Abstract:Ⅲ-posed problems exist in the Duncan-Zhang model parameters upon the inclusion of different inversion strategies.These ill-posed problems are graphically demonstrated and analyzed, including with inversion-base,with inversion-based,and with inversion-based.On the basis of functional analysis in combination with the Mohr-Coulomb criterion expressions,this study explains two ill-posed problems in the Duncan-Zhang model parameters inversion.Furthermore, a method for the reduction of these two ill-posed problems is proposed.The results show that the Duncan-Chang model parameter expressions produce the root causes of these two ill-posed problems.

Abstract:Scientific and rational determination of the representative values of geotechnical parameters constitutes a premise for the design of a safe and economic project.In this paper,an approach based on a Bootstrap resampling technique is proposed to determine the standard values of geotechnical parameters that have a confidence probability of 95% over the Bootstrap sample mean.First,the Bootstrap method is briefly introduced and a set of shear strength parameters is utilized to elaborate the procedures.Two examples were analyzed to assess the influence of the number of Bootstrap simulations(i.e.,the size of bootstrap samples) and the variability of original data on the convergence and accuracy of standard values.It was shown that the standard values determined using the proposed Bootstrap method have good convergence and accuracy.When the number of Bootstrap simulations was at least 100,the number of bootstrap simulations and the variability of original data had a negligible impact on the convergence and accuracy of standard values.Therefore,this method is capable of assessing the uncertainty in geotechnical parameters.

Abstract:Heavy compaction tests were conducted to investigate the compaction characteristics of gravelly clay.Combining the results of a CT scan,the effects of gravel content and water content on maximum dry density,optimum water content,and clay's compaction degree were studied in detail.The undrained shear strength of gravelly clay with different gravel content and water content were also studied.It was found that there were extra voids between gravel and clay even when the gravel content was relatively low.Consequently,it was difficult for the pore water to flow throughout the soil and the air in the inter gravel voids was blocked by the water so that the dry density of the clay was significantly reduced.Simultaneously,the compaction effort applied to the clay was also reduced because of the existence of the gravel skeleton,thus the degree of compaction of the clay decreased with the increase of gravel content.The results of the compressive tests also showed that the undrained shear strength of gravelly clay depended on the gravel and water content.As the gravel content increased,the undrained shear strength decreased,especially in the case of high water content.

Abstract:The classification of soil is an elementary part of geotechnical engineering design.This classification allows for a preliminary qualitative judgment of the characteristics of a soil.Furthermore, using a set of criteria,the soil can be classified that can assist in how it can be employed in an engineering project.In this paper,sand layer survey data of an embankment dam foundation, were subjected to two common classification methods,the code for investigation of geotechnical engineering (GB50021-2001) and standard for engineering classification of soil(GB/T50145-2007).Three hundred and forty-one sand samples were classified using these two methods.The results of this classification allowed for a statistical analysis of grading envelope,and the physical and mechanical properties of the covering layer sand samples.Finally,the characteristics of the two classification methods were compared according to the results of the statistical analysis.

Abstract:To study the quantitative difference of particle and pore size,shape,and arrangement in the natural loess in the different geographic regions of China,scanning electron microscope analysis of undisturbed loess in Lanzhou,Xi'an,and Yuncheng were obtained.Using autocad,the boundaries of the particles and pores of the material were mapped,then the boundaries were pulled away and color coded.These objects were then imported into image analysis software to obtain the long axis,short axis,perimeter,area,and long axis direction angle of each object. Next,the resulting analysis parameters were obtained to calculate the quantitative parameters that reflect size,shape,and directional arrangement of each object.Finally,the quantitative parameters of the natural loess particle and pore from different areas were compared.The analysis results showed that the mean diameter of particles in Lanzhou is the largest and the particles in this area are the furthest from being circular.The particles of loess in the three regions are uniformly arranged in space.The mean diameter of particle pores in Lanzhou material is close to that found in Xi'an and the shape of particle is closer to a circle.The mean diameter of the particles is near to the mean diameter of pore and the shape of particles is close to a circle.

