Settlement Of Pavement Research Articles

Settlement Characteristics of Urban Underground Comprehensive Pipe Gallery under Different Backfill Conditions

In order to solve the problem of differential settlement of pavement after the backfilling of urban underground comprehensive pipe corridors based on a pipe gallery project in Xiong’an New Area, the mechanical calculation model of the pipe gallery foundation pit backfilling process was simulated by ABAQUS, and the pavement settlement and the change of the pipe gallery model under different construction conditions were simulated and verified. The results show that many external environmental factors have an impact on pavement settlement, and methods such as increasing the compaction degree of backfill soil and the slope of the foundation pit, reducing the width of the pit floor, and controlling the vehicle load after work can avoid the pavement damage caused by uneven settlement.

New Foundation Treatment Technology Using Cement Soil Composite Tubular Piles Supported by Optical Fiber Sensing Technology

The purpose is to optimize the foundation’s treatment process and improve the foundation’s construction effect to better apply the cement soil composite tubular piles. This exploration is to study the cement composite tubular piles. First, the principle and application of optical fiber sensing technology are discussed. Then, the application design and conditions of the cement composite tubular pile are discussed. Finally, a new foundation treatment technology supported by optical fiber sensing technology is proposed and comprehensively evaluated based on the application of cement soil composite tubular piles. The research results show that: (1) the new foundation treatment technology reflects the optimization of the optical fiber sensing technology for the foundation treatment. Moreover, it is further optimized through the application of cement soil composite tubular piles. (2) When subjected to the same load, the longer the core pile is, the smaller the cement soil composite pile’s settlement is. When the inner core pile is 20 m ~24 m long, the settlement of the cement soil composite pile is small. When the length of the inner core pipe pile is 16 m ~20 m, the settlement range of cement soil composite pile becomes larger. (3) With the increase of friction coefficient, the settlement distance of cement soil composite tubular pile will decrease. The above data show that compared with the traditional foundation treatment technology, the new foundation treatment technology designed based on the application of composite tubular piles, supported by optical fiber sensing technology, can well solve the foundation construction problems, avoid pavement settlement, cracking, and other phenomena, and ensure the overall safety of the road. This exploration fully reflects the advantages of the new technology of foundation treatment and ensures the quality of road engineering. It provides a reference for the development of foundation treatment technology of construction projects and contributes to the development of the construction industry.

Numerical Assessment of Microtunnelling Induced Pavement Settlement

Numerical Assessment of Microtunnelling Induced Pavement Settlement

ПОШУК ШЛЯХІВ ВИРІШЕННЯ ПРОБЛЕМИ РУЙНУВАННЯ ПОКРИТТІВ ПІШОХІДНИХ ДОРІЖОК ТА МАЙДАНЧИКІВ ІЗ ФІГУРНИХ ЕЛЕМЕНТІВ МОСТІННЯ

One of the indicators that affect the aesthetic appeal of the city's environment is the appearance of sidewalks, landscape-gardening and pedestrian paths, grounds, parking lots. In recent years, more and more often road coatings of such zones are made of figured paving elements (FPE). Visual surveys of pedestrian zones of several resort towns were carried out. During the inspection, a large number of defects in the coatings in these areas that arose during their operation were noted. Such defects spoil the appearance of cities, which, in turn, negatively affects both the quality of life of local residents and the number of visitors to these settlements, which, accordingly, will bring less tourism income to the city. The paper draws attention to the need for timely work to replace obsolete and damaged coatings, and the construction of new ones with improved quality characteristics. Consequently, the question arose of improving the quality, reliability, and durability of road coatings of pavements, footpaths and grounds made of figured paving elements. It is proposed to solve the task by improving the design-technological solutions of road coatings. To do this, it is proposed to increase the area of the underside surface of the elements that make up the coating. Increasing the area of the underside base will increase the bearing capacity and reduce the settlement of the pavement, since the vertical load through the underside base will be transferred to a larger volume of the carrier layer located under the road coatings. New variants of road coatings made of figured paving elements are proposed, the underside surface of which has pyramidal elements of the correct form, located at a distance from each other. Pyramidal elements will not only increase the bearing capacity and reduce pavement settlement but will also prevent horizontal shift when a horizontal load is applied. It is necessary to study the operation of the proposed road coatings under the influence of horizontal and vertically applied loads, determine the deformation zone that forms under the coatings, analyze the research results, and then choose the most optimal variant.

