SECONDARY CONSOLIDATION IN UNTREATED AND BIOPOLYMER TREATED PEAT

SECONDARY CONSOLIDATION IN UNTREATED AND BIOPOLYMER TREATED PEAT.

CONTENTS. INTRODUCTION PEAT SOIL- CHARECTERISTICS SECONDARY CONSOLIDATION IN PEAT SOIL CASE STUDY STABILIZATION OF PEAT SOIL BIOPOLYMER STABILIZATION SECONDARY CONSOLIDATION IN BIOPOLYMER TREATED PEAT SOIL CONCLUSION REFERENCES.

INTRODUCTION. Secondary consolidation refers to the long-term consolidation or settlement of soil that occurs after primary consolidation has taken place. Peat soil is one of the most challenging natural foundation materials available on Earth due to their highly unpredictable engineering properties. Secondary consolidation in peat soil is critical for ensuring the stability of structures, managing environmental impact, preserving ecosystems, and making informed decisions in construction and engineering projects. Stabilization of peat soil is crucial and involves several methods like mechanical, chemical and biopolymer etc..

PEAT SOIL - Characteristics. Organic soil containing a considerable amount of organic matter derived from plant remains. Possess poor engineering characteristics like high water content (> 100%), high compressibility, low shear strength, high permeability, low unit weight, high spatial variability, and are subjected to further decomposition based on the surrounding environmental conditions..

SECONDARY CONSLIDATION IN PEAT SOIL. Peat soil undergoes significant primary consolidation (immediate settlement) upon loading, followed by prolonged secondary consolidation. Secondary consolidation often leads to non-uniform settlement across the construction site. Continuous settlement during secondary consolidation can cause structural damage to buildings and infrastructure. Ongoing settlement and subsequent structural damage often require costly remedial measures or repairs to mitigate the effects..

SECONDARY CONSLIDATION IN PEAT SOIL (Cont.). Factors affecting secondary consolidation in peat soil Organic Content Water Content Variations Fiber Structure Time-Dependent Processes Load history.

CASE STUDY. EXPERIMENTAL STUDY ON SECONDARY CONSOLIDATION OF KUNMING PEAT SOIL A series of conventional consolidation tests and 60 d creep consolidation tests were carried out on undisturbed peat soil samples taken from Kunming for the consolidation and secondary consolidation characteristics. Studying the challenging properties of peat soil and its impact on geotechnical engineering..

CASE STUDY (Cont.). METHODOLOGY The test soil sample is taken from a project site in Xishan District, Kunming City, Yunnan Province. Physical property indexes of soil samples were measured through laboratory tests. Table 1. Physical and mechanical parameters of peat soils.

CASE STUDY (Cont.). METHODOLOGY Test types Conventional Consolidation Tests: Conduct conventional consolidation tests to analyze the primary consolidation behavior of Kunming peat soil samples. 60-day Creep Consolidation Tests: Perform 60-day creep consolidation tests to investigate the secondary consolidation characteristics of Kunming peat soil samples..

CASE STUDY (Cont.) RESULT ANALYSIS. Fig.1 e-lg p curve of peat.

CASE STUDY (Cont.) RESULT ANALYSIS. Pre consolidation pressure: The e-lg p curves were obtained. The compression curves of peat soil are in inverse S-shape. The compression coefficient in the range of 5.7~8.8 MPa-1, which is much higher than the lower limit of the definition of high compressibility soil (0.5 MPa-1), so Kunming peat is high compressibility soil. The ln(1+e)-lg p double logarithmic method proposed by Butterfield is used to calculate the pre consolidation pressure..

CASE STUDY (Cont.) RESULT ANALYSIS. Figure 3. e-lg t curve of peat (Source: Li et al., 2021).

CASE STUDY (Cont.) RESULT ANALYSIS. The e-lg t compression curves of peat soil are inversely S under the consolidation pressure at all levels in the graded loading. The EOP point and secondary consolidation coefficient Cα are obtained by Casagrande drawing method. When the consolidation pressure is 25kpa, the main consolidation completion time is the shortest (about 100 minutes). In the range of 25 ~ 200kPa, with the increase of consolidation pressure, the main consolidation completion time increases gradually. When p is greater than 200kPa, the completion time of main consolidation does not increase or even decreases slightly, which is related to the structural failure of soil..

CASE STUDY (Cont.) RESULT ANALYSIS. The Cα/Cc value of peat soil in Kunming is 0.052 is larger than other typical non-organic soft soil in China..

CASE STUDY (Cont.) Secondary Compressibility Of Peat Soil In Kunming.

CASE STUDY (cont..) Secondary compressibility of Peat Soil in Kunming.