Abstract:The compression modulus of soil is the important indicator that can be used to evaluate the compressibility of soil and calculate foundation deformation,validating its importance in engineering research.In this study,soils from Beijing,were analyzed to determine the variability of geotechnical parameters and the relation between the physical and mechanical indices.The analysis results showed that there was little variability in the physical property indices,but the variability of the mechanical indices was relatively large.For example,the compressibility of silt was affected by the gravity stress,the natural density,the saturation,the porosity ratio,and other factors.The mechanical properties of cohesive soils were affected by the gravity stress,the moisture content,the natural weight density,and the liquidity.A multivariate linear regression model of the compression modulus,the moisture content,the natural density,and the gravity stress was developed.This model indicated that there was regional representation in the soils tested.

Abstract:Aiming at backfilled foundation,formulas of reinforcement depth and cumulative settlement have been obtained by dimensional analysis.The proposed formulas have been validated combined with the existing engineering data.The results show that the formulas can more accurately predict reinforcement depth of backfilled foundation and cumulative settlement,and also can analyze the relationship between cumulative settlement and reinforcement depth.The results showed that the ratio of cumulative settlement and reinforcement depth varies with many factors, and only in certain distance and rammer radius,can it be extended as a constant.In the last,we analyze the impact of the hammer radius and thickness on the effect of dynamic compaction.The conclusion has a certain reference value for similar practice.

Abstract:In this study,the characteristics of a geotechnical CT visualization system are introduced and the application of CT technology for soil testing are systematically summarized,including research advances in the observation of the initial structures of soil and the structural evolution of loess,frozen soil,expansive soil,and coarse-grained soil.In addition,this study indicates potential future research directions,including the development of quantitative computer imaging analysis systems,the use of the mesoscopic structures that are visualized by CT images for the establishment of numerical models,and the development of CT scanning devices for dynamic soil testing.

Abstract:The steady-state response of an Euler-Bernoulli beam placed on a Kerr foundation and subjected to a concentrated load moving with a constant speed has been investigated.A steadystate response solution of the Kerr foundation beam was derived and the influence of train velocity, compression stiffness,and shear stiffness of the foundation beam on the dynamic response were analyzed considering possible foundation damping.The results illustrated that foundation damping can significantly reduce deflection of a foundation beam,and compression stiffness has more effect on deflection than the shear stiffness.

Abstract:A finite member element method is proposed for the analysis of the deformation of a bridge slope pile located on a steep slope.A modified finite member element method based on the composite stiffness principle and double-parameter ground model was established that was suitable for the calculation,and analysis of the stresses on the slope pile.Next,taking into account the load response of the bar system,a modified matrix of the bar element incorporating the P-Δ effect was developed.The next step involved writing a MATLAB program which was used to analyze a real example.The results showed that the precise,proposed method was valid.Also,the P-Δ effect was too considerable to be ignored in the design and calculation and double-parameter model works better than m-model on shallow ground.

Abstract:A finite element method was used to ensure the accuracy of calculation used to simulate the infinite domain of a large portion of soil around piles.In the analysis of a practical project,a lot of computer time was required to run the analysis.In the case of large scale pile group problems, a standard computer has been unable to meet the requirements of the finite element calculation, which limits its application in practical engineering.The finite element method was used to calculate the interactive coefficient of pile-pile interactions.On the basis of the superposition principle, the proposed method is expected to be applicable to the calculation of large pile group.The method can not only reduce the amount of calculation time for a pile group problem but also can improve the accuracy of the calculation.Conversely,the piles were simulated by beam elements to consider the engineering characteristics of piles under horizontal loads.

