Slope Foundation Research Articles

Study on Water Damage Mechanism and Emergency Restore of Fill Subgrade upon Squashy Slope Foundation in Mountain Area

This thesis takes the typical fill subgrade of squashy slope foundation of Qinglong-Xingyi Expressway in Guizhou Province as an example. Through engineering geological analysis, it was found that the topography and geomorphology conditions, formation lithology conditions and highway construction conditions were the basic conditions of water damage to highway subgrade, and hydrometeorological conditions are the direct cause of water damage of highway. Coupling calculation analysis using SEEP/W and SLOPE/W revealed the mechanism of short-term continuous heavy rainfall. When the short-term continuous heavy rainfall reached a certain level, the soil at the geotechnical interface reached saturation. At this time, the surge of pore water pressure at the geotechnical interface led to the sudden drop of effective stress, leading to the sudden decline of side slope stability, which was the starting condition for the formation of landslide caused by the water damage to subgrade. The implementation of emergency restore and the effect evaluation indicated that comprehensive treatment measures of the anti-sliding support combined with integrated drainage should be adopted for the prevention and control of the water damage to the subgrade. Underground drainage measures could effectively drain groundwater, playing a role in reducing groundwater level and pore water pressure in slip soil.

Study on deformation law of slope foundation under different external loads

The external load has a great influence on the stability of the transmission tower foundation. Considering that the external load on the foundation is more complicated, the external load is simplified to the basic center. The analysis of the deformation law under the external load is helpful to grasp the dangerous part of the foundation after being subjected to external force. In order to highlight the variability in the direction of the external load, the external load is set to a certain size, and the load direction is regularly changed. Using the finite element difference software FLAC3D to analyze the internal deformation law of the model under nine working conditions. The results show that the deformation of the foundation in the horizontal and vertical directions will change regularly with the direction of the concentrated force. When the direction of the concentrated force is within a certain range, it will play a positive role in the stability of the foundation.

Three-Dimensional Simulation of Seismic Slope–Foundation–Structure Interaction for Buildings Near Shallow Slopes

AbstractBuildings constructed adjacent to the slope crest in seismically active areas might be exposed to serious danger when they are subjected to strong earthquake excitations. The ground conditi...

Static and Dynamic Stability Analysis of the Gravity Anchorage Slope Using the Three Dimensional Finite Element Method

Stability evaluation of the high and steep slope formed by foundation excavation of a gravity anchorage is a key problem in safe construction and operation of the suspension bridge. Taking the gravity anchorage slope of Taoyuan Jinsha River Suspension Bridge of Dayong Expressway in Yunnan Province as a case study, through the field investigation and geological borehole data, a three dimensional finite element model was established to evaluate the stability of the anchorage foundation slope under the excavation and earthquake actions. The reinforcement effect of the support system including the anti-slide piles, bolts, pre-stressed anchor cable and lattice beam was studied. Using the support system, the maximum displacement of the slope decreased by 41%, and development of the plastic zone of the slope was controlled during the earthquake. The research results are used in the construction and design of this project, and also can be used for reference by the similar projects.

Genesis and Architecture of Sequences of Quaternary Coral Reef Terraces: Insights From Numerical Models

AbstractThe variety of coral reefs morphologies highlights their sensitivities to several forcings; fossil reefs stack in sequences that are accordingly diverse. In order to understand their genesis and architectures, we devised a numerical approach, accounting for Quaternary sea level oscillations, vertical land motion, initial slope, wave erosion, and reef growth. We first test our model on the subsiding sequence of Hawaii and on the uplifting sequence of Wangi‐Wangi (Sulawesi) that bears active barriers. We then construct a parametric study that we analyze based on a comprehensive yet compact description of sequences as barcodes, that depict the vertical distribution of a few geometrical characteristics (number, width, and height of the terraces and barriers). We find that geological factors suffice to explain the variety of architectures of reefal sequences at first order, regardless of additional ecosystemic processes. Vertical land motion and foundation slopes are the prime players, while reef growth rates only play a minor role. Barriers may develop both in uplift and subsidence mode, and their preservation attests for the erosional power. Last, we reappraise the genesis of sequences and find that sequences do not fingerprint discrete events of sea level oscillations but a continuous process harrowed by stochastic events: Major sea level fluctuations can be overrepresented by several terraces or conversely absent; reoccupations may yield composite terraces representing multiple events. Overall, sequences shall not be regarded as stacks of reef bodies forming during sea level highstands, which implies that the commonly assumed bijective relationship between sea level highstands and terraces shall be abandoned.

