Evaluating the Behavior of Embankments after Widening considering Soil Consolidation and Splicing Mode

Increased traffic volume has made it necessary to increase highway capacities by widening embankments and pavements. Differential settlement of foundation consolidation and rational utilization of existing embankments are the main problems encountered in road reconstruction. In this paper, the finite difference method is used to simulate the construction process of using the existing embankments directly in the reconstruction project of expressway, and the fluid-solid coupling model of foundation settlement is established to calculate the differential settlement between foundation and subgrade. The influence of road widening mode and embankment height on differential settlement is analyzed. The mechanical response of subgrade under differential settlement is simulated and the law of uneven settlement of main reconstruction forms is investigated. The dynamic response of existing embankments soil under the action of rammer is systematically evaluated. The results show that, with the increase of consolidation time, the differential settlement is gradually obvious at the junction of the new and existing embankments, and there is a possibility of landslide along the junction of new embankments, which should be dealt with in engineering. The smaller the height difference between the existing foundation and the new foundation is, the more the position of the maximum settlement point of the foundation moves towards the new foundation. The greater the height of the new subgrade is, the greater the uneven settlement is. The criterion based on the single rammed energy and compaction stopping standard is proposed to determine the reinforcement depth of existing embankment.

Finite Element Simulation of Vacuum Preloading at Palembang – Indralaya Toll Project

Methods for the prediction of soil behavior during the application of vacuum preloading are available but have not been used precisely and have not been proven yet in Indonesia. There are two common approaches to vacuum preloading simulation, based on the application of a uniform external load to the vacuum area, and based on suddenly lowering the groundwater level to create vacuum conditions, respectively. This affects the settlement, lateral deformation, and pore pressure predictions. The objective of this research was to improve the prediction of soil behavior based on high-quality field data by using state of the art vacuum preloading simulations. The results were compared with those of a series of instrumentation equipment, i.e. a settlement plate, an extensometer, and a piezometer. This research used data from the Palembang-Indralaya Toll Road, a section of the Trans Sumatera Toll Road that is approximately 22 km long and has an embankment height of about 4 m to 9 m. It was built over a swampy soft soil area, using vacuum preloading to improve the soil. Axisymmetric analysis of vacuum preloading was conducted for a single-drain system, plane-strain analysis was conducted for single- and multiple-drain systems, and 3D analysis was conducted for single-drain, multiple-drain, and cluster-drain systems. The results show that the proposed method produced a good correlation between the predicted data and the recorded monitoring data.

Experimental Investigation of Flood Energy Dissipation through Embankment Followed by Emergent Vegetation

The combination of hard (artificial) and soft (natural) solutions i.e., composite defense systems against flooding and tsunami opens a new window for engineering innovation for researchers nowadays. In this study, the experimental investigation of flood energy dissipation phenomena through composite defense systems comprising of embankment and rigid vegetation models in an open channel flume, is conducted. The flow regime through the composite defense system is classified in two main types, which are further subdivided in two sub-categories. Various combinations of embankment and vegetation and spacing between embankment and vegetation are analyzed. Against the selected range of initial Froude numbers, three different sizes of embankment models, three spacings between the embankment and vegetation (Ldv) and vegetated corridors of two different porosities (PR), are tested to examine the effect of these three parameters on the characteristics of the generated hydraulic jumps and flood energy dissipation within the defense system. It is found that embankment size and vegetation porosity have a greater impact on flood energy dissipation while the selected range of Ldv is less effective. Amongst the assessed composite flood defense systems, the maximum energy dissipation (55%) is observed for the combination of maximum embankment height and vegetation porosity (93%). For fixed combinations of embankment size and Ldv, the maximum increase of energy dissipation (18%) is found for decreasing vegetation porosity from 97% to 93%.

Discrete element modelling of rockfill railway embankments

There is a need of reducing the uncertainty in traffic loading-induced settlements within railway embankments. A previously developed model for unbound stone-based materials has been implemented for modelling rockfill embankments. Particles were represented by simple breakable tetrahedral clumps of spheres with four asperities each. Both corner breakage and particle splitting were allowed. Embankments with heights between 2 and 10 m were generated by successive dumping and compaction of layers of clumps on top of each other, mimicking the construction of real embankments. Cyclic loading of the embankments representing railway traffic, for both breakable and unbreakable assemblies, was carried out. Results show that the mechanical response is marked by a substantial degree of uncertainty exacerbated by particle degradation, especially for intermediate to high embankments. An analysis of particle rotation showed that particle rearrangement mostly accumulates in the top layers, resulting in a lack of influence of embankment height on settlements. Breakage, even being of (very) limited magnitude, had a statistically significant effect. Good agreement with common geostatic theories predicting horizontal pressures was also observed. Regarding resilient response, linear stiffening with embankment height is observed with a minor influence of breakage. All in all, it is shown that the specific scale, boundary and stress conditions of embankments results in a behaviour deviating from that observed under triaxial conditions. Therefore, the key contribution is showing that it is possible to realistically model high rockfill embankments under a large number of loading cycles and furthermore including degradation, something not attempted to date. Graphic abstract