Abstract:Much investigative work has been conducted on cone penetration tests on flat ground; however,research on cone penetration tests on slopping ground is scarce.Two-dimensional discrete element method simulation of cone penetration tests on sloping ground were performed,in which the tip resistance and micro-macro mechanical behavior of the cut slope was studied.The experimental results showed that the peak value of the normalized tip resistance does not increase when the slope angle is below a specific value,but increases when the slope angle is high.Nevertheless, the residual value decreases slightly with the increase of slope angle,indicating that the boundary of cut slope greatly affects the regolith,not the subsoil.As penetration proceeds,the deformation of the soil at the two sides of the cone is asymmetric with dilation on the upslope and compression on the downslope.This asymmetry increases with the slope angle.As the cone penetrates into the regolith,the force chains at different sides of the cone are asymmetric with higher stress on the upslope.However,as the penetration proceeds into the subsoil,the force chains tend to be symmetric.The critical depth of penetration symmetry increases with slope angle forming a linear relationship.

Abstract:In the laboratory,when dense sand,stiff clay,and undisturbed soil were subjected to strength tests,these soils experienced a pronounced strain-softening behavior.A progressive failure in these materials was due to a reduction of strength produced by increasing strain.However, the standard soil test method provides that the material's peak strength is considered to be its failure strength based on the relationship between stress and strain.Progressive strength failure in soils has been previously ignored during the analyses performed using the traditional limit equilibrium approach on the basis of peak strength.In this paper,a new finite element limit equilibrium method is proposed in which strain-softening properties of the soil were assumed.And it was shown that this method can predict the stability of strain-softening soils for engineering purposes.

Abstract:Based on the analysis of the types of topography,the slope structures,and the geological hazards,within 1:1000-scale topographic maps,geologically disaster-prone areas were identified and divided into study zones.In the examined hilly gully region of the Yan'an Prefecture, the safety for life and property of the local residents were threatened by potential loess landslides, loess collapse,and rocky collapse from an unstable slope.However,the hazard from this unstable slope is difficult to prevent due to the presence of local residents and the steepness of the loess slope and rocky scarps.This study can provide certain reference for similar research in future.

Abstract:The log-log and semi-log plots of the theoretical time-drawdown relationships for confined, unconfined,and leaky aquifers possess different characteristics,which can be used to identify the type of aquifer.By adjusting hydrogeological parameters,the calculated values of time-drawdown can best-fit with observed data from pumping tests,then the nearest hydrogeological parameters of pumping field can be obtained.This method was applied to six pumping tests in Tianjin area,which resulted in determination of the types of aquifers and the value range of their hydrogeological parameters.For the similar pumping tests and engineering,especially in Tianjin area,the method and values specified in this paper can be used for reference.

Abstract:Using the prediction methods of "criterion of activity in quiescence" and "periodicity", the mid-term prediction of Ludian,Yunnan M_S6.5 earthquake on August 3,2014 was reviewed. Furthermore,the Ludian earthquake occurrence date was retrospectively rethought base on the method of "rhythm of multiplied nine days in different years".

Abstract:This study firstly gave a brief retrospection of the research on Corioli force since it was advanced.Corioli force is generated due to the rapid movement of two fault walls during earthquake. Base on this theory,the aftershocks of some earthquakes which occurred outside the Chinese Mainland,including some large earthquakes in Taiwan,and Turkish of Central Asia,were discussed.Furthermore,Corioli force effect caused by earthquake rupture can be used to predict the magnitude of aftershocks and its normative universality over the world was also analyzed.

Abstract:Anomalies in the daily and monthly mean value curve of crustal deformation anomalies before the Tangshan M4.2 and M4.8 earthquakes in 2010 and 2012 were analyzed.This study examined the earthquake reflecting ability at the Yixian seismic station.Stress and strain sensitive points were identified around the focal region of the formation and evolution of the source.A relevant earthquake anomaly may have existed if several set of instruments or different components in the same observation all showed anomalies.The reliability of a group of anomalies was better than a single anomaly.The shape of anomalies may have differed in the same observation before different earthquakes.This difference must be detected in order to reasonably identify anomalies.Similarity among anomalies in the short and imminent stage dominates earthquake preparation.

