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Fu W.-G.,China Jingye Engineering Corporation Ltd Company
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2014

The overall processes of 5 unexpected dangers in foundation pits are introduced from their initiation to treatment. The discussions on the results of dealing with the dangers show that the current management system of emergency rescue is hard to make timely and accurate judgment and proper decisions, so the more efficient system named core technology expert system can be tried. Its running mechanism is as follows: (1) The key to the emergency rescue is to judge danger accurately, and the core technology experts are invited to undertake this role. (2) After the dangers happen, the emergency leading group and designers for foundation pit should judge the criticality first, and then the core technology experts further judge and report to the relevant government departments. (3) The project owner dominates the rescue work and the government mainly monitors the legitimacy of the procedure, and government power can be used when people really need to be evacuated. The proposed emergency management system can ensure the benefits of construction units, government and related dwellers. Source


Fu W.-G.,China Jingye Engineering Corporation Ltd Company
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2013

In the technical code, the bearing capacity characteristic value of composite foundation is the sum of bearing capacity characteristic values of piles and soils adjusted by empirical coefficients, which is called the characteristic value design method. Due to the difficulty of determing the empirical coefficients, it is not easy to obtain the accurate results. The bearing capacities of the piles and the soils are based on the load tests. In the load tests, the bearing capacity characteristic values of the composite foundation and soils are directly confirmed by the relative deformation value, but the bearing capacity characteristic value of pile is indirectly confirmed by the absolute deformation value that first determines the ultimate bearing capacity of single pile and then the characteristic value. The above methods and indexes are not matched, and it is a significant reason leading to the inaccurate calculated results by means of the characteristic value design method. In the limit state design method, when the piles reach the limit state, the soil state is regarded as the limit state. The ultimate bearing capacity of the composite foundation is the sum of the ultimate bearing capacity of the piles and the assumed ultimate bearing capacity of the soils, and the characteristic value takes half. This method needs less empirical coefficients, and it is practical, more correctness and safety when the conditions are enough. Source


Fu W.-G.,China Jingye Engineering Corporation Ltd Company
Yantu Lixue/Rock and Soil Mechanics | Year: 2015

The designing and calculating methods for compressive bearing capacity of a single pile can be divided into two types, i.e. characteristic value method and ultimate value method, in the Chinese codes related to pile foundations. The bearing capacity of a single pile is obtained by directly summarizing the skin friction and the tip resistance. These methods have some conceptual and theoretical disadvantages, since the skin friction and tip resistance cannot be simultaneously mobilized due to different mechanical responses and deformation requirements at the pile skin and the pile tip. The ultimate value method is more direct, reliable, accurate and clear in concept, and is more ready to be used in parallel to international standards. Hence it is suggested here that this method is preferred in the standards. A contradiction may occur in determining the uplift bearing capacity of a single pile according to the results of pull-out tests using the different standards. Because of this, the natural unit weight of pile should be used in calculation, instead of the buoyant unit weight of pile. Further research should be conducted to explore the following two phenomena in revising the relevant codes: one is that the unit skin friction decreases when exceeding the effective length of the pile, and the other is that tension coefficients for pull-out pile in some engineering is far less than the recommended values in the relevant codes, especially when pile length is longer. ©, 2015, Science Press. All right reserved. Source


Fu W.-G.,China Jingye Engineering Corporation Ltd Company | Yang Z.-Y.,China Jingye Engineering Corporation Ltd Company
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2012

The prestressed anchors by pull-out resistance, cut-off curtains and mini-piles by shear strength together improve the overall stability of composite soil nailing walls. At present, it is the most mature and effective method for calculating the overall stability, which accumulates and reduces the resistance of these composite components. The key to the formulae is the reduction coefficient of breakdown resistance coefficient produced by the soil resistance, soil nails and composite components (the resistance coefficient is the ratio of the resisting torque produced by the components to the downturn torque produced by soil). They are empirical data and can be obtained from actual engineering data by inverse calculation arrangement according to certain assumptions. The studies on some critical excavations and the verified results show that there are reasonable ranges of combination coefficients when these components work individually and jointly, that is, they are 0.5~0.7 for prestressed anchors, 0.3~0.5 for cut off curtains and 0.1~0.3 for mini-piles. In addition, the sum of the breakdown resistance coefficients of soil and soil nails has the reasonable lower limit and it is about 0.86~0.97 (regardless of the other components function). When this condition is satisfied and the overall stability safety coefficient requirement is met, the movement of the excavations is generally small. Source


Fu W.-G.,China Jingye Engineering Corporation Ltd Company
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2014

There are three test types of ground anchor such as basic test, creep test and acceptance test in China, and performance test, proof test and extended creep test in US, and investigation test, suitability test and acceptance test in EU. In addition, there are some tests for some determinate aspects of anchor performance in US and EU such as lift-off test, oscillating load test, testing of corrosion protection, test for cyclic work load, etc. The demands for anchor tests in US code is relatively simpler while more strict and precise in EU code. The meaning and function of basic tests on anchor attract no enough attention in China. It should be more zetetic but not proof for testing and understanding the anchor performances more adequately. Source

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