Study of the Long-Term Deformation Characteristics of Municipal Sludge Solidified Soil under the Coupling Action of Dry-Wet Cycles and Initial Static Deviatoric Stress

Aiwu Yang,Guofang Xu,Shaokun Yang,Wei Zhang,Song-He Wang

doi:10.1155/2020/8824414

Aiwu Yang, Guofang Xu + Show 3 more

Open Access

https://doi.org/10.1155/2020/8824414

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Abstract

A self-developed curing agent is used to solidify the municipal sludge taken from Tianjin. Then, the long-term deformation characteristics of the sludge solidified soil are investigated by means of unconsolidated undrained creep tests with different dry-wet cycles for considering the influence of climate. The experimental results show that the attenuation rate of the shear peak strength of municipal sludge solidified soil decreases gradually with the increase of the number of dry-wet cycles, and the strength remains unchanged when the number of dry-wet cycles is greater than 10. The variation laws under different initial static deviatoric stresses are basically identical. When the applied stress is less than the yield stress of the sludge solidified soil, the duration curves of creep show only attenuated stage, i.e., with very small deformation, and the deformation reaches a constant in a short period of time. When the deviatoric stress reaches the long-term strength of the soil, the instantaneous deformation of the sludge solidified soil becomes large and damage occurs quickly. Under the same deviatoric stress, the creep deformation increases with the increase of the number of dry-wet cycles. When the load applied in each step is of the same magnitude, the higher the initial static deviatoric stress is, the larger the deformation of sludge solidified soil will be. It is found that the stress-strain relationship and the relationship between creep strain and time can be well described by an exponential function and a hyperbolic function, respectively. On this basis, a creep model is proposed for the long-term deformation considering the effect of dry-wet cycle times and initial static deviatoric stress. The model is further validated by comparing the predictions with the test results under different deviatoric stresses; the good agreement between which shows the potential application of the model to relevant practical engineering.

Highlights

With the rapid development of economy and the acceleration of urbanization, municipal sludge treatment has become a hot issue that a great number of countries cannot avoid and needs to be solved urgently [1,2]
Qian et al [8] investigated the potential for utilization of Municipal Solid Waste Incineration (MSWI) ash as solidification binder to treat heavy metals-bearing industrial waste sludge. e results showed that the matrixes with heavy metals-bearing sludge and MSWI ash have a strong fixing capacity for heavy metals: Zn, Pb, Cu, Ni, and Mn
Many other materials are used with cement to solidify municipal sludge

Summary

Introduction

With the rapid development of economy and the acceleration of urbanization, municipal sludge treatment has become a hot issue that a great number of countries cannot avoid and needs to be solved urgently [1,2]. When certain proportion of jarosite and alunite was added to cement solidified sludge soil, it was found that the incorporation of them had a significant reduction in soil strength, while the leaching content of heavy metals was significantly reduced [12]. There are few reports on the mechanical properties of municipal sludge solidified soil under the dry-wet cycle, and there is even a lack of experimental data on the long-term deformation during operation process. In this paper, a series of triaxial creep tests were carried out on the sludge solidified soil under unconsolidated and undrained conditions, so as to explore its long-term deformation law under the coupling action of dry-wet cycle and initial static deviator stress. In this paper, a series of triaxial creep tests were carried out on the sludge solidified soil under unconsolidated and undrained conditions, so as to explore its long-term deformation law under the coupling action of dry-wet cycle and initial static deviator stress. en a model for reflecting the creep characteristics of solidified soil is proposed. e model can provide valuable information to the prediction of solidified soil deformation under long-term loading

Testing Materials and Methods

Testing Scheme

Creep Property

Creep Model of Sludge Solidified Soil

Findings

Conclusions