Applied Mechanics and Materials Vols. 773-774

Abstract: Peat soils occur in many countries and formed naturally through the decomposition of plant and animal matter. These soils are known as a very problematic soft soil due to its low bearing capacity and high compressibility. These two main factors may be based on the characteristics of the soil itself. This study is focused on its physical properties and shrinkage measurement. It is also to investigate the shrinkage measurement that obtained from the diameter at four dimensional points and bar linear shrinkage method for both location peat sample. There are varies method that can be used in order to obtain a full description of the shrinkage behavior of peat. The sample was taken from two different locations which are Parit Nipah and Pontian. Linear shrinkage method is used to determine the soil shrinkage from linear measurements on a bar mould with disturbed soil that passing 0.425mm sieve. However, this method was modified by using undisturbed sample to compare the result with bar linear shrinkage method and the measurement was obtained by the reduction of its diameter at four points of the sample. Linear shrinkage values obtained from Parit Nipah and Pontian by following British Standard method are 34.77% and 33.09% respectively while modified linear method gives the value of 35.25% for Parit Nipah and 32.85% for Pontian. Modified method shows that peat soil from both locations shrinks in irregular shape due to Point C of Parit Nipah and Pontian peat sample has the smallest diameter compared to other points within 24 hours oven-dried. It also shows that Parit Nipah peat soil has a higher percentage of linear shrinkage for both method instead of Pontian peat soil. The linear shrinkage values that obtained from bar linear shrinkage and modified linear shrinkage gives smaller different values which is nearly same for both method.

Abstract: The measurement of a small strain stiffness can be conducted via measuring the velocity of the material. The stiffness is an indicator for the strength of the material. It is an important parameter to understand the response of the material when it received the loads. The seismic surface wave has an advantage technique to measure the stiffness of the materials due to factors of time consuming and non destructive method. In addition, the test can be conducted on the surface of the material, thus ease to conduct the test. The continuous surface wave is using a steady state seismic source which can be controlled it frequency. Thus, sufficient energy at specified frequency can be obtained. This can be influenced the quality and reliability of the data. In addition the stiffness at specified depth can be identified. In this paper, in-house development of the equipment and the system was described. A few testing was conducted on different materials in order to assess the reliability of the developed system as well as the stiffness of the materials. As a result, the stiffness assessment on the concrete mortar, asphalt pavement and concrete wall showed the values were in the range of 0.25 to 0.33GPa, 0.05 to 0.13GPa and 0.35 to 0.51GPa respectively.

Abstract: Construction, buildings and infrastructure founded on soft clays are often affected by settlement problem. Therefore, Prefabricated Vertical Drain (PVD) is one of the best solutions to accelerate soil consolidation by shortening the drainage path. In this study, numerical investigation was carried out to pursue a better understanding of the consolidation behavior of soft clay improved with PVD. The consolidation process accelerated by PVD with surcharge of 50 kPa was analysed using the ABAQUS software by adopting an elastic model. The aim of this study is to compare the settlement and the required time to fully consolidate the soft soil at different drain spacings (1.0 m, 1.5 m and 2.0 m) for two different thickness of the clay layer. The results shows that the time required to completely consolidate the soft soil for 12 m and 20 m thickness of clay layer with different spacings are in the range of 3 months to 66 months. The settlement rate and excess pore water pressure dissipation are increased when the spacing of the drain closer.

Abstract: Soil stabilisation is defined as a technique to improve the engineering characteristics in order to improve the parameters such as shear strength, compressibility, density, hydraulic conductivity. There are many techniques that can be used for different purposes by enhancing some aspects of soil behaviour and improve the strength and properties of soil. One of the cheapest techniques is by using Polyurethane grout, which is workable for construction and enhances the performance of soil compressive strength. Polyurethane (PU) foam is non-toxic, having an indefinite life span and non-environment unfriendly. PU is a chemical substance that normally used in polymer industries for instance resilience foam seating, rigid foam insulation panels and microcellular foam seals. In this research, different percentages of PU content are mixed with sand to test the compressive strength of modified sand. The compressive strength of sand is determined by conducting the Unconfined Compression Test (UCT) with the mold samples of 50mm diameter and 100mm height. The test determines the compressive strength and generates the stress-strain relationship of the modified sand. It is shown that the compressive strength of modified sand will gradually increase with an increasing PU content percentage (varying from 10% (20 kPa) – 95% (500 kPa). Conclusively, this research could be used as the benchmark of ground improvement technique.

Abstract: Peat soils have been known for their problematic characteristics which include high water content, high compressibility and low shear strength. In this study, an attempt was made to investigate the effect of 1 week addition of modified Urea-CaCl₂ liquid medium with and without Sporosarcina pasteurii on the shear strength of unsterilized dried peat soil using the Unconfined Compression Test. After the treatment period, significant increase in the shear strength of the soil was found to be highest for peat + medium at 42 kN/m², moderate for peat + medium + Sporosarcina pasteurii at 27 kN/m² and unchanged for peat + water control at 24 kN/m². Although the growth dynamics of all the microbes involved in the calcite formation in the treated peat soil were not known, the addition of the modified Urea-CaCl₂ liquid medium into the soil clearly had contributed to the marked increased in the shear strength of the soil. It is probable that the medium had promoted a better growth of indigenous calcite bacteria population in the soil which may have been suppressed by the slow growing S. pasteurii population being added daily to the soil

Abstract: Bearing capacity and settlement are two important parameters in geotechnical engineering. The bearing capacity of circular foundations on sandy soils is important to geotechnical practicing engineers. Design of foundations includes soil parameters and bearing capacity of foundation. This paper presents the results of laboratory experimental model tests of circular footings supported on sand deposit under static load. The finite element software Abaqus is used to compare the results. The effects of the relative density of the sand (30%, 50%, and 70%) and the diameter of circular footing (75 mm and 100 mm) are investigated. It can be concluded that the experimental test results fit quite well with the results of numerical method.