Model test and numerical investigation of the effect of the impervious layer’s slope on seepage characteristics under hydraulic structures

Although the impervious layer under a hydraulic structure is rarely flat, the effect of the impervious layer’s slope, under the hydraulic structure, on seepage characteristics has not been studied to date. Therefore, this study investigated the effect of the downhill and uphill impervious layer’s slope (downhill/uphill foundation slopes) on the uplift pressure, seepage discharge and exit gradient under hydraulic structures. In order to reach this goal, a numerical model has been developed in which the general equation of fluid flow in non-uniform; anisotropic soil is solved by the finite volume method on a structured grid. The model validation was performed using the measured data from experimental tests. The results of the model validation indicated that the model calculates the seepage discharge and uplift pressure with a maximum error of less than 3.79% and 3.25%, respectively. The results also indicated that by increasing the downhill foundation slope (DFS) the uplift force decreases, but the exit gradient and seepage discharge increase. Moreover, by increasing the uphill foundation slope (UFS), the uplift force increases but the exit gradient and seepage discharge decrease. In addition, the results demonstrate that by increasing the length of the cut-off wall the effect of the DFS on decreasing and UFS on increasing the uplift pressure force becomes more severe. However, the effect of the DFS on increasing the seepage discharge and UFS on decreasing the seepage discharge becomes milder as the length of the cut-off wall increases. By increasing the DFS, from zero to −15%, the exit gradient increases 19.75% and 14.4% for 1 m and 6 m cut-off lengths, respectively.

引发陡斜坡坡面泥石流的高强度降雨主成份分析

引发陡斜坡坡面泥石流的高强度降雨主成份分析

Accurate Numerical Simulation Study on Bearing Capacity and Sliding Surface of Slope Foundation

The bearing capacity of slope foundation is an important condition for the stability of mountain transmission line. At present, the methods for studying the bearing capacity of slope foundation are mainly as follows, such as the Limit Analysis Method, Slip-Line Field Method and Numerical Simulation Method. In this paper, the numerical simulation method with high accuracy is used to study the bearing capacity changes of slope foundation under different slope ratios, slope border margin and foundation conditions with the help of the finite difference software FLAC3D. Based on the correlations obtained from above, the reasons and laws for the changes of the ultimate foundation bearing capacity can be found, which can provide some guidance for related engineering design.

Geotechnical Problems of Botan Bridge Piers Construction (Siirt, Turkey)

The Botan Bridge in Siirt (Turkey), now under construction, will carry a road across the River Botan and the lake which will be created by the Pervari Dam, 180 m high. The bridge has two piers with height of 115.88 m, and the total length of deck is 450 m which is built in accordance with the free cantilever method. The paper deals with foundations used in Botan Bridge for dam reservoir crossing bridge structures. Some of the geotechnical problems of construction of these foundations are highlighted. The slope debris deposits and basement rocks being ophiolite and the metamorphic rocks (calc schist, chlorite schist and meta-sediments) contribute to the geotechnical problems. Ophiolite, calc schist and chlorite schist, contains significant percentage of chlorite, feldspars, carbonates and serpentinites; their effect needs to be assessed in the interpretation of pier foundation construction and slope stability calculations. For this purpose, in situ and laboratory tests have been performed. Ophiolitic rock mass properties are an important factor for slope stability of rocks and foundation construction.

Study of the seismic performance of hybrid A-frame micropile/MSE (mechanically stabilized earth) wall

The Hybrid A-Frame Micropile/MSE (mechanically stabilized earth) Wall suitable for mountain roadways is put forward in this study: a pair of vertical and inclined micropiles goes through the backfill region of a highway MSE Wall from the road surface and are then anchored into the foundation. The pile cap and grade beam are placed on the pile tops, and then a road barrier is connected to the grade beam by connecting pieces. The MSE wall’s global stability, local stability and impact resistance of the road barrier can be enhanced simultaneously by this design. In order to validate the serviceability of the hybrid A-frame micropile/MSE wall and the reliability of the numerical method, scale model tests and a corresponding numerical simulation were conducted. Then, the seismic performance of the MSE walls before and after reinforcement with micropiles was studied comparatively through numerical methods. The results indicate that the hybrid A-frame micropile/MSE wall can effectively control earthquake-induced deformation, differential settlement at the road surface, bearing pressure on the bottom and acceleration by means of a rigid-soft combination of micropiles and MSE. The accumulated displacement under earthquakes with amplitude of 0.1‒0.5 g is reduced by 36.3%‒46.5%, and the acceleration amplification factor on the top of the wall is reduced by 13.4%, 15.7% and 19.3% based on 0.1, 0.3 and 0.5 g input earthquake loading, respectively. In addition, the earthquake-induced failure mode of the MSE wall in steep terrain is the sliding of the MSE region along the backslope, while the micropiles effectively control the sliding trend. The maximum earthquake-induced pile bending moment is in the interface between MSE and slope foundation, so it is necessary to strengthen the reinforcement of the pile body in the interface. Hence, it is proven that the hybrid A-frame micropile/MSE wall system has good seismic performance.

