Advances in Pile Foundations, Geosynthetics, Geoinvestigations, and Foundation Failure Analysis and Repairs

Based on the load transfer mechanism about the bi-level model, this paper studies on the influence about frictional force in side-pile of cement soil plug which pre-stressed pipe pile is implanted into a large diameter bidirectional cement mixing pile in a concentric manner. On the basis of the analysis of soil-compacting direction, theory of cavity expansion has been adopted to analyze the disturbance on the side soil in the pile driving process of pre-stressed pipe pile in MPSC. According to the lower core pile, the radial stress of pile-soil contact surface before and after the complete occlusion of cement soil plug is calculated combining the shear strength of foundation soil after disturbance. The eigenvalues of lateral friction before and after complete occlusion of soil plug are adopted according to comparison between the length of soil plug and outer pile. Considering extruding densification of core pile, improvement coefficient is implied in modifying the ground soil and outer pile, the calculation Equation for lateral friction of MPSC has been developed.

Based on the shear displacement method, together with the Mylonakis & Gazetas model for pile-soil mutual action and the layer foundation model, the flexible factors for pile-soil are obtained. Considered the performance of the fill, an analysis method on pile-soil-fill mutual action in the composite foundation was proposed, and the correlated program is also developed by using Matlab. In order to validate the feasibility of the proposed approach in this paper, six static modeling tests on the composite foundation with the rammed soil-cement tapered piles and cylindrical piles had been performed, and the proposed method in the paper is used to analyze three model tapered piles, respectively. Experimental and theoretical results show that the bearing capacity of the composite foundation with rammed tapered piles increased with the taper angle increased under the condition of the same replacement ratio, and the rational taper angle scope is between 1° and 1.5°.

Geddes stress solution is widely applied in settlement calculation of pile foundation. In order to find the solution, skin friction of pile and tip resistance of pile were simplified as concentrated force; However the influence of changing diameter and length of pile on additional stress in the ground due to skin friction of pile and tip resistance of pile can not be taken into account. The Y-section pile is a new style pile, its section is complicated. On the base of the numerical computational method for vertical additional stress and displacement at random point in the ground under the skin friction and tip resistance of Y-section pile, The settlement calculation methods of single pile on Y-section pile was established on the base of Mindlin stress solution and Mindlin displacement solution, and the settlement induced by compression of pile and penetration of pile tip were considered in the calculation method. The settlement calculation method of single pile on Y-section pile on the base of Mindlin stress solution and Mindlin displacement solution was contrasted. The rationality of the two settlement calculation methods were both verified by contrast with in-site test data.

The main purpose of this study is to provide basis and reference for the economical and rational selection of tube types used in the Plastic Tube Cast-in-place Concrete Pile (TC pile). In order to economically and rationally select plastic tube and determine the control index of plastic tube, 5 calculation procedures are drown up and studied combining with the basic parameter of plastic tube and application. The optimization of waved tube shape is discussed. Research shows that the maximum stress of plastic tube occurs at the initial stage of steel pipe uplifting; it is optimal in the condition of same wall thickness that the ratio of wave height to space is 0.38; it is not appropriate to use circular wave tube or large-wave-angle tube but reasonable to use trapezoidal or curved wave tube; the selection of plastic tube in practical engineering has large relationship with pile spacing and geological situation; the displacement along the radial direction is small, which can be disregarded in actual project. The selection method, principle and control index of single-wall PVC plastic waved tube suitable for TC pile are proposed. The water injection technology and method to reduce project cost are obtained.

The static load tests for pile composite foundation of X-section pile and circular section pile in the same area are conducted on trial pile in soft soil reinforcement engineering of a sewage treatment plant in the North of Nanjing, China. The load-settlement curves, pile-soil stress ratios and distributions of axial force are obtained. The comparison of test results on single-pile composite foundation of the two indicates that the vertical bearing capacity of X-section pile is 20% greater than that of the circular section pile with the same use of concrete because of the larger side friction. The results also show that the pile-soil stress ratio of X-section pile is higher than that of circular section pile, and the settlement of circular section pile is larger than that of X-section pile under the same loading. The axial forces of both X-section pile and circular section pile decrease from the pile top to the bottom. Therefore, in the same area, the bearing capacity of single-pile composite foundation of X-section pile is better than that of circular section pile. The in-situ test results are very significant for the theory study and engineering application of X-section pile composite foundation.