Abstract:Earthquakes can result in huge losses of human life and property.According to extensive field surveys,a significant number of foundation failure cases are due to sand settlement,as foundation upsetting and cracking can be caused by large deformations or differential settlements. Seismic waves are a type of random and irregular dynamic pulse and have a great influence on the seismic settlement of sand.By setting the boundary value in a time history curve to 60% of the maximum peak acceleration,various seismic waves can be divided into two types:vibration-type waves,which have more than two wave crests within the boundary value,and impact-type waves.Different types of seismic waves have different effects on the liquefaction and compression of sand,possibly due to the problem of energy release.However,traditional methods for calculating the seismic settlement of sand neglect the different types of waves;they merely consider the maximum acceleration amplitude to simplify this complex problem by using an equivalent sinusoidal quantity.This simplification may cause larger errors during practical applications.In this paper,the nonlinear finite element software ABAQUS,which is a frequently used commercial software for numeric calculations,is used to develop a bounding surface hypoplaticity model for sand that includes a UMAT subroutine.The formulation of this constitutive model is based on the bounding surface plasticity theory,which a large number of laboratory experiments have proven to be effective in describing the cyclic behavior of sand.The dynamic simple shear test has a few advantages in assessing the seismic behavior of soil.Primarily,since it applies cyclic shear stresses onto horizontal planes and permits the continuous rotation of principal stress axes,this test replicates field loading conditions much more accurately than the cyclic triaxial test.By simulating the dynamic simple shear test using sand with different relative densities under different types of seismic wave loading,this paper studies the influence of wave type on the process of seismic settlement and the final settlement value,as well as the deformation of sand under earthquake loading.Finally,a series of time-history curves comparing shear strain versus vertical strain were be obtained from this series of numerical experiments,and were compared with laboratory results. The main conclusions are as follows.The wave band prior to the maximum peak acceleration governs the controlling effect on seismic settlement;however,the left wave band also has an obvious influence when the peak value attains 80% of the maximum value under vibration-type seismic loading.An analogous experiment yielded similar compression results;under the same conditions but under the influence of different types of seismic waves,the compression results were disparate,as vertical strains caused by vibration-type seismic waves were greater than those caused by impact-type waves.By taking into account the wave type,this method is much more practical for the simulation of sand seismic settlement at actual sites.As the model parameters related to the dilatancy effect are constant,there is a certain amount of bias between the simulated and experiment results.Further research into these parameters is needed.

Abstract:A geomagnetic FHD-2B proton magnetometer was installed at the Yongan station in October 2009.After years of stable operation,a large set of reliable precursor observation data has been generated. The instrument is operating smoothly at present,and the data profiles contain few burrs,small lines,and low noise.However,the instrument may encounter a variety of problems in its daily observation process,influencing its normal operation.In order to improve the quality of the instrument's maintenance, it is necessary to conduct a summary of the commonly occurring instrument problems and their corresponding solutions.The FHD-2B proton magnetometer comprises communications technology, computer technology,data acquisition,and computer software processing:the magnetometer is a set of integrated and comprehensive technology.Each functional unit is independent and connected to one another, so that the failure of any unit can affect the overall instrument performance,leading to a decrease in the continuous collection rate,accuracy,or quality of the observation data.This study describes a particularly problematic situation at Yongan station,including repair methodology that involves the investigation of communication failures and faulty data acquisition for the FHD-2B proton magnetometer data, and the subsequent improvements,so that the readers can share the experience of equipment maintenance, as well as the implementation of an improved equipment maintenance program.Interference factors, such as meteorological factors,human disturbances,and unknown reasons,are discussed.The improved maintenance program,which enhances the quality of observation data,requires the station staff to document in the instrument observation log,the data preprocessing and the weather changes,providing detailed and reliable information for forecasters to accurately identify and analyze disturbances and seismic anomalies.Scheduled and effective magnetometer equipment maintenance and the keeping of daily observation log records are critical for ensuring reliable and long-term observation data is obtained for seismic monitoring.

