Instrumentation, Testing, and Modeling of Soil and Rock Behavior

This paper presents an experimental investigation on the influence of embedment depth on the anchor failure mode. It is widely understood that a deep anchor will behave differently compared to a shallow anchor. A test set-up is developed in this research to capture soil deformation during anchor uplifting, which consists of a camera, a loading frame, a Plexiglas mould, and a computer. A series of model tests are performed to investigate the influence of the anchor embedment depth on soil deformation. A set of images are captured while a semicircular anchor is being uplifted against the Plexiglas window. A soil displacement field is calculated from two images using the Digital Image Correlation (DIC) method. The failure surface is studied by locating the maximum shear strains deduced from the soil displacement field. Based on this study, it is found that the anchor behaviour is substantially influenced by the anchor embedment depth. A similar punching failure mode is observed in loose sand regardless of the anchor depth. However, in dense sand a restrained failure mode is observed in a deep anchor opposite to the mode with failure plane extending to ground surface in a shallow anchor. This study improves the understanding of soil-anchor interaction and helps to design an efficient anchor system.

Both numerical analyses and model tests were performed to study the interactive behavior of underreamed anchor groups in sand. A constitutive model named SHASOVOD which could simulate the strain hardening-softening and the volume dilatancy of cohesionless soils during shearing, in conjunction with FLAC^3D software to execute the numerical analysis. The results measured from model anchor tests were compared with those calculated by numerical analyses. The load-displacement behaviors calculated numerically consisted with those measured by the tests of the single anchor and the paired anchors. According to the numerical results, the interference induced by the paired anchors is smaller than that induced by the triple anchors. When the spacing between neighboring anchors is small (such as S_h=2D, D is the anchor diameter), yielding zones of soil around each anchor highly superpose, the average capacity of an anchor group is much smaller than the capacity of a single anchor. The superposition of yielding zones decrease with horizontal spacings; the behavior of each anchor in the anchor group tends to a single anchor as the horizontal spacings exceed a threshold value of 10D.

A 26 m deep metro station was excavated in the soft clays within downtown Shanghai, where exist many commercial and residential buildings. The minimum distance between the excavation and the buildings in the proximity was only 7 m. In order to ensure the safety of the adjacent buildings and associated facilities, building settlements were monitored throughout the construction. Field data indicated that the buildings underwent significant settlements during construction. The magnitudes of building settlements were governed by the distances between buildings and excavation pit, structural types, and foundation types. Based on the analysis of field measurements, some interesting findings about excavation-induced building settlements were obtained.

The proposed Nanning outer ring expressway crosses the region of widespread distribution of expansive soil. If using the design proposal of displacing soil, more than 1.4 million cubic expansive soils will be abandoned to considerably increase the construction investment and seriously damage the ecological environment. Therefore, Guangxi Communications Planning Surveying and Designing Institute and Changsha University of Science and Technology corporate to generalize the new treatment technology of expansive soil embankment. And the use of expansive soil as embankment fill is based on the fact expansive soil is sealed with nonexpansive soil or geosynthetics and expansive soil fill is not in direct contact of water. The various soil properties testing and road performance testing were carried out to determine whether the Nanning expansive soil can be directly used as embankment filler or not. In terms of testing results, the analysis demonstrations are performed on the strength, deformation and compactability of the expansive soil. The results show that all the expansive soils can be directly used to fill the subgrade of Nanning outer ring expressway except one whose consistency is not satisfying the requirement. The theoretical basis and design parameters are provided for implementing the physical treatment plan.

As the basic equation of soil mechanics, the Terzaghi consolidation equation of soil can be expand into Taylor polynomial model which meets the precision demands on engineering. Thus the equation is suitable to solve in nonlinearity for using the method of Pade rational approximation. Based on variables discretization and matrixation, the solution of uni-dimensional consolidation equation of saturated soil is transformed to the process of rational approximation on matrix exponential function. The approximation procedure indicates that the rational approximation is effective on functions expression for those functions are characterized on their expression prone to compute. Moreover, the induction process shows that the consolidation equation by variables discretization and step approximation is suitable for programming because of good approximation and the stability on numerical calculation. These are ready for the theoretical basis in the numerical simulation of rational approximation on multi-dimension consolidation also.