Based on the results of static load tests, this paper presents an experience formula for calculating bearing capacity characteristic value of CSLSP (cement-soil long-short piles) composite foundation. Considering the settlement relationship among piles, the embedding soil and composition foundation, a method is proposed by studying on bearing coefficient of the embedding soil and suitable value of s/b (ratio of settlement of composition foundation to width of load board) . It is indicated that cement-soil piles have been destroyed firstly before soil in common and value of s/b have reached the upper limit. According to the results of static load tests and calculation, the upper limit value of s/b and bearing coefficient of the embedding soil for SP (single pile) composition foundation is 0.010 and 0.399, and decrease to 0.0052 and 0.318 respectively for CSLSP composition foundation when elastic model of cusion is 20MPa. It is also indicates that the upper limit value of s/b and bearing coefficient will decrease with the increase of elastic model of cusion.

Open-ended steel pipe piles are now widely used as the foundations of bridges. The pile-soil interface behavior is of particular interest in granular soils, because the shaft friction plays an important role in resisting the applied load. Rational design of the shaft capacity depends on a good understanding of the mechanisms of interface shear during pile installation and static loading. There are two new CPT-based methods that are able to take into account the effects of friction fatigue and soil plugging. An improvement is made in this paper to consider the influence of plugging degree on the soil-squeezing ratio which is closely related to the radial effective stress and consequently the shaft capacity. The modified design framework shows better agreement with the field measurements of two instrumented piles than the two existing methods.

This paper presents an analytical solution on wave propagation in a large-diameter pile for low strain integrity testing. Based on three-dimensional (3D) wave equation that considered the vertical displacement and combined the initial and boundary conditions, the frequency-domain analytical solution on the transient dynamic response of large-diameter pile in low strain integrity testing is deduced by Laplace transformation and separation of variables method. The time-domain dynamic response is obtained by numerical inverse Fourier transformation. A case history is studied to analyze the 3D effects on pile head. The results indicate that the velocity waveforms are different among the measure points with various distances apart from pile center. The peak values and arrival times of incident waves have a greater difference, but the reflected waves from pile bottom have little difference. The phases and peak values of high-frequency interference waves have some differences but the interference frequencies are almost the same. The time-delay is conspicuous when r<2/3R, but it is no longer enhanced when r≥2/3R. The peak value rapidly decreases as the increase of r from 0 to 0.2R. However, the peak values from 0.2R to R have little difference. The measured waveform can be well simulated by the analytical solution.

Based on the unified limit force profile, a analysis referring to the behavior of cast-in-place concrete pipe pile with large diameter(PCC) under lateral load was set up through performing a series of numerical simulations of models with either different pile size or different soil strength parameters using FE. Furthermore, three parameters(N_g, α₀ and n) involved in the unified limit force profile of soil were back analyzed, and reasonable ones for PCC analysis were determined. A simplified method for calculating the ultimate bearing capacity of PCC under lateral loads was established paying respect to the approximate equivalence between the depth of the location of maximum moment and that of plastic slip line. The calculation results based on this method were compared with FE solution a good agreement was found. Therefore, it could be useful for the design and analysis of PCC under lateral load.

The deformation and stress in-situ monitoring plan of representative section of Wuhan-Guangzhou railway passenger dedicated line in China was introduced. The monitored compressions of piles and soil between piles in different depth were analyzed. Then deformation development trends of piles and soil among piles in CFG pile composite foundation was investigated following the construction processes of railway subgrade, namely, filling, rest of loading, surcharge precompression, unloading surcharge, and so on. Based on the tested vertical stress both of CFG piles and soil among piles, their developing trends were investigated for every construction phase, and the pile-soil stress ratio was researched too. In-situ monitored data shows that: (1) Under the filling height 6.2m, the tested settlement of composite foundation is 15.67mm, which proves CFG pile composite foundation is effective on control settlement of subgrade. (2) The compression of pile is not equal to that of soil among piles during subgrade construction, and their difference reduce gradually as a result of stress adjust in composite foundation, with the pile-soil stress ratio tend to one fixed value.