Automated Mapping of Transportation Embankments in Fine-Resolution LiDAR DEMs

Fine-resolution LiDAR DEMs can represent surface features such as road and railway embankments with high fidelity. However, transportation embankments are problematic for several environmental modelling applications, and particularly hydrological modelling. Currently, there are no automated techniques for the identification and removal of embankments from LiDAR DEMs. This paper presents a novel algorithm for identifying embankments in LiDAR DEMs. The algorithm utilizes repositioned transportation network cells as seed points in a region-growing operation. The embankment region grows based on derived morphometric parameters, including road surface width, embankment width, embankment height, and absolute slope. The technique was tested on eight LiDAR DEMs representing subsections of four watersheds in southwestern Ontario, Canada, ranging in size from 16 million cells to 134 million cells. The algorithm achieved a recall greater than or equal to 90% for seven of the eight DEMs, while achieving a Pearson’s phi correlation coefficient greater than 80% for five of the eight DEMs. Therefore, the method has moderate to high accuracy for identifying embankments. The processing times associated with applying the technique to the eight study site DEMs ranged from 1.4 s to 20.3 s, which demonstrates the practicality of using the embankment mapping tool in applications with data set sizes commonly encountered in practice.

Soil shrinkage and consolidation study on flood embankments in swamp irrigation areas

Research in this paper discusses shrinking and consolidation of flood embankments soil in swamp irrigation areas. The flood embankments are made from swampy soil materials. The focus of this research is the reduction of dyke embankment height that occurs due to soil shrinkage and soil consolidation. Investigations about the time of consolidation and land subsidence that occurred on the embankment at certain periods after the embankment established were also carried out in this study. The research sites are some swamp irrigation areas in the Tulang Bawang Watershed, around North-East Lampung, Indonesia. This research was carried out by conducting laboratory tests on soil samples and field observations on the reduction in height of flood embankments in the study area. The research shows that the main cause of total decrease on the embankment is due to linear shrinkage, consolidation of soil under the embankment, an immediate subsidence, and the subsidence of the embankment themselves. Their contribution to total decrease of embankment is 42.51%, 34.48%, 18.32%, and 4.62%, respectively. Results also indicate that the ratio between the percentage of embankment consolidation in downstream area happen faster than the one in upstream area of the river.

SIDOARJO MUD DRAINAGE SYSTEM

Sidoarjo or Lusi mud has an area of ​​640 ha and an average embankment height of 10 meters and submerges three sub-districts, namely Porong District, Jabon District and Tanggulangin District. In 2018, the Sidoarjo mud embankment has decreased or subsided by up to 8.5 meters at several points, which was caused by the condition of the embankment which was almost full and caused the soil condition of the embankment to become unstable. For this problem, it is necessary to build a drainage channel at the edge of the embankment to overcome the overflow of the embankment and flow it to the Porong river which is on the south side of the Sidoarjo mud embankment. From the calculation of the planned rain discharge, it is found that R2 = 72.95 mm after the planned rainfall is obtained, then the next is to look for the flood discharge plan which then plans the dimensions of the channel on the west and east sides of the embankment after obtaining the dimensions of the channel, then the next is planning the resistance pond and draining it to the porong river. with Siphon Network Pipe