This paper is a summary of the strategies employed to treat the longitudinal cracks in several pavement maintenance projects in Hunan and Guangdong and lessons drawn from the process of treatment. Once the longitudinal cracks appear, the first step was to observe these cracks so as to understand their developing tendencies and to assess the existence of void under pavement slabs. In the case of the pavement with voids under slab, grouting was needed to stabilize the slab first. Subsequently, according to various developing tendencies of cracks, feasible strategy options would be selected, including crack sealing or filling to minimize water infiltration, load transfer restoration, isolation treatment to prevent the cracks from propagating, etc. Among these strategies, sawing isolation cuts to prevent cracks from propagating seemed to be a novelty. Furthermore, to each option of strategies, lessons drawn from the field projects are provided for reference to the future cement concrete pavement maintenance to ensure the effectiveness of treatment.

Based on damage mechanics, rock mechanics and finite element method, finite element program of damage additional displacement is compiled. A set of stochastic fractures is chosen, its dip is NW30°. The damage effect of jointed rock tunnel is discussion under different dip angle, density (damage factor) and filling condition (tension & pressure shear stress transfer coefficient). The analysis shows that damage additional displacement absolute value of tunnel vault and bottom increase with damage factor increasing. And their relationship is nonlinear. The tunnel damage effect is unrelated with tension shear stress transfer coefficient when dip angel of stochastic is 0° and 90°. Damage effect of key point on vault and bottom is basically contrary under the same dip angel. The smaller is dip angel, the greater is damage effect of vault settlement and bottom hump. The damage effect of tension shear stress transfer coefficient is larger than that of pressure shear stress transfer coefficient. But the damage effect of variation of tension shear stress transfer coefficient is less than that of pressure shear stress transfer coefficient.

As one kind of railroad tracks, the slab track has already widely been applied in the high-speed railroad. In order to satisfy the high-speed railroad security and the comfortableness, the slab track's ultimate subsidence is controlled very strict during construction and operation. Examined in this paper is the roadbed subsidence rule of Wuhan-Guangzhou railway passenger special line in China. The site observation of roadbed settlement is utilized and the subsidence curve has drawn up. Goes a step further, based on the numerical calculus method and the forecast assessment, the roadbed settlement rules of the different ground reinforcement processing have been represented. It is shown that the ultimate subsidence satisfied the request of design.

In this paper, on the basis of micropolar (Cosserat) continua approach, a constitutive model for simulation of granular material (e.g. sand) response in the elastoplastic range has been presented. Numerical analyses on strain localization in this type material are carried out in the last part of this paper. The influence of the evolution of the internal length scale micropolar parameters on the formation of strain localization is investigated.

The paper deals with the model about nonlinear consolidation phenomena. Stresses history of soil have a great influence on soil consolidation properties. Under external loads soil properties will change from over to normal consolidation regimes. Considering the impact of the stress history on consolidate characteristics of different depths foundation soil, according to different drainage conditions and the actual distribution of load and weight stress along the depth, a consolidation model has been developed, which can describe the consolidation phenomena of over-consolidation ratio changes with the soil depth and in a horizontal homogenous clay changing from an over to a normal consolidation regime. The equation of the model has been solved by use of numerical method. And consolidation curves of different depths clay also have been obtained. In this paper it has been analyzed that some parameters, such as the load size and soil pre-consolidation pressure etc, have a significant effect on the characteristics of soil consolidation. The results show that the dissipation of excess pore water pressure is faster with larger load on the ground. Therefore the over-consolidated soil is more easily changed into a normal consolidation. If τ is denoted the relationship between final effective stress and original effective stress, the time for soil to consolidate is longer with larger τ.