CASE STUDY (Cont.) CONCLUSION. The e-lg t curves of peat soil show an inverse S type. Similar to the normal undisturbed soft clay, the peak value of Cα in peat soil increases rapidly to the peak value and then decreases gradually with the increase of consolidation pressure p. Peak value of Cα in peat soil is higher than that in the normal undisturbed soft clay, ranging from 0.04 to 0.12, and the peak value is not in the pre consolidation pressure, but in the later 200kPa. According to the classification standard of soil based on the εα of secondary compressibility coefficient, Kunming peat soil belongs to high secondary compressibility soil..

STABILIZATION OF PEAT SOIL. Conventional method of treating soft soils in the past includes the implementation of surcharge loading, prefabricated vertical drain, and electroosmotic treatment to quicken the rate of consolidation. Those method will not be that useful in the case of soils with high organic matter as the time required for secondary and tertiary settlements will be pretty high compared to that of clayey soils. Methods such as dynamic replacement and mixing have been adopted to create a stiffer dual layer of soil deposit comprising peat and sand, which considerably minimizes secondary settlement..

STABILIZATION OF PEAT SOIL (Cont.). The application of chemical stabilizers in organic soils such as cement, fly ash, and lime has shown tremendous improvement in mechanical properties such as shear strength and compressibility. Due to the increasing demand for sustainable, cost-effective, and environment-friendly materials for stabilization, alternative materials have been explored and applied to stabilize organic soils..

BIOPOLYMER STABILIZATION. Biopolymer stabilization in peat soil involves using natural polymers derived from organic sources to improve the soil's engineering properties. This include starches, cellulose-based materials, chitosan (derived from crustacean shells), and various polysaccharides. Biopolymers interact with peat particles, binding them together and forming a stable matrix. Biopolymers can modify the structure of peat soil, creating a more stable arrangement of particles. This alteration contributes to improved load-bearing capacity and reduced settlement..

BIOPOLYMER STABILIZATION (Cont.). Advantages Of Biopolymer Stabilization Environmentally Friendly: Biopolymers are derived from natural sources and are often biodegradable, making them environmentally friendly alternatives to synthetic stabilizers. Improved Soil Properties: Biopolymer treatment enhances soil cohesion, reducing its susceptibility to erosion and improving stability, modify the soil structure, reducing its compressibility and potentially minimizing settlement under load,Enhanced Load-Bearing Capacity. Erosion control: Improve the soil's resistance to erosion, preventing loss of soil particles due to water or wind action..

BIOPOLYMER STABILIZATION (Cont.). 14000 (b) Fine soil 13000 ChB (2012) (2016) 1000 0 (109 (2015) 128MPa Lati6etaL (2016) Ayeheen et al. (2016) Hataf et al. (2018) Stath Chowl Xanthan (2.0%) Biopolymer type.

SECONDARY CONSOLIDATION IN BIOPOLYMER TREATED PEAT SOIL.

SECONDARY CONSOLIDATION IN BIOPOLYMER TREATED PEAT SOIL (Cont.).

SECONDARY CONSOLIDATION IN BIOPOLYMER TREATED PEAT SOIL (Cont.).

CONCLUSIONS. Soil with high compressibility, including secondary and tertiary settlements, high water content, insufficient shear strength, and high permeability, is generally unsuitable for foundation material. Appropriate treatment is needed to transform these soils into suitable foundation materials due to their highly unpredictable engineering properties. To overcome the concerns and drawbacks of common soil chemical and mechanical stabilization practices, bio-mediated and bio-inspired approaches have been actively studied in geotechnical engineering research. Biopolymers like xanthan gum are found to increase strength by more than 50% for organic soils..

REFERENCES. Abdulameer, A. N., Gabr, M. H., & Mohamad, I. S. (2019). Laboratory investigation of biopolymer-treated peat soil. Geotechnical and Geological Engineering, 37(6), 4279-4293. Latifi, N., Horpibulsuk, S., Meehan, C. L., Abd Majid, M. Z., Tahir, M. M., & Mohamad, E. T. (2017). Improvement of problematic soils with biopolymer—an environmentally friendly soil stabilizer. Journal of Materials in Civil Engineering, 29(2), 04016204. Latifi, N., Horpibulsuk, S., Meehan, C. L., Majid, M. Z. A., & Rashid, A. S. A. (2016). Xanthan gum biopolymer: an eco-friendly additive for stabilization of tropical organic peat. Environmental Earth Sciences, 75, 1-10..

REFERENCES. Li, X. M., Fu, Y. J., Chen, C., & Yin, S. (2021, June). Experimental study on secondary consolidation characteristics of Kunming peat soil. In IOP Conference Series: Earth and Environmental Science (Vol. 787, No. 1, p. 012001). IOP Publishing. Rasheed, R. M., & Moghal, A. A. B. (2022). Critical appraisal of the behavioral geo-mechanisms of peats/organic soils. Arabian Journal of Geosciences, 15(12), 1123..

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