Papers by Keyword: Soft Soil

Abstract: Soft soil consists of inherent properties where it is unstable in geotechnical condition with low shear strength. The present of soft soil is one of the problematic ground conditions that can pose great challenges in the related field. Moreover, soft soil is not suitable for being used in the construction of highways and buildings due to its undesirable characteristics such as high-water content, low shear strength, low bearing capacity and low permeability. Thus, soil improvement will be crucial in future geotechnical practice for designing structures in weak soil. The aim of this study is to investigate the effectiveness of the use of coconut shell ash (CSA) as an additive material to improve the strength of the soft soil. Preliminary tests were carried out on the soft soil sample for identification and classification purposes. Then, engineering tests were carried out such as compaction tests to determine the optimum moisture content (OMC) and maximum dry density (MDD), Un-confined Compression Test (UCT) to assess the unconfined compressive strength of the soft soil when mixed with 0, 5, 10, and 15% of CSA. Finally, this study resume that the coconut shell ash can act as a stabilizer that will lower the cost of treatment and will benefit the environment.

Abstract: Stone columns have been used widely to improve the engineering properties of the weak soil. Most of the previous works considered a circular section for the stone columns. In the present study, finite element analysis has been carried out to investigate the effect of stone columns shape and length on the settlement and bearing capacity of soft soil. Accordingly, three types of cross sectional shape for stone columns have been selected which they are circular, rectangular, and square sections with equivalent area. Various length of columns are adopted with diameter of 0.75m that achieved length to diameter or equivalent diameter ratios (L/d=2, 4, 6, 8, and 10) of columns spacing (S/d=3). The results show that the stone columns has tangible effects on the settlement of the soil while has minor effects on the bearing capacity. The settlement of the treated soil with stone columns have L/d=2, reduces by 18.0, 17.3, and 19.3% for circular, rectangular , and square sections respectively. With increasing length of the columns to L/d=10, further reductions in the settlement obtained of (27.1, 28.1, and 27.0%). Bearing capacity of the soil increased slightly with length of the stone columns. Almost all cross sectional shapes of the columns give bearing capacity about same. The increased in the bearing capacity of the treated soil with stone columns have L/d=2, not exceeded 10% for all sectional types. The average increments in bearing capacity when L/d=10 are 12 and 15% at settlement 50 and 100mm respectively. Insignificant changes in bearing capacity upon increasing length of columns from L/d=2 to 10 of maximum 5%. The plastic zone recedes with the increasing length of the stone columns. Finally, from the results obtained, it can be concluded that the stone columns shape has negligible effects on the settlement and bearing capacity of the soil.

Abstract: Soft clayey soils cover wide Iraqi areas specially the regions close to rivers and the southern part of this country Heavy weight structures like: highways, dams, multiple story buildings are suffering unacceptable settlement, when constructing on soft soils. The high contamination of water in such soils decrease the effective stress and reduce bearing capacity. The need was appeared to improve such problematic soil by the use of new technique of stone column treated with different percentages of natural bentonite by a series of field tests using full scale concrete footing constructed on soft soil in addition to a laboratory model to investigate settlement with time at constant stress. The soil that used in this study is natural clayey soil, brought from a location south of Diyala governorate, from a farm area. The study includes also: The effect of stone column diameter treated with bentonite on the behavior of footing constructing on soft clayey soil, The effect of stone column length on the behavior of footing on such soils. Results of field and laboratory model tests reviled that the treated model by stone column mixed with 40% bentonite is the ideal one, which reduces the settlement by 55%. In other hand problems of uneven settlements appear when using 60% bentonite as a mix proportion. The Ideal slenderness ratio (Ds/Ls<25%). The effective depth of stone column treated with bentonite is (1/3H).

Abstract: A series of consolidated-undrained (CU) triaxial compression tests and dynamic triaxial tests on mucky clay material were performed in the present paper, and the dynamic behaviors of mucky clay material for different dynamic stress amplitudes and initial static deviator stresses were studied. It is indicated that both the accumulated strain and the pore water pressure increase rapidly with increasing number of cycles. While after a certain number of cycles, the accumulated strain tends to be stable and there is enough time for the equilibrium of pore water pressure. Results also show that the influences of dynamic stress amplitudes and initial static deviator stresses on the accumulated plastic strain and pore water pressure of the mucky clay material are significant.

Abstract: Several investigators have extended the numerical analysis to model ground improvement using soil-column to support structures. Cement columns are widely used to improve the load deformity characteristics of soft soils. This technique would increase soil bearing capacity and reduces soil deformation owing to improving of soil strength and stiffness. The aim of this paper is to determine the rigid pavement structure deformity on soft soil for the cases of with and without column soil cement. Two geometrical models were used in this analysis: (a) without column soil cement and (b) with column soil. The result indicated that the presence of soil cement column considerably contributes to the decrease in deformation due to the increase in stiffness.

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.

Abstract: To meet the requirements of foundation bearing capacity, end bearing piles are adopted by most of the Sluices built on soft soil foundations. However, after the completion of the sluice, there will be settlements on both sides of the backfill, which will result in base cavity, form water seepage channels, and endanger the buildings and dams. In this paper, a new steel sheet pile diaphragm wall scheme is proposed to resit seepages under this situation. Steel sheet pile diaphragm walls are disposed on the river side of the building and connected with the chamber floor to prevent wound infiltration and sliding sideways. The practical results show the effectiveness of the proposed scheme.

Abstract: Soft soils are well represented as the foundation of buildings all over the world. Settlements of buildings that are built on soft soils are developing over decades and often uneven. This can cause structural damages to constructions and as consequence unplanned repairs or even collapses of buildings in general. To justify the use of different models of soil mechanics it is necessary to carry out their verification. Verification of the model consists of compliance to the simple laboratory experiments and of the adequacy of the field tests description. And the most important thing is that the results of calculations should be based on comparison between series of field observations. The principal difficulty of comparing calculation results with field observations is that the actual soil deformation is developing over a long time, and most of the calculation methods are aimed to obtain finite values of deformations. Comparison between data of finite deformations and data of field observations is not quite correct, because, as a rule, in-situ (field) observations recorded incomplete development process of deformations but not only the final result of settlement. Therefore, to compare these calculations and observations we should select calculation models that can examine the development of deformations in time. Based on the above, it is interesting to analyze the applicability of the most common engineering methods and calculation models of the soils that underlie different calculation programs used in practice.

Abstract: At coastal beach soft soil area, reclamation projects may have great effect on the deformation of the existing underground pipeline. In this paper, the engineering specification method and the finite element method are used respectively for the pipe deformation calculation of the application of platform on piles to handle such underground pipeline deformation control. The results show that the application of platform on piles can effectively diminish the settlement deformation of the existing underground pipe. Co mparing the two calculation results and the monitoring results, the finite element calculation results are more in line with the actual. By appropriately increasing the width of the platform and the pile spacing, the initial design program can achieve a more optimal solution.

Abstract: Soft soil’s properties including low bearing capacity and large deformation leads to the necessity of reinforcement of foundation when it is made of soft soil. This article illustrates the features and applications of different methods, through the comparison of them.