The Effect of Suffusion Phenomenon in the Increasing of Land Subsidence Rate

Elmira Khaksar Najafi,Hadi Faghihmaleki

doi:10.28991/cej-2016-00000036

Elmira Khaksar Najafi, Hadi Faghihmaleki

Open Access

https://doi.org/10.28991/cej-2016-00000036

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Abstract

Land subsidence is defined as gradually ground surface settlement in an aquifer due to the compaction of unconsolidated sedimentary deposits. Since in an aquifer, deposits consist of cohesive or non-cohesive alluvial soil layers. The consolidation theory cannot be explained as the only reason for land subsidence. According to the susceptibility of alluvial soils to suffusion, internal erosion is also considerable to enhance the rate of the local settlement. Suffusion is explained as a process of soil particle movement in the soil body due to the effect of seepage flow on it. The subsidence rate in southwest and south of Tehran in Iran is very considerable whereby some structures have suffered significant damages due to this phenomenon. In this research, the contribution of suffusion and land subsidence was investigated in damaged building located at Ghale Morghi Street in southwest of Tehran, as a case history. Because of the incapability of available methods, in this article, a probability pattern is also proposed using statistical analysis for determination the likelihood of internal instability in alluvial soils in regard to soil cohesiveness.

Highlights

In the recent decades, the excessive withdrawal of ground water resources owing to the population increment has wound up a challenging problem in the geotechnical engineering because of land subsidence, causing fundamental damages in arid and semi-arid regions
The properties of soil aggregation, coefficient of uniformity (Cu) and soil porosity (e) are the basic inputs used in the geometric available criteria and soil cohesiveness’s effect has been ignored, it is very effective in the occurrence of suffusion
For any other project, this trend can be used to present a pattern in accordance with special situations of that project

Summary

Introduction

The excessive withdrawal of ground water resources owing to the population increment has wound up a challenging problem in the geotechnical engineering because of land subsidence, causing fundamental damages in arid and semi-arid regions. The lowering of groundwater surface brings about the space of the aqueducts formerly filled by water to be empty and leaves spacious canals through soil mass These canals play an important role in the producing and increasing hydraulic gradient, leading to erosion. Unconsolidated sedimentary deposits in aquifers consist of cohesive and non-cohesive soils For this reason, the consolidation theory is not the only reason for land subsidence. Finer particle are removed through the voids of larger particle by seepage flow, and an intact soil skeleton formed by the coarser particle leaves behind, which is susceptible to settlement Both hydraulically and geometrically conditions are simultaneously requisite factors to transfer soil particle through the soil structure. For any other project, this trend can be used to present a pattern in accordance with special situations of that project

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