Settlement Calculation Research Articles

A novel short pile foundation system bonded to highly cemented layers for settlement control

While design methods of deep foundations are mainly developed for homogenous soil deposits, the presence of highly cemented layers could lead to underestimation of resistance and overestimation of settlement of pile foundations. This study presents a novel approach using competent caliche layers bonded to the top and bottom of a continuous flight auger (CFA) pile as a new composite foundation system named caliche stiffened pile (CSP). The key objective is to optimize the required pile length in a cost-effective approach without ameliorating soil properties. Settlements of the CSP foundation for a high-rise building were monitored and full-scale tests were conducted to measure piles’ capacity. Finite element back analyses were performed to avoid adverse effect of sample disturbance in settlement calculations. A back calculation of a test fill embankment was performed to determine soil stiffness parameters by simulating an unscheduled imposed load to the structure. Impacts of the CSP on controlling the settlement of pile foundation and optimizing the required pile length are investigated using finite element analysis and a parametric study. The proposed CSP foundation can reduce the CFA pile settlement significantly in the presence of caliche layers with thickness equal or greater than a pile diameter at CFA pile head and toe, where the CSP is located.

Study on Calculation Method of Foundation Nonlinear Settlement Based on In Situ Loading Test

In this paper, a nonlinear deformation modulus method is proposed for foundation settlement calculation. In the proposed method, the nonlinear deformation modulus under different stress levels is obtained from the load-settlement curve of in situ loading test, which are then applied to the layerwise summation method for calculating foundation settlement. On this basis and referring to the Duncan-Chang model, a variable modulus constitutive model suitable for numerical calculation of foundation settlement is further proposed. The required parameters of this model are the same as those of the nonlinear deformation modulus method and can be determined by the in situ loading test. The validity of the proposed calculation methods of foundation settlement is verified by the in situ loading tests under different plate sizes. The results illustrate that both the nonlinear deformation modulus method and the variable modulus constitutive model compare quite well with the test results, and the deduced results can better reflect the nonlinearity of foundation settlement.

Three-dimensional analytical solutions to the half infinite thermo-elastic body pressed by a rigid cylindrical structure in thermal environment

The novelty of this paper is to propose exact three-dimensional analytical solutions to the half infinite thermo-elastic body pressed by a rigid cylindrical structure for the first time, in which uniform heat flux flowing from rigid structure into the half infinite body is considered. Using recent general solutions expressed by four harmonic functions and extending potential theory method to consider heat effect, the governing integral equations are first derived. Then, the equations are analytically solved and displacement, stress, and temperature field components expressed by elementary functions are obtained. To validate the presented solutions, the correctness of the solutions is exactly examined, and normal contact displacement and stress without heat effect are compared with those in literatures. Furthermore, a numerical example which is the stainless steel thermo-elastic body pressed by a displacement restrictor is studied. Displacement, stress, and temperature distributions are analyzed, and the influence of heat flux on the pressed depth is also discussed in detail. The analytical solutions presented in this paper are rather important in engineering practice and can provide a basis for indentation analysis, displacement restrictor design, foundation settlement calculation, and so on.

Preventive Structural Risk Assessment of Buried Gas Pipelines in Liquefaction of Ground

Recently, a number of earthquakes have been detected in Korea and damage has been reported. Actually, ground liquefaction was reported due to the earthquake that occurred in the Pohang. In Korea, the risk of liquefaction in the event of an earthquake is relatively higher as there are many landfill areas such as Busan's coastline, Incheon, and Cheongna International City. In this study, the effect of underground structures when liquefaction occurs is evaluated by dividing it into stages of liquefaction. Moreover, detailed evaluation methods for buried gas pipelines are presented in case of regional liquefaction that can be used in all regions. For the risk assessment of liquefaction, the Standard Penetration Test (SPT) result or Cone Penetration Test (CPT) result of the borehole is used. To evaluate buried gas pipelines, Finite Element (FE) analysis is performed using the subsidence calculation method linked with the borehole data. By defining ground and gas pipe variables, structural analysis is conducted in several cases, and the desired area is evaluated based on this. A Winkler foundation spring-based optimal finite element analysis model is developed to evaluate the structural seismic performance of gas pipelines across areas where liquefaction is expected.

