during the 2011 off the Pacific Coast of Tohoku earthquake

Immediately after the 2011 off the Pacific coast of Tohoku Earthquake, special safety inspections were carried out at over 300 dams in the affected area. Damage was identified at more than 10% of the inspected dams, with embankment dams showing a slightly higher ratio. Damage to embankment dams included relatively wide and/or long cracks mainly on the crest of earthfill dams, cracks in the impervious membrane of asphalt faced rockfill dams (AFRDs) and temporary increase in leakage. However, none of the dams under the jurisdiction of the Ministry of Land, Infrastructure, Transport and Tourism (MLIT) sustained damage severe enough to threaten the safety of the dam, although an old earthfill embankment dam for an irrigation pond located outside the area regulated by the River Law was breached due to the earthquake. In this paper, the results of special safety inspections are summarized, as well as those of subsequent detailed investigations of several embankment dams under the jurisdiction of MILT. The features of the earthquake motions observed at the dam foundations during the earthquake and their effects on the behavior of embankment dams are also discussed.

Reliability-based design of earth-fill dams based on the spatial distribution of strength parameters

In this study, a reliability-based design for the improvement of earth-fill dams is presented and the effect of improvement of the embankment for safety against earthquakes is evaluated. An inclined core is considered as the means of improvement for the earth-fill embankment. First, the spatial distribution of the strength of the earth-fill materials is discussed, following which the damage level of earth-fill dams is evaluated, using the elasto-viscoplastic finite element method (EVP-FEM). By averaging the resulting damage level with the Monte Carlo method, the expected failure costs are calculated. Finally, the effect of this improvement is evaluated by comparing the expected total costs for the original and the restored states of the embankment.

Soil moisture dynamics in levees during flood events - variably saturated approach

Growing occurrence of extreme floods in the Czech Republic has attracted attention to the security of protective earthfill embankments along the rivers. A suddenly increased amount of water on the waterside slope of the embankment may have destroying or even catastrophic consequences. Predictions of seepage patterns through the earth body are usually done considering the saturated flow beneath the free water level only, neglecting the saturated-unsaturated character of the soil water dynamics within earthfill dams. The importance of water dynamics within an earth dam is known and may be addressed using numerical simulation models. In this study the solution based on transient simulation of seepage through protection levee using saturated-unsaturated theory is presented. Simulations were carried out by a two-dimensional numerical model based on Richards’ equation for water flow in porous medium. It has been shown that proposed approach is, with certain limitations, suitable for large scale engineering applications.

Performance Monitoring of a Rammed Aggregate Pier Foundation Supporting a Mechanically Stabilized Earth Wall

The use of rammed aggregate pier (RAP) foundations for support of retaining walls and earth fill embankments has increased in recent years to become a geotechnical solution for rapid construction of earth structures in soft ground conditions. A nominal 6-m mechanically stabilized earth wall was constructed over piers installed in relatively compressible soil to investigate the performance of RAP foundation elements in terms of stress-deformation and settlement behaviors for such applications. Geotechnical instrumentation consisting of total earth pressure cells, settlement plates, and vibrating wire piezometers was installed within the pier elements and at the foundation surface for short- and long-term monitoring of pier response. Monitoring data indicate: (1) mobilization and concentration of vertical stress on pier elements and matrix soil; and (2) load transfer response for the boundary condition associated with support of geogrid-reinforced earth fill. The practical implications of the experimental research findings are briefly discussed.

Staged Construction and Settlement of a Dam Founded on Soft Clay

Alibey Dam is located near Istanbul in Turkey on the Alibey Stream, 4.5km north of its point of confluence with Golden Horn, an ancient submerged river mouth. It was constructed as an earthfill dam over 30-m-thick soft valley sediments. Before the construction of the dam, field and laboratory tests were performed to determine the geotechnical characteristics of the foundation soils. During the construction and many years after the construction of the earthfill embankments, including the cofferdams and the intermediate fills, the response of the foundation soils was monitored by extensive field instrumentation generating a unique long-term (over 25 years) database. With proper instrumentation and careful monitoring of the collected data, field construction rates could be adjusted and the earth dam was safely constructed on the thick soft deposits. Approaches to settlement prediction were evaluated in a historical context, starting with the simplified one-dimensional approach available at the time of construction to more sophisticated analyses including the employment of modern numerical methods, in terms of the recorded data. Standard subsurface exploration and field testing supplemented with conventional laboratory testing provided the relevant material parameters that were used in the finite element method. The only exception to this was the overall hydraulic conductivity of the deposit, which controlled the rate of consolidation. Early field observations were used to assign the appropriate hydraulic conductivity. An elastoplastic soil model in a coupled analysis of consolidation was employed in the analysis that yielded realistic predictions of field behavior in response to the complex construction history. The accurate prediction and monitoring of the behavior of soft and thick soil layers subjected to staged construction, as in the case of Alibey Dam, is very important for planning of the construction as well as the expected behavior after construction.

