Ultimate Consolidation Settlement of the NC Clay Layer using Cam Clay Plasticity in the Abaqus

Project Overview

This tutorial focuses on the simulation of the ultimate consolidation settlement of a Normally Consolidated (NC) clay layer using the Cam Clay Plasticity model in Abaqus. This example is based on Example 4.3 from the Sam Helwany book.

The objective is to simulate the consolidation process of the clay layer under an applied compressive load and determine its ultimate consolidation settlement. The numerical results obtained from Abaqus are then compared with the corresponding results presented in the Sam Helwany book.

Model Description

The soil profile consists of two layers. The upper layer is sand with a height of 6 m, while the underlying layer is clay with a thickness of 1 m.

The clay layer is assumed to behave as an elastoplastic material following the Extended Cam Clay model.

Normally Consolidated Clay

The clay layer is considered to be Normally Consolidated (NC). This condition is determined by comparing the in-situ vertical effective stress at the center of the clay layer with the pre-consolidation pressure.

When the in-situ vertical effective stress at the center of the clay layer is equal to the pre-consolidation pressure, the clay is considered to be Normally Consolidated.

Geostatic Step

The analysis begins with a Geostatic step. In this step, the effective weight of the soil is applied using body force to establish the initial stress state in the soil.

Application of Compressive Load

In the second step, a compressive load of 100 kPa is suddenly applied to the top surface of the soil.

The applied load causes excess pore pressure and initiates the consolidation process within the clay layer.

Consolidation Analysis

Following the application of the compressive load, the consolidation process is simulated through six consecutive steps. The time period assigned to these steps increases progressively in order to capture the development of consolidation settlement over time.

The time periods used for the six consolidation steps are 1, 10, 100, 1,000, 10,000, and 100,000 seconds, respectively.

Cam Clay Plasticity

The clay layer is modeled using the Extended Cam Clay plasticity model. This model is used to represent the elastoplastic behavior of the normally consolidated clay during the consolidation process.

Ultimate Consolidation Settlement

The main objective of the analysis is to determine the ultimate consolidation settlement of the NC clay layer.

The settlement response is obtained from Abaqus throughout the consolidation process, and an ultimate consolidation settlement diagram is generated from the numerical results.

Comparison of Results

The consolidation settlement obtained from Abaqus is compared with the corresponding result presented in the Sam Helwany book.

This comparison provides a basis for evaluating the numerical simulation of the consolidation behavior of the NC clay layer.

What You Will Learn

• How to model a two-layer soil profile in Abaqus.
• How to define sand and clay soil layers.
• How to establish the initial geostatic stress state.
• How to apply soil body force in a Geostatic step.
• How to identify Normally Consolidated clay.
• How to define the Extended Cam Clay plasticity model.
• How to apply a sudden compressive load of 100 kPa.
• How to perform a consolidation analysis in Abaqus.
• How to define multiple consolidation steps with different time periods.
• How to calculate the ultimate consolidation settlement of NC clay.
• How to compare Abaqus results with the Sam Helwany book.

Key Features

• Two-layer soil profile.
• 6 m sand layer.
• 1 m clay layer.
• Normally Consolidated (NC) clay.
• Extended Cam Clay plasticity model.
• Geostatic initial stress analysis.
• 100 kPa sudden compressive loading.
• Six consecutive consolidation steps.
• Consolidation time periods from 1 to 100,000 seconds.
• Ultimate consolidation settlement calculation.
• Comparison with Sam Helwany Example 4.3.
• Free Abaqus tutorial.