Numerical Simulation of the Effect of Repeated Load and Temperature on the Behavior of Asphalt Layers

Roads and highways are used by different vehicle types, and the heavy vehicles among them can be considered the most critical in loading, which causes failure in the pavement structure and increases rehabilitation and maintenance costs. In this study, the composite effects for wheel loads and temperature were considered in the finite element analysis using Abaqus 6.14. The asphalt layer was modeled as an elastic material, while the base and subbase layers were modeled as an elastoplastic material following the Mohr-Coulomb model. Also, the impact of wheel loads on flexible pavement settlement and the main output of analyzing pavement structure are almost represented by the vertical stresses and the surface deformation, which are considered the critical response point. A single unit truck was tried with two thicknesses of the asphalt layer, 14 cm, and 25 cm, with two different temperatures. Since base and subbase layer thicknesses remained constant, it does not affect the displacement variation. However, it was found that the increase of asphalt layer thickness from 0.14 m to 0.25 m leads to a decrease in the vertical displacement of about 0.59% and becomes 0.77% when the temperature increases to 50℃.

The Control Standard for Settlement of Pavement Based on the Model of Acceleration Interference

The control standard of pavement settlement caused by urban tunnel excavation is the focus of academic research at present. The establishment of settlement control standard gradually develops from safety control standard to comfort control standard. Based on the acceleration interference model, this paper presents a method to determine the pavement settlement control datum caused by the new tunnel penetrating the existing highway. Firstly, the vibration acceleration along the vertical direction of the road was selected as the comfort index, and the ideal sine function and Peck formula were used to describe the longitudinal curve of the road surface and the characteristics of the road surface settlement groove caused by tunnel construction. Secondly, considering the acceleration interference model, based on theoretical derivation, the calculation formula of vertical acceleration under the influence of road surface smoothness is obtained. According to superposition principle, the calculation formula of vertical acceleration under the influence of road surface smoothness and tunnel excavation is obtained. Thirdly, based on the relationship between acceleration value and subjective feeling of human body, the determination formula of pavement settlement control benchmark is proposed. The results show that the control datum formula is consistent with the engineering practice. Reducing the speed and the width coefficient of pavement settlement groove are effective methods to improve the comfort.

Thaw settlement of runways in permafrost regions under aircraft load

Thaw settlement is a major factor influencing deformation, subsidence and collapse, which poses a major threat to the aircraft safety. Therefore, a numerical model of runway structure in permafrost regions is established and verified by comparing with references. The evolution of thaw settlement, transverse non-uniform thaw settlement and thaw settlement mechanism are studied based on the verified numerical model with the aircraft load of A380-800. The evolution of thaw settlement shows that the influence area and maximum value of thaw settlements increase rapidly in the first five years and increase slowly over time. The thaw settlement is mainly concentrated in the subgrade, and gradually expands to the natural surface over time. The transverse non-uniform thaw settlement shows that the thaw settlement of pavement is smaller than that of natural surface at the same depth, and the differential thaw settlement at the pavement and natural surface becomes increasingly prominent over time. The mechanism of thaw settlement shows that the changes of temperature field affects the content of unfrozen water, thermal parameters and mechanical parameters of runway materials, which causes the thaw settlement of runway. This study provides technical support for the design, construction and maintenance of runways in permafrost regions.