Consolidation settlement induced by dissipation of the excess pore water pressure due to pilling in soft clay and negative skin friction caused by it were analyzed. Piling or the pile driving process usually induces excess pore water pressure in the surrounding soil. When this excess water pressure dissipates later on after the pile driving process is complete, settlement of the surrounding soil occurs and a negative skin resistance along the pile shaft develops, which is undesirable. In this paper, three-dimensional Biot's consolidation theory was introduced into FEM analysis to take into account the nonlinear consolidation behavior of the soil. The pile-driving process was defined and analyzed in terms of the expansion in a cylindrical cavity. In general, the results based on the FEM method and 3D Biot's theory were consistent with the actual field measurements on site; with an even better accuracy than the results computed based on Tergazhi's theory. Therefore, the method proposed in this paper is rational and exhibits greater promising potential for application in engineering designs.

The buildings on the ground and the pipelines underground, especially water supply pipes and gas supply ducts, can be destroyed by ground fissures in Xi'an City. In order to study the influence of Xi'an ground fissures movement to buried pipeline, using reinforced concrete and loess simulated as underground pipes and stratum, two sets of large-scale physical model tests (1:5) on buried pipe cross-ground fissure were conducted with settleable test platform simulated as the movement of ground fissures. The difference between two tests is different setup when buried pipeline cross-ground fissures: one is opposite joint test setup and the other is straddle test setup. Test data and the damage of buried pipelines after the excavation were presented, and two failure modes are summarized. At the same time, there are differences in soil stress and damage between two pipelines when ground fissures moves. In order to avoid larger damage, opposite joint test setup is a better choice. This will have invaluable contribution to buried pipeline design of Xi'an.

Many structures, such as bridge bents, offshore platforms, and tall buildings are subjected to significant torsional loads. Therefore the pipe pile foundations of these structures not only are subjected to vertical loading caused by structural weight and horizontal loading due to wind- or wave-induced loading, but also sustain large torque loads. Based on swipe loading test procedure and the probe method of fixed displacement ratio, the three dimensional finite element numerical analyses were conducted to explore the failure mechanisms of pile foundation in different loading plane such as V-H, V-T, H-T and in V-H-T loading space under combined loading. The failure envelopes in different loading spaces were obtained through computational results. Also, the soil deformation mechanism under various combinations of horizontal, vertical and torsional loads is shown. According to the relationship between the actual combined loading and the computed failure envelopes, the stability of pile foundation could be evaluated based on yield design theory. The general purpose finite element program ABAQUS was utilized for this study. Nonlinear analyses were conducted using a simplified elastic-perfectly-plastic model with Tresca yield criterion for undrained clay.

Collapse may easily happen during the hole-drilling of the ultra-long bored cast-in-situ piles, which influences the pile-hole making, the quality of underwater concrete, the drilling speed as well as the construction cost. On account of Pier A's foundation of the Maocaojie Bridge, the paper deals with the construction methods for smooth boring, pile-hole collapse prevention and quality guarantee of concrete placement, on condition of the complicated geological environment. By virtue of the force analysis of the hole wall and the Mohr-Coulomb failure criteria, the research proposes the concept of the minimum depth for the pile hole and illustrates the accuracy of this concept, which may supports similar construction.

Jet grouting soil-cement-Pile strengthened Pile (JPP) is a new kind of composite pile, and is a great ground improvement technology in soft ground. Based on the variational principle, the total potential energy of single JPP pile is established, and it is expanded to a simple equation of matrix form, in which a finite series is used to denote the vertical displacement of JPP, load transfer function is used to describe the force-displacement relationship. In light of minimum potential energy, a practical method is obtained for the load-settlement relationship of single JPP pile. Using this practical method, the settlement of single JPP pile can be estimated quickly. Comparisons between results using this practical method and model test measurements indicate that the method can predict the performance of single JPP pile. Finally, factors of vertical behavior of JPP pile, such as slenderness ratio, ratio of pile head settlement to pile base settlement and Young's modulus of core pile and soil-cement pile, are analyzed.