Abstract: In recent years, electrical resistivity method (ERM) has widely being applied as an alternative tool in engineering, environmental and archeological studies. A global image of groundwater seepage problem was difficult to obtained using conventional geotechnical method due to the efficiency of cost, time and result coverage. This study was conducted using electrical resistivity survey in order to investigate the potential of the problematic zone due to the groundwater seepage problem. ABEM SAS 4000 equipment set was used in during the resistivity data acquisition stage. Six (6) resistivity spread lines (SP) were performed across the slopes area using 2-D electrical resistivity imaging. The raw data was processed using RES2DINV and SURFER software for 2-D and 3-D subsurface image. Interpretation of electrical resistivity results was verified using the existing borehole and geochemistry results. Geochemistry results analyses were used Atomic Absorption Spectrometer (AAS) for determining cation and Ion Chromatography (IC) is for anions. Anion elements were studied consists of chloride, bicarbonate, nitrate and sulfate while cation elements consists of sodium, potassium, calcium and magnesium. All the elements were analyzed by using Piper Diagram to determine geochemistry facies in the groundwater. It was found that low resistivity value (ERV) which associated to groundwater (10 ~ 100 Ωm) can be found starts from the ground surface (0 m) to a greater (> 10 m) depth of the subsurface profile. The finding of the study water seepage can be categorized as Ca-HCO that indicator a typical of shallow fresh groundwater. The finding of the study is important to determine source process of water seepage on that area. This study has successfully demonstrates that the application of ERM with supporting borehole and geochemistry data was able to provide a comprehensive results due to the groundwater leakage detection.

Abstract: The observations and tests under small scale in 1-gravity condition are intended to obtain a comparative behavior of a model and prototype of geotechnical case by imposing the scaling relations. Simulations to represent a related structure, sub-soil and failure mechanism need to be prepared prior to do observations in this modeling. To simulate pile loading test (PLT) on clay, the following models of: clay, pile, driving simulation and procedure of PLT based on ASTM D4410 were set-up. The PLT in reduced scale environment was then followed by performing normal practice of full scale PLT in original clay site. Load settlement curves obtained from both “pile loading test” in small and full scale simulations showed closely good agreement. Further observation and investigation on simulation of pile loading test in clay revealed that modeling the following: clay sub-soil resulted in new properties of clay, e_m=e_p+λLn(N) which reflects stress scaling factor, N, pile size and pile driving hammer need scaling factor n and n³ respectively whereas PLT time needs time scaling factor, t_p (n)^0.5.

Abstract: In Malaysia, total dumping sites are 73 sites, controlled dumping sites are 71 sites and sanitary landfill are 11 sites. These disposal sites will increase over time because population in Malaysia has been increased at a rate of 2.4% per annum or about 600,000 per annum since 1994. The increase in population would increase the amount of waste generated. Thus, it will increase the number of dumping sites. The dumping area which has a full capacity of waste will eventually closed. These closed dumping area which are to be developed for new development are prone to settlement. The settlement at dumping area are to be predicted and simulated using Power Creep Function. The heterogeneous content of waste soil from dumping area are complicated to characterize and classified. The content of waste dumped at the dumping area is important to analyse because the degradation process changes with time. The degradation process are called power creep function. Power Creep Function (PCF) is time dependent deformation which is under constant stress. The two constant variables which are M’ and N’. M’ is the compressibility constant and N’ is rate of compression varies with age placement condition. The input parameters for PCF are H₀, ∆σ, t, Tr, M’ and N’. These parameters are simulated based on two cases whereby, case 1 where M’ and N’ are kept constant and time (t) increases from 25 days to 75 days. Tr is kept constant at 1 day. Case 2 is where M’, N’ and Tr are kept constant and time (t) increases from 240 days to 730 days. The settlement prediction at the dumping area for Case 1 is 0.024 meters to 0.042 meters and for Case 2 the settlement is in the range of 0.074 meters to 0.130 meters. The prediction of total settlement for dumping area would be used to determine the depth of foundation for the new development at the dumping area.

Abstract: Soil velocity profile often used as subsurface characterization by using geophysical technic. Seismic refraction is one of geophysical technique to determine primary wave (p-wave) velocity of soil profile. In this paper, seismic refraction technique has been performed on two different types of soft soil (peat soil and RECESS clay) for comparison of its p-wave velocity soil profile. From p-wave velocity soil profile comparison, its show the peat soil has soil velocity range from 211 m/s – 534 m/s at depth of 0 – 4 m while the soft clay show soil velocity range from 248 m/s – 1842 m/s at depth of 0 – 5.5 m. The profiles of peat soils and RECESS clay have been verified using peat samplers and existing borehole data. Both of velocity soil profiles, indicated that peat soil have lower velocity compare with soft clay due to its unique and soft soil characteristics. The difference of p-wave velocity soil profile between peat soil and soft clay are clearly showed both soils have different soil p-wave velocity with different soils characteristics.