The unconsolidated-undrained fast shear tests of saturated-unsaturated remolded soil samples under different moisture content (which is 1.1%, 10.1%, 14.9%, 19.9%, 24.2%, 29.9%, 37.7%, respectively) and normal stress (which is 50kPa, 100kPa, 200kPa, 300kPa, 400kPa, respectively) were studied by the modified SDJ-1-type strain direct shear apparatus and U.S. Lab VIEW data acquisition system. The shear strength parameters of unsaturated soil samples, i.e. general cohesion and general internal friction angle were obtained based on Mohr-Coulomb strength theory. The test results showed that the general cohesion firstly increased and then reduced with the moisture content increasing, and the general internal friction angle increased with the moisture content decreasing. The shear stress-shear displacement constitutive equation of the unsaturated soil was established based on equal displacement assumptions and the test results. The fitted results coincided with the experimental results very well. The concept of general shear strength parameters was proposed in the paper, and would provide a simple and practical method to obtain the strength parameters for engineering practice.

Subgrade soils are very important materials to support highways. Resilient modulus (M_r) has been used for characterizing stress-strain behavior of subgrade subjected to repeated traffic loadings. Several constitutive equations have been suggested to estimate the resilient modulus. The main objective of this study was to validate the predictability of the existing constitutive equations and evaluate the use of one or more of those equations in predicting resilient modulus of cohesive soils in Shanghai. Two predictive models to estimate regression coefficients k₁, k₂, and k₃ obtained from the lab tests was developed. The predicted regression coefficients compare well with measured ones, and the measured and predicted modulus values are not significantly different.

Microstructure and micromechanics play significant roles and are considered to govern the macroscale behavior of granular soils. Laboratory experimental methods such as X-ray tomography and solidified-then-sectioned method are the traditional way for microscale analyses. But these methods are usually time consuming, expensive, or exceedingly difficult to perform. In the current study, a series of three-dimension discrete numerical simulations are performed to simulate the direct shear tests with different initial porosities and confining stresses. Particle behaviors (particle rotation and displacement) are investigated. Information of contact parameters (contact normal and contact force) which is not readily observable in the laboratory is obtained. Statistical analyses are performed and spherical histograms are employed to present the distributions of three-dimensional contact normal and normal contact force. Rotation of the principal stress directions, which is proposed theoretically and observed experimentally by some previous researchers, is successfully captured.

A series of undrained triaxial tests were performed on coarse aggregate using discrete element model. In order to take the shape of grains, each particle is formed by clumping two equal-sized particles together. The distance between the centers of two particles is equal to 1.0 times the particle radius. The numerical model of coarse aggregate is generated, and the desired porosity is obtained by a radius expansion method. Using numerical undrained triaxial tests the micro-mechanical properties of the numerical material are calibrated in order to match the macroscopic response of the real material. Numerical simulations are carried out under the same conditions as the physical experiments (porosity, boundary conditions and loading). The peak stress and pore water pressure behavior of the numerical material is studied. The relationship between macroscopic mechanical properties and microscopic parameters such as contact orientation and contact forces can be achieved in this way. The calibration procedure reveals that the peak stress of the coarse aggregate sample depends not only on local friction parameters but also on the shear modulus and Poisson's ratio. The larger the value of the applied shear modulus, the higher the resulting stress peak. Furthermore, the pore water pressure response depends strongly on local friction. The numerical results are quantitatively in agreement with the laboratory test results.

Traditional fractional visco-elastic models with constant parameters cannot well depict the rheological behavior of geomaterials. The purpose of this paper is to weaken or eliminate the defects of fractional visco-elastic models by replacing some constant parameters with variable ones. Numerical simulation with the corresponding experimental data shows that the modified model can better describe the rheological behavior of geomaterials. Moreover, it is worth pointing out that the fractional order has a strong relationship with the deviatoric stress, which is suggested to be exponential in this paper.

