Conference Agenda

<p><strong>ABSTRACT:</strong></p>

<p>This paper presents a case study for a landslide rehabilitation project comprising of in-situ grouted soil nailing and pre-stressed ground anchor for slope stabilization, hybrid Reinforced Earth® structure for widening of existing road, drainage measures to prevent development of hydrostatic pressure. The site is located on National Highway 55, Siliguri-Darjeeling Road in the state of West Bengal in India with 3 major landslide location S1(35m), S2 (101.3m) and S3 (34.3m). This case study highlights one of the world’s tallest (101.3m) Reinforced Earth® structure at S2 location.</p>

<p>A massive landslide occurred in Tindharia during earthquake on September 2011. The landslide affected all three locations, resulting in collapse of a portion of road on valley side of the existing highway. The Darjeeling Himalayan Railway (DHR), a UNESCO heritage property was also severely affected due to this landslide.</p>

<p>Terre Armée India provided a permanent and sustainable solution for restoration of the project. This project is unique in terms of technical challenge and hence mix of various innovative techniques were proposed. The TerraLink® technology (hybrid reinforced earth structure) is being used as solution comprising of high adherence GeoStrap® (geosynthetic strips) for soil reinforcement for widening with limited space (2m) at base, TerraNail® (soil nails), FreyssiAnchors® (Ground Anchor System) as in-situ passive soil reinforcing elements with GeoTrel were used, with minimum cut and fill volume. This paper presents the various challenges, design, drainage and construction methods and innovative technology.</p>

<p>The village of Ludrigno is located at the bottom of the Seriana Valley (Bergamo, Italy) in a position frequently affected by avalanches that break off from the slopes above. The first historical information about these phenomena dates back to the 17^th century and throughout the years the avalanche events have repeatedly destroyed buildings and caused loss of lives. The present article intends to present the modelling analyses carried out on the dynamics of avalanches with the aim of dimensioning the mitigation works in terms of the minimum height of the interception embankment and the analysis of the maximum stresses to which it may be subjected when impacted by the avalanche. The design choice fell on a geogrid reinforced avalanche protection embankment 140 m long and 10 m high, as it was the best solution both from a static point of view and in terms of environmental integration. The article deals with the stability analyses carried out on the reinforced embankment due to the avalanche impact and how these determined the choice of the reinforcing geogrids, based on their long-term design strength. In addition, the parameters that determine the long-term design strength of the geosynthetic reinforcements will be analysed, with particular attention to the reliability of the reduction factors to be applied and the certifications that guarantee the behaviour of the materials. The aim of the article is therefore also to highlight the relevance of this topic, which involves design, quality control and safety of the works and the population.</p>

<p>The Gallivaggio landslide falls within the San Giacomo Filippo municipality (Sondrio) and affects a portion of slope situated in the lower Spluga Valley. The rock cliff overlooks the “Madonna di Gallivaggio” Sanctuary (17th century), a restaurant, a few houses and a section of the National Road no. 36 “del Lago di Como e dello Spluga” which leads to the tourist resort of Madesimo and to the Spluga Pass on the Swiss border. Hence the need for careful planning of control and design tools aimed at both risk management and risk mitigation.</p>

<p>The first monitoring activities of the rock cliff date back to 2006, while in 2011 a survey activity with GBInSAR technology was started by the Geological Monitoring Centre of ARPA Lombardia (CMG).</p>

<p>On 29^th May 2018, a rock mass of about 5.500-6.000 m³ detached from the top of the rock cliff, completely filling up the existing catchment ditch behind the protection wall, demolishing part of the defence works and affecting the Sanctuary, the National Road and part of the other accommodation facilities situated at the foot of the rock face.</p>

<p>The main elements of this project lie both in the estimation of the expansion area of the landslide phenomenon and in the definition of the dimensions of the reinforced earth embankment. In order to define the geometry of the debris cone as well as the impact energies of both single and mass collapses on the defence structures both 2D and 3D numerical models were applied.</p>

