Vertical ground motions are comprised of both upward-propagating P-waves and inclined SV-waves. However, in common practice of site-response analysis- either via the VS30 term in a GMPE or a 1D site-response analysis- the P-wave

effects are typically not incorporated. To effectively represent such effects in site response analysis of vertical ground motions, a better understanding of soil response to cyclic compressional loading is required. In this paper, we study soil response to cyclic compression in the lab, in which pure compression is achieved by constraining radial deformations. Radial deformations can be constrained by loading within a rigid cell, such as an oedometer, creating 1D compressional boundary conditions. However, wall friction within the rigid cell can cause rotation of principal stresses, and hence ultimately lead to shear within the sample. Alternatively, in the present study, we suggest loading in a triaxial device under Ko-conditions, thus obtaining pure compressional loading. In the developed methodology, radial deformation is monitored during loading and constrained via adjustments of the cell pressure. Such an approach requires extremely slow loading and close monitoring of various parameters. We compare the results obtained with the suggested approach to cyclic loading within a rigid cell on a uniaxial compression device. Stress-strain loops are found to be comparable but not identical.

Compacted clays are used in the construction of embankments, dikes and as landfill sealing. Dynamic shear modulus and damping, dependent on the confining stress and shearing strain amplitude, are required in the seismic analysis of such geotechnical structures. A series of multi-stage tests in a conventional fixed-free resonant column device were conducted to determine these material properties for three medium to high plasticity kaolin clays. A compaction state corresponding to optimum water content at Proctor density was used as a reference. Water content was subsequently modified to reproduce a 3% drop in density. The associated three states were then tested to assess the effect of consistency on the dynamic soil properties. Particular attention was paid to the proper calibration of the device. Design equations are provided for use in practice.

Characterising the dynamic behaviour of soils under significant initial static bias is important for the safety of slopes, embankments, and tailings storage facilities (TSFs). However, this is a complicated task as: (i) the case history database is dominated by level ground sites, (ii) published laboratory element testing programs are often primarily carried out without an applied initial bias, (iii) there is uncertainty as to how liquefaction resistance varies with bias and/or density, and (iv) the criterion for selecting liquefaction triggering in such conditions has not achieved consensus. These issues are a particular challenge for filter-stack TSFs where the tailings can be in a very loose state owing to their moist placement, are under significant bias near the lower portion of the slope, and being often predominately siltsized do not fall well into common categorisations of “clay-like” and “sand-like” soils.

This paper presents a series of cyclic constant volume direct simple shear (DSS) tests on samples prepared in a very loose state, tested under a range of static bias values. The significant effects of bias are highlighted by this testing, along with the low magnitude of cyclic-induced excess pore pressure that developed at the point of “runaway” shear strains in the direction of the static bias. These observations are then compared to typical approaches to select a liquefaction criterion from strains and excess pore pressure in nonlinear dynamic analyses.

In this paper, setting and testing methods for deformation characteristics of soils for a dynamic ground response analysis were studied. First, we proposed a parameter setting method using an optimization technique and it was confirmed that the proposed method could set the parameters more accurately than three designers with different experience. Second, deformation characteristics tests with some cyclic numbers were carried out. The result showed that a slight difference in cyclic numbers causes quite large differences in the shear stiffness in large strain levels. In

addition, a series of ground response analyses was carried out using the above mentioned parameter setting method with some test results. The result showed that differences in the number of cycles at each strain level may affect the results of the dynamic ground response analysis. Moreover, it was also confirmed that using the shear stiffness obtained from monotonic loading test results we can accurately evaluate the dynamic response of the surface ground observed in the hybrid dynamic ground response analysis and simulate real soil behavior.