Stratified rock mass has been widely existing in geotechnical engineering. Although many constitutive models have been adopted to describe the characteristic of the rock mass, like Mohr-Coulomb model and Hoek-Brown model, there are still few studies have been done on the constitutive model that can describe the stress-strain relationship of stratified rock mass. In the present paper, numerical solutions for prediction the strength of stratified rock mass is built, which is based on the Ubiquitous-Joint model for describing characteristic of stratified rock mass. Then its result is compared with that from the analytical solution based on Mohr-Coulomb model for validation.

When soils are subjected to dynamic loadings, their stress states not only alter in stress ratios but also in principal stress orientations cyclically. Under these complicated stress paths the pore water pressure of soils may develop to the level of damage due to liquefaction even at a relatively low shear stress ratio. Therefore, to investigate the characteristics of pore water pressure buildup under such stress paths, a series of experiments were conducted with hollow cylinder apparatus. The samples are saturated silt from the sea entrance of Yangtze River with the relative density of 70% and 30%. The tests employed three kinds of cyclic loading schemes including changes of principal stress orientation (i.e. cyclic triaxial, torsion shear and principal stress rotation tests). According to the testing results, the dissipation energy (accumulated shear work per unit volume) was calculated for each sample. Based on it, the influences of cyclic stress ratio, frequency, relative density and cyclic stress path on the pore water pressure buildup were analyzed. In light of the concept of collapse, the collapse energy was proposed as a dynamic strength criterion. Subsequently, an energy-based pore water pressure model was proposed, whose parameter could reflect the collapse energy.

Both temperature and shrinkage loading influence the long-term performance of bi-block ballast-less tracks. In this paper, an interactive finite element method was utilized to model the stress-displacement response and crack behavior of bi-block ballast-less track that is resting on subgrade foundation and subjected to temperature and shrinkage loading. The influence of various factors such as the slab reinforcement type, the slab thickness, the slab-reinforcement ratio, and the slab crack interval were also studied. In general, the results indicated that the slab-reinforcement ratio and the slab crack interval spacing had a significant influence on the slab remaining strength, concrete tensile stress, steel tensile stress, and slab crack width. All these factors need to be well accounted for during design. By contrast however, the slab thickness parameter exhibited negligible influence and can, therefore, be ignored during design.

A number of undrained triaxial creep tests were performed for remolded Hong Kong marine clay (HKMC). The tests performed include three types: (1) three single-load-staged undrained triaxial compression creep tests; (2) one multi-load-staged undrained triaxial compression creep test, and (3) one multi-load-staged undrained triaxial extension creep test. Based on the test results, the undrained creep stress-strain Behavior are investigated. It is found that the relationship of axial strain rate (ɛ˙_a) against time (logt) for the single-load-staged creep tests is nearly linear, and for different creep loads the slopes of lines are almost the same. In multi-staged creep test, however, the creep deformation of current step will be affected by the current deviator stress as well as the creep history in the previous step. The parameters, m and α, will not be a constant, but changes with the current deviator stress and stress history. Based on the test results, two equations are found to determine the parameters of m and α.

Pre-consolidation pressure provides valuable information about soil behavior and, specifically, settlement under an induced load. Soil is expected to have less settlement before its pre-consolidation pressure and much more settlement after that point. The pre-consolidation pressure and the compressibility of the soil can be determined from the results of a one dimensional consolidation test. Different methods have been developed to obtain the accurate pre-consolidation pressure from one dimensional consolidation test data. This paper presents and discusses the results of the one-dimensional consolidation test data from an extensive testing program. The test specimens used were obtained from multiple borehole locations and were extracted using Shelby tube samplers. The focus of this paper is the comparison of three pre-consolidation stress determination techniques, which were performed on each specimen of the large sample pool. The methods used were the Casagrande method, strain-energy method, and intersecting tangent method. The implementation of these methods will be evaluated. In addition, the subjectivity of each method will be addressed. The final results of the techniques will then be compared and contrasted.

