Advanced Materials Research Vols. 243-249

Abstract: The direct shear tests were conducted with undisturbed and reconstituted soft clay, then the structural influence on shear strength was studied, and the laws were got. No matter shear strength of slow shear or consolidated quick shear on undisturbed and reconstituted soil have not peak values, strength line of reconstituted soil is a slash, but the shear strength line of undisturbed soil is obviously a broken line. The internal friction angle of undisturbed and reconstituted soil is basically the same. There are good linear relationship between internal friction angle and plastic index of clayey soil. The amplitude of internal friction angle of reconstituted soil decreasing with plastic index increasing is less than that of undisturbed soil. From w_f-lgp curve can be seen, with the increasing of vertical stress, water content of shear failure decrease gradually, and linear correlation of each curve is very good.

Abstract: The main influences of plants on the mass stability of slope are those that affect the strength of soil. Plants enhance soil strength by directly reinforcing soil material with their roots. In this paper we do not consider slope hydrology but focus on quantifying increases in plant root growth. Root length is a function of growth time. In this paper, the sigmoidal models have been used to analyze plant root growth with time. Field studies of slopes of YU Tong road , two kind of tree, weeping willow, alamo and three kind of plant, Tall fescue, Bermuda grass and White clover indicate that slope reinforcement, due to the roots of these species, increases exponentially with time below the soil surface. Differences in the root length of tree and plant are illustrated by Logistic model, Richards model based on measured data.The measured data are a large scattering and is diffcult to find growth trend and predict the final length in one season. The data must be process before used in practical engineering. Sigmoidal models are a good tool to determine the growth-time curves of root length. For this purpose, two different sigmoidal models were used to define the curves of root growth, namely Richards model and Logistic model. The coefficients of Richards model for plant were 0.9964591, 0.998516, 0.9964465 and Logistic model for tree were 0.984001, 0.9957275 respectively. The analysis results show that Logistic model, Richards model are suitable models for explaining root growth.

Abstract: The finite element calculation results indicated: interaction of the superstructure-the pile raft foundation-foundation, the stress of the pile raft foundation appeared "disc type" distribution, namely, was big in the middle, and was small in the edge. Generation of differential settlement was due to the upper structure secondary stress and raft internal force. Through adjusting the foundation soil stiffness and pile length, pile diameter and pile distance, the influence of variable stiffness on differential settlement was analyzed. The results showed that changing the pile arrangement and adjusting the stiffness of foundation soil was optimal scheme of the pile raft foundation in high-rise building.

Abstract: During the period from October 2000 to November 2005, the canister in the CRT deposition hole DD0092G01 was heated with a maximum heat power of 2600W and the temperature and consequently the stress in the surrounding rock volume were elevated. This study investigated if the temperature and possible heat induced damage can be predicted by 2-Dimensional numerical simulations. FLAC2D(5.00) was used to model the excavation and the heating process of the deposition hole. Temperature in the rock was calculated by treating the case either as a horizontal two dimensional or a vertical axisymmetric problem and obtained results were compared with the measured results, whereas stress was calculated from horizontal two dimensional thermal-mechanical coupling analysis and calculated results were applied to approximate damage analysis.

Abstract: Deformation of the geo-grid rein-forced retain fly ash wall and the reinforcing effect of geogrid reinforcement, depends largely on the role of interface properties between the geogrid and fly ash. Interface in the numerical simulation of the mechanical properties of the main elements reflected in the geogrid on the constitutive parameters,for example, shear stiffness,Cohesion,Modulus, reinforcement length and so on. In this paper, geogrid reinforced fly tangential stiffness, cohesion, elastic modulus, reinforcement length and other parameters on geogrid reinforced retaining wall deformation characteristics of fly ash for numerical simulation and comparative analysis,Obtained parameters on geogrid reinforced retaining wall mechanical behavior of fly ash, stability and reinforced the effect of law, Provide theoretical and analytical basis for the geogrid reinforced and reinforced fly ash characteristics of the interface wall wide application in engineering.

Abstract: Roadway loose scope nearby the excavation section was tested by sound wave loosing zone testing instrument. According to the analysis: the shorter distance to the excavation section, the more influence by blasting vibration; the influence is decreased along with the distance increased, and finally to stabilize. Meanwhile, numerical simulation on effective stress of rock nearby blasting section was did with ANSYS/LS-DYNA, got the same conclusion as testing. The research result can provided a basis for reasonable selection of blasting parameters, reduce blasting vibration effect.

Abstract: Earthquake effects of two typical deep soft sites selected from Tianjin(site 1)and Shanghai(site 2) are studied when the vertical inputting earthquake waves are located in different depth of sites. As far as the shear wave velocity of soil layers is concerned, seven kinds of soil layers in site 1 and eight soil layers in site 2 are selected as the vertical imputing interfaces of earthquake waves. Two acceleration waves recorded during Taft earthquake and Northbridge earthquake are selected, and the peak values of two waves are adjusted to be 0.35m/s²、0 70m /s² and 0 98m /s², respectively. The earthquake response of sites is calculated by SHAKE91 program. The results are compared to those of site when the input interfaces of earthquake waves are located in bedrock with shear wave velocity larger than 500m/s. The conclusion is as following: With the depth of input position (or shear wave velocity) increasing, the value of the ground acceleration response spectrum gradually closes to the actual data.; For the general building the soil layer with shear wave velocity for 400m/s or so can be chosen as the input interface, and the building with long natural vibration period should be treated seriously, and the soil layer whose shear wave velocity is above 500m/s can be chosen as the input interface.

Abstract: Dynamic characteristics of the building is its own inherent characteristics, natural frequency is one of the main features. Using the earth pulsation and environmental incentive as inspiration vibration sources, testing and analysis of building the pulsation of the response signal and dynamic characteristics. Use of a complex building pulse test the dynamic performance is analyzed and the building of vibration frequency. Will get into the frequencies of the universal design software inversion get complex building conversion layers under actual work force value, and theoretical design value and the column were compared, and discuss the reasons.

Abstract: The prediction accuracy of vertical ultimate bearing capacity of statically-pressured pipe pile is difficult to ensure with traditional methods, because it is influenced by comprehensive factors, such as pile body, soil around pile and construction conditions. In this paper, a support vector machine (SVM) model based on the influencing factors importance evaluation was established to predict the vertical ultimate bearing capacity of single pile. This method would consider grey relational analysis and variable projection importance analysis as the attribute preprocessor facilities, which could determine the vertical bearing character in typical geological conditions through the analysis results of these two methods. Then, the SVM model was established with the main factors influencing ultimate bearing capacity as input to predict ultimate bearing capacity of single pile. The results showed that this method would have better precision of prediction, and the established model would have better generalization ability, which would open up a new way for the theoretical analysis of bearing characters of statically-pressured pipe pile and provide references for future relevant research.

Abstract: Through the analysis on monitoring data of the deep foundation pit in Tianjin, it was observed that the lateral deformation of the retaining wall at the corner was smaller than the deformation in the middle. Based on the analysis of the results drawn from finite element simulation of the excavation process and the monitoring data, appropriate supporting structure stiffness parameters values used in Plaxis and Qimingxing are recommended for designing deep foundation pits in soft soil area.