Applied Mechanics and Materials Vols. 353-356

Abstract: Through experiments that were carried out to study the rock-like specimens with nine fissures under uniaxial compression by YNS2000 electro-hydraulic servo test system, to reveal the mechanism about strength and mechanism about crack expansion evolution laws of rock containing multiple fissures. Applying numerical simulation (RFPA) for the whole failure process of rock containing multiple fissures with reasonable parameters, the results present the influence mechanism of different confining pressures for strength and crack expansion characteristics. The experimental results show: the peak strength of specimens with nine fissures degrades obviously compared with complete specimens; Specimens containing multiple fissures begin to crack with tension cracks, and break with shear cracks finally. With the increase of confining pressure, the compressive strength of rock containing multiple fissures increases gradually; And crack expansion generally occurs on the middle diagonal fissure-plane under high confining pressure.

Abstract: Soil nailing has become an important excavation support system for its good performance and cost-effectiveness. It is complicated to predict deformation of soil nailing during excavating. The Artificial Neural Network (ANN) is developed very quickly these years, which can be applied in diverse applications such as complex non-linear function mapping, pattern recognition, image processing and so on, and has been widely used in many fields, including geotechnical engineering. In this paper, the artificial neural network is applied for deformation prediction for soil nailing in deep excavation. The time series neural networks-based model for predicting deformation is presented and used in an engineering project. The results predicted by the model and those observed in the field are compared. It is shown that the artificial neural network-based method is effective in predicting the displacement of soil nailing during excavation.

Abstract: The distribution of hydraulic pressure in fractured rock mass surrounding caverns after excavation and technique of stochastic generation of joint network are investigated based on discrete element method. In order to seal the oil in underground caverns with water in the actual engineering, a water curtain with water pressure is installed, and the changes of hydraulic pressure are simulated with a series of curtain pressures. It is shown that some joints that have been drained out during excavation can not be saturated if the water curtain pressure is less than a certain value. Water curtain pressure with a certain value gives a strong safe guarantee of saving oil in the underground petroleum storage caverns.

Abstract: The influence of excavation on surrounding buildings has been studied widely,but there was little attention to its reliability of reinforcement. In this paper, which was based on an excavation project of a security housing in Tianjin, about fourty thousand square meters, numerical analysis on wire poles were carried out by using finite element software Plaxis2D,and the comparative analysis is made with monitoring results.The results show that,when there is no reinforcement, foundation pit excavation will cause the displacement of wire poles more than allowed; after reinforcement, the numerical results of wire poles displacement conform to the requirements,monitoring data also shows that the wire poles displacement is in the allowable range. Results indicate that the reinforcement can improve the soil deformation effectively, and the design method is reliable.

Abstract: Shield tunnel through the river under shallow covering usually facing the phenomenon of tunnel floating due to the thickness of overburden layer inadequate,and resulting in flooding accident due to the overburden layer split.Aiming at the project of Hangzhou metro line one through the Tangjia river under ultra-shallow covering,checking the thickness of overburden layer and taking the measures of anti-floating plate,uplift pile and jet-grouting piles to resist tunnel floating;through the control of soil chamber pressure,driving speed and grouting pressure in the process of construction,tunnel axis is controlled within±30mm,the amount of surface uplift is less than 10mm,tunnel segments without breakage and leakage.The results show that using anti-floating plate,uplift pile and jet-grouting piles,and controlling the construction parameters strictly are effective measures to resist tunnel floating and ensure construction safety.

Abstract: Geocell protective slope is a kind of important ecological protection form, which is widely used in the geotechnical engineering field. Based on the finite element software ABAQUS, and combining with protective slope bodys mechanics performance in shallow soil, the finite element model of geocell slope protection is established under the conditions of rainfall seepage, and then we simulate the shallow and the overall stability of slope in rainfall seepage cases. The results show that the safety factor of slope body increased by about 14% when using geocell slope protection and it reduces the displacement of slope surface effectively, it prolongs the destruction time of the slope under the condition of continuous reduction of soil shear strength, and it further helps reducing the collapse or part of slope sliding of slope disasters.

Abstract: This paper based on a foundation pit in Tianjin shown the monitoring data and simulated the excavation process by finite element software ABAQUS. The lateral and vertical displacement of the top of slope obtained by calculating at different excavation stages were compared with the measured values. At last this paper made a conclusion about the deformation rules in the process of excavation, which can provide reference for design and construction of similar engineering.

Abstract: This paper investigates the strength and deformation characteristics of the sandstone-like material containing the preset filling joints. The test specimens are designed with different height-diameter ratio. The uniaxial compression and shear tests were performed during the experimental studies. The results show that: (1) the failure models of the 3 kinds specimens including ones without joints, ones with "cruciform" joints and ones with "intersecting parallels" joints are similar to the general trend, e.g. X-shaped conjugated single-slope shear failure and single-slope shear failure under compression and shear tests ; (2) under uniaxial compression, the performance of intact specimen is clearly affected by its size, and the strength of jointed one is significantly affected by the weakening of the structure. This impact depends on the joints conditions, e.g. joint density, with filling material or without filling material; (3) Deformation modulus E and Cohesion c have no significant change for the 2 kinds jointed specimens, but the internal friction angle is obviously affected by joints and their fillings. The internal friction angle decreases rapidly with the increase of joints number.

Abstract: Tailings dam is an important part of engineering construction of tailings pond. Stability analysis of tailing dam is of great significance, because it is the significant security risk of the project of tailings. FLAC3D program which based on Lagrange algorithm is especially suitable for solving the nonlinear large deformation problems in rock and soil mechanics engineering. After the adequate mastery of the soil layer structure, the physical and mechanical properties and the determination of the calculation parameters, the engineering software of FLAC^3D and the numerical analysis method are utilized to analyze the integral stability of the tailing dam of Guangxi Xinfa Aluminum Company in Jingxi county. It can provide a scientific basis for the stability analysis of engineering construction of another tailing pond.

Abstract: Slope stability is one of the problems of road construction which should be faced with and solve. Rainfall can reduce the shear strength of slope soil and raise the underground water level which can lead to increase slope soil pore water pressure. The influence of rainfall infiltration on slop is mainly to change the slope seepage field, increase dynamic and hydrostatic water load on the slope soil and decrease of soil shear parameters. More abundant rainfall of typhoon area could make the road slope stability more fragile. Based on Matoushan Mountain along 104 state roads in Taizhou city, Zhejiang province, slope instability disciplinarian on the condition of rainfall is studied using the method of numerical simulation in this paper. As the results, when the rainfall intensity was 0.006 m/h and continuous rain was in 24 hours, the slope surface compressive stress tends to zero which began to appear tensile stress area on the condition of self-weight. And when the rainfall intensity was 0.01 m/h and continuous rain was in 24 hours, the large area of the slope surface was tensile stress area which means to appear break zone in slope surface and likely to landslide at the same time.