9 research outputs found
Scaled boundary point interpolation method for seismic soil-tunnel interaction analysis
Get PDFThis is the author accepted manuscript. The final version is available from Elsevier via the DOI in this recordThe scaled boundary method (SBM) is an effective numerical approach for analyzing elasto-statics of bounded and unbounded media. To enhance abilities of the scaled boundary approach, this method can be coupled with mesh free technology. In this paper a point interpolation based SBM is proposed to analyze seismic soil-tunnel interaction problems. In the proposed approach, boundary of the domain is modelled with the scaled boundary point interpolation method while the interior domain is modelled by the conventional finite element method (FEM). This is the first time that a mesh-free scaled boundary method is used to analyze seismic problems. The presented method has some advantages over previously presented mesh-free SBMs. In the scaled boundary point interpolation method, the shape functions have the Kronecker delta function property and do not require radial basis functions to discretize the boundary of 2D problems. A shaking table test is designed and used to verify the proposed method. It is shown that the proposed numerical approach leads to results that are in a good agreement with those of the designed shaking table tests
An investigation on the effects of adding nano-SiO2 particles with different specific surface areas on the physical and mechanical parameters of soil–cement materials
No full textSoil cement is a mixture of Portland cement, soil and water, in which hydration of cement and compaction causes the materials' constituents to bond together, making a dense and durable composition with low permeability and abrasion resistant. According to the definition of ACI 116R, soil-cement is a mixture of soil and a certain amount of cement and water which has been compacted to a high density. A more comprehensive definition has been provided in ACI 230 IR, which defines the soil-cement as a hard material with specific engineering properties produced by mixing, compaction and curing of soil, aggregate, Portland cement, additives and water. All types of soils can be used in soil-cement construction, except the organic and plastic soils and reactive sands. The most efficient soils for soil cement are those containing 5 to 35\% of fines passing sieve 200. However, the soils containing more than 2\% of organic materials are strictly unacceptable. Soil-cement application in dams and pavements construction has grown rapidly in recent years. These mixtures are similar to concrete, the main difference being the type and size of aggregate particles used. Soil-cement is principally made of round natural fines, while concrete is made of aggregates. Because most of the recent researches are focused on the addition of nano- on concrete, in this paper, we decided to use nano- particles in soil-cement and observe the out coming effects. Since there are no particles passing sieve 200 in concrete and this restriction does not apply to soil-cements, some tests were carried out on thenano- + soil-cement matrix because of the meaningful difference between concrete and soil-cement. The test procedure consists of moisture-dry density, unconfined compressive test, and hydraulic conductivity. In these tests, silica fume (with specific surface area of ) and, nano- (with specific surface areas of 200 and ) were added to soil-cement. The results show that adding certain amounts of nano- particles to soil-cement matrix can improve compressive strength and reduce impermeability and speed hydration reactions in the matrix in the presence of nano- particles
تأثیر نوع و مقدار محصولات پایه ی سیلیسی در پارامترهای رفتاری و مقاومت برشی مخلوط خاک - سیمان
No full textSoil cement consists of Portland cement, soil, and water, in which hydration of cement and compaction causes the materials to bond together making a dense and durable composition with low permeability and resistance to abrasion. According to ACI 116R, soil-cement is a mixture of soil and a certain amount of cement and water which has been compacted to high density. A more comprehensive definition has been provided in ACI 230 IR, which defines soil-cement as a hard material with specific engineering properties produced by mixing, compaction and curing of soil, aggregate, Portland cement, additives and water. All types
of soils can be used in soil-cement mixture, except the organic and plastic soils and reactive sand. The most suitable soil for soil-cement contains 5\% to 35\% of fine passing sieve 200. However, more than 2\% of organic materials in soil are strictly unacceptable. Soil cement application in dams and pavement construction has grown rapidly in recent years. Although soil-cement is similar to concrete, the main difference is in the type and size of aggregate particles used. Soil-cement is principally made of round natural fine aggregates while concrete is made up of coarser aggregates. Most of the recent researches are focused on the addition of various types of cement to mixture. In this paper, we decide to use nano- particles in soil-cement and observe the out-coming effects. According to what was mentioned above, tests were conducted on the soil cement/nano- matrix in order to find the stress-strain behavior of these materials. The test procedure consists of tri-axial tests on the soil-cement-silica matrix. In these tests, silica fume (with specific surface area of 21/g) and nano- (with specific surface area of 200 and 380 /g) were added to soil-cement. The studied parameters are curing time, types, and contents of silica production. The results show that adding certain amounts of nano- particles to soil-cement matrix can improve shear strength and change behavior of the matrix
Procedures used for dynamically laterally loaded pile tests in a centrifuge
No full textMost of the experimental work carried on pile behavior on centrifuge has been limited to monotonic or cyclic loading, or both. As dynamic loads generated by shocks and earthquakes are difficult to model in centrifuge, not much work has been reported in the literature on the impact mechanism to produce shock in-flight, though seismic loads can be well simulated by in-flight shakers. A complete experimental procedure, i.e., hammering system, measurements, and test procedures, has been developed to test on centrifuge lateral impact on piles. In the first part of the paper following the test procedure, the experimental set-up is detailed from the soil preparation and piles equipment to the horizontal hammering or impact system. Innovative parts of the system such as the impact system and its monitoring are described. The second part describes the feasibility and the practice of the impact device and the adopted procedure to test on centrifuge different types of piles _jacked, cast-in, and 1 g driven_ in sand. The first series of tests are focused on the evaluation of possible errors and influences due to pile position, boundary effects, and repeatability of tests. Scale effects have been studied by carrying out a series of modeling of models tests at 40 and 60 g. In conclusion, all these preliminary centrifuge tests have demonstrated that the complete experimental set-up including the impact system and its use procedure is achieved and able to perform horizontal impacted piles tests on centrifuge
Experimental study on the dynamic behavior of laterally loaded single pile
No full textInternational audienceTo improve the understanding of soil–pile interaction under horizontal dynamic loads and seismic events, a parametric centrifugal study was undertaken. Flexible piles with pile caps of different masses and instrumented with 20 strain gauges on the length of the pile were used for this purpose. The piles were impacted by a new horizontal impact device and the resulting displacement and acceleration for different levels of force were measured. The inherent basic parameters of soil–pile-interaction have been evaluated. An analysis of the damping in relation with depth and during vibration of pile is carried out. The equation of the movement of a beam equivalent to the pile under dynamic loading has been established and all the terms of this equation was determined using the experimental results. It shows that the value of internal damping of pile compared to other terms in the equation is insignificant. The term of inertia was divided into two parts, one related to the mass of the pile and the other related to the mass of the associated soil. The contribution of each term to the equation at different periods (or time of) of vibration was illustrated. Distribution versus time of the displacements and the reactions of the soil at any depth were deduced from the profiles of the bending moments by a double integration and a double derivation respectively. Then the dynamic P–y curves or loops were constructed based on these results. A static test has been performed with the same pile installed in the same conditions so that to obtain the static P–y curves. The procedures of experimental tests and P–y curves construction are explained and a comparison between static and dynamic P–y curves is also indicated