A numerical analysis is presented to simulate settlements of a pile group for a bridge on the Beijing-Tianjin Intercity Rail Passenger Dedicated Line in China. The pile group consists of eight cast-in-drilled-hole piles with a diameter of 1 m and an approximate length of 50 m. The finite element program Plaxis 3D was used in the analysis. The foundation soils were represented with the Mohr-Coulomb plasticity material model. The piles were represented with pile elements. Between the pile and the surrounding soil, interface elements were automatically generated by the program. In the analysis, the effects due to soil stiffness, pile length, and pile spacing were considered. The calculated results for the simulation of the pile installation sequence were compared with the measured results obtained from the field monitoring during and after construction. The settlements of the pile group under the anticipated super-structural loads were also calculated. Furthermore, allowable bearing capacity of the pile group was determined in the calculations and the safety factors for each calculation step was obtained. The results of the numerical analysis provide some insight to the settlement analysis of pile groups in soft clayey soils and the finite element program Plaxis 3D can be a useful tool for numerical analysis.

The Chin's plot method is the most widely used method in Singapore to assess the ultimate skin friction and ending bearing separately based on static pile load test results. In this study, a large number of pile load tests for driven piles were back analyzed using the Chin's plot method. The obtained data were examined in order to evaluate the appropriate design ranges for skin friction coefficient, K_s and end bearing coefficient K_b, which are the two key parameters for pile capacity estimation in design. It was revealed that, generally, the currently adopted design ranges were over-conservative for displacement piles. New design ranges and limits for K_s, K_b and unit end bearing, q_b, were suggested, and their typical values for conventional designs were recommended. Further, the importance of pile load test in the design of piling foundation was emphasized. Whenever practicable the ultimate pile bearing capacity should be obtained from pile load tests, and all indirect estimations of pile capacity should be evaluated against the static load test results.

Driven piles have been widely used as a foundation element to support bridge superstructures and substructures in places where shallow foundations may not be suitable. Recent adoption of reliability based approach (LRFD) in AASHTO Guidelines has yielded suggested resistance factors in evaluating strength limit states of driven piles. In this paper, several aspects of driven pile control and QA/QC issues will be discussed. The method of incorporating pile set up capacity within the framework of LRFD was not addressed in AASHTO, but will be fully evaluated and appropriate method for incorporating set up in sand and clay will be given in this paper with the suggested resistance factors corresponding to different target reliability. Finally, the issue of appropriate acceptance criteria based on sampling theory and target reliability with respect to dynamic pile testing results at a production site will be described. The purpose of this paper is to provide a holistic approach to driven pile control and QA/QC through dynamic pile testing and calibrated first order reliability (LRFD) based approach. The presented methodology should provide a practical approach for state DOTs to handle their driven pile projects.

X-section cast-in-place concrete pile (referred to as XCC pile) is one of new type pile which can increase the bearing capacity effectively for embankments over soft soils. Based on FLAC^3D, this paper's accuracy was verified by the analysis of large-scale model test results firstly. Then the mechanical properties on compressive capacity of XCC pile embedded on soft soils were preliminarily studied. Circular pile which was in the same concrete consumption and soil conditions was comparatively analyzed. The mechanical properties of XCC pile group which were influenced by pile position, the friction coefficient of pile-soil, the modulus of pile, and the stiffness of pile end soil were discussed. The results show that the performance of XCC pile under vertical load is similar to those of circular pile. It is also shows that the compressive capacity of XCC pile increases with the increasing of stiffness of pile end soil, the increasing of pile modulus, and the increasing of friction coefficient of pile-soil.

In this paper, a kind of the Mesh free method was utilized to conduct a series of computational modeling to evaluate the bearing behavior of extended-length piles. The computational program code and boundary conditions were generated based on the elastic-plastic behavior of the surrounding soil, reinforcements, and the non-continuous interface between the piles and the soil. This was then verified with the Marc (a commercial available software package) by analyzing a classical mechanics problem. Lastly, the bearing capacity and response behavior of long-length bridge pile were analyzed including the relationship between the piles length-diameter ratio, pile settlement, and the non-linear behavior of the load-settlement curve. Overall, the results indicated that the optimal length of the pile is directly related to the stiffness of the soil, i.e., the stiffer the soil, the longer the allowable pile length.

