Three soil-arching evolution patterns in unreinforced piled embankments were observed in a series of two-dimensional (2D) model tests using a multitrapdoor test setup. These include the triangular expanding pattern, the tower-shaped evolution pattern, and the equal settlement pattern. The inclination of the slip surfaces and the height of the vertical slip surfaces that enclose the tower-shaped arches were found to be the critical parameters describing the arching evolution. Three analytical models were proposed to describe the evolution processes of the three arching-evolution patterns and to find the stress distributions of the corresponding processes. Load distribution equations were also derived from these models. Using the empirical relationships between the inclination of the slip surfaces and the tower height and settlement, the stress distribution ratio during the entire evolution process was calculated. The models matched the model tests well.@en

Three soil-arching evolution patterns in unreinforced piled embankments were observed in a series of two-dimensional (2D) model tests using a multitrapdoor test setup. These include the triangular expanding pattern, the tower-shaped evolution pattern, and the equal settlement pattern. The inclination of the slip surfaces and the height of the vertical slip surfaces that enclose the tower-shaped arches were found to be the critical parameters describing the arching evolution. Three analytical models were proposed to describe the evolution processes of the three arching-evolution patterns and to find the stress distributions of the corresponding processes. Load distribution equations were also derived from these models. Using the empirical relationships between the inclination of the slip surfaces and the tower height and settlement, the stress distribution ratio during the entire evolution process was calculated. The models matched the model tests well.@en

To evaluate the disposal technology for fine oil sands tailings, the appropriate engineering properties of the tailings should be ascertained. A laboratory study was conducted by Delft University of Technology (the Netherlands) on the geotechnical properties and dewatering behavior of the fine oil sands tailings (MFT, TT), obtained from Shell Canada’s Muskeg River Mine. In this program, the tailings were characterized by performing various laboratory tests including index property tests, flocculation tests, column settling tests, oedometer tests, shrinkage and swelling tests, water retention tests, cracking tests and air drying tests. In this paper, a summary of the main tests results is presented. The data obtained for the MFT and flocculated MFT are compared to identify the effects of flocculation on the dewatering behavior. @en

This paper presents a comparison between blind predictions of field tests of atmospheric drying of mature fine tailings (MFT) presented in IOSTC 2014 and field results. The numerical simulation of the consolidation and atmospheric drying of selfweight consolidating fine material is challenging and requires significant knowledge of the material, climate and the interaction between the two. This paper presents the outcome of a study which developed a numerical model, undertook material characterization and predicted the behaviour of full scale field tests undertaken in Shell Canada’s Muskeg River Mine near Fort McMurray, Alberta. The blind predictions were published in IOSTC 2014. A comparison between the observed and simulated behaviour in terms of settlement and void ratio yields a number of conclusions regarding the model: (i) all of the major observed features can be predicted by the numerical model; (ii) the quantification of the behaviour is well represented; (iii) due to the fast initial consolidation, the amount of material recorded as being deposited was underestimated; (iv) significant shear strength development requires a void ratio reduction which either requires a significant overburden or atmospheric drying. @en

Excavation of clayey soils by mechanical tools is often hindered by the stickiness of the clay on metal parts. Hindrance may occur at the cutting tool itself, or during the subsequent transport of the soil through the excavation system. The effects of stickiness were also experienced in a recent tunnel boring project carried out in The Netherlands. In this study the soil parameters that influence stickiness of clayey soils are investigated. Stickiness can be described in terms of adhesion and adhesive friction. These parameters can be determined in the laboratory by undertaking shear box tests during which the clay is sheared over a standard metal surface. The relation of the basic clay classification parameters (Atterberg limits, percentage of clay, clay mineralogy) with adhesion and adhesion friction has been examined. For one clay type, a potters clay, the variation of the adhesion parameters with the moisture content of the clay has been investigated. For a given metal surface, adhesion and adhesive friction are shown to depend on the clay mineral but also on clay fraction, plasticity, moisture content, degree of consolidation and normal stress. Although for an improved understanding of the phenomenon much more testing on different types of clay is required, the first results indicate that prediction of the occurrence of stickiness is possible if the operational parameters of the tunnel boring machine and the adhesion and adhesive friction parameters of the soil material are known. Using the operational parameters, the driving forces in the system can be estimated while knowing the adhesion properties of the clay-metal contact allows the calculation of the resistive forces in the system. The standard soil investigation should therefore include shear box tests to determine these adhesive parameters. During tunnel boring stickiness can occur in three zones: at the cutting wheel, in the mixing chamber and in the slurry line during pipeline transport. Simple force balance models that examine the movement of the clay along the cutting teeth, along the arms of the cutting wheel or along the walls of chamber or pipeline have been made. If the driving forces are smaller than the resistance along the metal-clay surface, no movement will occur along this surface and sticking is assumed to take place. Several factors are important in the analysis: • the cohesion and internal friction of the clay, • the adhesion and adhesive friction between clay and metal, • the shear resistance between clay lumps, • the roughness of the contact surface. @en