<p>The paper describes (I) the geotechnical modelling, with subsequent confirmation with site surveys; (II) the design of the solutions for the safety and protection of the territory and for the enhancement of environmental and anthropic resources; (III) the construction of the reinforced earth embankment.</p>

The construction of Pelješac Bridge and of roads connected to the bridge is currently the largest and most ambitious infrastructure project in Croatia. Due to the use of reinforced soil technique, the project was completed largely on time. The preliminary project foresaw conventional and expensive viaducts to bypass the deep valleys intercepted by the road layout. In order to reduce the cost and to increase the construction rate, it was proposed to replace traditional viaducts in Doli and Brijesta using geogrid reinforced embankments. This project solution turned out to be cheaper and faster respect the traditional ones; be-sides the above-mentioned works, and on the base of the time and cost effectiveness of the reinforced soil solution, it has been evaluated the possibility to modify the design of wing walls and abutments of the Dumanja Jaruga viaduct, crossing a valley over 25 m deep. Design and construction of the above strategic infrastructures were a great challenge and certainly a great success, thanks also to the great work done by the general contractor, who was able to finish the job very precisely and accurately, despite the logistical difficul-ties given by the position and by the time scheduled imposed by the construction of the bridge support structure.

<p>The use of geosynthetic vertical drains combined with pre-loading is a cost-effective ground improvement technique widely adopted to improve the bearing capacity and settlement response of fine-grained soft soil deposits. If the design procedure aims to keep settlements within allowable limits in a given time-interval, a proper choose of the in-plane water flow capacity and discharge capacity of the geosynthetic drains as well as their length and spacing is required. To this purpose well known design procedures, generally referred to the case of homogeneous soil deposit, are widely adopted together with observational methods.</p>

<p>This paper focus on the latter approach and describes the results of an almost two-year long monitoring period of the settlement performance of the foundation soils of two tanks founded on a heterogeneous fine-grained soil deposit improved using 97-mm-wide and 3-mm-thick wick drains, consisting of a three-dimensional porous polyester filament core protected from clogging by a nonwoven polyester filter.</p>

<p>The whole set of settlement measurements, obtained through topographic survey of settlement platforms, are presented and discussed in the paper. The application of well-established observational methods and a back analysis of the settlement measurements allowed showing the relevant role of the lithological and mechanical heterogeneity of the foundation soils. These led to a scattering in the measured settlements in a portion of the preloaded area, and, for the case at hand, pointed out the minor relevance of the smear effect on the rate of consolidation.</p>

<p>MSE retaining wall with concrete facing panels is a pretty popular system used globally to support or enable the construction of infrastructure, forming retaining walls, abutments and wing walls.</p>

<p>Polymeric reinforcement strips have been introduced in the MSE wall market as an alternative from traditional reinforcements and they represent a significant advantage for both performances and cost-effectiveness. MSE walls with polymeric strips are also recommended for non-conventional situations such as marginal fills, chemically aggressive environment or in warm climates, where other reinforcements might be strongly affected by corrosion.</p>

<p>Generally, the performance of an MSE structure depends on the interaction between the reinforcements and the surrounding soil, which is linked to the properties of the materials used and the construction methods adopted. Polymeric reinforcing strips, encased in LLDPE coating, have proved to perform like other non-extensible linear reinforcements, reaching higher values of pullout resistance compared to other polymeric reinforcements. MSE walls with geostrips can be designed following the most known International Standards, however, some considerations on the design methods applicability and nature of the reinforcements are provided in the paper.</p>

<p>MSE walls with polymeric strip were first introduced to the European market in the mid-1970s and their market has been growing ever since all over the world but only recently has been developed in North America.</p>

<p>This paper presents two case studies of MSE wall projects reinforced with geostrips recently realized in Maryland and California.</p>