NUMERICALLY PREDICTING SETTLEMENTS OF WASTE COCONUT FIBER (WCF) MIXED FLEXIBLE PAVEMENT IN HOMOGENEOUS SANDY SOIL BY USING PLAXIS 3D

Surface settlement of flexible pavement in coastal reason occurs for the movement of heavy vehicle, liquefaction of soil layer during seismic shaking, land sliding etc. In coastal area, surface settlement is higher than other geographical area because several sandy layers present in the coastal reason. Surface settlement disturbs the longevity of flexible pavement in homogeneous sandy layer. Waste coconut fiber (WCF), fly ash, coir etc. are suitable additives for reducing such types of settlement. In the present study, numerical analysis performs PLAXIS 3D and various (5, 10, 15, 20, 25) percentages of WCF mix with the asphalt by weight for reducing surface settlement of flexible pavement. Mohr-Coulomb failure criterion uses in the numerical analysis and liquefaction has not considered in the present study. However, WCF increases elastic modulus of flexible pavement and it reduces settlement of the pavement. Minimum surface settlement occurs at the maximum percentage of WCF and it is 1.68mm. Therefore, mixer of WCF protects the flexible pavement against severe damage.

Numerical Simulation of the Effect of Repeated Load and Waste Polypropylene on the Behavior of Asphalt Layers

Roads are utilized by many vehicle kinds and heavy vehicles among these may be seen as the most essential for cargo loading, causing paving failure and increasing expenses for rehabilitation and maintenance. In this study, in analyzing a finite element employing Abaqus 6.14, composite effects for wheel loads and temperature were addressed. The asphalt layer was designed as an elastic material, while the base and sub-bases were modeled according to the Mohr coulomb model like an elastic material. And studying the impact of wheel loads on flexible pavement settlement and the main output of analyzing pavement structure is almost represented by the vertical stresses and the surface deformation which are considered as the critical response point. A truck type 2S-2 was tried with two thicknesses of asphalt layer 140 mm and 250 mm and considering that base and subbase layer thicknesses remained constant so it does not affect the variation of displacement. It was found that the increase of asphalt layer thickness from 140 mm to 250 mm leads to a decrease in the vertical displacement of about 0.59% and studied the effect of modified asphalt with polymer and how it effect pavement vertical displacement with an obvious reduction from 0.590 mm to 0.265 mm under the repeated load of 36 ton and The vertical stress decreased from 5.036 kPa to 1.899 kPa

Experimental Study on Embankment Failure Law and Reinforcement Technology for Highway Widening Project over Silt Soils

Abstract In the highway widening project, it is of great importance to take measures to control the differential settlement between the new and old embankment, therefore improving the stability of the new embankment. This article presents a series of model tests to analyze the failure law of the new embankment and compare the reinforcement effects of different reinforcement technologies. The test results show that the new embankment is unstable because of the slope slippage under ultimate load. In the reinforcement test of gravel pile, reaming phenomenon occurred at the top of the pile, and both of the values in pavement settlement and embankment lateral deformation are similar to those of the unreinforced embankment. In the geogrid reinforcement test, the embankment settlement can be reduced by restricting the lateral deformation of the new embankment with geogrid, where the settlement is 41 % less than that of the unreinforced scenario. In the cement fly ash gravel (CFG) reinforcement test, the pavement load is transferred to a deeper layer of the embankment by CFG piles, a soil arch effect with the surrounding soil is formed to restrict the lateral deformation and slippage, and the pavement settlement is 46 % less than that of the unreinforced scenario. According to the test results, the order of effectiveness for the reinforcement methods is CFG piles > geogrid > gravel pile.

English

English

Numerical simulation analysis on settlement of backfill materials under traffic load

In order to solve the problem of settlement cracks around the manhole, the finite element software MARC is used to simulate the settlement of the manhole and the pavement around the manhole, and the influence of different backfill materials (sand, clay, self-made backfill material) on the settlement difference between the manhole and the pavement is analysed. The results show that the performance of self-made backfill material is better than that of traditional backfill material. It is of great significance to ensure the quality of backfill, reduce the settlement of pavement and protect the urban environment.

