Stability Of Pit Research Articles

Analysis of Rock Slope Stability on the Basis of Limit Equilibrium Method

To analyze the rock slope stability of open pit, limit equilibrium theory is used and the safety factor of slope stability is calculated by Geo-slope software. Then, the region where local instability or overall instability may occur is determined. Finally, some optimization plans and appropriate protective measures are suggested, providing a theoretical basis for engineering practice.

Study on Slope Stability & Stress-Deformation of Foundation Pit Based on FEA

In order to study the slope stress-deformation characters and stability of foundation pit after excavation, analyzed the examples based on the FEM theory, the results show :both the horizontal displacement of slope edge and settlement of slope top are small after support, and they are within the standard, deformation is not the reason for fissure: safety factor of slope is smaller than 1 after excavation, while the safety factor reaches require after support.

Design of Enclosure for Subway Station Foundation Pit in Southward Extension Line of Chengdu Metro Line One

This paper summarizes the design of open-cut subway station in Chengdu Metro line one. The station is built by cut and cover method and divided into three special parts with four different cross-sections used for main line and transfer track. Such retaining techniques as bored piles, steel pipe struts, soil nails, rock-bolts, steel-meshes, shotcrete and anchored steel cables are comprehensively used to maintain the stability of foundation pit. The anti-buoyancy coefficient of the open cut station is also derived and attains the requirement of safety and stability for the foundation pit after the utilization of these enclosure measures. The application of the design and construction technique for the subway station may provide guidance for the building of analogous subway station under similar geological and hydrogeological conditions in Chengdu.

A Method of Calculation on the Deformation of Column Piles in Deep Foundation Pit

During excavation of deep foundation pits, the effects of vertical deformation on column piles are often neglected while those uplifts may lead to destruction of internal supports. The factors leading to the column piles' vertical deformation mainly include basal uplift and vertical loads. In this paper, the causation and mechanism of the column piles' uplift are discussed. The influence of the additional bending moment due to the column piles' vertical deformation on the overall stability of the founda-tion pit is analyzed. A calculation method of the permissible value of vertical deformation is present¬ed. The method is verified by a practical case to be feasible.

Reinforcement Scheme and Numerical Simulation for Sequential Excavation of the Deep Foundation Pit

The deep foundation pit engineering of Wanda Plaza in Yinchuan city is taken as a case study and the corresponding numerical model has been built. The deformation and stability of the foundation pit during sequential excavation has been analyzed by using of the FLAC3D software. The weak positions which may lose the stability are predicted by the results from the numerical simulation. A soil-nailing reinforcing scheme has been proposed to maintain the stability of the foundation pit. To analyze the support effects of the soil-nailing, the Cable structure elements have been adopted to simulate the interaction between soil and soil-nailing. The calculation results show that the maximum horizontal displacement occurs in the middle part of the pit wall and the minimum occurs in corner part of the pit wall. The soil nailing support significantly decreases the deformation of foundation pit by dispersing internal stress of soil. The reliability of the simulation results has been verified by the comparative analysis between the numerical simulation results and the deformation monitoring data of foundation pit. The proposed reinforcement scheme is not only helpful to ensure the safety of Wanda Plaza foundation pit，but also provides valuable experiences for the reinforcement of similar foundation pit engineering.

Study on Mechanical Property and Displacement of Latticed Soil Nailing Support

Latticed soil nailing support is a new type of revetment structure, which combined lattice support and soil nailing. It effectively improves the global stability of the foundation pit. Currently, the theoretical research about this supporting method is still not consummate. In this paper, on the basis of soil mechanics and code, the stability of latticed soil nailing support are analyzed by the theory of the retaining wall, soil nail and the model of supporting piles. Then calculate the displacement in the limit state by elastic fulcrum method and the instantaneous displacement by layer-wise summation method. The total displacement can be calculated by the combination of the two displacements above, which is between 3.38mm and 15.43mm and close to the measured data. Simulate excavation and supporting process of the pit by finite difference method, analyze the mechanical property and displacement of latticed soil nailing support. Thus the theory of the calculation method to this supporting model is obtained, offering a reference for the similar projects.

Complexity and New Ideas of the Auti-Bursting Stability of Confined Water Foundation Pit

With the excavation depth increase，the bursting stabilization had become a major factor affecting the security of foundation pit. On the base of research situation about foundation pit stabilization and a large number engineering practices，the factors and the complexity that affected the stability of foundation pit were analyzed. The new ideas about mechanism and determining methods of bursting in foundation pit were proposed，that with the “hydraulic fracturing” to explain the mechanism of bursting and the factors that affect the stability of foundation pit as a system to analyze the anti-bursting stability and the factors that affect bursting stability could be divided into two types, system strength and system stiffness.