The determinations of effective friction angle are ambiguous for many geotechnical practical applications. This research conducts 40 sets of direct shear tests to observe the variations of friction angles for normally consolidated soils using concepts of friction law in physics. Based on the test results, the observed values of effective friction angle have shown a statistical normal distribution within a bounded interval. For a more reliable stability design, the effective friction angle can be determined directly by taking into account the mean value and different values of standard deviation dependent upon the risk evaluation.

This paper contains an experimental study conducted in laboratory dealing with a reproduction of landslides in layered soils by shearing tests on triaxial apparatus. The samples are reconstituted with alternating layers of sand and marl, disposed in plane layers or inclined layers about 40 degree angle. The study is based primarily on a thorough visual analysis of the samples before and after failure. It allows distinguishing the failure mode of each layer. It also helps to localize the plane failure, especially in inclined layers. However, it shows the evolution of pore pressure and deviatoric stress based on nature of layers, their arrangement and inclination.

The plus sign in the Mohr-Coulomb's equation conceals an inherent hypothesis. According to the principle of superposition of forces in physics, it expresses that the shear stresses contributed by the cohesions and the frictions are occurring on a shear plane simultaneously. However, such assumption has never been questioned since the application of this equation in 1776. This paper proposes that before the combination of any two types of shear stress, they shall be examined if they are identical physical events with the same spacetime coordinates. This research conducts a series of stress-controlled and strain-controlled direct shear tests to verify this assumption. Test results have shown that both cohesion and frictional resistance occurred neither simultaneously nor in the same space. In conclusion, for a given failure plane of a soil, it is likely to occur only one type of shear stress under a physical spacetime.

As a new geocomposite, glass fiber cement soil has better mechanical properties for the reinforcement effect of glass fiber, and it can be widely used in such projects as subgrade replacement, subgrade strengthening, slope protection, foundation cushion, etc. However, the mechanical properties of glass fiber cement soil with different glass fiber contents under different confining pressures still need further research. In this paper, glass fiber cement soil with different ages and glass fiber contents were researched through laboratory triaxial shear test under different confining pressures. Based on the laboratory test results, the strength and deformation properties of glass fiber cement soil and the rational mixing ratio of glass fiber were analyzed. It was found that confining pressure and glass fiber content played important roles in affecting the stress-strain behavior of glass fiber cement soil samples at the same age. This research is helpful for wider application of glass fiber cement soil.

A true triaxial testing apparatus with rigid compound and sophisticated loading system was applied to carry out series of tests to study the stress-induced anisotropy of sand under three dimensional stress states. The additional loads were applied from σ₁, σ₂, and σ₃ direction based on initial three dimensional complex stress states. The different stress and strain relationships in different directions were investigated. Stress-strain matrix was studied by analyzing the measured stress and strain in different principal directions. It was found that there is remarkable anisotropic stress and strain behavior in different principal directions which is much different from traditional triaxial testing results.

The need to address dwindling supplies of natural resources has led researchers to seek out alternative uses for industrial bi-products. In this study, we investigate the application of ash produced in coal burning power generation plants to substitute natural aggregate in concrete and backfill. Ash from circulating fluidized bed combustion (CFBC) was mixed in various proportions with the bottom ash from pulverized coal (PC). Specimens were tested in accordance with standard specifications to evaluate engineering properties. Variables included mix proportions and preloading, and all samples were subjected to compressive strength tests, soil compaction tests, direct shear tests, California bearing ratio (CBR) tests, triaxial permeability tests, and scanning electro-microscopic (SEM) observation. These tests were performed to verify the feasibility of CFBC ash mixtures for use as backfill material or controlled low strength material. Test results indicate that the optimum moisture content of the six mixtures decreased with an increase in the proportion of PC bottom ash and increased with an increase in preloading. Cohesion and internal friction angle increased with an increase in loading. The highest CBR value was attained with a ratio of CFBC ash to PC bottom of 1:1.5 by weight. The coefficient of permeability increased with the amount of PC bottom ash.

