Applied Mechanics and Materials Vols. 580-583

Abstract: In this paper, a soil-water coupled finite element analysis incorporated the macro-element method is carried out to investigate the effect of variable permeability coefficient on the consolidation of the ultra-soft ground using vacuum preloading. Sys cam-clay model is employed as the constitutive model of the ultra-soft soils. When the drain space becomes from 60cm to 40cm, there is significant acceleration in the numerical settlement of the ground using the constant permeability coefficient, which is quite different from the observational results. When the variable permeability coefficient where a liner relationship between the void and the logarithmic value of permeability coefficient is adopted is employed, there is a good accordance between the numerical and observational settlements. According to the distribution of variation in the void, the largest variation in the void occurs at the top several layers and therefore the predominant settlement can be attributed to the volumetric compression of the top several layers.

Abstract: To investigate the settlement deformation of subgrades, we used fractal theory and soil section technology to study the original foundation soil, and soils filled with 4%, 8%, 12%, 16%, 20% and 24% of A material. The results show that under consolidation pressure of 500 KPa and after one dry-wet circulation, the fractal dimension was 1.7 in the original soil, 1.78 in the soil filled with 4% A material, and 1.93 in the soil filled with 24% A material. Along with the increased dopant amount of A material, the fractal dimension of soil mass gradually increased, but after the dopant amount reached 24%, the increasing rate was very slow. With the increased addition of A material, the compression deformation gradually weakened, but after the dopant amount reached 24%, the changing rate was very small. We derived a prediction model between the dopant amount at a certain particle size and the fractional dimension. This model can be used to predict the dopant amount at a certain size. The reasonableness of this model when using single size was validated via engineering practice.

Abstract: In order to explore the disintegration characteristics of compacted loess, through the unsaturated soil disintegration instrument by independently developed,conduct the soaking disintegration experimental study on remolded soil unsaturated samples,obtained a series of experimental results:①The curves can be divided into the slow disintegration, rapid disintegration and stabilization of disintegration in three stages，the degree of compaction and water rate impact on rapidly disintegrating stage;②When the degree of compaction is certain,the disintegration rate decreased with the water contented increasing,the decreased amplitude is increasing with the moisture content increased to18%,the disintegration characteristics disappeared with the moisture content increased to 22%;③When the initial moisture content is certain, the disintegration rate decreased with the degree of compaction increasing, The time significantly prolonged when the disintegration completed. the decreased amplitude is increasing with the degree of compaction increased to 95%,the disintegration characteristics basically disappeared. Based on the relationship of degree of compaction and the moisture content to void ratio, the thesis establishes the model between the disintegration rate and the effective porosity ratio,the formula can be used to calculate the disintegration rate of compacted loess.The specific conclusions are:①When the critical moisture content increased to 22%,the disintegration characteristics disappeared;②When the critical degree of compaction increased to95%，the disintegration characteristics also disappeared.

Abstract: With the further development of urban construction, engineering blasting has had a wide range of applications. However, its application environment has become more and more complex relatively. Underwater blasting, one of the applications of engineering blasting, has been increasingly used in construction of subsea tunnel and immersed tube in recent years though it has a complex influence on surroundings in operation. For the study of shock wave absorption technology of underwater blasting, this paper analyses the effectiveness of bubble curtain shielding technology used in the underwater explosion by field experiment. The test result shows that intensity of underwater shock wave approximately reduced by 80% after passing through the bubble curtain, which indicates that the bubble curtain can effectively reduce the shock wave pressure in water; vibration caused by shock wave in water approximately reduced by 20% after passing through the bubble curtain, which reflects propagation law of shock wave has changed due to the effect of the curtain.

Abstract: The self-balanced test technology has been widely applied in the eastern soft soil region for many years due to its economy and convenience. However, few engineering practices could be found in the northwest loess region. In this paper, self-balanced load tests were conducted in the large-tonnage piles of a bridge project in Gansu Province. The methods determining the position of pile balanced point were studied. The positions of balanced points of test piles were also simulated using Finite Element Method (FEM). The test results show that the self-balanced method has good applicability for loess in the northwest region. The pile side friction is fully exerted and the test data could be reasonable and reliable. Besides, the shortages of traditional empirical method could be made up for if FEM is adopted, which makes the accuracy of the balanced point position improve effectively and provide a reference for field trials.

Abstract: Under the condition of plane strain, a 2D elastoplastic FEM is used to analyze the behavior of composite soil nailing bracing of deep excavation, then finite element method of stability analysis is applied to evaluate the stability of the soil-nail wall. The authors analyzed the difference between composite soil nailing and normal soil nailing. Through analyzing the effect of bracing parameters on the deformation behavior and stability of the excavation, some useful conclusions are obtained to provide certain references for the design and construction of composite soil nailing.

Abstract: With the development of the economy, the increasing height of slopes in surface mine will seriously threaten the security in Coal Mine Area. Therefore, how to accurately evaluate slope stability has become one important problem. Based on reliability theory and fuzzy theory, a new reliability analysis method-fuzzy point evaluation method is presented in this paper. It is more practical and efficient for slope reliability assessment because traditional evaluation method doesn’t consider the fuzziness of parameters. As a typical example, we applied the technique to a surface mine case under seepage conditions, and made comparison with the traditional reliability analysis approach. The results indicate that the conclusions from both methods are essentially consistent. However, because considers the fuzziness of parameters, fuzzy point evaluation method has more actual instructive significance comparing with the traditional mothod.

Abstract: Coarse-grained soil is the main material of embankment dams, it is one of the major study objectives of soil mechanics. This paper introduces a method that utilizes percolation theory to explore the influence of soil density on mechanical property from the micro perspective. First it proposes the concept of stress network among particles; then it introduces the method of applying renormalization group theory for deducing; finally it derives the conclusion that in a uniform coarse-grained soil, the porosity and the mechanical property present a relationship of linear.

Abstract: The problems of the amendments in the updated edition of SNIP 2.02.01-83 * “Foundations of buildings and structures" SP 22.13330.2011 “Foundations of buildings and structures” are discussed in the article". Theoretically, the depth of the core is not justified anywhere and the restrictions are made only on the basis of experimental data. The importance of the amendments should be displayed theoretically. In according to the newly adopted regulatory framework the results of the foundation settlement calculations for the limited states of the second (II) group by the layer-stack summation method with the justification of the amendments in the updated edition of SNIP 2.02.01-83 * "Foundations of buildings and structures" SP 22.13330.2011 "Foundations of buildings and structures” are shown in this article. In the second part of the article the optimum width selection calculation results of projected foundation and identification of the economic benefits of decisions made are shown.

Abstract: The semi-rigid base asphalt pavement structure was choose often used to the highway in our country, but the semi-rigid base asphalt pavement early damage almost has become a common phenomenon.In this paper, the rule and trend of mechanics response about pavement structure (the vertical displacement and tensile stress) were analyzed under the semi-rigid base choose different elasticity modulus and thickness by ANSYS for muti-layer foundation of semi-rigid base pavement design to provide reference.