Numerical Simulation Study on the Influence of Different Factors on the Uplift Bearing Capacity of Root Piles, Straight-Shaft Piles, and Pedestal Piles

Root pile (hereafter called RP), which is a promising new type of noncircular cross-section-shaped pile and meets the requirements of the development of the uplift pile, was introduced for promotion. On the basis of validation of experimental and numerical results, finite element models were established to study the influence of the arrangement of roots and dimension parameters on the uplift bearing capacity and the economy of RP compared with that of the straight-shaft pile and pedestal pile (hereafter called SP and PP, respectively). The results show that the uplift bearing capacity of RP is higher than that of SP and PP, and the longer the pile length is, the more the bearing capacity of RP would increase compared with that of SP and PP. In order to further improve the bearing capacity of RP, the bearing mechanism of the root was analysed, and the suggested values of root size and spacing of layers are given. In addition, the most economical way to increase pile bearing capacity is to increase pile length rather than increasing pile diameter.

Comparative Analysis of the Compression and Uplift Bearing Characteristics of PHC Pipe Pile on the Same Site

Introduction: The analysis of single pile behavior is an important foundation for the analysis of group pile foundation and other complex pile foundations. Methods: Based on the analysis of the load transfer of the compression pile and the uplift pile, the DoseResp model is used to fit the normalized load transfer function. Results: The results show that the load transfer function of the uplift pile and the compression pile has similar characteristics, the goodness of fit of the DoseResp model to the test data is greater than 0.99, which can better reflect the load transfer law of the pile. The fitting parameters in the DoseResp model mainly depend on the end resistance sharing ratio, A2 (Top asymptote)is independent of pile type and soil property parameters and is close to 1. The DoseResp model is applied to the PHC pipe pile, and the method to determine the parameters of the model fitting is proposed, which can accurately determine the side resistance distribution of PHC compression and uplift pipe pile along the pile body. Under the same load, the amount of uplift on the top of the uplift pile is significantly greater than the settlement on the top of the compression pile. Conclusion: The end resistance sharing ratio of the compression pile and the uplift pile is between 5.76 and 12.80. The ultimate bearing capacity of the compression pile is 3.61 ~ 3.81 times of that of the uplift pile under the same geometric parameters.

Study of Reinforcement Scheme for Tunnel Heaving due to Excavation of Sunken Plaza over Subway Tunnels

The excavation of large area close to the top of the tunnel, is likely to lead to a big displacement and deformation of the tunnel, even endanger the safety of subways operation. Therefore, it has become a problem urgently to be solved that how to accurately predict and reduce the deformation of subway tunnel caused by excavation of sunken plaza. Build a numerical model in the finite difference software FLAC 3D, then according to the order of the construction organization, calculation and analysis four different reinforcement schemes in the process of the excavation of sunken plaza, the reinforcement schemes are Without reinforcement measures, adopt gantry soil-cement mixing pile reinforcement scheme, sinking square are at the bottom of the uplift pile reinforcement scheme and comprehensive use of soil-cement mixing pile of door and sinking square with uplift pile reinforcement scheme, then comparison and evaluation the effects of the four kinds of reinforcement schemes around the selected four indicators, they are the maximum vertical settlement of the tunnel, the maximum horizontal displacement value of the tunnel, the maximum convergence of a tunnel diameter and the minimum radius of curvature tunnel deformation curve .From the analysis, some conclusions can be drawn.

Study on Design of Uplift Piles According to the Elastic Foundation Beam Theory

Taking the every arranged uplift pile in a practical project for example and selecting the column strip on the scale board as the research object, this paper analysis mainly focuses on the pullout capacity of piles at different locations with different vertical loads from columns by using the Winkler elastic foundation beam model. The results show that design with assumption that uplift piles evenly share the net buoyance would lead to successive failure of the piles. Then further parametric analysis was conducted to study the influence of stiffness, thickness and column space on the vertical forces of piles. The conclusions could provide positive reference to related uplift pile design.

Analysis of Anti-Floating Measures and Construction Parameters of Shield Tunnel through River under Ultra-Shallow Covering

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.

Analysis of the Results of Pile Trial for the Subsidiary High-Rise Building of the Shandong Provincial Center for Culture and Art

The high-rise towers and podium of the Shandong Provincial Center for Culture and Art adopt post-grouting drilling bored pile (pressure loaded pile) and compaction-under reamed bored pile (uplift pile) respectively. Based on an off-site self-balanced static-load test of the two kinds of piles, the bearing capacity, displacement, technology for pile-forming, construction period, and engineering cost are presented in detail, and the design basis for the two piles obtaining high bearing capacity on soft soil is also preliminarily put forward. The results of this study provides a design reference for the similar projects in the western new district of Jinan City.