CONSOLIDATION INTEGRATED BUOYANCY EQUATION FOR SOFT GROUND IMPROVED WITH LIGHTWEIGHT POLYURETHANE FOAM

ABSTRACT: Consolidation settlement occurs when a saturated soil is subjected to an increase in overburden pressure that causes a volume change in the soil. When a lightweight material is used as a ground improvement, the stress is reduced as the soft soil is partially removed and replaced by the lightweight material. In addition, the improved ground with lightweight material has a potential to uplift due to the buoyancy of lightweight material. The uplift force reduces the stress imposed on the underlying soil as it acts in the upward direction, thus further reducing the consolidation settlement. This study is executed to produce an alternative equation for consolidation settlement incorporating the buoyancy effect for lightweight polyurethane (PU) foam as a ground improvement method. A Rowe Cell consolidation laboratory test was conducted on untreated marine clay soil as well as on improved marine clay with different thicknesses of lightweight PU foam. Validation of the laboratory test results was done by finite element analysis, PLAXIS 2D. The thickness of PU foam governs the buoyancy and the hydrostatic pressure of water displaced by PU foam, which is incorporated in the alternative equation. The alternative consolidation settlement equation is applicable for ground improved with lightweight polyurethane foam and found to be more economical and practical as the buoyancy is taken into account in the equation. ABSTRAK: Mendapan pengukuhan berlaku apabila tanah tepu mengalami peningkatan tekanan beban yang menyebabkan perubahan isipadu tanah. Apabila bahan ringan digunakan sebagai penambahbaikan tanah, tekanan akan berkurang kerana sebahagian tanah lembut dikeluarkan dan diganti dengan bahan ringan. Selain itu, tanah yang diperbaiki dengan bahan ringan berpotensi untuk terangkat ke atas keranan daya apung bahan ringan. Daya angkat bahan ringan mengurangkan tekanan yang dikenakan ke atas tanah kerana daya bertindak ke arah atas, dan seterusnya megurangkan mendapan pengukuhan. Kajian ini dijalankan untuk menghasilkan persamaan alternatif bagi mendapan pengukuhan dan digabungkan dengan kesan daya apung untuk busa poliuretena ringan (PU) sebagai kaedah penambahbaikan tanah. Ujian makmal mendapan pengukuhan menggunakan peralatan Rowe Cell dilakukan pada tanah liat marin yang asal serta yang diperbaiki dengan ketebalan busa PU ringan yang berbeza. Pengesahan hasil ujian makmal dilakukan dengan analisis elemen terhingga, PLAXIS 2D. Ketebalan busa PU mempengaruhi daya apung dan tekanan hidrostatik bagi kedalaman air yang disesarkan oleh busa PU dan digabungkan dalam persamaan alternatif. Persamaan alternatif mendapan pengukuhan tersebut boleh digunapakai untuk pembaikan tanah menggunakan bahan ringan busa poliuretena dan didapati menjimatkan kos dan praktikal kerana keapungan diambilkira didalam persamaan tersebut.

Perbandingan Pengujian Konsolidasi Menggunakan Alat Rowe Cell dan Oedometer pada Tanah Lanau Lunak

Soil consolidation testing using an oedometer and rowe cell. Oedometers are often used on clay and soft soils. However, in the development of the rowe cell device, the results of lowering soft soil were better than the oedometer. The advantage of this rowe cell is that it can determine the saturation value of the soil samples tested. The rowe cell tester can measure the pore water pressure at the beginning and end of each consolidation stage. This rowe cell can provide suitable settlement for soft soils. This consolidation test to obtain soil parameters such as Cv and Cc by using the rowe cell tool. After that, from the test results, the two tools were compared.

Compressibility of Palm Kernel Oil-Based Polyurethane Foam Using Rowe Cell Apparatus for Ground Improvement

Ground improvement methods are carried out to enhance the soil properties in order to ensure the unsuitable site locations with poor soil conditions can be developed for future development. Injection of lightweight material namely polyurethane foam is found to be one of the alternative methods that provide cost-effective and reliable techniques for ground improvement. Petroleum-based polyurethane is widely used in geotechnical application but nowadays the cost is getting more expensive due to high depleting rate and high production cost. Instead of using petroleum-based PU, this study is focusing on performance of palm kernel oil-based PU as an alternative method for ground improvement. The palm kernel oil-based polyurethane foam is anticipated to be more economical since it is produced from the renewable source, where it does not lead to permanent depletion of resources which has a limited global availability. The objective of this study is to determine the expansion and compressibility of palm kernel oil-based polyurethane with different mixing ratio. The samples were tested using Rowe cell apparatus to determine the compressibility, swelling index and pre-consolidation pressure of the polyurethane. The results of the finding show that the expansion and compressibility of the palm kernel oil-based polyurethane foam varies with the mixing ratio of isocyanate and polyol liquid. The compressibility index of PKO-BPU is found to be higher than petroleum-based polyurethane and low in expansion.

Large-scale Rowe cell experimental study on coefficient of consolidation of coal mine tailings

Tailings are the co-product of mining activities which is usually deposited in the form of slurry with high water content and compressibility. Consolidation properties of tailing materials are important for any disposal and storage actions, posing significant challenges in mining industry. In the present study, laboratory experiments were performed to investigate the compressibility and consolidation properties of coal mine tailings. The investigation were carried out on material with different grain-sizes upon application of incremental loads in a large-scale Rowe cell. The samples were collected from open pit Turów Coal Mine in Poland. Remolded samples were manufactured in laboratory as three batches of different size-ratio between fine and coarse particles, i.e. 0.5, 0.75, 0.25. Simultaneous measurements of settlements together with pore water pressure were used for determination of coefficient of consolidation, cv. For this purpose gradient method was used which is applicable for whole the consolidation curve including secondary consolidation.

The Modified Rowe cell set for obtaining vertical and horizontal flow in soft organic soils

W pracy przedstawiono zmodyfikowany system z komorą Rowe’a (MRCS). Dwie główne modyfikacje zostały przeprowadzone: dodano trzeci, pneumatyczny kontroler oraz przełożono górny zawór do pomiaru przepływu poziomego. Dzięki temu, system został przystosowany do badań zarówno konsolidacji, jak i przepływu dla tych samych warunków brzegowych w tym samym czasie oraz do badania przepływów poziomych z możliwością większej precyzji zadawania poziomego drenażu do środka i na zewnątrz próbki gruntu.