Effects of Climate Changes and Spatial Soil Moisture Variability on the Geomechanical Response of Segmented Buried Pipes.

Abstract

Moisture content of soils as well as the geomechanical soil properties (soil modulus, ﾅ) are affected by seasonal fluctuations in temperature and rainfall. This phenomenon is even more amplified when we consider the climate change issue.

In the case of segmented buried pipes, the soil-structure interaction which drive the global behavior of the set of pipes (redistribution of the applied loads, -absolute or differential- settlements, etc.) is also totally impacted by the effects of climate change and therefore leads to pipe failure.

In this paper, we are interested in analyzing the effects of the climate change on the response of segmented buried pipes like stormwater or sewer pipes, made of reinforced concrete, by considering three scenarios in addition to the current climate situation and which is considered as the reference situation:

ﾕ Scenario 1: low emissions (RCP2.6) or colder situation,

ﾕ Scenario 2: similar to current situation (RCP4.5),

ﾕ Scenario 3: high emissions (RCP8.5) or warmer situation.

To the temporal variability, we also add the spatial variability of the properties of the soil due mainly to its composition process. Finally, an element which adds complexity to the modeling is the fact that the characteristics of the joints between two segmented pipes are not fully mastered.

A probabilistic analysis is conducted on a simple model which includes the soil-pipe interaction and considers the spatio-temporal variability of the moisture content of the soil, has been carried out in order to quantify the distribution of outputs of interest such as joints opening, differential settlements as well as stress gradients in the pipes, the joints and the surrounding soil.

The obtained results show that:

ﾕ Even if we consider the scenario 1 which is supposedly similar to the current climate, the failure rates are comprised between 2 to 3 times the current failure rates.

ﾕ Whatever the scenario considered, the failure rate due the Autumn-Winter seasonal fluctuation is harmful.

ﾕ The failure rates through the indicators of performance (structural, hydraulic or tightness) are the highest for the scenario 3.

A holistic view of failure consequences is also studied by counting direct and indirect damages in order to include it in a risk-based framework.