Lateral Deformation Characteristics and Control Methods of Foundation Pits Subjected to Asymmetric Loads

Using the foundation pit at the Jianye Road Station of Hangzhou Metro Line 6 as a case study, the deformation characteristics of a foundation pit subjected to asymmetric loads is investigated in this paper using PLAXIS 3D numerical simulation software. The influence of active pressure zone reinforcement, passive pressure zone reinforcement, and increased thickness of the diaphragm wall at the loaded side on the maximum lateral displacement of diaphragm wall retaining structure of foundation pit is also systematically analyzed. The results show that the deformation of the diaphragm walls on both sides of the foundation pit is strongly inconsistent when subjected to asymmetric loads and is affected by the asymmetric load value and its distance to the foundation pit. In order to reduce the lateral deformations of foundation pit subjected to asymmetric load, two displacement control methods are adopted in the numerical simulations. It is shown that reinforcing the active pressure zone can reduce the maximum lateral displacement of the diaphragm wall on the loaded side to a certain extent but the reinforcement should have a certain depth, resulting in poor efficiency. On the other hand, reinforcing the passive pressure zone can effectively reduce the difference in lateral deformation between the two sides of the foundation pit by increasing the depth and width of the reinforcement zones. It is also observed that the increase in the thickness of the diaphragm wall can reduce the adverse effect of asymmetric loads on the foundation pit. The research results can provide reference for using measures to reduce the influence of asymmetric loads.

A Case Study on Field Monitoring Analysis of Deep Foundation Pit in Soft Soils

Field monitoring in the process of excavation of foundation pit is an important measure to reduce the risk. This paper describes a case study of the filed monitoring data during the process of deep foundation pit excavation in soft soil areas. The displacements of the diaphragm wall top were analysed and found that the horizontal displacement showed the convex shape, while the vertical displacement showed the concave shape. Based on the field monitoring data, the deformation mode of lateral displacement of the diaphragm wall belonged to the composite mode. The relationship between maximum lateral displacement and excavation depth showed a strong linear correlation. The horizontal displacements of bracing pillar decreased with the increasing of bracing stiffness, while the effect of bracing stiffness on vertical displacements of bracing pillar could be ignored. The settlement profile computed using the method of Hsieh and Ou was in good agreement with the field observations and better described the development trend of the ground surface settlement. The ratio of the maximum ground surface settlement (δvm) to the maximum lateral displacement of the diaphragm wall (δhm) was in the range of 0.74∼0.88, belonging to the range of 0.5∼1.0 proposed by Hsieh and Ou. This paper provides a reference basis and related guidance for similar projects.

The Affectivity of Various Wind Condition and Shear Wall Opening in Multi-Story Building on Displacement by Changing Shear Wall Location and its Configuration

Shear wall system is used as one of the most lateral load resisting systems in mulit-story building. Shear wall is quite effective in resisting wind and seismic load in medium-rise and high-rise building. Shear wall provided high stiffness and strength, which can be used to resist large lateral as well as vertical load, making the performance of the building beneficial in various wind load conditions. This study has been focused on the displacement of the different lateral load resisting system for high-rise buildings under various wind load conditions. In this paper, a study was carried out by changing the locations of shear wall radically to determine the structural configuration of a multistory building accordantly. This study has been focused on the effect of addition of shear wall at different location and configuration in buildings without shear wall as well as with shear wall. Besides that, from the software results, the behavior of the shear wall with and without opening was able to observed by obtaining the lateral displacement when acted by 10kN point load at the top left of the wall. The accuracy of the software was able to verify by comparing the result obtained from ETABS and SAP2000 and it was found that the percentage difference between values obtained from that two software is below 20 percent. The maximum lateral displacement at 40m/s and 50m/s is 1.8 and 2.8 times bigger than maximum lateral displacement at 30m/s respectively. The lateral displacement of the shear wall increases as the opening size increases.

Study on Numerical Simulation of Construction Processing for No.1 Shaft of Weihe Tunnel

In order to analyze the construction processing for No.1 shaft of Weihe Tunnel on Baoji-Lanzhou Passenger-dedicated Railway, a two-dimensional numerical model for the simulation of the shaft was built with the finite difference method. Mohr-Coulomb model was chosen as the soil constitutive model. The result shows that the maximum lateral displacement appears at the upper part of the shaft, and the lateral displacement is in effective constraint at the shaft’s bottom. After the construction, the maximum uplift at the shaft’s bottom is in the center, while the uplift decreases from the shaft’s center to its both sides. The maximum pressure stress turns up at the bottom sides of the shaft, and the maximum tensile stress appears at the middle of the shaft.

Research on Influence of Concrete Pouring Sequence on Stability of High-Formwork Support System

ANSYS finite element analysis software is used to simulate the changes of maximum lateral displacement of the high-formwork support system in different sequences of pouring concrete. In the condition of loading which was applied from one side to the other side, the maximum lateral displacement of the frame had a sudden increase in each loading process. In the condition of loading which was applied symmetrically, the maximum lateral displacement of the high-formwork steadily rising nearly straight with the load applied. So the symmetrical pouring concrete ways is better for the whole stability of the high-formwork.

Parameter Sensitivity Analysis on Deformation of Composite Soil-Nailed Wall Using Artificial Neural Networks and Orthogonal Experiment

Based on the back-propagation algorithm of artificial neural networks (ANNs), this paper establishes an intelligent model, which is used to predict the maximum lateral displacement of composite soil-nailed wall. Some parameters, such as soil cohesive strength, soil friction angle, prestress of anchor cable, soil-nail spacing, soil-nail diameter, soil-nail length, and other factors, are considered in the model. Combined with thein situtest data of composite soil-nail wall reinforcement engineering, the network is trained and the errors are analyzed. Thus it is demonstrated that the method is applicable and feasible in predicting lateral displacement of excavation retained by composite soil-nailed wall. Extended calculations are conducted by using the well-trained intelligent forecast model. Through application of orthogonal table test theory, 25 sets of tests are designed to analyze the sensitivity of factors affecting the maximum lateral displacement of composite soil-nailing wall. The results show that the sensitivity of factors affecting the maximum lateral displacement of composite soil nailing wall, in a descending order, are prestress of anchor cable, soil friction angle, soil cohesion strength, soil-nail spacing, soil-nail length, and soil-nail diameter. The results can provide important reference for the same reinforcement engineering.

Study on Deformation of Steel Cylinder during Artificial Island Construction

A model is founded to simulate the process of artificial island construction by numerical analysis method. The displacement and deformation of the steel cylinder are analyzed. From the results, the settlement of steel cylinder is great, and the maximum is 28.5cm. At the same time, the steel cylinder has lateral displacement in the process of the island construction. The maximum lateral displacement is 12cm. The major influencing factor to the deformation of steel cylinder is the construction of filling sand inside and outside of island and flinging stone. Therefore, the settlement and displacement of steel cylinder should be monitored nearly during this construction step.

The Influence of Vertical Loads on Lateral Deformation of Steel Reinforced Concrete Column

The influence of vertical loads on steel reinforced concrete column is analyzed, based on the maximum lateral displacement of 2 different steel reinforced concrete columns under different vertical loads. The vertical loads, the section properties of the steel reinforced concrete column and horizontal loads are the influencing factors.