Gypsum-karst problems in constructing dams in the USA

Gypsum is a highly soluble rock and is dissolved readily to form caves, sinkholes, disappearing streams, and other karst features that typically are also present in limestones and dolomites. Gypsum karst is widespread in the USA and has caused problems at several sites where dams were built, or where dam construction was considered. Gypsum karst is present (at least locally) in most areas where gypsum crops out, or is less than 30–60 m below the land surface. These karst features can compromise on the ability of a dam to hold water in a reservoir, and can even cause collapse of a dam. Gypsum karst in the abutments or foundation of a dam can allow water to pass through, around, or under a dam, and solution channels can enlarge quickly, once water starts flowing through such a karst system. The common procedure for controlling gypsum karst beneath the dam is a deep cut-off trench, backfilled with impermeable material, or a close-spaced grout curtain that hopefully will fill all cavities. In Oklahoma, the proposed Upper Mangum Dam was abandoned before construction, because of extensive gypsum karst in the abutments and impoundment area. Catastrophic failure of the Quail Creek Dike in southwest Utah in 1989 was due to flow of water through an undetected karstified gypsum unit beneath the earth-fill embankment. The dike was rebuilt, at a cost of US $12 million, with construction of a cut-off trench 600 m long and 25 m deep. Other dams in the USA with severe gypsum-karst leakage problems in recent years are Horsetooth and Carter Lake Dams, in Colorado, and Anchor Dam, in Wyoming.

Liquefaction assessments by field-based methodologies: foundation soils at a dam site in Northeast Turkey

Recent examples show that strong earthquakes can cause damage to dams, notably tailings or hydraulic fill dams or relatively small earth fill embankments. Liquefaction is known to be one of the most dangerous consequences of the dynamic loading of an embankment dam and hence must be considered during the dam site selection and construction stages. This paper presents the liquefaction analyses undertaken for the Demirozu dam site in Northeast Turkey. The liquefaction assessments are mainly based on field-performance data using SPT- and CPT-based methods in conjunction with the results of the available cyclic triaxial tests. The presence of a very shallow groundwater table, loose sandy layers and the seismic features of the region result in a high susceptibility to liquefaction. The results obtained from the SPT- and CPT-based criteria for evaluating the liquefaction potential are generally consistent and show that the thickness of the liquefiable layers increases in the area between the left bank and the central part of the proposed dam. Further studies are required to evaluate the suitability and efficiency of measures which could be taken to avoid liquefaction-induced problems at the dam site.

Left upstream slope design for the Çatalan Dam, Adana, Turkey and its behaviour under actual earthquake loading

An investigation and remediation of instability along upstream cut slopes for an earthfill dam in differentially weathered rock in southern Turkey is described. The major instability problem was a 45-m high and 200-m long previously cut slope next to the main axis of the dam, above the diversion tunnels and water outlet structures. The slope was first designed and excavated in 1986 based on the temporary berm approach. Rising water level in the reservoir would change the shear strength parameters and the pore-water pressure in the slope; thus, probable deep failure would damage the entrance of the diversion tunnels and water outlet structures, as well as the earthfill embankment of the dam. In June 1996, the slope face was re-excavated and protected against wave erosion by placement of a layer of rock riprap over a layer of bedding and a filter material. A strong earthquake ( M S = 6.2) occurred during a period of rapid drawdown in 27 June 1998. The slope remained stable, although numerous tension cracks developed in Quaternary terrace deposits near the reservoir area.

A software architecture for the virtual construction of structures

In addition to being a tedious procedure, the complexity of structural construction makes the task of manually generating simulation models quite complicated. The paucity of simulation expertise in the construction industry exacerbates the problem. This research addresses the issue through the development of a generic system architecture that would facilitate the creation of automated model generators for structural construction. The architecture is based on the object-oriented programming paradigm, which supports the use of modularity and hierarchy in the software development process. The generic system architecture developed in this research was used to create an automated model generator for automatically generating and executing a simulation model for the construction of an earth-filled embankment. The simulation results obtained were compared with those obtained through the execution of a manually generated simulation model. A trace obtained from the execution of the automatically generated simulation model was also studied. Both the comparison and the trace tests conducted demonstrated the satisfactory functioning of the automated model generator.

886077 Vane shear testing for staged construction : Walker, W L In: Use of In Situ Tests in Geotechnical Engineering (papers to the Conference, Blacksburg, 23–25 June 1986)P1108–1118. Publ New York: ASCE, 1986 (ASCE Geotechnical Special Publication No 6)

Staged construction was used for the earthfill embankment of Birch Dam in order to compensate for low strength clays in the foundation. Sampling and testing of foundation soils verified the expected strength gain obtained through consolidation. Vane shear testing of in situ foundation soils supplemented laboratory triaxial testing in evaluating this strength gain. Increased drilling depths to penetrate the embankment required that the vane shear tests be abandoned, but not before sufficient data was developed to provide evidence of the usefulness of vane shear tests regarding the evaluation of strength gain through consolidation.