Instability Mechanism of Du Yun Pass Tunnel Entrance Weathered Stacking Area Analysis

The stability of the tunnel portal section under poor terrain and geological condition has always been the focus of construction safety. The stability problem has become more complex for the erosion accumulation area under the valley. In this paper, firstly the stability of the tunnel portal is classified. Combined with engineering cases, the FEM numerical method is used to simulate the supporting structure and construction process of the tunnel. Based on the distribution of the plastic zone and displacement of surrounding rock, the mechanism of the instability of the tunnel portal is analyzed. Through the optimized construction scheme that arranges pile foundation in tunnel arch foundation, the bearing capacity of foundation has been greatly improved, which has effectively prevented the instability of surrounding rock caused by the slope deformation and foundation settlement. The conclusions that have been drawn in this paper can be used for reference for related projects.

Solos: Subsídio Para Estudos de Geologia de Engenharia

The objective of this paper was to discuss in simplified and multidisciplinary terms and through an engineering geology point of view the different variables related to the development of residual, transported, organic, expansive and lateritic soils, contributing to standardize concepts of geotechnical interest mineralogical and chemical data from five profiles whose respective saprolitic soils were formed by the action of weathering processes on gneissic metamorphic rocks in tropical and subtropical climatic environment were presented and discussed. The residual soils developed from these rock, besides the great abundance in the state of Rio de Janeiro, have thicknesses greater than 10 meters, being associated with large landslides and mass movements occurred in the last 50 years both in that state and in others. The article emphasizes finally that the presence of relict heterogeneities in saprolitic soils and saprock inherited from their source rocks should not be discarded in the analysis of slope stability and foundations projects.

Discussion of ‘Experimental investigation of shear strength of sands with inherent fabric anisotropy’ by Tong et al. (doi:10.1007/s11440-014-0303-6)

The authors have presented some interesting experimental studies on strength anisotropy of sand using direct shear tests. It is indeed surprising to see that the minimum peak friction angle is not observed when the sample is sheared along the bedding plane orientation. The authors also mentioned that it is desirable to develop theoretical modelling of the observed soil response. It is emphasized by the authors in this paper and a previous one [1] that it is practically more convenient to formulate the anisotropic failure criterion of sand in terms of the shear plane (or failure plane) orientation, as some existing geotechnical analysis methods which rely on shear strength of soils such as slope stability analysis and foundation failure analysis explicitly assume a potential failure plane without referring to the loading direction. The discusser thinks that a failure criterion formulated this way would be useful for special cases in which the failure planes are known but may not be suitable for general cases in which the failure planes cannot be easily determined. This discussion will show that the observed strength anisotropy of sand can be successfully modelled by a fabric-tensor-based sand model, in the formulations of which the potential failure plane orientation is not required. 1 Finite element simulation of the strength anisotropy of sand in direct shear tests

A Discussion of the Stability of Foundation Pit or Slope with Soft Interlayer or with Back Berm

The soft soil in Pearl River Delta regions is characterized with high water content, high compressibility and low bearing capacity. Therefore, when building the structures on such foundation, it’s necessary to pay attention to the deformation and stability. The projects' practice shows that, when analyzing the stability on foundation pit or slope with soft interlayer, it should not only calculate the overall stability of the slope, but also calculate the stability or bearing capacity of the foundation. Although sometimes the stability of the slope meets the requirements, it doesn’t means that the bearing capacity of the foundation meets the requirements because of the existence soft interlayer, the limitations of the circle slice method and the difference between the sliding surface and the actual sliding surface.

The Bearing Capacity and Failure Mechanism of Foundations near Slope Based on Nondimensional Parameters

The foundation on slope problem is a special case of the very large bearing capacity problem. Researchers have studied the bearing capacity of slopes as such problems arise quite frequently in practice. The aim of this paper is to study the effect that changing the position of an infinitely long strip foundation, from the edge of the slope to a certain distance away, has on the bearing capacity of a slope. The influence of various nondimensional parameters, such as strength ratio, slope height ratio and so on, on the bearing capacity of slope foundation is also analyzed by the finite element method. Conclusions are as follows: as the foundation is moved away from the slope by increasing D/B, there is a change over point from a slope failure mechanism to a flat ground failure mechanism. As the strength ratio increases for a set D/B, there is a considerable change in the shape of the failure surface initially, followed by only minor changes from strength ratio 10 onwards and so on.