EVALUASI TINGGI EMBANKMENT JALAN PADA TANAH LUNAK DIPERKUAT GEOTEXTILE DAN FONDASI CERUCUK

<p align="center"><strong>Abstrak</strong></p><p> </p><p class="11daftarpustaka">Kalimantan memiliki daratan rendah tanah lunak mencapai kedalaman 25 m. Tanah lunak memiliki kapasitas dukung rendah dan deformasi besar untuk menopang beban-beban. Infrastruktur seperti embankment untuk konstruksi jalan di atas tanah dasar lunak, biasanya direncanakan dengan suatu tinggi rencana, meskipun embankment untuk konstruksi jalan sering runtuh akibat lemahnya kekakukan tanah dasar tersebut. Ada beberapa pedoman teknik telah dipublikasikan bagaimana cara membangun embankment di atas tanah lunak, tetapi pedoman tersebut hanya menunjukkan prosedur kerja konstruksi, di mana ujung pangkal fondasi <em>cerucuk</em> seperti kayu atau bambu adalah diikat dengan cara konvensional. Konstruksi embankment harus memenuhi untuk kriteria stabilitas dan penurunan. Penelitian ini untuk pemenuhan persyaratan stabilitas seperti faktor keamanan embankment dihubungkan dengan kapasitas dukung tanah lunak dengan perkuatan untuk mengevaluasi tinggi embankment disediakan dengan beberapa formula empiris berdasarkan aturan geoteknik. Hasil simulasi perhitungan diperoleh tinggi embankment kritis <em>H_cr</em> sebesar 1,06 m untuk kohesi tanah <em>c_u</em> sebesar 11,5 kN/m² dan <em>H_cr </em>sebesar 1,70~1,73 m untuk kohesi <em>c_u </em>sebesar 17,5 kN/m² dengan fondasi <em>cerucuk</em> berjarak <em>s</em> sebesar 10<em>D.</em> Variasi susunan <em>cerucuk</em> berjarak s of 3,3<em>D</em> memberikan nilai signifikan kapasitas dukung batas dan konstruksi embankment lebih tinggi, hal ini adalah tidak memberikan nilai signifikan oleh indeks plastisitas tanah.</p><p class="11daftarpustaka"> </p><p class="11daftarpustaka">Kata kunci: <em>tinggi</em> <em>embankment,</em><em> tanah lunak</em><em>, geotextile</em><em>, fondasi cerucuk</em><em></em></p><p align="center"><strong> </strong></p><p align="center"><strong> </strong></p><p align="center"><strong>Abstract</strong></p><p class="11daftarpustaka"> </p><p>Kalimantan island has lowlands of soft soil in down depth 25 m. The soft soil has low bearing capacity and large deformation to support loads. Infrastructure such as embankment for road construction on the soft soil, it is usually planned by a height target. However, the embankment for road construction is often collapsed due to weak stiffness of soil subgrade. Therefore, the local government has been used geotextile and installed timber pile for reinforcing the soft soil. There are several technique guidelines published how to build embankment on soft soil, but that guidelines are only shown the prosedure for working the construction. The soft soil installed timber pile perior to lay geotextile and construct an embankment. Where the top of cerucuk foundation such as timber or bamboo is tied by conventional system. The embankment construction have to satisfy for stability and settlement criteria. In this research, the stability requirement such as factor of safety of embankment is conducted by bearing capacity of soft soil with reinforcement to evaluated a critical height of its embankment, which is provided by several empirical formula based on rule of geotechnics. The simulation results were obtained critical height of embankmentt <em>H_cr</em> of 1,06 m for soil cohesion <em>c_u </em>of 11,5 kN/m² and <em>H_cr </em>of1,70 ~ 1,73 m for cohesion <em>c_u </em>of 17,5 kN/m² with cerucuk foundation on spacing <em>s</em> of 10<em>D.</em> Variation of rearrange of cerucuk spacing <em>s</em> of 3,3<em>D</em> are given significant values of ultimate bearing capacities, and more heighly of embankment construction, it is not given a significant value by plasticity index of soil.</p><p class="11daftarpustaka"> </p><p class="11daftarpustaka">Keywords: <em>Embankment height,</em><em> soft soil</em><em>, geotextile</em><em>, cerucuk foundation</em></p>

Numerical Modeling of Encased Stone Columns Supporting Embankments on Sabkha Soil

The present research work is concerned with the construction of road embankments on a specific soil called Sabkha in Algeria. This soil is not only soft and very humid during the flooding seasons but also has frequent small areas of very soft soil which we here call Locally Weak Zones (LWZ). LWZ is characterized by low strength and high compressibility. The paper presents the results of two-dimensional axisymmetric numerical analyze that were carried out using PLAXIS 2D 2017, for the modeling of an embankment supported by stone columns on Sabkha soil. The study focuses on the evaluation of the maximum bulging of the stone column and on the settlement of the embankment. It has been demonstrated that Ordinary Stone Columns (OSC) were ineffective due to excessive bulging (221.16 mm) caused by the lack of lateral pressure. On the other hand, the Encased Stone Columns (ESC) showed good behavior, namely a much reduced bulging (42.09 mm) and a reasonable settlement (0.962 m vs. 1.560 m for an OSC) so that it is possible to build safe very high embankments. The numerical analysis also shows that the length of the encasement should just be greater than the depth of the LWZ. Besides, an extensive parametric study was conducted to investigate the effects of the variations of embankment height, stiffness of geosynthetic, the depth of the locally weak zone, area replacement ratio (ARR), and the stone column friction angle, on the performance of the (ESC) - embankment composite in (LWZ). Some important guidelines for selecting the ideal encased stone column (ESC) to support embankments on over locally weak zone were established through this numerical study.

ANALYSIS OF CALCULATION RESULTS OF STUDYING THE STABILITY OF SLOPES WHEN THE TENSION LOAD IN THE EMBANKMENT SUBGRADE

Design characteristics for the stability of the slopes of the subgrade. The steepness of slopes of embankments up to 3 m high on category I-III roads should be assigned taking into account the safe driving of vehicles in emergency situations. An analysis of the values of the design characteristics of the steepness of the slopes shows that the design characteristics in the irrigated zone, when the groundwater level increases and impacts in the subgrade, aggressively acts in the spring period of road slope stability. During the research, it was found that the slopes of all pickets, at a load of 0.15 MPa, where the height of the embankment H=2.0 m are stable, if you do not take into account the impact of capillary water, soil saturation in the embankment. At a load of 0.20 MPa, all pickets with an embankment height of h≤2.0 m are unstable in the capillary water-saturated state.