<p>Geo-tubes are geosynthetic tubular containers, of various length and diameter, which are filled by pumping a fluid mixture of water and soil: the permeability of the geosynthetic allows the water to drain so that at the end of the installation a relatively solid nucleus can be obtained. Taking advantage of this feature, geo-tubes have been widely used for the storage of sludge of various types and origins.<br />In this perspective, the paper presents a case-history of an application of this type in Northern Italy, where fine sediment accumulated on the bottom of a dike was removed and stored inside six geo-tubes, organized in a stacked configuration: in the cross section, the first base layer was made of two tubes, placed side by side, and above which a third element was positioned. Referring to a single geo-tube, its configuration during the filling phase and the tension in the geotextile can be evaluated by means of a conventional calculation method of literature. Otherwise, for the case here presented, given that there are not closed-form solutions available for the consolidated phase and the stacked configuration, a numerical analysis was performed by means of the Flac 2D code, in order to highlight critical aspects of this composite structure worthy of particular attention, as well as to investigate its seismic behavior.</p>

<p>Modularized MSE wall is a supporting structure with the characteristics such as simple and clear structure system, high industrialization process in the production and construction. Comparing with the traditional supporting structure, modularized MSE wall has lower requirement on the construction spacing and geology environment, except beauty contour and green initiative, which makes it well used in urban structure, building and road project, especially in the design and construction of mountain area highway. With the advantage of overcoming the limitation of geomorphology and geology, it becomes a worth well alternative solution. In this article, based on the project in the Montenegro BB expressway, the authors introduce the challenges of designing modularized MSE wall in high embankment with complicate geology condition, meanwhile，analyzing the problems and solutions during the design and construction, to provide the experience and reference for the future use.</p>

<p>The Central Luzon Link Expressway (CLLEx) is a four-lane expressway linking several exist-ing expressways in the Central Luzon region of the Philippines to shorten the travel time be-tween main cities, mitigating the severity of traffic congestion. CLLEx is divided into two phases, Phase One is 30 kilometers long connecting Tarlac City to Cabanatuan City and Phase Two is 35.7 kilometers long connecting Cabanatuan City and San Jose City passing through the municipalities of Talavera and Llanera in Nueva Ecija. Geotechnical problems such as em-bankment instability and excessive post-construction settlements of the embankment were the primary concerns in the project. Among several ground treatment methods, geosynthetics solu-tion was chosen by the Department of Public Works and Highways (DPWH) due to ease of construction and cost effectiveness. High stiffness geotextile is used as a basal reinforcement to enhance the embankment stability and bearing capacity. Prefabricated vertical drains (PVDs’) together with surcharging is used to accelerate the consolidation settlement of the soft foundation. Design calculation was carried out to determine the design tensile strength of the high stiffness geotextile required, as well as the spacing and depth of PVDs’ and surcharge height. This paper also discussed the construction sequences of the embankment. </p>

<p>Prefabricated Vertical Drain (PVD) is a composite geosynthetics material which designed to have a high permeability property. It is often used to accelerate consolidation process on a compressible soft soil layer. In order to reach a minimum number of 90% consolidation at the beginning of the building or structure construction project, a certain number of preloading is required. The number of preloading depends on the load that would be acting on the ground in the future. There are several methods of preloading, such as: conventional earth embankment, vacuum with membrane, and membraneless vacuum. In this paper, a test area of 800 m² located in the north coast of Central Java would be tested using PVD with membraneless vacuum preloading method. An approximately 80-90 kPa of vacuum pressure would be applied during vacuum preloading period. The vacuum pressure successfully reached the edge of the area with almost the same pressure as exerted by the vacuum pump. The difference value of vacuum pressure at the edge with the vacuum chamber are ranging from 2-6 %. At the toe of PVD material, vacuum pressure is about 3% smaller than the vacuum pressure measured on the top of the PVD. After three months of vacuum, the result showed that 70-80% of total predicted settlement was reached. Soil investigation data from before and after vacuum showed that q_c value of CPT test was slightly increased whereas SPT value increased by 1.5 times. Laboratory test data showed that the natural water content value decreased by 1-4%, unit weight increased by 4-9%, void ratio value decreased by 10-20%, and shear strength increased by 5-20%. The recorded bouncing potential two months after vacuum was 2-3%.</p>