Applied Mechanics and Materials Vols. 90-93

Abstract: The direct shear mechanical characteristics of gravel, sand and steel particle were studied systematically using DRS-1 high normal stress direct and residual shear apparatus. The results show that the shear mechanical characteristics of gravel, sand and steel particle is different under different normal stress condition. For steel particle, the curves of shear stress-shear displacement present strain softening regardless of the magnitude of normal stress, and the shear displacement corresponding to the peak shear stress increases with the normal stress. Under low normal stress condition, the volume of fine gravel and steel particle expand, but the fine sand contracts at the beginning of direct shear and then contracts. Under high normal stress condition, the volume of steel particle contracts at the beginning of the direct shear and then contracts, but the fine sand and fine gravel contract throughout the direct shear. The particle breakage has significant effect on the shear strength of fine sand and fine gravel. Under the same high normal stress condition, the volume of fine gravel is greater than that of fine sand, which indicates that the fine gravel is easier to be crushed than the fine sand.

Abstract: It is of significance for pile foundation design and construction to predict the penetration depth accurately of the displacement pile under a fixed pressure. A new type cone penetrometer and corresponding exploration methods are developed through increasing weight of the device, enhancing the strength of probing rod and probe, and embedding a new function on measuring the total penetration resistance. Not only applied appropriately to various strata except for pebble bed, functions such as the total penetration resistance determination, soil layer classification and soil compression modulus and dynamic-static friction ratio calculation are also provided. Data of total penetration resistance, static point resistance and side friction are measured with the new type cone penetrometer, a new coefficient of dynamic-static friction ratio is introduced and employed to calculate the dynamic side friction, a new estimation method, with which the influence of dynamic side friction is take into account, on penetration depth evaluation of the displacement pile is established and proposed subsequently. Validity of the new method is verified by means of case study of pile engineering and the results indicate, for its high accuracy, the method proposed is of practice and theoretical significance, as well as valuable for popularization.

Abstract: According to the monitoring results of soft clay treated by preloading with plastic drainage pipe, the consolidation settlement effect of soft clay with 50kPa preloading load, 21m plastic pipe, 1.2m and 1.5m distance was compared with that of 30kPa preloading load, 6m plastic pipe, 1.5m and 2.0m distance. The analysis showed that, the preloading method with deep plastic drainage pipe can accelerate the dissipation of excess pore water pressure in deep soft soil. The over-flow penetration may occur in the confined water. The elastic deformation appears and recoveries after unloading. This is not conducive to the consolidation of soft clay layer 4. The plastic drainage pipe whose depth and distance should be 18~20m and 1.5m respectively to the consolidation soft soil in Pudong.

Abstract: Cone penetration test is a fast and efficient in-situ test technique. With the development of sensor technology and the use of new probes, such test is employed in more fields and reveals more soil parameters. Based on advanced CPTU equipment, soil types were classified. As CPTU has the function of porewater pressure test, the value of porewater pressure varies a lot when the soil changes, which is shown clearly in the CPTU feature map. So it can be easier to judge soil boundaries and its result is in good agreement with the borehole. Multi-function CPTU system is equip with SCPTU module, which enable to measure shear wave velocity of the soil easily. To meet the needs of conventional CPT equipment, the relationships between shear wave velocity measured by SCPTU and other CPT indexes were analyzed; then, two empirical formulas which suitable for kinds of soils are proved more consistent with the measured results, so it is a good method to estimate shear wave velocity without seismic wave test. With a view to get greater economic and technical benefits, more cone penetration testing experience in different regions should be accumulated for geotechnical engineering investigation and design.

Abstract: Slope stability analysis remains an active and important area of study for geotechnical engineers. The vast majority of slope stability analysis is performed in two dimensions. But in real practices, 3D slope results are more reasonable. Due to the remarkable increase in computational power and falling costs in recent years, meaningful 3D analysis can now be performed on a conventional desktop or laptop computer. In the present paper, a two-dimensional limit equilibrium model was established by LiZheng Slope Analysis Software. Using the FLAC3D program, a 3D plane strain model was proposed and the stability analysis was implemented, placing the results in context with 2D methods. The results show that safety factors got from the 3D plane strain model were closest to the Simplified Bishop method, and the average deviation of these two methods is 1.6%, the largest deviation is 3.2%. With the refinement of FE mesh or improvement of element type, the deviation could be smaller.

Abstract: In order to solve the problem of great error in calculating the Yellow River alluvial plain highway’s foundation settlement with delamination summation-method and regulate formula method,we put forward the reason of calculating the final settlement by drilling standard penetration number.It is according to the principles of delamination summation-method and elastic theory method and it is combined with engineering prospecting tests results.Finally,we inference the empirical formula in calculating the final settlement by standard penetration number.The comparison of the calculation of the final settlement by drilling standard penetration number and the statistics by actual observation of jinan-heze expressway has proved the correctness of calculation formula.

Abstract: The combined pile composite foundation has the advantages of good technical and economic effects, yet there are no mature analysis methods to practise in design and test at present. This paper has studied the three and four-element composite foundation by the plate loading test, in which the pressure cells, pressure manometers and sensors are laid on the top of the piles and soil. The results show that the stress on the top of piles and soil increases with the increase of total load, the increasing rate being directly proportional to the strength or relative rigidity of piles and soil. The various increasing rates of piles and soil stress versus load make great difference between the three and four-element composite foundation in the variation of the load sharing ratio and the stress ratio versus load. The settlement of the combined piles composite foundation varies gradually with pressure, and the p-s curve may be simulated by hyperbola curve so as to establish the failure criterion and obtain tangent modulus. As the pressure increases, the inter-pile soil enters plastic state earlier than the piles, so the latter have to bear majority of the load, which makes the settlement rise. The composite foundation should be designed according to settlement-control principle.

Abstract: Based on bolt support project of the 107th working face in Huangling the 2nd mine, the lesion range of large-span rectangular coal roadway is defined by the equivalent ellipse method to determine the support parameters. Site monitoring results indicate good support effect and correct support parameters. This paper provides new effective approach to support scheme for large-span rectangular coal roadways.

Abstract: This paper chooses anchored support engineering of ore dynamic pressure soft rock roadway Qinan, Huaibei city as an example, and with the help of nested mechanical analysis model of anchored support structure, the paper analyzes the range of elastoplasticity, the range of anchor note area, stress and displacement of original rocks of the reinforced project, and simulates three-dimensional finite element numerical and underwent engineering detection of the project. Practicality and validity of quantitative control design method of anchored support structure are proved by comparing the theoretic research, calculation results, and field measurement results.

Abstract: Due to the capacity limitation, congestions caused by the excessive amount of passenger flow appear in many Mass Transit Railway(MTR) hubs. Computer simulation is one of the most effective way to solve this problem. In this paper, an identification and elimination of capacity bottlenecks method was proposed based on dynamic movement of passengers simulation. Possible optimized solution was investigated through a case study in XiErqi Station, which is the transfer hub of Line13 and Changping Line in Beijing MTR. The proposed model was validated both statically and experimentally. Two optimization measures were dicussed after digging out the passenger feature and the essence of the congestions. One is improving passenger flow organization, the other is reforming operation organization. Then the simulate experiments were done through a proprietary software developed by Beijing Jiaotong University----SRail System. The simulation result shows congestion was alleviated effectively. It is proved that the method is feasible and effective.