Extended UH model and deformation prediction of high-speed railway subgrade

For the rapidity of trains in high-speed railway, it is crucial to guarantee the reliable and safe operation. Strict controls are needed to prevent excessive subgrade deformation. In order to perform more accurate subgrade deformation calculation, the constitutive model used in simulation should demonstrate the small-strain stiffness for uneven settlement calculation, and illustrate time-induced deformation for post-construction deformation. An E-UH model is established based on the original UH model. In the E-UH model, the elastic hysteresis relation is added to describe the initial high stiffness and nonlinear stiffness decay. In addition, the E-UH model also couples the equivalent formula between overconsolidated characteristics and time-induced deformation. Then the effectiveness of this new model is testified by element test prediction. By means of the second development interface of a finite element software, the E-UH model is developed as a subroutine and applied to numerical simulation of subgrade deformation. The simulation represents that the E-UH model is capable of performing deformation prediction during the subgrade construction and post-construction phases, and indicates that considering small-strain stiffness can make the uneven settlement more prominent. This research provides a practical and efficient constitutive model for numerical simulation of the high-speed railway subgrade deformation.

Study on optimization of pouring time for late poured band

The setting of the late poured band is an effective measure to control the differential settlement and the stress concentration of the foundation. However, the lag of the pouring time of the late poured band will also bring adverse effects to the construction process. Taking a large commercial complex as an example, Midas GTS NX finite element software is used for the overall foundation modeling, and the collaborative calculation of settlement is carried out by adjusting the composite foundation scheme. The calculation results of conventional codes are compared and analyzed, and the scheme is verified and optimized. Then, the variation value of differential settlement on both sides of the late poured band with loading is studied by simulating the graded loading of each area in the whole process of construction. By comparing the variation value of differential settlement and the calculation value of differential deformation that the stiffness of the late poured band can resist and the limit value of codes, the time node of late poured band pouring in advance can be obtained, and finally the influence of early pouring of the late poured band on the collaborative settlement of the foundation is verified and calculated. The results show that: the settlement calculation of finite element analysis is generally smaller than that of standard calculation; The settlement at the edge of the raft is small, and the settlement at the center of the raft and the places with large load is large; Considering the interaction of the whole raft and subgrade under the raft, this method can verify and optimize the design scheme of composite foundation and save the pouring time of the late poured band. The experience and achievements so made can be used as a reference for similar projects.

Large-Scale Plate Load Tests to Determine the Collapse Potential at Santorini 150 kV GIS Substation Site

Two large-scale plate load tests were carried out at the foundation level of the Santorini 150 kV GIS Substation, where the subsoil was identified as collapsible. The purpose of these load tests was to establish in-situ, the magnitude of the expected settlements due to the collapse of the subsoil structure after inundation, while applying a bearing pressure equal to the maximum expected according to the structural design. After completion of the tests, which are described in detail, the resulting settlements were found to be acceptable, so no soil improvement measures were required and it was concluded that with the design and execution of these innovative load tests, it was possible to measure under actual field conditions the magnitude of settlement due to collapse of the soil structure. This led to a more economical foundation solution, compared to the one that would have been adopted were only laboratory tests taken into account in the calculation of settlements.

Discussion on Calculation Method of Soft Soil Foundation Settlement in Guangdong-Hong Kong-Macao Greater Bay Area

The modulus of compressibility of muddy soil in Dawan District is low, and the equivalent value of modulus of compressibility within the calculated depth range of foundation settlement is generally less than 2.5MPa, which exceeds the value range of empirical coefficient calculation basis for settlement calculation in the specification, and has the characteristics of large settlement. This time, according to the measured data of a coastal foundation settlement in Dawan District, the maximum settlement is fitted with the hyperbolic method, and the theoretical value of the total settlement is calculated according to the Code for Design of Building Foundation (GB50007-2011). Based on this analysis, the fitting curve equation of the empirical coefficient of settlement calculation when the equivalent value of the compression modulus is 2.5~4.15MPa is given, and the recommended value of the empirical coefficient of settlement calculation when the equivalent value of the compression modulus is 1.5~2.5MPa is calculated, so as to improve the calculation deviation of the original formula.

