Several building codes recommend performing effective stress ground response analysis when a liquefiable stratum is identified. While total stress ground response analyses have been well verified against downhole array recordings and centrifuge test experiments, effective stress analyses have yet to be thoroughly validated. To this end, a database of potentially liquefiable sites instrumented with at least a pair of surface and at-depth accelerometers, that have recorded ground motions of varying amplitudes and pore pressure buildup has been compiled. A first step toward the validation of the effective stress model is to assess their response with respect to the expected behavior of liquefiable soils. The second step is to study the performance of such models in ground response analysis of sites contained in the database.

This paper first compares the pore pressure response as a function of shear strain against existing empirical correlations published in the literature representing the expected behavior of liquefiable soils. In the second part, the prediction of common ground motion intensity measures (IM) is investigated. IMs are used in various simplified seismic design procedures such as the assessment of liquefaction, seismic slope stability, structural response and the estimation of the damage potential of earthquakes. However, their assessment resulting from ground response analysis procedures has not been widely investigated to date. The uncertainty in the prediction of several IMs evaluated at the ground surface from each ground response model is thus quantified and compared. The selected IMs include the Arias Intensity (AI), significant durations (D5-95 & D25-75), number of equivalent loading cycles (Neq), cumulative absolute velocities (CAV & CAVSTD), shaking intensity rate (SIR), mean period (Tm), smoothed spectral predominant period (To) and predominant spectral period (Tp).

Over the past century various approaches have been developed to handle slope stability, including the well-known ordinary method of slices that includes the Fellenius and Bishop solutions, as well as the more rigorous procedures due to Janbu, Spencer, and Morgenstern and Price (M&P).

In 1982, Gussmann introduced the kinematic element method (KEM) that easily accommodates varying non-circular failure surfaces based on non-associated plasticity to solve. KEM provides a systematic approach that rigorously accounts for the kinematics and statics of failure. Itt gives an provides an upper bound solution that can implicitly account for reversal in shear force direction due non-homogeneous ground conditions. Although quadrilateral elements are typically adopted to accommodate more realistic internal force distributions, one may use the methodology within the method of slices framework. The general algorithm can be presented as a matrix method or as a recursive procedure. Within the context of slope stability, the solution provides an optimized failure mechanism and the corresponding factor of safety.

This paper presents a version of the KEM based on the latter procedure and proposes an extension to elasto-plasticity that allows a simultaneous treatment of the kinematic and static problems. Examples are given to compare the KEM solutions to those provided by the Bishop and M&P strategies. The effect of restricting the interelement boundaries to vertical lines was found to overestimate the factors of safety and resulted in more rigid failure surfaces. The KEM as originally conceived by Gussmann (1982) provided upper bound solutions while those of KEM in terms of the method of slices were consistent with those based on limit equilibrium principles.

Gussmann, P. (1982). Kinematical Elements for Soils and Rocks. In Z. Eisenstein (Ed.), Fourth International Conference on Numerical Methods in Geomechanics. 1, pp. 47-52. Edmonton: University of Alberta Printing Services.

Earth slide movements are affected by the shear behavior of the material on their shear zone. In many cases, the earth slide shear zones are made of weak clay layers. Traditional geotechnical lab testing utilizes standard loading rates for determining the shear behavior of clay. When an earth slide movement creates field shear rates that are faster or slower than the typical laboratory test ranges, the available shear strength along the rupture surfaces can differ from the laboratory predicted strength. The effect of the clay shear strength rate dependency on observed behavior of earth slides founded on clay beds are examined in this paper. This paper demonstrates how some of the earth slides characteristics can be explained by considering the rate dependency of the shear strength of clay. This paper provides a review of available clay shear strength within an earth slide shear zone from pre-failure to during failure conditions. The pre-failure peak and residual shear strength rate are reviewed. The residual strength during failure and its dependency on the clay mineralogy, clay content, pore fluid chemistry, and stress history is discussed. In general, the lower shear rate, the smaller the available shear strength along a rupture surface. Both peak and residual shear strength reduce with slower shear rate before the failure. After full development of the rupture surface, the shear strength increases nonlinearly with the increase in shear rate. The nonlinear increase in the clay strength during failure is due to the clay viscosity shear thinning characteristics during the failure. The clay viscosity depends on the clay mineralogy, pore fluid chemistry, and liquidity index. By corelating the clay viscosity with the stress history, clay mineralogy, and clay content; an estimation of the available shear strength of clay beds are provided.

Loess contains predominately silt-sized quartz grains that are bonded by various cementation agents, that is of significant interest to the understanding of the mechanical properties of lightly cemented soils. Loess is problematic upon wetting as its metastable structure can rapidly transform from a cemented solid body to a fluidized material. The results of series of isotropically consolidated undrained tests (CIU) compare the large-strain behaviors of intact and reconstituted specimens, that show state-dependent flow instability due to the effect of structure. A constitutive understanding is gained using NorSand model by comparing the computed undrained behaviors of intact and reconstituted loess at the same state parameter. The results confirms the strong effect of structure on flow instability. The drained-to-undrained transition in the loading path of loess is simulated, and indicates a rapid reduction in strength under such a transition for loess, thereby the triggering mechanism of loess flowslides.

The Chin Coulee landslide is situated on the northern slope of the Chin Coulee reservoir, adjacent to Alberta Highway 36. The landslide is approximately 350 m wide and up to 45 m deep. Its length is approximately 200 m long, with the toe of landslide located within the reservoir. The total landslide volume is estimated at approximately 2 million cubic meters. Highway 36 is located upslope from the crest of the landslide and it has been affected by landslide retrogression to the extent that realignment has been necessary to maintain the highway operational.

Alberta Transportation actively monitors the Chin Coulee landslide as part of its geohazard management plan. Resource allocation for geohazard management needs to meet public safety and highway operation requirements, as well as resource availability and the presence of other geohazards in the province. To that end, understanding the landside mechanisms, triggers and potential evolution are fundamental for defining the most cost/effective landslide management strategy. This paper presents the use of historic aerial photographs in combination with modern digital photogrammetry tools to investigate the development of the Chin Coulee landslide, and its evolution towards its current state. The authors have found that this technique makes use of important legacy information available in the province and enhances the current practices for landslide investigation.