Analysis and Prediction of Pavement Settlement Caused by Jacking Construction of Ultra-Shallow Rectangular Shield Frame Bridge

The primary purpose of this paper is to analyze and predict the ground settlement law of large-span rectangular shield frame bridge jacking project, to provide a reference for the optimization design and safe construction of similar projects. In this paper, combined with the jacking project of ultra-shallow buried soft soil layer rectangular shield frame bridge, through the on-site monitoring, the settlement deformation law of the longitudinal and transverse sections of the expressway pavement during the jacking construction process is discussed, and the reasons for the large settlement and rebound are analyzed. The basic laws of the road surface settlement with time are summarized. Based on the Kriging spatiotemporal prediction model, the road surface settlement is predicted. The research shows that the transverse settlement trough of the pavement caused by the rectangular shield frame bridge’s jacking construction is stable within 15 m–20 m on both sides toward the axis and symmetrical along the coordinate axis and the alignment roughly conforms to the normal distribution. The influence range of settlement trough becomes greater and greater with shield jacking, and the final settlement curve is W-shaped. After comparing the predicted curve with the measured road settlement curve, we found that the two curves are in good agreement, and the prediction result of the Kriging spatiotemporal prediction model is valid, which can reflect the process of road deformation development during the jacking process of the shield.

Numerical Analysis of the Causes of Curved Soil Levee Breaches in Seasonal Freeze-Thaw Areas

The phenomenon that curved soil levees in seasonal freeze-thaw areas were repeatedly damaged after being repaired indicated that the failure mechanism of it has certain unique characteristics. To clarify this, a 3D fluid-solid coupling model was adopted to investigate the failure mechanism from the perspective of hydrodynamics and temperature. The results showed that during flood season the water pressure at the curve was much higher than that at the straight area. High water pressure can cause higher water content at the curve. Meanwhile, the curved levee is in essence a breach-sealing portion of levee. Hence, the frost-thaw damage of revetment and differential settlement of pavement are more likely to occur during winter. Damage of revetment can aggravate the erosion at the curve while differential settlement can induce the transverse fracture. These findings can provide a reference for reasonable differential settlement control as well as instruction of protective measures.

Numerical analysis on the features of road deformation in the construction process of heat supply pipeline works

Shallow Tunneling Method has been widely applied in the construction of pipe gallery. However, due to the complexity of strata and the particularity of environment, improper construction may cause uneven settlement of urban road, even pavement collapse. In the paper, in reliance on Beijing Xi’anmen Street Heat Supply Pipeline Works and by virtue of drilling and survey, the engineering geological conditions and pavement structure of the target area were ascertained, Finite Element Method was utilized for numerical calculation, so as to determine the surface settlement & deformation laws under different construction situations, including the change law of longitudinal and lateral pavement settlement following the progress of excavation, and also the final pavement settlement and settlement scope, etc. It was found by research that, under the joint action of variable section of pipe gallery and shaft pipeline, the section height of pipe gallery has marked effect on the change of pavement settlement, the settlement speed of pavement monitoring point appears to be “double-peak type”.

Adaptability evaluation of pavement structure to replacement treatment subgrade of black cotton soil

Abstract Aiming at the typical engineering problem of black cotton soil (BCS) subgrade under the alternation of dry and wet climate in the region of Nairobi, Kenya, this paper takes the pavement structure as the research object, and the numerical calculation model of BCS subgrade is established based on the consolidation coupling theory of unsaturated soil. Taking the modulus and thickness of the subbase as variables, the deformation characteristics and additional stresses of different pavement structures are analysed. Then the adaptability of different pavement structures to replacement treatment subgrade of BCS is evaluated by gray incidence decision analysis method. The results show that whatever the pavement structure is, neither subgrade modulus nor thickness is sensitive to the pavement surface deformation, and the deformation differences between each pavement structure are more obvious in wet season; the additional stress at control layer bottom and pavement surface decreases with the increase of subbase modulus, whereas the stress may increase at subbase bottom; the additional stress at subbase bottom, control layer bottom and pavement surface all decreases with the increase of subbase thickness for pavement Structure I and II. For pavement Structure III, the change of subbase thickness is not sensitive to the additional stress at the control layer bottom and pavement surface, whereas the stress at subbase bottom increases with the increase of subbase thickness. It is concluded that the most adaptable structure is pavement Structure I, which can minimize the comprehensive level of pavement settlement and additional stress.