Swelling and collapse behavior of expansive marl and its implications in foundation engineering

Expansive soils increase their volume upon wetting, but under high vertical stresses may exhibit collapse, with the latter aspect being rather overlooked in foundation engineering. Oedometer swelling/collapse tests on expansive Pliocene marls of various calcium carbonate content and plasticity index sampled from Nicosia, Cyprus, indicate that, unlike the free swelling strain, the swelling pressure is rather insensitive to the initial degree of saturation. Consequently, significant collapse strains upon wetting are not unlikely to occur in practical situations. The paper discusses the implications of this behavior in the case of shallow foundations and proposes methods of analysis. Under certain conditions, foundation design based on settlement calculations that use as input the fully saturated soil properties may be unconservative and supported structures may be exposed to severe risk of damage. For the design of mat foundations, stepwise distributions of the equivalent modulus of subgrade reaction across the mat as a function of the average bearing pressure are proposed based on the results of coupled finite element simulations. These distributions allow prediction of the peak bending moments produced at the end of the wet and dry seasons due to ground swelling and shrinkage, respectively, for the climatic conditions of Cyprus.

ГЕОЛОГИЧЕСКИЕ ОСНОВЫ РАСЧЕТА ОСАДОК ГРУНТОВЫХ ОСНОВАНИЙ

The article discusses the geological regularities of the transformation of the stress-strain state of the soil foundation through the formation of dissipative geological structures that interact between the geological environment and the foundation. The technology of calculation of the ground base settlement is presented. A specific example of estimation of strip foundation settlement shows that the proposed technology is efficient and can be further used for practical purposes

ОСОБЕННОСТИ РАСЧЕТА ЖЕЛЕЗНОДОРОЖНОГО ПУТИ НА БЕСШПАЛЬНОМ ОСНОВАНИИ

The paper proposes a method for calculation of strength and settlement of a sleeperless construction that considers a maximum number of factors that affect reliability and safety of a railway track.

ON THE METHODOLOGY OF PASSPORT DOSES CALCULATION FOR UKRAINIAN SETTLEMENTS RADIOACTIVELY CONTAMINATED DUE TO THE CHORNOBYL NPP ACCIDENT.

scientific substantiation of the new methodology for estimation of passport doses of the settlementswhich belong to Zone of Unconditional (obligatory) Resettlement, or 2nd zone and Zone of Granted VoluntaryResettlement, or 3rd zone in the framework of dosimetric passportization in accordance with the legislation ofUkraine. 37 years after the accident, radioactive contamination of the environment has significantly decreased. However, it is still necessary to carry out ecological and dosimetric monitoring and apply countermeasures in certain territories of Ukraine affected by the accident at the Chornobyl Nuclear Power Plant: restriction of the consumption of locally produced milk, forest products, etc. The methodology, which was since 1996 used to estimate the passport doses of Ukrainian settlements, no longer corresponds to the current level of scientific knowledge about radioactive contamination of environment. The new methods of passport doses calculating presented in the work involves the use of a model whose parameters are determined by the types, quality and completeness of radio-ecological and dosimetric monitoring carried out on the radioactively contaminated territories in 1986-2013. The methodology takes into account the specific of radioactive contamination of each settlement. The passport dose of external exposure is reconstructed only from 137Cs radionuclide, because the contributions of other Chornobyl radionuclides influence the radiation dose only in the first years after the accident. The passport dose of internal exposure is formed as a result of the consumption of 137Cs contaminated food products. It is calculated depending on the availability in the settlement in the current year of the results of measurements of the 137Cs radionuclide activity incorporated in the human body using a whole body counter (WBC) and the activity of 137Cs in the private milk. At the same time, priority is given precisely to the results of WBC measurements of 137Cs. A new methodology (Methodology-2023) for passport doses calculation of Ukrainian settlements was substantiated. A comparison of passport doses based on the results of radioecological and dosimetric monitoring in 2011 calculated by Methodology-2023 and passport doses calculated by Methodology-96 was made.Passport doses calculated by Methodology-2023 increased by 40 % on average compared to doses calculated by Methodology-96. At the same time, passport doses of internal radiation calculated by the new methodologyincreased by 1.5 times, and passport doses of external radiation increased by 1.7 times. The passport dose of 2011, calculated by Methodology-2023, exceeds the legally established limit of 1 mSv in 71 settlements, most of which are located in Korostenkyi raion of Zhytomyr Oblast.