Stability on Supporting Structure of Deep Foundation Pit with Infiltration

The FLAC3D was used to the fluid-solid coupling numerical simulation of considering the initial state of unsaturated to soil for the deep foundation pit engineering under different rainfall infiltration conditions. By comparing the bending moment, the shearing stress and internal forces of support under the infiltration conditions between non-rainfall and rainfall, the paper focus on the stability of deep foundation pit. Research on the stability of deep excavation under rainfall conditions was a useful attempt. From the detail study of the stability of a foundation pit of Qinhuangdao under rainfall infiltration conditions, the paper have drawn some useful conclusion on the design of building foundation pit, which can be the basis of excavation design and construction under rainfall conditions.

Dynamic Inversion Study of Soil Mechanical Parameters in Wuhan Metro Gold Garden Station Foundation Pit

Based on the deep foundation pit works of Wuhan Metro Line 2 Gold Garden station, orthogonal test method, finite difference method and BP neural network method are synthetically used to do the inverse analysis study of mechanical parameters of foundation pit. The mechanical parameters are substituted in the finite difference process of deep foundation pit to simulate and calculate. The deformation and bearing situation of building enclosure and soil in the construction process of foundation pit is acquired, which is returned to the design and construction management to provide reference for design modification, construction optimization and engineering prediction, to ensure the security and stability of foundation pit and to greatly reduce investment outlay.

The Stability of Unsaturated Soil Foundation Pit Reinforced with the Cement-Mixed Sheet Pile Wall

The non-uniform distribution of matric suction in the unsaturated soil has a great impact on the stability of the unsaturated soil foundation pit. By means of the strength reduction finite element method, the stability of the unsaturated soil foundation pit reinforced with the cement-mixed sheet pile wall was analyzed. The overall safety factor of the unsaturated soil foundation pit reinforced with the cement-mixed sheet pile wall is greatly reduced and the position of potential sliding surface goes upward with the gradually decreasing of matric suction. With the constant height of the cement-mixed sheet pile wall, the shallower the embedding depth of the cement-mixed sheet pile wall is, the smaller the safety factor of the foundation pit slope is. The results show that the safety factor of the overall stability of the unsaturated soil foundation pit decreases with the deep excavation and the gradually decreasing of the matric suction.

Reliability-Based Stability Analysis of Foundation Pit Supported by Micro-Pile Composite Soil Nailing

Considering the co-action of micro-pile and soil nailing, the state equation of limit equilibrium and the performance function of inner global stability of foundation pit supported by the micro-pile composite soil nailing is set up with the slope limit equilibrium theory and the circular sliding slice method. The calculating model of sliding surface for inner global stability of foundation pit is established with the geometry controlling method and the optimization searching of the most dangerous sliding surface is achieved. Then with the shear strength indexes of soil as random variables, the partial derivatives of the performance function to all random variables is deduced and the reliability index of inner global stability of foundation pit supported by micro-pile composite soil nailing is calculated with the design checking point method. Finally, the effects of coefficients of variability of the random variables on reliability index are analyzed.

Assessment of Vibrations Generated by Structure Demolition Part I: Influences on Surrounding Environment

A triangular transfer hall is planned be built to distribute passenger flow rationally and improve multi-line transfer capability in the city of Shanghai, China. A large-scale reinforced-concrete bracing system, which is established to ensure the stability of the foundation pit, will be demolished with the completion of foundation pit. The influences of construction vibration on the surrounding environment are concerned. An evaluation method, which is generally applied to the ground vibrations caused by operation of machines, road and railway traffic, and construction activities such as piling and blasting, is then extended to assess the ground vibrations generated by structure demolition. It is found that the ground vibrations generated by demolition construction will affect the environment and human activities if without any vibration control measures.

Reliability Analysis of Stability of Foundation Pit Supported by Composite Soil Nailing

Based on the limit equilibrium theory and the circular slip surface method, the state equation of limit equilibrium and the calculation model of the most dangerous sliding surface for inner global stability of foundation pit supported by the prestressed anchor composite soil nailing is established with the disturbing force method. And the searching and solving method of the most dangerous sliding surface is optimized with the SLP optimization method and the simplex optimization method. Then with the mechanical parameters of soil as random variables, the reliability index of inner global stability of foundation pit is calculated with the design checking point method. Finally, a practical project is used to analyze the sensitivity of the reliability index to the coefficients of variability of all random variables.

Study Influence of Groundwater Seepage on the Deep Foundation Pit

Consideration of influence of the groundwater seepage and supporting measures to deep-foundation pit,the deformation characteristics of surrounding soil of the foundation pit are given. Seepage and deformation characteristics of surrounding soil are simulated to predict deformation of the deep foundation in ha er bing and stability of deep-foundation pit is analyzed base on the influence of the seepage. The analysis results are compared with observed data and it is showed that the calculated results with the model considering coupling response of permeability coefficient are closer to observed value than those results with the other model. So, the model considering fully coupling response of permeability coefficient is reliable and applicable.