A new driven cast-in-place Y pile was developed according to the innovative design concept of Y pile and the traditional construction technology of driven cast-in-place pile in China. In this paper the pile-soil stress ratio was calculated based on the hypothesis that the pile body was modeled as an equivalent constant section elastic bar. The influence factors and variation of the pile-soil stress were analyzed. Then the theoretical results were compared with the field data obtained from a ground improvement project for an expressway bridge abutment using driven cast-in-place Y piles. According to the field static loading test and theoretical analysis, the driven cast-in-place Y pile can improve the bearing capacity significantly with the same engineering quantity. It can be indicated that Y pile is either a friction-based friction pile or end-support friction pile and has a great bearing capacity. Besides the Y pile composite foundation has better bearing characteristics while the foundation settlement and post-construction settlement of embankment are substantially reduced. The results from this study can provide reference for the future design of similar composite foundation.

There are many civil engineering projects in Taiwan utilized geosynthetic reinforced soil retaining walls (GRSRW). Usually, a reduction factor is used to avoid creep from the reinforcements over the duration of the structure's lifetime at the designing phase. However, GRSRW are composed of reinforcements and backfill soils, which are relatively complicated in considering of the soil-structure interactive creep behavior. Questions are consequently rising: If there is creep deformation of a GRSRW, is it coming from soil creep? What would be the total amount of the deformation after years? Is the amount acceptable by civil engineers? Are the tensile forces in the reinforcements increased with time? The complex soil-reinforcement interactive creep behavior of GRSRW can be analyzed by using finite element method to get more know-how. With the aim of understanding the creep behavior of GRSRW, the PLAXIS finite element computer program, which contains suitable models for time-dependent behavior, is employed in this study to simulate the creep behavior of a 5 meter standard designed GRSRW. The predicted results obtained from the PLAXIS simulation can be used to evaluate and to handle the creep behavior of GRSRW.

In recent years, Geosynthetics and piles have become the commonly applied method of embankment reinforcement, giving rise to what is typically known as Geosynthetic-reinforced pile-supported embankment. The reinforced earth platform includes one or more layers of Geosynthetics at the base of the embankment. With this method, the weight of the embankment and the surcharge are largely transferred onto the piles so that the soft soil between the piles carry less load and the embankment settlement is reduced. A numerical study was conducted to investigate the stress distributions and the transfer behavior of the Geosynethic-reinforced embankments on deep-composite columns. Five influencing factors were evaluated which included the elastic modulus of the deep-composite columns, the elastic modulus of the soft soil, the tensile stiffness of the Geosynthetics, the spacing of the columns, and the number of Geosynthetics. Numerical results suggested that the elastic modulus ratio of the deep-mixed columns to soft soil has great influence on the average stress concentration ratio of the piles to the soft soil.

A finite element differential method was proposed in this paper to analyze the deformation behavior of a beam with variable cross-sectional dimensions, taking into account the gap in the tensile stress zone. In the analysis, the deformation of the beam and settlement of the subsoil were defined separately so as to have different functions with or without positive stresses in the tensile zone. Then, by introducing the Winkler and the elastic semi-infinite space models, a basic reaction equation was established that was subsequently solved using the Lemke algorithm. Lastly, two practical examples were analyzed and the results indicated better accuracy when the gap in the tensile stress zone was taken into account.

Large dynamic loading which is applied on railway tracks in cycles can result in deterioration of track geometry. Normal maintenance measures such as tamping could lead if not enough satisfactory, to renewal, which is expensive and disruptive to revenue traffic. In this paper the application of geosynthetics for maintenance of existing ballasted tracks is investigated. Especially the costs and benefits expected are presented.