Permanent Deformation Behavior of Compacted Loess under Long-Term Traffic Loading

AbstractThe long-term permanent deformation behavior of subgrade soil repeatedly subjected to traffic loading has a significant effect on the settlement of pavement during operation. Many studies c...

Stabilization of problematic soil by utilizing cementitious materials

Due to the urbanization and the need to develop the transportation services, it is inevitable to deal with ground characterized by undesirable geotechnical properties. The problematic soils are divided into swelling soils, collapsible and dispersive soils. The arid to semiarid climate of the Middle East has provided the conditions for the expansion of them. The presence of problematic soils in Iraqi Kurdistan has given rise to many damage to the construction projects of this region. The under-construction road of Gali Ali Bag designed in the vicinity of the Erbil-Haji Omeran highway in Iraqi Kurdistan was faced with pavement settlement and collapse of side slopes due to the passing through the collapsible soils. The presence of collapsible soils in the vicinity of the aforesaid international highway grew concerns about the occurrence of such settlements during its construction. Therefore, how to treat or reduce the collapsibility, especially by the use of practical methods on the site, was addressed as one of the major challenges. In this study, the behavior of treated host soil by four cementitious materials including cement, quicklime, gypsum and NaCl was determined by applying indirect and direct methods. The results show that the addition of 6% quicklime will have the greatest effect on the reduction in collapsibility. After implementing this plan on the site, the collapsibility index decreased by an average of 2.92%.

STUDY ON THE DYNAMIC NUMERICAL ANALYSIS METHOD FOR THE SETTLEMENT OF FLEXIBLE PAVEMENT

In view of the problems of a single parameter of rock and soil materials, unclear boundary simulation and a simplified dynamic load in the current calculation of pavement settlement, the stochastic finite element-infinite element coupling method was adopted in this study to simulate the roadbed of rock and soil, with a dynamic response analysis and a flex- ible pavement settlement calculation of roadbed were carried out under stochastic dynamic load. Discrete methods and dynamic stochastic finite element formulas for rock and soil random fields were particularly dealt with in this study. The results show that the method to stimulate roadbed is true with high calculation accuracy and strong engineering guiding significance. The displacement of flexible ground at any depth can be obtained by calculating the settlement of flexible pavement with the aid of the Matlab computer program.

Mechanical Evaluation of Bottom Ash from Municipal Solid Waste Incineration Used in Roadbase

As a by-product from the incineration of municipal solid waste, bottom ash has a broad application prospect of resource utilization. In this study, bottom ash was selected as partial aggregate alternative and used as roadbase materials. The cemented aggregate containing bottom ash was evaluated through both experimental and numerical analysis. According to the results, the unconfined compressive strength of samples increases with the curing time, and the failure strain of sample decreases with the curing time. The unconfined compressive strength and failure strain of samples are influenced by the types of bottom ash. The increase of compressive strength with the curing time can be attributed to that the hydration reaction of cement will be more complete when the curing time is longer. The representative value (7 days) of unconfined compressive strength of samples meets the strength requirement (≥2.5 MPa) of the road subbase layer of heavy traffic highway in China. Subsequently, the surface settlement decreases with the increase of the modulus and thickness of roadbase and the distance from the centerline, while the settlement increases with vehicle load increasing. The modulus of the roadbase is not the main influences on the pavement settlement, under the condition that the strength of samples meets the requirements. However, increasing the thickness of roadbase can reduce the settlement at the center of the pavement effectively.