Advanced Materials Research Vols. 168-170

Abstract: The influence of mineral admixtures on mortar brittleness is analysed in this paper. Test results show that the mortar brittleness increases with the increasing of compressive strength and the passage of age. When the content of binding materials rises, the compressive strength also increases, but the brittleness decreases at the same time. The more the content of fly ash is, the more the brittleness falls. Silica fume added can not only enhance compressive strength but also reduce brittleness of the mortar. MgO added can cut down the brittleness, but can reduce the compressive strength a little at the same time, especially for early compressive strength.

Abstract: Cyclic triaxial and cyclic torsional shear tests were performed on undisturbed marine silty clay by the hollow cylinder apparatus, and the Young’s modulus and shear modulus were obtained respectively. Furthermore, the influence of effective confining pressure and stress ratio on dynamic Poisson’s ratio was investigated on this basis. It was found that the dynamic Poisson’s ratio increases with generalized shear strain, but decreases with increasing effective confining pressure and stress ratio. The effect of effective confining pressure and stress ratio on dynamic Poisson’s ratio was weakened as the generalized shear strain was increasing. The dynamic Poisson’s ratio was about 0.48 when the Poisson’s ratio was increased to 1.8E-2 or so, and the test was terminated. There was no shear dilatation during all tests because the Poisson’s ratios were smaller than 0.5. It indicates that the marine silty clay tested in this paper has a good stability under cyclic loads.

Abstract: AE signal waveform Envelope is damped oscillation process, its maximum amplitude descending edge Envelope is exponential rule decay oscillation process ，others noises higher than oscillation delay. The thesis analysis rock AE and noise signal in the mine，on the basis of Fourier transform spectral analysis to found the noise spectrum characteristics, setting up noise database, according to the site data acquisition rock AE and environmental noise signal, with its characters spectral data to wavelet multi-scale decomposed，supplemented by Fourier transform spectral analysis, basing on noise spectral characters, some scale of wavelet decomposition is mulled, the signal of wave coefficient of the approximation elements reconstructed， eliminating disturbance and noise, showing real rock sounds. Results demonstrate that the recognition technique can advance effective data reliability and data analysis precision, making reality significant for monitoring and prediction on rock crack regular and development orientation.

Abstract: It is a complicated problem for consolidation analysis of unsaturated soils. Nowadays’ theories are very theoretical, and the parameters in them are so many that it is difficult to solve the equations, i.e., they are not excellently fit for application in engineering. So it is significant to get a simplified theory for consolidation analysis of unsaturated soils. In this paper, according to the phenomena observed in consolidation’s experiments for unsaturated soils, it is assumed that pore-air pressure undergoes an instantaneous dissipation and the consolidation of unsaturated soils can be described as the process of dissipation of excess pore-water pressure. Then a simplified consolidation model is put forward. And based on the principle of the whole soil mass conversation, the continuity equation is founded. Subsequently one- dimensional consolidation equation is derived, which is similar to Terzaghi’s equation for consolidation of saturated soils. Finally, the numerical results from the derived equation are compared with the experimental results from laboratory tests reported in the literature, and the agreement is good. It can be concluded that the hypothesis is rational and the simplified computation is practical in engineering.

Abstract: Rock pile is a typical kind of adverse engineering geologic phenomenon in mountainous engineering construction. In this paper, the Shui-ma(from Shuifu to Maliu Bay) expressway subgrade of rock pile in Yunnan Province is analyzed, and the mechanical properties of the rock pile are studied through indoor experiments. The results indicate that the main factor determining the engineering properties of rock pile is the particle composition, while the most influencing factor is the content of coarse particles. The relevant results can provide reference to engineering properties study of rock pile for other place.

Abstract: In order to evaluate the class of exposure to sulfate attack of soil, different methods were intended to measure the sulfate concentration of soil in contact with concrete in different countries. Different methods of soil extracts preparation were used to determine the sulfate ion content of soil in this paper. Two artificial soils and one natural soil were prepared in these tests. The experimental parameters investigated in the study were: acid or water extract, water to soil ratio and agitating time. When samples were prepared by water-extracting method, water to soil ratio (2:1, 5:1 and 10:1) and agitating time (3min, 6h, 16h and 24h) were considered. The results show that the difference of sulfate concentration determination results using different methods was significant. The determination results of dilute hydrochloric acid extracting solution are higher than that of water extracting solution of the same soil sample. The sulfate concentration determination results of the same soil sample have increased with the increase of water to soil ratio or agitating time. The water to soil (W/S) ratio is more sensitive than agitating time to the sulfate concentration determination results.

Abstract: Based on the theory of interaction between deep excavation support structure and subsoil, the influencing coefficient is presented in this paper in the condition of different foundation model. The calculation result shows that the foundation deformation considering interaction among soil springs is large than those not considering the interaction, and also larger than engineering practical condition. Theoretical analysis indicates the stiffness change of soil spring is related to spring rigidity in both active region and passive region when it is calculated by incremental method. The example proves that the method presented in this paper has good preciseness comparing with the results of engineering practical condition. So the theory of incremental method of deep excavation considering interaction is consummated.

Abstract: In order to analyze the influences of axial compression ratio and loading speed to the dynamic response and failure mode of RC columns subjected to blast loading, the collapse test for 6 reinforced concrete column models were conducted. Results show that there are three kinds of failure types: shear failure, flexural failure, flexural-shear failure. It tends to failure in shear mode when compression ratio is 0, and tends to failure in flexural or in flexural-shear mode when compression ratio is 0.5 and 0.25 respectively. The peak value of the exerted load and end moment will increase with the increasing of axial compression ratio in the first stage (approximately when compression ratio is less than 0.25) and then will decrease. The peak value of extra axial forces will decrease with the increasing of axial compression ratio.

Abstract: In order to insure the safe and reliable road-tunnel composite structure, it is important to consider the influence of different foundation treatment ways on the differential settlement of the composite structure. Based on the nonlinear FEM, connecting with the western corridor connecting project from Shenzhen to Hong Kong in China, a numerical model has been established to estimate the settlement of the road- tunnel composite structure under three different foundation treatment ways, such as pressure grouting, PHC piles (prestressed high-strength concrete piles) and foundation in natural state. This study shows that the influence of the different foundation treatment ways on the transverse and longitudinal differential settlement of the composite structure of road-tunnel is strong. The results from this study provide a useful guideline for settlement control of other similar projects composed of tunnel and road structure.

Abstract: In the numerical analysis of foundation consolidation by using dynamic compaction, many kinds of non-linear conditions exist. This paper adopts large deformation on the relationship between strain and displacement. Non-linear governing equation of soil, based on finite element method, is established. Iterative calculation form is raised. Finally, non-linear numerical analysis is done to a calculation example.