Distributed temperature sensing (DTS) can be used to monitor the production process of diaphragm walls. DTS is able to differentiate between already present or fresh bentonite suspensions during refreshing of the bentonite slurry in the trench. During concrete casting, DTS is able to differentiate between the bentonite suspension and concrete. As a result, the continuity of the casting process and the arrival of good grade concrete at crucial locations in the trench can be monitored. Tests conducted on laboratory models provided reference information for interpretation of field data. Field experiences have shown the benefits of DTS tests and the predictive value of the reference measurements. Results are compared with crosshole sonic logging measurements at the same location.@en

In this study, installation of jacked piles in sand is simulated using Press-Replace Method (PRM) and Material Point Method (MPM) and the results are compared together. This comparison is important because a realistic and yet efficient simulation of installation of jacked piles is an appealing step towards the design and analysis of this type of displacement piles. It is shown that PRM as a method that is founded on small-strain finite element method can produce pile and soil responses that are in a promising agreement with those of MPM which is a finite-deformation analysis method.@en

A trapdoor system has frequently been used to study soil arching and its development in recent years. The load transfer in the fill of piled embankments is very similar to a trapdoor system with multiple trapdoors. There are multiple arching models described in different standards and guidelines for piled embankments that can be subdivided into three archingmodel families. To study the soil-arching type and its development, a series of model tests with sand fills were carried out in a two-dimensional (2D) multi-trapdoor test setup. The tests considered four factors—the fill height, trapdoor width, pile width, and grain size of the sand—with four values for each factor. Triangular slip surfaces were found at very small deformations using the particle image velocimetry (PIV) technique. These surfaces evolved in ways that could be related to the three types of stress-distribution ratio curves, with development patterns similar to the arching families of piled embankments: (1) the rigidmodel family, (2) the equal-settlement-plane-model family, and (3) the limit-equilibriummodel family. The limit-equilibrium-model family occurred in tests with narrow trapdoor widths. @en

The purpose of this paper is to present long-term measurements in a full-scale study on a basal reinforced piled embankment that make it possible to validate calculations used for the design of the geosynthetic reinforcement (GR). These calculations are normally carried out in two steps. To validate steps 1 and 2 together, it is necessary to measure GR strains. To validate calculation steps 1 and 2 separately, arching A needs to be measured, which is the pressure on the pile cap above the GR. An extensive monitoring project was conducted over a period of four years, in a basal reinforced piled embankment on 17 m of soft clay and peat. This study presents the measured GR strains and load distribution including arching, accompanied by measured groundwater levels and deformations. The subsoil support of the geosynthetic reinforcement disappeared quickly, arching developed over the first three months, and an annual cycle in the load distribution became apparent. Arching effects increase during the summer when conditions are relatively dry, resulting in a larger load on the piles and a reduction in the load on the GR. Additionally, the measured changes after an extremely rainy week are presented.@en

The ever increasing demand for new transport routes led to the need of improving the current Naples underground system. It is actually composed by 7 lines connecting most of the suburban areas of the Neapolitan environment to the city center. Line 6 is one of the under construction lines of the system. Although the digging operations are still in progress, the line is already operating among Mostra and Mergellina Stations. Nowadays a 3 km tunnel, from Mergellina to Municipio Station is missing. This paper aims to discuss the tunnelling induced effects of the upcoming part of the line. A number of Finite Element Analysis has been performed with Plaxis 3D Tunnel, as to predict the tunnelling induced displacements field and the role played by both soil and machine parameters on it. The monitoring data will then be compared with the numerical analysis results in order to verify and validate them.@en

