Final Project Report: Plan for a Model PIMS

Development of the performance information and management systems (PIMS) to monitor labor market outcomes of program participants, and guide program management of active labor market programs (ALMPs)

Novel invariants for almost geodesic mappings of the third type

Two kinds of invariance for geometrical objects under transformations are involved in this paper. With respect to these kinds, we obtained novel invariants for almost geodesic mappings of the third type of a non-symmetric affine connection space in this paper. Our results are presented in two sections. In the Section 3, we obtained the invariants for the equitorsion almost geodesic mappings which do not have the property of reciprocity. In the Section 4, we obtained the invariants for almost geodesic mappings of the third type which have the property of reciprocity.Comment: 18 pages, 0 figure

Shakedown for slab track substructures with stiffness variation

In this paper, shakedown analyses are carried out to predict the long-term response of slab track substructures under repeated moving train loads. The train loads are converted into a distributed moving load on the substructure surface by using a simplified track analysis. Based on Melan’s static shakedown theorem, a well-established shakedown analysis method is extended to determine shakedown limits of the slab track substructures. The influence of a linearly increasing stiffness modulus on the shakedown limits is considered by conducting finite- element analysis with a user-defined material. It is found that a rise in stiffness modulus or stiffness variation ratio can either increase or decrease the shakedown limit, depending on the competitive effects of the two mechanisms. Furthermore, the subgrade thickness determines the dominant mechanism

Uplift resistance of horizontal strip anchors in sand: a cavity expansion approach

This letter presents an analytical cavity expansion theory-based method for predicting peak uplift resistance of shallow horizontal strip anchors buried in sand. Based on an analytical two-dimensional stress solution for loading analysis around a cylindrical cavity, the method was developed by assuming that the peak anchor uplift resistance can be approximated by the cavity breakout pressure. In the new cavity expansion model, the ultimate failure is reached once the plastic zone develops to the ground surface, and the biaxial state of in-situ ground stresses is taken into account. A database consisting of 75 model tests on shallow strip anchors in sands was compiled to valid the new method. The predicted results and measured data are in reasonable agreement, with a mean over-prediction of the peak uplift resistance by 1.6%. The reliability of the new solution was also checked by comparing with other commonly used analytical solutions. It is shown that the present solution can provide a simple analytical tool for predictions of the peak uplift resistance of strip anchors in sand while a sliding-block failure mechanism dominates

Two-dimensional elastoplastic analysis of cylindrical cavity problems in Tresca materials

This paper presents analytical elastic-plastic solutions for static stress loading analysis and quasi-static expansion analysis of a cylindrical cavity in Tresca materials, considering biaxial far-field stresses and shear stresses along the inner cavity wall. The two-dimensional static stress solution is obtained by assuming that the plastic zone is statically determinate and using the complex variable theory in the elastic analysis. A rigorous conformal mapping function is constructed, which predicts that the elastic-plastic boundary is in an elliptic shape under biaxial in situ stresses, and the range of the plastic zone extends with increasing internal shear stresses. The major axis of the elliptical elastic-plastic boundary coincides with the direction of the maximum far-field compression stress. Furthermore, considering the internal shear stresses, an analytical large-strain displacement solution is derived for continuous cavity expansion analysis in a hydrostatic initial stress filed. Based on the derived analytical stress and displacement solutions, the influence of the internal shear stresses on the quasi-static cavity expansion process is studied. It is shown that additional shear stresses could reduce the required normal expansion pressure to a certain degree, which partly explains the great reduction of the axial soil resistance due to rotations in rotating cone penetration tests. In addition, through additionally considering the potential influences of biaxial in situ stresses and shear stresses generated around the borehole during drillings, an improved cavity expansion approach for estimating the maximum allowable mud pressure of horizontal directional drillings (HDDs) in undrained clays is proposed and validated

Centrifuge Modelling With Transparent Soil and Laser Aided Imaging

Transparent synthetic soils have been developed as a soil surrogate to enable internal visualization of geotechnical processes in physical models. While significant developments have been made to enhance the methodology and capabilities of transparent soil modelling, the technique is not yet exploited to its fullest potential. Tests are typically conducted at 1 g in small bench size models, which invokes concerns about the impact of scale and stress level observed in previously reported work. This paper recognized this limitation and outlines the development of improved testing methodology whereby the transparent soil and laser aided imaging technique are translated to the centrifuge environment. This has a considerable benefit such that increased stresses are provided, which better reflect the prototype condition. The paper describes the technical challenges associated with implementing this revised experimental methodology, summarizes the test equipment/systems developed, and presents initial experimental results to validate and confirm the successful implementation and scaling of transparent soil testing to the high gravity centrifuge test environment. A 0.6 m wide prototype strip foundation was tested at two scales using the principle of “modelling of models,” in which similar performance was observed. The scientific developments discussed have the potential to provide a step change in transparent soil modelling methodology, crucially providing more representative stress conditions that reflect prototype conditions, while making a broader positive contribution to physical modelling capabilities to assess complex soil–structure boundary problems

Shakedown Limits of Slab Track Substructures and Their Implications for Design

This paper presents an approach to shakedown of slab track substructures subjected to train loads. The train load is converted into a distributed moving load on the substructure surface using a simplified track analysis. Based on the lower-bound dynamic shakedown theorem, shakedown solutions for the slab track substructures are obtained over a range of train speeds between zero and the critical speed of the track. It is found the shakedown limit is largely influenced by the ratio of layer elastic moduli and the ratio of train speed to critical speed rather than their absolute values. An attenuation factor, as a function of the critical speed and the friction angle of subsoil, is proposed to effectively obtain the shakedown limit of the slab track substructure at any train speed. In light of the shakedown solutions, improvements to the existing design and analysis approaches are also suggested

Undrained expansion of a cylindrical cavity in clays with fabric anisotropy: theoretical solution

This paper presents a novel, exact, semi-analytical solution for the quasi-static undrained expansion of a cylindrical cavity in soft soils with fabric anisotropy. This is the first theoretical solution of the undrained expansion of a cylindrical cavity under plane strain conditions for soft soils with anisotropic behaviour of plastic nature. The solution is rigorously developed in detail, introducing a new stress invariant to deal with the soil fabric. The semianalytical solution requires numerical evaluation of a system of six first-order ordinary differential equations. The results agree with finite element analyses and show the influence of anisotropic plastic behaviour. The effective stresses at critical state are constant, and they may be analytically related to the undrained shear strength. The initial vertical cross-anisotropy caused by soil deposition changes towards a radial cross-anisotropy after cavity expansion. The analysis of the stress paths shows that proper modelling of anisotropic plastic behaviour involves modelling not only the initial fabric anisotropy but also its evolution with plastic straining.The research was initiated as part of GEO-INSTALL (Modelling Installation Effects in Geotechnical Engineering, PIAP-GA-2009-230638) and CREEP (Creep of Geomaterials, PIAP-GA-2011-286397) projects supported by the European Community through the programme Marie Curie Industry-Academia Partnerships and Pathways (IAPP) under the 7th Framework Programme