This study proposed an anti-frost geomaterial, comprising waste foundry sand (WFS), fly ash (FA), expanded polystyrene (EPS) beads, Portland cement and water, which is known as WFS-FA-EPS mixture. Twenty series of mixtures were prepared and investigated with regards to the effect of mixture component on the frost heave mitigation of the material. A freeze chamber was set up to impose frost action onto the mixtures. Results indicate that WFS-FA-EPS mixture is able to mitigate or eliminate frost heave if the mixture is properly designated. Compared with common earth fills, the mixture presents high micro-porosity, small frost heave, and low thermal conductivity. The frost heave mitigation of the mixture mainly depends on the volumetrically buffering capacity of EPS beads and cohesion force by cement content.

The response of a soil-structure system subjected to monotonic or cyclic loading is influenced significantly by the mechanical behavior of soil-structure interface. In this paper, the friction characteristics of the crushed rock-concrete interface and the role of the crushed rock deformability were examined through a series of monotonic and cyclic direct shear tests. The physical modeling technique of parallel gradation was adopted where two parallel gradation curves of the crushed rocks were prepared and used in the tests. The tests were carried out in dry condition and with two initial void ratios representing both loose and dense states. Two concrete interfaces of different roughness were used in the interface direct shear tests. The validity of the physical modeling technique of parallel gradation is also discussed.

In excavated earth structures (e.g. Deep Excavation, Cut slope, and Underground Construction etc.) unloading is the most predominant factor that affects on the behavior of soil mass. Although in engineering practice, loading mode is usually applied without really considering the influence of unloading factor; and shear strength parameters are often deduced from the conventional triaxial compression test. There are some doubts when applying the shear strength characteristic to analyze the stability of unloading cases. In this study, a comparison in soil shear strength between loading and unloading modes was pointed out, which was based on two series of tests for remoulded clay conducted on the Advanced Stress Path Triaxial Testing System. The test results showed that the quantities of shear strength in both cases were almost the same, but there were some discrepancies between them in the stress-strain and excess pore pressure characteristics.

Drilled shafts socket in rock have been used widely as a foundation system for highway bridges. The method of p-y curves has been considered as the most universally accepted method of analysis. In this paper, recent research at Ohio Department of Transportation, including both field lateral load tests on large-size drilled shafts in rock and theoretical study using 3-dimensional finite element (FE) simulation techniques, will be described. Using FE simulation results, coupled with field testing data, theoretical models for p-y curves in rock mass are derived. One case involves a rock mass where elastic rock properties could be treated as isotropic materials and the rock strength is governed by Hoek-Brown strength criteria. The second case involves a rock mass with dominant joint sets such that the elastic rock properties could be characterized as an equivalent transversely isotropic material while the strength of rock is governed by anisotropic strength criteria. The validity of the proposed p-y criteria is presented by way of comparisons between predicted shaft load-deflection and moment-depth curves and measured field data.

In this study, a numerical triaxial test simulation on the dense sand was carried out using the three dimensional particle flow code (PFC3D) with a linear contact model. The influences of the friction coefficients on the stress-strain behavior of the sand were analyzed. Numerical test results show that the higher friction coefficients lead to the higher peak strength for the dense sand. Further, the formation and development of the shear band was also investigated. Numerical simulation test proved that PFC3D can simulate triaxial test very well. It also showed that the microscopic parameters of the model can greatly influence the macroscopic behavior of the granular materials. The PFC3D numerical simulation method is able to capture the very small-strain behavior of the dense sand.

Developing reliable and versatile constitutive models for geomaterials has been challenging tasks for nonlinear finite element analysis of geotechnical engineering systems. The fuzzy set plasticity theory has been developed to account for the nonlinear soil stress-strain response under complex stress paths. The theory in many ways resembles the bounding surface plasticity, where the plastic modulus is a function of the distance between the current and image stress states in the stress space. Based on the concept of fuzzy set theory in mathematics, a membership function whose value ranges from 1 and 0 is introduced in the Fuzzy Set Plasticity Theory to specify the plastic modulus at a given stress state. In this paper, the laboratory test results of hollow cylinder tests on Hostun sand from the CASE data base were selected to assess the fuzzy set plasticity model by simulating the sand behaviors under those complex stress paths.