The ever increasing demand for new transport routes led to the need of improving the current Naples underground system. It is actually composed by 7 lines connecting most of the suburban areas of the Neapolitan environment to the city center. Line 6 is one of the under construction lines of the system. Although the digging operations are still in progress, the line is already operating among Mostra and Mergellina Stations. Nowadays a 3 km tunnel, from Mergellina to Municipio Station is missing. This paper aims to discuss the tunnelling induced effects of the upcoming part of the line. A number of Finite Element Analysis has been performed with Plaxis 3D Tunnel, as to predict the tunnelling induced displacements field and the role played by both soil and machine parameters on it. The monitoring data will then be compared with the numerical analysis results in order to verify and validate them.@en

The ever increasing demand for new transport routes led to the need of improving the current Naples underground system. It is actually composed by 7 lines connecting most of the suburban areas of the Neapolitan environment to the city center. Line 6 is one of the under construction lines of the system. Although the digging operations are still in progress, the line is already operating among Mostra and Mergellina Stations. Nowadays a 3 km tunnel, from Mergellina to Municipio Station is missing. This paper aims to discuss the tunnelling induced effects of the upcoming part of the line. A number of Finite Element Analysis has been performed with Plaxis 3D Tunnel, as to predict the tunnelling induced displacements field and the role played by both soil and machine parameters on it. The monitoring data will then be compared with the numerical analysis results in order to verify and validate them.@en

A constitutive model for granular materials which considers grain crushing effects is developed in the framework of hypoplasticity. As grain crushing occurs the behaviour of granular material can usually be significantly affected. Several empirical relations between peak strength, uniformity coefficient and stiffness of sand depending on stress level or amount of grain crushing have been derived in the past. In this paper, such relations are employed to improve a basic hypoplastic constitutive model based on the changes of stress level or grain size distribution. In the proposed modified hypoplastic model only two additional physical parameters, namely uniformity coefficient and mean grain size are incorporated. The validation of the modified model for three different sands under triaxial test response with cell pressures up to 30 MPa is presented and shows a significantly better correspondence with regard to the original basic hypoplastic model.@en

A constitutive model for granular materials which considers grain crushing effects is developed in the framework of hypoplasticity. As grain crushing occurs the behaviour of granular material can usually be significantly affected. Several empirical relations between peak strength, uniformity coefficient and stiffness of sand depending on stress level or amount of grain crushing have been derived in the past. In this paper, such relations are employed to improve a basic hypoplastic constitutive model based on the changes of stress level or grain size distribution. In the proposed modified hypoplastic model only two additional physical parameters, namely uniformity coefficient and mean grain size are incorporated. The validation of the modified model for three different sands under triaxial test response with cell pressures up to 30 MPa is presented and shows a significantly better correspondence with regard to the original basic hypoplastic model.@en

In order to find the relationship between the cone resistances measured in horizontally and vertically aligned cone penetration tests, a test series has been performed in a 2 m. diameter rigid wall calibration chamber using a 36 mm. cone. This calibration chamber contains an unsaturated uniform sand, which can be prepared at different densities. It is found that the horizontal cone resistance is higher than the vertical cone resistance at a given point, whilst the side friction is lower horizontally than vertically. A simple cavity expansion model is used to explain the ratio of horizontal over vertical cone resistance.@en

This paper presents the results of model pile penetration in a photoelastic material. The soil in this test is represented by an assembly of photoelastically sensitive glass particles. This allows for the determination of stresses in the assembly by the photoelastic method. Displacements around the pile are measured using digital image correlation. Tests were performed in a medium dense particle assembly. The development of stresses and strains, in particular the development of horizontal stress, around the pile tip and pile shaft is quantified and presented in this paper.@en

Several measurements were carried out in a basal reinforced piled embankment in the Netherlands. The present paper focuses on the influence of truck passages on the axial forces in the piles. The changes in axial forces in the piles were measured using two systems: (1) optic fibres attached to a square steel tube pile, measuring pile strains at ten positions along the pile length and (2) the total pressure on the pile cap with total pressure cells. Additionally, the axle loads of passing trucks and the load on the subsoil between the piles were measured. The measured changes in pile strains show that most truck load is transported to the subsoil by friction along the pile shafts. Comparison between measurements and calculations show that the truck wheel loads are spread stronger than assumed by Boussinesq.@en