Abstract:Owing to the abundant and various digital data within the Tianjin Seismic Station Network, difficulties occur in data exchanges between various networks when stations parameters cannot be accurately combined.The development of an integrated management system realizes data-sharing through the secondary development of liss data flow and through the fast output of large earthquake seismic events. There was need for new parameter calculations that simultaneously combined the station equipment parameters and data together,to ensure the accurate use of the data.The use of this new system will improve the efficiency of the seismic station network and the utilization rate of the observational material. The Tianjin Seismic Station Network released an integrated management system based on VB.Net in 2011.The system realized link monitoring and journal management as well as regulating the daily work and raising the monitoring capability of the link.The growth of digital observation data has caused the problem of how to provide data services and how to help if the need for a seismic trace becomes urgent. Thus,we developed a new system that utilizes the advantages of PHP and MySQL.It has the following functionalities.The administrator can add a user name,change a password,and grant user permissions. Normal users can search and download seismic events.As earthquake forecasters depend on the fast output of data during a seismic event,this new system raised the efficiency of data output.Simultaneously, the new system rapidly reports and determines the earthquake intensity,publishing both messages together; this message includes the result charts and vectorgraph.Thus,different offices can launch rescue workers and provide field monitoring on the basis of the produced message.The functionality of passing parameters in the system was added to prevent discrepancies between data and parameters.At the same time,online detection was added to draw curves of the damping changes and to produce exact figures.

Abstract:The government information service is increasingly dependent upon the Internet platform, which is especially important for administration during an earthquake.Earthquake information services based on the Internet platform,with the development and improvement of a national earthquake network system,have become the most important medium for providing an external service that disseminates earthquake data and information to the public.This could provide a web platform where domestic and overseas seismic scientists and technicians assemble global and local seismic data.Meanwhile,it could provide civilians with a source of general scientific information.Furthermore,a functional module such as a dynamic display module for map visualization of information on earthquake emergency shelters could display details provided by earthquake researchers to the public.The realization of quick and dynamic transmission of thousands of background data sets to the public is an urgent topic regarding the application of the Internet.This study explores earthquake disaster shelter data information,discusses the extraction of data from the database using the ASP language,and the format transmission of data into JSON data.Moreover,the specific programming process to efficiently deliver background data and information regarding earthquake emergency shelters using the jQuery function and Baidu Maps API function to the front page has been realized and explained.Furthermore,the information about the refuge field will be displayed by moving the mouse across the front page to an arbitrary coordinate point on the image. This study primarily focused on the specific process for realization of this system.displayed.This paper primarily focuses on the specific realization process of this system.

Abstract:Assuming that a stress wave in low strain tests spreads in semi-spherical mode,a method was established to calculate the disturbance of a tie beam in response to the frequency of the stress wave.This method is related to the geometry of the tie beam,bent cap,pier,and pile. Furthermore,a test method was designed to test the integrity of piles in a column-pile system,in which multi-channel equipment was required to record the behavior of the bent cap and pile. Tests were conducted to compare the integrity of the pile during the entire column-pile system procedure.The results showed that when pile top was free,the reflection signal could be detected after tie beam and pier were constructed.Sensors should be located vertically as a linear array that will facilitate the calculation of the stress velocity and allow the recording of the behavior of the reflection from the bent cap,pile toe,etc.In regard to abnormal signals,their peak time should be analyzed to determine their location according to the stress velocity of pier,tie beam,and bent cap.It is not recommended that the abnormal signals be analyzed using only the similar or opposite-phase method as has been the previous rule in pile integrity test when pile top was free.