Use of Foamed Cement Banking for Reducing Expressways Embankment Settlement

Expressways are often built on soft ground, the foundation of which is not processed adequately during the construction period. Consequently, the traffic safety and embankment stability will be seriously affected due to uneven settlement. The technology of holing the embankment and replacing foamed cement banking (FCB) could control the settlement of an embankment without road closure, thus reduce the impact of construction on normal operation of highways. In this paper, the principle of FCB is described. Additionally, a sedimentation ratio calculation method, through the analysis of the settlement load ratio, is proposed for calculating the roadbed replacement thickness. This paper takes the example of the test section EK0 + 323 on Shen-Jia-Hu expressway in Zhejiang Province and combines with site settlement monitoring data to confirm the effectiveness of the calculation method proposed.

Critical Dynamic Stress and Accumulative Deformation Evolution of Embankment Silty Clay Subjected to Cyclic Freeze-Thaw

In cold regions, the permanent settlement of embankment is mainly caused by the repeated freeze-thaw process and long-term repeated train loads. Meanwhile, the critical dynamic stress (σdcr) is an important parameter index for determining embankment stability. Therefore, the accumulative permanent deformation evolution and critical dynamic stress of embankment soil subjected to cyclic freeze-thaw were studied using dynamic triaxial tests. Firstly, a numerical model for calculating critical dynamic stress considering the repeated freeze-thaw process was proposed, which shows that the critical dynamic stress of embankment soil rapidly decreases in the first two repeated freeze-thaw cycles, whereas it tends to be stable after the subsequent freeze-thaw process. Next, based on the normalization of the critical dynamic stress, an explicit model for predicting accumulative plastic strain (εp) of embankment soil was established. The above model considers freeze-thaw times, repeated dynamic stress amplitude (σd), and loading times, in which all material parameters of Qinghai-Tibet silty clay were presented. Thus, the critical dynamic stress and accumulative plastic strain models established in this paper can be applied to judge the embankment stability and predict the embankment settlement induced by train loads in cold regions.

Experimental and Numerical Investigation on the Stability of Loess Embankment Treated by Chemical Solution under Freezing-Thawing Conditions

In order to study the influence of chemical solution on the stability of loess embankment in seasonally frozen regions, the compression index, shear strength index and embankment safety factor of compacted loess fillings that were treated by different concentrations of chemical solution were analyzed through laboratory test and slope stability analysis program. The experimental results showed that the collapsible coefficients of remolded loess treated by different chemical solution will all increase which comparing the distilled water, and then will change again after freezing-thawing cycles (FTCs). The compression index of undisturbed loess will show regularity with the increase of chemical solution concentration. The shear strength of remolded loess also changed under the chemical solution and FTCs. Besides, simulation of the strength parameters by limit equilibrium methods showed that the safety factor of loess embankment with treatment of solution was significantly higher than that of untreated one, and the FTC would cause a further deterioration. The embankment stability improved after treated by chemical solution without considering seepage of rainwater. These results would provide a novel method to the problem of embankment stability related to environmental condition changes.

HiStudy on the stability of road embankment due to the effect of water level changes on the slopes

This paper presents a study on the stability of road embankment due to the effect of water level changes on the slope. Two scenarios of the drawdown were considered. The first one is the case of the embankment with the water on one slope and the second one is for the embankment with the water on both two slopes. For the two cases, the water level on one side drops. Effects of various parameters such as the permeability of the road embankment soil, the rate of change in water level on the stability of the slope were evaluated, to found out the principle of the change of stability of the embankment. The results showed that the embankment stability reduces if there is a drawdown of the water level on the slope.

Observed Performance of Highway Embankment over Soft Marine Clay: A Case Study in Wenzhou, China

This paper presents a case history of observed performance of highway embankment over soft marine clay in Wenzhou, China. During the embankment construction, the changes of ground settlement, ground displacement, and lateral displacement of subsoil with the construction time were monitored and analyzed. The monitoring results indicate that the ground settlement and lateral displacement of subsoil account for about 75% in the process of embankment construction. The measured maximum values of ground settlement, ground displacement, and lateral displacement of subsoil are 37.88 mm, 21.50 mm, and 23.56 mm, respectively. After the completion of the embankment construction, the settlement gradually tended to be stable. It is suggested that the monitoring data of settlement and displacement of embankment are smaller than the design requirements, and the embankment stability is also ensured.

ANALISIS TIMBUNAN DI ATAS LAPISAN TANAH GAMBUT DENGAN METODE PRELOADING DI KALIMANTAN TENGAH

Road Construction above peat soil will increase drastically at the end of 2019, if we don’t know the characteristic dan behavior of peat soil, many construction problems and failures will occur. Peat soil has a low bearing capacity and high deformation. This research aims to find out slope embankment stability and total settlement of the subgrade road embankment construction that calculated with guidance from Pd T-06-2004-B above peat soils in Central Kalimantan. This case study focused on one of the bore holes that had a thick layer of peat soil and then improved it using the pre incremental loading method. Slope embankment stability analysis based on Pd T-06-2004-B using the bishop simplified method produces a safety factor of 1.59 and analysis of the total settlement of the subgrade with conventional methods results in a total reduction of 0.2793 m over the 10-year embankment service period which means the pre-loading construction method meets the minimum requirements for embankment heights with elevation from subgrade +2.22 m > +1.8 m. AbstrakPembangunan konstruksi jalan di atas tanah gambut akan meningkat secara drastis di akhir tahun 2019, apabila kita tidak mengetahui sifat dan karakteristik dari tanah gambut itu sendiri maka akan terjadi banyak masalah atau kegagalan konstruksi. Tanah gambut atau yang lebih dikenal dengan nama peat soil memiliki daya dukung tanah yang rendah dan penurunan yang besar. Penelitian ini bertujuan untuk mengetahui stabilitas lereng timbunan dan penurunan tanah pada konstruksi timbunan jalan yang dihitung dengan pedoman Pd T-06-2004-B di atas lapisan tanah gambut di Kalimantan Tengah. Studi kasus ini difokuskan terhadap salah satu bore hole yang memiliki lapisan tanah gambut yang tebal kemudian diperbaiki dengan metode prapembebanan bertahap. Analisis stabilitas lereng timbunan berdasarkan Pd T-06-2004-B dengan menggunakan metode bishop simplified menghasilkan faktor keamanan 1.59 dan analisis penurunan total lapisan tanah dasar dengan metode konvensional menghasilkan penurunan total sebesar 0.2793 m selama masa layanan timbunan 10 tahun yang berarti metode konstruksi prapembebanan memenuhi syarat minimum ketinggian timbunan dengan elevasi dari tanah dasar +2.22 m > +1.8 m.

Characterization of a gold tailings with hypersaline pore fluid

A series of samples obtained from adjacent to piezocone penetration test (CPTu) locations within a gold tailings storage facility with hypersaline pore fluid was tested to compare the inferred state parameter Ψ from CPTu results to the in situ density and critical state line (CSL) from reconstituted samples, and to assess the effects of salt concentration in the sample pore fluid on mechanical behaviour of the material. Preparation of samples with similar salt concentrations to those measured in situ gave CSLs that compared favourably to estimates of Ψ from the CPTu, in light of measured in situ density. Tests prepared without salt did not tend towards the same CSL as the salt samples, generally being at higher densities both following consolidation and during subsequent shearing. These results are consistent with the observed effects of salt on mechanical behaviour in previous testing on clays. The implications and limitations of the testing program are outlined and the need for further investigation of these issues is emphasized owing to the importance of perimeter embankment stability for a tailings storage facility.