Case Study of an Underpinning Pile Foundation for an Interval Tunnel Crossing an Existing Bridge

When urban subway tunnels cross existing bridge pile foundations, having a pile foundation underpinning that ensures the safe operation of existing bridges while enabling the safe construction of subway tunnels is the focus of attention. This paper takes the running tunnel project from Huaguoyuan West Station to Huaguoyuan East Station of Rail Transit Line 3 in Guiyang City, Guizhou Province as the background. The reasonableness and feasibility of the passive underpinning construction scheme for the Guihuang Viaduct was studied. The construction plan includes the following steps: underpinning pile construction, foundation pit excavation, the concreting of the underpinning bearing platform, and existing pile truncation. In order to ensure the structural safety of the existing viaduct during the construction of the pile foundation underpinning, a 3D numerical model of the construction of pile foundation underpinning and the whole process of tunnel construction was established. The settlement calculation results of the foundation pit and bridge pier were compared and analyzed with the field monitoring data to verify the accuracy of the numerical model. Further detailed analysis of the settlement of the bridge deck, the deformation of the existing piles, the axial forces of the existing piles, and the forces on the underpinning bearing platform was carried out. The results show that the bridge superstructure load can be transferred to the underpinning bearing platform smoothly after the existing pile truncation construction. The removal of obstacle piles during tunnel excavation has a very limited impact on the superstructure of the bridge, proving the reasonableness and feasibility of the construction plan.

Calculation of Building Settlement Induced by Tunneling Based on an Equivalent Beam Model

Calculation of Building Settlement Induced by Tunneling Based on an Equivalent Beam Model

Calculation of surface settlement and pile foundation deformation caused by shield machine tunnelling along curve section

The shield machine tunnelling along the curve section causes more disturbance to the surrounding environment than the straight section. Pile foundation is the most commonly used foundation form in high-rise buildings, and high-rise buildings have extremely high requirements for controlling non-uniform deformation. Therefore, it is necessary to study the surface settlement and the deformation law of pile foundations caused by shield machine tunnelling along the curve section. Considering the shield machine tunnelling factors along the curve section and the coupling effect of piles and soil, the analytical calculation formula of the ground settlement and the pile foundation deformation caused by the shield machine tunnelling along the curve section is deduced. According to the actual project situation, a finite difference model (FDM) is constructed, and the correctness of the FDM and analytical prediction formula is verified by comparing the on-site monitoring data. The research shows that the error among the FDM results, the analytical prediction results, and the on-site monitoring data are small, and the surface settlement and pile foundation deformation meet the construction control standards. The friction resistance of the shield shell, the integrative gap at the shield tail (IGST), and the over-cutting gap (OG) are the main factors leading to the surface settlement. However, the shield shell friction and OG are the main reasons leading to the inner settlement of the curve section being more prominent than the outer side. The difference in the pile foundation settlement on both sides of the curve section is slight, the maximum settlement difference rate is 1.8%, and the maximum horizontal deformation rate of the pile foundation on the inner and outer sides is 9.2%, which shows that the horizontal deformation of the pile foundation is more sensitive to the asymmetrically distributed construction factors.