The requirement of keeping a competitive edge against other means of transportation has increased the pressure on the railway industry to improve its efficiency and decrease the maintenance costs. In this paper, several solutions are presented to improve rail track foundations including optimum particle ballast grading and confining pressure as well as stabilising tracks overlying soft soils employing different techniques. This study specifically assesses the influence of shoulder ballast and its combination with geosynthetics to reduce the track settlement due to train load. Two dimensional plane strain finite element model is adopted to simulate the track deformation. Furthermore, the potential use of geosynthetics combined with recycled and blended ballast for reduction of rail displacement is addressed. The different location of geosynthetics in rail track substructure is examined. Rail track performance can be improved by including wider shoulder ballast with geosynthetic layer, and recycled and blended ballast reinforced with geosynthetics can be used during maintenance operation to curtail future track deformation.

Gabion wall have been used widely in the world for erosion control projects, soil reclamation work, stream channels construction, and retaining structures. The gabion wall can be improved by adding geogrid reinforcement embedded between the baskets. In order to evaluate the connection strength and interaction behavior of geogrid with wire mesh gabion basket filled with select rock infill, a large full-scale laboratory apparatus and testing setup that was developed. Observations were made for three types of geogrids paired with gabion baskets. More specifically, the normal surcharge loads, specimen width of the reinforcement, and rate of loading were used to examine the influences of different factors on the interaction mechanism of the simulated gabion-geogrid reinforced wall system. Test results have shown that the connection strength increased with the increasing applied normal loads and tend to level off at large surcharge loads. The interaction characteristics were affected by the ultimate tensile strength (UTS) of geogrid, selecting size of cobble rock, and normal load applied.

The matter element recognition model of subterranean tunnel rock quality evaluation is established using matter element model theory based on extenics recognition method. The stratification analysis method used to calculate weight coefficient of evaluation index is proposed. Through calculating the relational degree of the actual tunnel rock quality grades, deep and long diversion tunnel rock quality of Jinping second hydropower station is evaluated, and the conclusion is accord with the facts. It is shown that extenics recognition method is feasible to classify tunnel rock, which can comprehensively reflects the influence of multi-factor index on tunnel rock classification and can be used for reference to solve the similar questions in geotechnical engineering.

In this paper, aspects concerning the geomechanical characterization related to the case study of the underground complex of Venda Nova II built in the North of Portugal are presented. Focus is drawn to the extensive in situ characterization performed by LNEC. A statistical study was carried out in order to establish reliable confidence intervals for the parameters. A 3D model for the powerhouse complex was developed and used together with the monitored displacements and an advanced optimization algorithm to back analyze geomechanical parameters. The back analysis study validated the parameters obtained by the in situ survey and proved to be a reliable complement in this characterization.

Within a certain domain of rock mass in excavation, identification of all blocks cut by three-dimensional finite random or fixed discontinuities is a critical basic problem in jointed rock mass researches. The deterministic structures of rock mass can be measured by adopting digital photogrammetry measurement technology, which includes three-dimensional structural network simulation, intersecting lines of surface structure, closed-loop analysis and block fast searching. On this basis, analysis of unstable blocks sliding process is realized based on the classical theory of block during rock tunnel construction process. Engineering example analysis and accuracy test results show that this proposed method can identify the complicated block (including the concave form) cut down from numerous structures fast and effectively. Therefore this method shows its strong commonality and reliability, and it can also be used for rock tunnel excavation process advanced prediction and reinforcing scheme optimization.

Rockburst is one of the main geological hazards in high terrestrial stress zone. The prediction of possibility and intensity of rockburst are important issues. Ideal point method is a general multi-objective decision analysis method. The basic process is to construct the ideal solution and anti-ideal solution of evaluation objects, and make the degree of close to the ideal solution or away from the anti-ideal solution as classification criterion. It has not yet seen the application in rockburst prediction. It has great influence to the finial evaluation results for the reasonable weight values of the evaluation indices. Although there are a lot of methods to determine weights recently, these methods have their deficiencies. To solve these problems, weights back analysis method based on optimization theory are used, which changes the directly given weights methods to the problem of back analyzing index weights according to engineering samples. The method is fully derived by engineering samples, and no experience is necessary. Finally, the result using this method shows that this method is reliable. Ideal point method provides a new idea to predict rockburst, and weights back analysis method is universal and can be used in any weights problems.