Study on long-term stability of gas storage built in bedded rock salt is one of the most important contents of safety evaluation. This paper probes into long-term stability of gas storage built in bedded rock salt via the WIIPP model and proposes numerical solution of WIPP creep model. Conclusions can be drawn after creep numerical analysis on single storage cavern: (1) There exists differences between interlayer creep deformation and that of salt rock layer.(2)Size of internal pressure exerts important affect on convergent deformation of cavern. The lower the pressure, the larger convergent deformation of cavern is and ratio of convergence is nonlinear. And at early stage, bulk decreases evidently then gradually becomes steady

The detrimental consequences of expansive soils are more pronounced in areas having hot climate with low rainfall; most part of Pakistan falls in semi-arid zone. A study was under taken to find a cheap and simple method of treating expansive soils, mostly found in southern part of Pakistanl. Hydrated lime is the cheapest options because it is available in abundance in Pakistan. The study evaluated the effects of hydrated lime on compacted high plastic clay having high salt contents with focus on establishing a suitable range against high potentials for volume change, low strength, poor permeability and dispersivity. It was found that the lime is a good stabilizer. 6–10% of the lime by weight is recommended; CBR (soaked) strength increases to 34%, OMC increases by 3% with slight decrease in maximum dry density. and swell potential of compacted soil was reduced to < 5% whereas with addition of 10% limes the shrinkage was reduced to 4%. Addition of 10% lime increases permeability by six folds and treated soil behaved as non-dispersive. However, the use of the lime, in excess of 10% has adverse effects on strength of the soil.

The three indices for classification of expansive soil used as filler was the key and core of the physical treatment technique which was a major breakthrough in expansive soil embankment engineering. Test on soil properties, strength and deformation of road performance were performed for three kinds of expansive soil in Bai-Long Expressway in Guangxi Zhuang Autonomous Region in order to verify its rationality. In terms of testing results and the new classification criteria of expansive soil used as embankment filler determined by modified CBR strength, modified CBR swelling rate and consistency, it is concluded that the indices for the three kinds of expansive soils all satisfy the requirements. Therefore, the Bai-se expansive soils can be directly used as embankment filler. Accordingly, the applicability of the three indices for classification of expansive soils as embankment filler is verified by the laboratory tests and practical projects.

Chemical improvement, the effect of which is generally evaluated by swell-shrink index, is a common method to treat expansive soil. In order to establish the relationship between unsaturated soil theory and engineering problem, the soil-water characteristic curve is used to evaluate the improvement effects on expansive soil. Two modifiers, lime and fly ash with four various amounts, were added into the Baise expansive soil to conduct the free expansion ratio test. The tests of dewetting soil-water characteristic curve at the range of 5∼1000KPa were conducted by pressure plate apparatus. The expansibility and soil-water characteristic curve of the improved expansive soils are obtained. Based on the theory of unsaturated soil, the SWCC fitted by VG model for two modifiers with different mixing amounts are analyzed. It can be found that four indexes, saturated gravity water content, air entry value, residual water content and curve slope, can be used to evaluate the chemical improvement effects on expansive soil. The improvement effects can be determined only if three indexes met the requirements, but the saturated gravity water content is indispensable.

Based on the character of soil semi-infinite space when sampling penetration, the disturbance effects caused by sampling penetration, the strain formula which was provided by the deformation and strain formulas of spherical cavity expansion was derived in this paper, and which was compared with the results of Baligh and numerical Simulation by ABAQUS, verified the rationality of the solution. By calculating and analyzing the paper got the conclusion that the impact factors of the disturbance and the law of soil deformation were reasonable when sampler penetrated into soil in soft soil area.