Estimation of elastic settlement for skirted strip foundations subjected to vertical loading

Settlement calculations are an essential part of the design of offshore foundations, although most of the existing studies on skirted foundations focus on bearing capacity. In this study, finite element analysis is used to evaluate the elastic settlement (vertical displacement) of skirted strip foundations of arbitrary stiffness embedded in either a homogeneous or nonhomogeneous soil stratum with finite layer depth. Graphical solutions are presented, which enable the determination of the drained and undrained settlements at the center and edge of the skirted foundations. Closed-formed expressions that approximate the numerical solutions well are also proposed. Numerical examples are provided to illustrate how the solutions and expressions can be readily applied in hand calculation for preliminary design purpose.

Equations for Calculating the Foundation Settlement of Zhanjiang Formation Gray Clay Considering the Influence of Multiple Factors

The Zhanjiang Formation gray clay has physical properties similar to the muddy clay of other areas, such as a large void ratio and high-water content. At the same time, it also has mechanical properties that differ from muddy clay in other areas, such as high strength and low compressibility. When calculating the foundation settlement, the equation that calculates the foundation settlement as suggested by the code tends to produce values of compression modulus that are too small, which leads to larger calculated values. This study investigated the relationship between the pressure and deformation of Zhanjiang Formation gray clay foundations with different densities, water content, and stress histories by means of a plate loading model test. It revealed the influence of these factors on the deformation modulus, and the quantitative relationship between this modulus and the density of soils, water content, and the over consolidation ratio was established. In doing so, the aforementioned quantitative relationship was applied to the equation which calculated the foundation settlement as suggested by the current code, thereby proposing a pertinent formula relevant to Zhanjiang Formation gray clay foundations. The formula was subsequently applied to two engineering examples, and the settlement amounts output were in agreement with actual measured values, indicating it is reasonable and feasible for practical application. Therefore, it can provide a reference for the calculation of foundation settlements across the coastal area of Beibu Gulf.

Research on the Application of Foamed Lightweight Concrete (FLC) in the Construction of Highway Soft Soil Foundation Engineering with Buried High-Pressure Gas Pipes

In order to study the feasibility and superiority of foam lightweight concrete (FLC) for existing buried high-pressure gas pipeline section under soft soil roadbed, this paper takes the buried existing high-pressure gas pipeline section under the second phase of the Foqingcong Expressway project as the engineering background, and designs two soft soil roadbed treatment schemes, the pile composite foundation method, and the foam lightweight concrete (FLC). Through bearing capacity and settlement calculations, it was confirmed that FLC is feasible for soft soil roadbeds in the existing buried high-pressure gas pipe section, and the three major aspects of analysis, namely the safety benefits, economic benefits and ecological benefits based on the LCA carbon emission calculation, showed that the FLC soft soil roadbed treatment method can reduce the cost by 12% compared with the pile composite foundation treatment method, which is about 1.07 million RMB, and the carbon emission is reduced by about one third. This is a clear benefit advantage. Finally, the feasibility of FLC for buried high-pressure gas pipe sections under both soft soil roadbeds was further verified by field measurements of settlement and earth pressure, which has broad application prospects.

Land subsidence calculation model under the coupling effect of groundwater and coal mining

Land subsidence calculation model under the coupling effect of groundwater and coal mining

EVALUATION OF PLATE LOAD TEST RESULTS: A CASE STUDY IN ANKARA/TURKEY

Plate load test is widely used for bearing capacity and settlement calculations of foundations. In this study, 6 plate load tests were carried out to determine the bearing capacity and settlement of the foundation. High-speed railway project will be constructed in related area. The project location is in Ankara/Turkey. Bearing capacity of the station platform building foundation was determined according to plate load test and finite element analysis. Finite element analysis (FEM) software, Plaxis 2D, was used for the understanding of the settlement behaviour of soil. Soil strength and deformation parameters were determined according to plate load test and finite element analysis. Elasticity theory was used for analytical solutions. Field measurements, finite element analysis (FEM) results and analytical solution were compared at final of the study. Finite element analysis (FEM) and elasticity theory settlement calculation results have a strong correlation with field observations.