In order to conduct tunnel advance surrounding rock classification effectively, puts forward an advance surrounding rock classification method based on TSP 203 system and Extenics. The method extracts the useful information from the detection results of TSP 203, establishes the indicators system of advance surrounding rock classification and adopts extensible comprehensive evaluation method to conduct advance surrounding rock classification. In the progress of establishing surrounding rock advance classification index system, adopts six rock classification parameters which TSP203 could identify effectively. They are rock mass integrity coefficient, Poisson's ratio, static Young's modulus, the angle between main structural surface and the tunnel axis, discontinuous structural surface and the state of groundwater. Finally, the method is applied to practical engineering and the results show that the method has higher prediction accuracy in advance surrounding rock classification and provide a new idea for advance surrounding rock classification.

Tunnel constructions often encounter unforeseen disasters, such as water inrush, bursting mud and some other geological hazards, which cause great casualties, economic losses and environmental destruction. Taking one karst tunnel as an example, through applying the supplemental geology survey and geology analysis, the karst development law is discussed. The risk evaluation system with 4 ranks about karst tunnel is put forward. Main control factors of risk such as formation lithology, geological structure and underground water etc. were synthetically considered. Based on the risk rank, and according to applicable scope, merits and drawbacks of different geological prediction methods, integrated advanced geological prediction methods, was put forward to the prediction of water inrush, mad flush. A multi-step warning and prediction system was established, and it included macroscopic, long-term, short-term geological prediction methods and geological precursory prediction methods. The advanced forecasting program was designed for different parts with different ranks, and the disaster prevention measures were made with the prediction results. The integrated advanced geological prediction methods were applied successfully in karst tunnels.

According to imposing the radial velocity on the slurry bubble spherical grid to dilate cell volume, a three-dimensional numerical model of one slurry bubble in homogeneous expansion and non- homogeneous expansion has been established by FLAC3D method to simulate the uplift process of grouting. The calculation results show that both of simulation results adopting two kinds of expansion deformation modes are generally low compared with theoretical solution, but the error between the theoretical solution and the simulation results of non-homogeneous expansion mode is smaller than between the theoretical solution and the simulation results of homogeneous expansion mode. Furthermore, the surface uplift in non-homogeneous expansion mode is greater than the calculation uplift by homogeneous expansion mode, when the embedded depth of slurry bubble is shallow. However, with the embedded depth increasing, the difference of surface uplift between the two kinds of expansion modes respectively is decreased and the calculation results are almost same. These indicate that the non-homogeneous expansion mode is suitable for evaluating grouting in field condition. Moreover, the method of using radial velocity boundary condition to simulate the dilation process of grouting is feasible and convenient.

This paper presents basal friction tests to simulate the influence on the deformation and the failure modes in Jiaohe Ruins cliff due to increasing erosion in the basal sand layer. Previous research, including field investigation, physical testing and wind tunnel tests, has proved there are different scales of wind erosion in Jiaohe Ruins Cliff. A scaled cliff model is established with existing secondary unloading fissures scaled accordingly. A test set-up is used with a rotating platform to rub the model in order to simulate the gravity on the cliff. The influence of soil erosion depth is investigated by comparing the results from models with different erosion depths. Based on the results, it is found that the scaled model tests can be used to simulate the failure mode of the cliff. The cliff failure mode changes from fracturing-toppling to shearing-dropping with increasing basal erosion depth. When the sand layer is partially eroded, the silty clay cliff topples and falls along the unloading fissures due to gravity moment. When the sand layer is fully eroded, the cliff block falls in a shearing mode along the fissures. This research improves the understanding of the failure in Jiaohe Ruins cliff and provides a scientific reference for the reinforcement of this historical site.

Due to the geographical location of Colombia, the country is exposed to an important number of hazards of a natural source -especially terrain instability- which affect the integrity the hydrocarbon transportation lines. To control them risk evaluations are performed, oriented to determine the monitoring and geotechnical maintenance actions that mitigate such risks. Evaluation processes and monitoring recommendations are described.

Shales and other mudrocks are very common in the Colombian Eastern Mountain Range, where also they are involved in various types of natural and artificial slope instabilities. In this paper the more common geotechnical problems associated with these materials are commented and some historic cases are presented; likewise, the results of characterization research works that are coming up in the country are introduced.