Numerical Analysis of Block Caving-Induced Instability in Large Open Pit Slopes: A Finite Element/Discrete Element Approach

This paper addresses one of the most challenging problems in mining rock engineering—the interaction between block cave mining and a large overlying open pit. The finite element modeling/discrete element modeling (FEM/DEM) approach was utilized in the analysis of block caving-induced step-path failure development in a large open pit slope. The analysis indicated that there is a threshold percentage of critical intact rock bridges along a step-path failure plane that may ensure the stability of an open pit throughout caving operations. Transition from open pit to underground mining at Palabora mine presents an important example of a pit wall instability triggered by caving. Using combined FEM/DEM-DFN (discrete fracture network) modeling, it was possible to investigate the formation of a basal failure surface within an open pit slope as a direct result of cave mining. The modeling of Palabora highlighted the importance of rock mass tensile strength and its influence on caving-induced slope response.

Testing a seismic scenario for the damage of the Neolithic wooden well of Erkelenz-Kückhoven, Germany

Abstract A Neolithic wooden well was discovered and excavated between 1989 and 1992 near Erkelenz in the Lower Rhine Embayment. The construction, 3×3 m in size and 13 m deep, was exceptionally large for its time. The larger outer box-frame contained two smaller frames whose construction could be interpreted as an attempt to repair the damaged original well. The outer box was made from 160 oak elements of about 3 m length built in the blockhouse method. The large box is dated to 5090 bc and the two smaller ones to 5057±5 bc by dendrochronological analysis. At c . 8 m depth several elements of the large box are vertically sheared off and the broken parts moved inward and downward. The cause of this damage has not yet been determined. As the well is located only 3 km from one of the active tectonic faults in the Lower Rhine Embayment, a seismogenic origin of the damage is considered and tested in this paper. This question has relevance for determination of seismic hazard in an area with present-day moderate seismicity but documented occurrence of strong surface-rupturing earthquakes from the palaeoseismic record. First, a geotechnical model for the construction pit with a total volume of c . 540–550 m 3 is used to prove the stability of the open pit during well construction and to help explain how the well was built. The seismogenic hypothesis is tested in a deterministic approach using theoretically derived ground motion at the site of the well for two simulated earthquakes with magnitudes 6.2 and 6.8. Ground deformation and relative displacement calculated with a finite element model of the casing are found to be too small to account for the documented damage. Among other potential sources of damage, swelling, shrinking or rotting of the wood elements are possible explanations; however, a conclusive answer to this question remains to be found.

Using pit solution chemistry for evaluation of metastable pitting stability of austenitic stainless steel

AbstractThe stability of a corrosion pit is directly related to the pit solution chemistry. In order to know the stability of a meastable pit, the product of corrosion current density and diffusion depth (pit radius for an open hemisphere pit) is compared to the stability product obtained from the artificial pit electrode results. In this paper the stability of a metastable pit recorded on a 904L stainless at 54°C (2°C below the alloy CPT) is investigated. Assuming the geometry result of such a transient is an open hemisphere, pick current density and pit radius were calculated from Faraday's equation and then pit stability product (i·a) was calculated. This value was compared with the product of i·a associated with the pit solution chemistries (critical, saturation and supersaturation concentrations) which were obtained from the investigation on artificial pit electrode at the same temperature. SEM investigations on pit cavity generated from large metastable pit current transients with the stability product greater than the stability product associated with supersaturation concentration of pit environment proves that measured pit solution chemistry from artificial pit electrode is a reliable step for evaluation of pit stability.

Stability of a pit lifting vessel on a periodic system of vertical beams

Stability is considered for the unperturbed motion of a lifting vessel in two-sided guides in a vertical pit shaft, where allowance is made for the inertial behavior of the guides. A Hill equation is derived from the equations for the perturbed motion of the center of mass of the vessel and the elastic vibrations in the guides after certain simplifications. Numerical studies have been made on the stability of the solutions, and a region has been constructed for the main parametric resonance in this system.

Numerical stress analysis to assess stability of a combined open pit and underground mining operation in central Australia : Clark, I H; Fuller, P G; McLean, D Proc ISRM International Symposium on Static and Dynamic Considerations in Rock Engineering, Swaziland, 10–12 September 1990P103–112. Publ Rotterdam: A A Balkema, 1990

Numerical stress analysis to assess stability of a combined open pit and underground mining operation in central Australia : Clark, I H; Fuller, P G; McLean, D Proc ISRM International Symposium on Static and Dynamic Considerations in Rock Engineering, Swaziland, 10–12 September 1990P103–112. Publ Rotterdam: A A Balkema, 1990