Prediction Study of Capillary Rise Height on Unsaturated Soil

Based on the understanding of diseases of building’s foundation and manmade slope caused by water capillary rise, this thesis carried out a large number of laboratory tests by selfdeveloped absorption permeameter for unsaturated soil, in order to explore the capillary transport law of unsaturated soil. The thesis obtains some valuable results and conclusions: The moisture content shows minishing trend as the seepage fronts increasing, and reflects the gravitational potential of normal relations with the capillary action; (2) the water seepage frontal Hω% relation curve has no obvious inflection point, but the initial water content has an certain influence on the capillary moisture content distribution, the moisture content uses the initial moisture content of 12.5%, 9.8%, 8.0% and5.3% for testing showed an increasing trend at 4 cm and 16 cm sections, and the moisture content at the same section increased with the initial moisture content increasing, this reflects the rule that the smaller the moisture content is, the greater the matric potential, the water absorption capacity becomes stronger. (3)The moisture content difference between 4 cm and 16 cm of the initial moisture content is 12.5%, 9.8%, 8.0% and 9.8% is 1.48 %, 1.5 %, 1.7 % and 2.2 %, indicating that the smaller the initial moisture content is, the difference at the vertical section is greater. Finally, based on the relationship of Hω% curve, the thesis establishes the grey correlation prediction model, and forecasts the maximum capillary height of Lishi loess is 182cm.

In Instability and Failure of Steep Slope Embankment Test and Numerical Simulation Analysis of MeiHe Expressway in Guangdong Province

In Guangdong MeiHe highway K28 + 360 ~ + 360 section of the steep slope embankment as the research object, by adopting the combination of measurement and numerical analysis methods, analyze the failure process and mode of steep slope embankment. Based on the analyses, The following conclusions were obtained: the sliding surface of fill embankments on slope foundations of K28+360~+860 section was the original surface of the slope. Constructions of the highway would block the groundwater discharge and reduce the strength of the original surface of the slope, which would cause the slide of the fill embankments on slope foundations.

In Instability and Failure of Steep Slope Embankment Test and Numerical Simulation Analysis of MeiHe Expressway in Guangdong Province

In Guangdong MeiHe highway K28 + 360 ~ + 360 section of the steep slope embankment as the research object, by adopting the combination of measurement and numerical analysis methods, analyze the failure process and mode of steep slope embankment. Based on the analyses, The following conclusions were obtained: the sliding surface of fill embankments on slope foundations of K28+360~+860 section was the original surface of the slope. Constructions of the highway would block the groundwater discharge and reduce the strength of the original surface of the slope, which would cause the slide of the fill embankments on slope foundations.

Deformation and Failure Characteristics of Embankment upon the Slope in Permafrost Area under Different Foundation Slope

To investigate the effect of foundation slope on stability of embankment upon the slope in permafrost area, 3 groups of model tests with different foundation slope are designed using the mechanical similarity based on geotechnical centrifuge modeling, when the freezing-thawing depth of the embankment reaches the greatest. The results show that: (1) The foundation slope has effect on the stability of the embankment. The deformation mainly concentrates on the soil layers above the freezing-thawing interface, and the deformation mutation point takes place at the freezing-thawing interface. (2) According to fracture characteristics and failure severity of the embankment, failure modes can be divided into the cracking failure in shallow layer and in deep layer. (3) The cause of unstable failure is the deficiency of shear resistance strength of the weak belt, the soil layers above the freezing-thawing interface slips along the freezing-thawing interface under gravity load. (4) Under the experimental conditions, the critical value of the foundation slope influencing on the stability of the embankment is about 1:6 when the height of the slope embankment is 5.0 m.

Safety Evaluation Technology for Waste Dump Landslide of Open-Pit Mine Based on Fuzzy Mathematics

In recent years, frequent waste dump landslides brought the huge losses. Now, there is no mature theory system about the research on waste dump stability, this paper puts forward a disaster evaluation method for waste dump landslide which bases on fuzzy mathematics principle, the evaluation method is convenient and practical. Firstly, we established evaluation indicator system on the basis of analyzing landslide influence factors; first grade evaluation indicators included engineering geology, hydrogeology, dumping process and other factors; second grade evaluation indicators included geotechnical properties, foundation soft rock, foundation slope, atmospheric precipitation, underground drainage, drainage facilities, dumping way, dumping order, propulsion speed, mining disorderly, blasting vibration and force majeure. Secondly, we used analytic hierarchy process (AHP) to determine the indicator weight. At last, combining with the actual situation of some waste dump and using fuzzy mathematical theory, we had the safety evaluation to waste dump landslides, the result is in good agreement with the actual situation and shows that the method is a scientific guidance to the safety management of the waste dump.