Pumiceous particles have a distinct vesicular nature as well as a complex surface texture that makes them potentially vulnerable to crushing under cyclic loading. Pumiceous sand mixtures have received more scientific attention than pumiceous silts in this regard. Researchers have found the undrained cyclic behaviour of pumiceous sands to be significantly different from that of hard-grained sands because of the particle crushing that occurs during cyclic testing and/or sample reconstitution. The liquefaction resistance of pumiceous sands is also considered to be higher because of the pore-water pressure distribution in the sample that occurs during particle crushing. The undrained behaviour of pumiceous silt has only been studied once previously: such material did not crush during sample reconstitution and undrained cyclic testing, which was attributed to a cushioning effect taking place between silty, non-crushable particles and coarse sandy pumice particles. Whether there are thresholds of fines content and/or pumice content at which pumiceous soil mixtures start to behave more similarly to hard-grained soils are yet to be unravelled and remain relevant for engineers and scientists. This paper analyses particle crushing after sample reconstitution and undrained cyclic triaxial testing of three pumiceous natural soil mixtures (lacustrine tephra deposits) from northern New Zealand having fines (< 0.075mm) and pumice contents ranging between 20% and 70% and 30% and 51%, respectively. The results examine potential changes in (1) fines content, (2) pumice content, and (3) undrained cyclic behaviour by comparing both pore-water pressure and axial strain development of the pumiceous soils with other crushable and non-crushable soils.

The application of semi-empirical charts based on in-situ tests results represents the first step in the earthquake-induced soil liquefaction assessment. Among them, the CPT-based charts have been largely developed in the last decades, especially after the 2010-2011 Canterbury earthquakes in New Zealand, while the main drawback of the existing approach based on DMT is related to the lack of a correction factor for the fines content. In this regard, this study proposes a new empirical relationship between the Cyclic Resistance Ratio and the horizontal stress index where the effects of the fines content are incorporated. The new method is calibrated on a specific site located in the Emilia-Romagna plain (Italy), where an extensive soil characterization from in-situ and laboratory tests was available for the silty sand and sandy silt deposits affected by liquefaction after the 2012 Emilia earthquake. Even though verified only for Italian natural soils, the new approach allows to reduce substantially the discrepancy between the results obtained when the CPT-based and the DMT-based methods are applied.

The liquefaction assessment method in Japan has been developed based on the standard penetration test (SPT). A drawback of SPT is that the number of blows (N-value) is influenced sensitively by particle size and fines content. This caused underestimation of liquefaction resistance of sandy soil with non-plastic fines during the 2011 off the Pacific coast of Tohoku Earthquake (Tohoku) Earthquake. On the other hand, the cone penetration test (CPT) is also used worldwide where cone-tip resistance, skin friction and pore water pressure can be measured. A potential drawback of CPT for the purpose of liquefaction assessment is that the undrained cyclic resistance of soil, which is a dynamic property of soil, is measured indirectly in a static manner. To overcome these limitations, this contribution proposes a vibratory cone penetration test (VPT) for in-situ liquefaction assessment using a novel vibratory cone probe that vibrates horizontally with varying amplitudes of acceleration. The vibratory cone probe can be driven at a constant rate in the same manner with CPT, and the horizontal vibration of the probe can be conducted at any depth in which horizontal acceleration, cone-tip resistance and pore-water pressure can be measured. This contribution presents a case study of VPT using the novel vibratory cone probe, and demonstrates representative field test data where the cone-tip resistance drops sharply when the horizontal acceleration exceeds a threshold value in liquefiable subsoil, while such drop does not occur in non-liquefiable subsoil.

The paper presents several methods to evaluate the liquefaction potential of a site. From the simplified method based on the limit pressure to the application of cyclic loading, the pressuremeter has great potential to be compared with the equipment normally used to assess this liquefaction potential. The simplified method consists of constructing a curve limiting two parts of the plane where the pairs of values of the standard limit pressures and the cyclic shear ratio are represented. A method is proposed for correcting the limit pressure measured during pressuremeter tests in sands. A consistent relationship is obtained between the data set and the proposed diagram. The determination of the cyclic shear curve by cyclic tests is another promising approach. As in laboratory conventional testing, cyclic loading is applied to borehole walls at a predefined mean pressure allowing a cyclic stress ratio to be imposed. The protocol and results obtained with and without pore pressure measurement are presented. The methods are detailed and their validation on test databases in calibration chambers or on real sites in different countries is presented.