Seepage control at Cochiti Dam, New Mexico : Lillard, D E In: Seepage and Leakage from Dams and Impoundments (paper to the symposium, Denver, Colorado, 5 May 1985) P82–114. Publ New York: ASCE, 1985

Significant design data, design assumptions and computations, and performance of the seepage control features provided at Cochiti Dam are summarized in this paper. The dam is a rolled and zoned earthfill embankment. Evaluations of in situ permeabilities of the granular foundation materials were complicated by variations in thickness of overburden above bedrock, the complex and irregular stratifications of granular foundation materials, and the major thicknesses of foundation overburden above existing ground water table. Based on the results of field and laboratory tests, a design permeability curve as related to D//2//0 soil size was developed for seepage analyses. Based on seepage measurements during storage of the 1979 record pool, the measured foundation seepage quantities are less than the quantities of seepage estimated in design.

EMPINGHAM DAM - DESIGN, CONSTRUCTION AND PERFORMANCE.

Empingham Dam is an earthfill embankment 37 m high, 1200 m long. The dam foundation is Upper Lias clay extensively sheared and brecciated by valley bulging and periglacial disturbance. The weak foundation was the controlling factor in design and made a wide cross-section with extensive berms necessary. Determination of the reliable strength of the foundation was difficult and was to be confirmed at full scale by a trial bank placed early in construction and incorporated within the dam. The tender design allowed for the uncertain strength by indicating a range of dam volumes corresponding to the likely range of foundation strength values. Various measures, including 10 800 vertical sand drains and zoning of fills incorporating an inclined core, were utilized to minimize the volume of earthfill required. The bulk of the 5 Mm3 of fill was Upper Lias clay excavated from borrow pits upstream of the dam, and was placed over three summer seasons. The performance of the dam is monitored by a comprehensive range of instruments, including a movement monitoring system. Finite-element methods were used to predict early movements. The instrumentation records show the behaviour of the dam to be satisfactory.

Upstream slope protection for earth dams in the Prairie Provinces

A survey of the slope protection on 62 dams in the Prairie Provinces was undertaken to relate the field performance to design and construction practices. The slope protection included riprap, gravel, and glacial clay. The dams were earthfill embankments, which varied from 5 to 65 m in height, and impounded reservoirs with fetches of 1–35 km.The study involved the measurement of slopes and profiles, rock and particle sizes, voids, layer thicknesses, and the rating of the riprap condition. It also required the calculation of reservoir straight line and effective fetches, the application of existing wind data, and the estimation of significant wave heights.The observations indicated that 75% of the rock riprap was in good to excellent condition, 20% in fair condition, and 5% in poor condition. Unsatisfactory performance was due to thin riprap layers and uniform rock size, which did not provide a sufficiently dense cover for the bedding gravel. Also, some of the earlier designs, which utilized a straight line fetch criterion, had resulted in the underdesign of riprap for wide or circular reservoirs. Effective fetch calculations provided a more accurate measure of the exposure of the dam. Gravel and glacial clay slopes were found to provide economical slope protection where allowances had been made for flat slopes, adequate layer thickness, and periodic maintenance.Empirical procedures have been developed for the design and construction control of slope protection for small dams. A more rational design procedure, based on effective fetch and regional wind conditions, is proposed for riprap on large dams.

Structural Grouting of Oroville Dam Coreblock

A 290,000 cu yd concrete coreblock, a foundation structure for the impervious core of the 770-ft high Oroville Dame earth-fill embankment, was damaged by excessive deformations induced by embankment loads during construction. Structural cracking, more than 500 ft in length and with width varying from 1/4-in. to 6-in. impaired the hydraulic and structural performance of the coreblock. An exploratory core drilling operation and structural grouting program is described, including mix design and testing, grouting equipment and grouting performance. Over 6,000 bags of cement were injected in various grout mixes in several, continuous grouting operations to fill the cracks. Hydraulic plugging of an impaired drainage gallery was accomplished by intrusion grouting of preplaced gravel. Repairs were successfully carried out by the grouting program, and excellent hydraulic performance of the coreblock has been realized over the 8 yrs since the subsequent completion of embankment construction and reservoir filling. /Author/

Construction of Pueblo Dam

Pueblo Dam consists of a concrete massive-head buttress dam and spillway structure flanked by zoned earthfill embankments. Pueblo Reservoir is the terminal and principal storage feature of the multi-purpose Fryingpan-Arkansas Project in Colorado. Construction of Pueblo Dam was performed in two stages: (1)Foundation excavation and river diversion were accomplished during the first stage; and (2)construction of the earth embankments and concrete section of the dam were performed during the second stage of construction.