General report of TC103 numerical methods in geomechanics

This paper presents a General Report on 46 contributions, including poster presentations, submitted for the parallel sessions organized by TC 103: Numerical Methods in Geomechanics. The authors come from various regions of the world and the topics of the submitted papers are diverse. These contributions are reviewed from the viewpoint of the current research directions in relation to the numerical schemes and their key results. The overview of the latest work is provided in this general report, dividing the broad paper topics into several important subjects

Liquefaction Analysis of a Petroleum Tank-Ground-Pile Ring System in Reclaimed Ground Near Seashore

In this paper, liquefaction analysis (LIQCA2D, LIQCA3D) of a petroleum tank-ground-foundation system is conducted using a dynamic finite element-finite difference method. The nonlinearity of the ground is simulated with a kinematic hardening elastoplastic model, which has been verified by a series of hollow cylindrical torsional shear tests and been proved that it can well predict the behaviors of soils such as the liquefaction strength curve, the stress-strain relation as well as the effective stress paths during cyclic loading. In the numerical analyses, an FEM-DEM analytical method is adopted to the soil-water coupled analysis. The petroleum tank is built on a reclaimed ground and is near to seashore. In order to enhance the seismic strength of the tank-soil system, a ring-shaped steel pile wall is designed for the tank. At first, two-dimensional (2-D) and three-dimensional (3-D) finite element analyses are conducted for the tank without the remediation method to identify the difference between 2-D and 3-D analyses. Then, a 3-D dynamic analysis is conducted for the tank in two different cases, that is, with and without the remediation. The mu-nose of the research is to evaluate numerically the effectiveness of the remediation method when a tank is built on a potentially liquefied ground

Prediction of pile response to lateral spreading by 3-D soil-water coupled dynamic analysis: shaking in the direction of ground flow

Numerical predictions of a series of shake table tests are presented in this paper in order to examine the accuracy of a 3-D effective stress analysis in predicting the behavior of piles subjected to liquefaction-induced ground flow. For a rigorous assessment of the analysis, “Class B” predictions are reported in which numerical and constitutive model parameters were set before the event, and the target motion was used as an input motion in the analysis. Modeling of the stress-strain behavior of sand, identification of the initial stress state and critical numerical parameters in the 3-D seismic analysis of the soil-pile system are discussed in detail. Combined effects of kinematic loads due to large lateral ground movement and inertial loads on pile behavior are examined through a series of tests using different shaking direction, excitation amplitude and mass of the footing (load from the superstructure). By and large, very good agreement was obtained between the predicted and measured peak responses of the pile foundation, whereas the analysis underestimated the displacements of the sheet-pile wall and was less accurate in predicting the residual deformation of the foundation piles. Reasons for these discrepancies and limitations of the analysis method are discussed

The pull-out capacity of mobile platform legs from saturated silt

Many new types of structures are extensively used in offshore engineering in recent few decades. Such as the mobile platforms, suction caissons, anchors, spudcans, and so on. The capacities of these structures during penetration, operation and remove are crucial issues for engineers. In this paper, the model test and numerical simulation are conducted to estimate the pullout capacity of the mobile platform’s leg submerged in saturated silt. The platform’s leg is simplified as a square shape with a dimension of 30cm 30cm, while the buried depths are 1cm, 3cm, 5cm, respectively. The modified Cam-Clay model and finite deformation theory are applied in numerical simulation. We did the short-time pullout in experiment and numerical simulation. The peak pullout force is about 1-4 times larger than the model’s weight. The pullout resistance is influenced by the object buried depth, soil property and so on. It is shown that during uplift, the negative pore water pressure under the object provides the main role to the resistance capacity. As the increase of negative pore water pressure and decrease of the soil confining pressure, the soil failure and large deformation happens, then the structure extricates itself from the silt. The numerical result is acceptable to predict the breakout although couldn’t simulate the separation of object and soil

General report of TC103 numerical methods in geomechanics

This paper presents a General Report on 46 contributions, including poster presentations, submitted for the parallel sessions organized by TC 103: Numerical Methods in Geomechanics. The authors come from various regions of the world and the topics of the submitted papers are diverse. These contributions are reviewed from the viewpoint of the current research directions in relation to the numerical schemes and their key results. The overview of the latest work is provided in this general report, dividing the broad paper topics into several important subjects

Accuracy of prediction with effective stress analysis for liquefaction-induced earth pressure on a pile group

Numerous buildings with pile foundation adjacent to quay walls were seriously damaged during the 1995 Kobe earthquake. The mechanism of the earth pressure on a pile group has not yet been clarified, and the precise prediction of the earth pressure is also very difficult. In this paper, we predicted the earth pressures on a pile group due to liquefaction-induced ground flow by a 3-dimensional soil-water coupled dynamic analysis. We simulated the series of large shaking table tests in order to validate the analysis. As a result, the predicted earth pressures on the piles and displacement of footing showed a quantitative agreement with the measured ones

Numerical modelling of hydraulic fracturing

In this paper we present a numerical model for hydraulic fracturing purposes. The rock formation is modelled as a poroelastic material based on Biot’s Theory. A fracture is represented in a discrete manner using the eXtended Finite Element Method (X-FEM). The fluid flow is governed by a local mass balance. This means that there is an equilibrium between the opening of the fracture, the tangential fluid flow, and the fluid leakage. The mass balance in the fracture is solved with a separate equation by including an additional degree of freedom for the pressure in the fracture. The fracture can grow in arbitrary directions by using an average stress criterion. We show a result of hydraulic fracture propagation for a 2D circular borehole. The fracture direction is consistent with the expected direction