Pulverized fuel ash is used as a replacement for a part of cement in grouting engineering and density of cement pulverized fuel ash grout is a critical parameter for the grouting quality. In order to measure grout density dynamically and accurately, a new type nuclear density transducer was developed based on the basic principle of interaction between γ-ray and substance. The nuclear density transducer is suitable to measure almost all types of cement pulverized fuel ash grout with different water-pastern ratio, which is widely performed in dam curtain grouting and foundation reinforcement grouting. Principle and key technical points of the nuclear density transducer were discussed in this paper. In addition, the experimental researches of the new transducer were described.

Microindentation is regarded as an efficient method to identify the mechanical properties of materials. However, its application to geomaterials, such as rock and concrete, is still an open issue in recent years. In this study, a microindentation device named Rochart is developed in order to characterize the nonlinear elasto-plastic behaviour of rocks. The application to a large number of rocks is shown in comparison of traditional test results. Taking into account the triaxial stress condition of rocks, the device is also designed to conduct the microindentation test with confining pressure by adding a pressure cell. The description of the machine and its calibration procedure are presented is this paper. The microindentation tests under different confining pressures are carried out on a typical rock — sandstone. The obtained curves show a confining pressure sensitive behavior of rocks in microindentation tests.

A forensic investigation was conducted to determine the underlying cause of a premature pavement failure. The premature pavement failure was occurred in the form of rutting and alligator cracking. Through extensive field and lab testing, it was found that the moisture susceptible base is the primary cause of the premature failure and the porous asphalt concrete (AC) being the secondary cause. It is noted that the base layer was built according to plan and met the current material and field density requirements. As part of the field investigation, ground penetration radar (GPR) was utilized to survey the entire area. AC cores were taken to correlate the dielectric measurements from GPR with the lab measured density to generate the density/air-void map. More than 50 cores were taken to accurately determine the air void content. The results indicate that the air void exceeds 10% and did not meet the specification requirements. Based on the lab results, there are 36% of the cores fall into the category of either penalty or remove and replace. It was concluded that material requirements which are only based on the field density and moisture content are inadequate to control the construction quality, as it was not able to protect against premature failures illustrated in this paper from occurring. Even though it is tedious to conduct the moisture susceptibility tests to determine strengths at different moisture levels, it is a viable tool to minimize the premature pavement failures.

The roadway is the main connection between two places, as well as the most important national infrastructure and public facility. This study looks at the problem of defective roadway infrastructure leading to government compensation from the view point of traffic engineering and traffic management. In some cases, people may lose their lives because of the improper installment of the roadway facilities, the government compensation then becomes the only way to remedy these losses. This study is being conducted in view of the severe problem of road defects causing traffic accidents. It is divided as three types: (1) summary and analysis of 14 road defects that lead to government compensation; (2) case studies on existing road defects; (3) survey of roadway users on road defects and road use satisfaction. Of the 500 issued surveys, 377 returned as valid samples, a 75.4% recovery rate. The survey showed that of the 14 commonly encountered road defects, road users thought "unevenness of man-hole covers with road" to be the most dangerous, the second being "pot holes or depressions," and the third "damage caused by construction." According to "the degree of satisfaction of road use and management," roadway users were more dissatisfied with "construction" than with "management."

Incipient motion of solid grain in solid-liquid two-phase flow is often concerned in Geotechnical Engineering, such as soil piping, contact scouring, and flowing soil. The random deposit location, grain size, seepage forces, fluid velocity, and the structure of grains on the surface of passage causes the randomness of the incipient motion of solid grains. A random variable of dimensionless exposure was introduced to denote the location randomness. The probability of the variable distribution was counted as uniform. In consideration of buoyant weight, hydrodynamic pressure, hydrostatic pressure, friction shearing force, uplift force, cohesive force of grains, and the relationship among force arm, force balance and exposure, a calculation model for critical velocity of solid grain was established by means of moment equilibrium analysis. Integrating the critical velocity equation and submergence probability distribution equation, a quantitative relationship between the critical velocity and the incipient motion velocity of grains was built, which offers a practical formula for calculation of the critical velocity under certain incipient motion criterion.