Evaluating the Design Criteria for Light Embankment Piling: Timber Piles in Road and Railway Foundations

Three-dimensional finite element (FE) simulations were performed to further develop the Swedish design guidelines for geogrid-reinforced timber pile-supported embankments, also known as lightly piled embankments. Lightly piled embankments are constructed mainly in areas which typically have highly compressible soils, and the method utilises untreated timber piles as its key feature. The timber piles are installed in a triangular arrangement instead of the more common square arrangement, with a centre-to-centre distance of 0.8–1.2 m. The aim of this study was to evaluate the current standard using FE modelling setups with square and triangular pile arrangements with varying centre-to-centre distances, based on a typical road foundation case. The evaluation mainly focused on comparing the embankment settlements, as well as the load and stress distribution in the embankment, the piles and the geosynthetic reinforcement. As part of the evaluation, a state-of-the-art study was done on international design guidelines and analytical models. From the FE simulations, no evident difference in mechanical behaviour was found between the triangular and square piling patterns. The maximum allowed centre-to-centre distance between piles can potentially be increased to 1.4 m, decreasing the number of piles by as much as one third.

Laboratory Model Tests on Consolidation Performance of Soil Column with Drained-Timber Rod

Timber pile is an ancient technology applied in soft ground improvement for more than 1000 years. With the rise of many high-rise buildings, many types of modern mechanized-construction piles are widely developed and applied; for example, steel pile, precast concrete pile, sand pile, and gravel pile are widely used instead of timber piles. Yet, in some special conditions, timber piles have certain advantages due to their environment-friendly characteristics, which result in obvious economic benefits and suitability. To overcome the weakness of the traditional timber pile technology and expand its application in engineering practice, a drained-timber pile technique was put forward. This technology is to wrap the permeable filter-type drainage geotextile around the timber pile, so that the timber pile not only has the replacement function to strengthen the foundation but also has the drainage function, can accelerate the pore water discharge, and speeds up the soft soil foundation consolidation. The reduced scale soil-column consolidation model was designed to perform the consolidation tests for the soil column with a drained-timber rod. In total, eight types of soil-column consolidation tests were carried out to verify the feasibility and effectiveness of the drained-timber pile technique. The results revealed that, under the same loading and consolidation time, the drained-timber rod can obviously increase the degree of consolidation when compared with traditional timber rod. It can be expected that the drained-timber pile technique has a good application prospect for the construction of medium-small hydraulic structures and for the treatment of super soft clay.

The effect of land subsidence on real estate values

Land subsidence in the Netherlands, mainly occurring in its western and northern peat and clay soils, causes significant damage to houses and infrastructure, estimated at EUR 17 billion until 2050, through differential settlement of shallow foundations, negative skin friction and fungal decay of timber piles. Various studies and reports both in The Netherlands and abroad have addressed the potential economic impacts of subsidence on houses: yet, these studies lack spatially detailed data and instead rely on generic assumptions on expected damage restoration costs. By using a hedonic pricing model, this study examines the impact of subsidence on housing prices in the Dutch cities of Rotterdam and Gouda. In contrast to earlier studies, subsidence and its impact on property values are examined at house level. We test for the effect of subsidence with data related to (i) general (uniform) subsidence (mm yr−1), (ii) differential subsidence of a building and (iii) subsidence of the surrounding area in relation to the house. Results show that uniform subsidence has the largest impact on property values with approximately −6 %, while “differential” and “surrounding” subsidence show respectively −2 % and no effect. These results could prove useful to policymakers, homeowners and housing corporations by generating a better understanding of the impact of subsidence on property values and subsequently to create awareness and spur investments in measures to mitigate damage. It should be noted that these results are specific to the research area are therefore not immediately scalable to other cities as local conditions differ.

REHABILITATION OF MARINE TERMINAL PIERS

This paper presents practical methods and techniques for rehabilitation and strengthening marine terminal piers in the USA. These piers are waterfront structures for berthing of large cargo vessels and cruise vessels. Typically, the piers consist of timber or concrete deck supported on multiple pile bents. The piers are subjected to large impact forces from the mooring of the vessels acting at the fenders and bollards, in addition to the other normal vertical dead and live loads. Depending on the size of the vessels, the design service loads on the bollards are in the range of 100 tons to 200 tons. Other possible severe loads are from the winds and waves during the hurricanes. The piers are continuously exposed to outdoor, marine and coastal environments, which are corrosive in nature. For these reasons, all piers of 15 years or more are normally up for repair/rehabilitation. Typical deteriorations found are: cracked and spalled concrete, rust in exposed reinforcing bars, broken timber piles, timber piles with reduced cross sections, cracked concrete piles, corroded steel piles, and displaced out-of-plumb piles. The paper presents the methods for repairing the above-mentioned defects. For concrete crack and spall repair: sealing with epoxy, concrete patching and shotcrete are used. For pile repair: concrete jacketing of piles is used for splicing or strengthening of piles.

Design Criterion of Reinforcement on Thick Soft Clay Foundations of Traditional Construction Method in Indonesia

It is commonplace that the ground near river is thickly covered with soft clay. Thus, in order to prevent it from the natural hazard, it is necessary that local people construct a robust embankment of countermeasure by constructing river bank in the soft ground, with low level of bearing capacity. To solve the problem aforementioned, local people are widely known to apply traditional method such as timber or bamboo pile. To establish this method, the Ministry of Public Works has published a technical guideline for reinforced soft ground before embankment. The guideline shows the process of mattress construction including: 1) cutting the ground for site preparation; 2) installing timber piles; 3) laying geo-grid on top of the piles and; 4) putting and compacting a granular material on the geo-grid. The guideline assists engineers to construct an embankment on the mattress. Unfortunately, the guideline never details a reasonable design based on geotechnical engineering. Hence, this paper aims to propose and discuss, a criterion of bearing capacity of reinforced soft clay using several empirical calculations. The model cases were simulated for small footings subjected by static loading on the mattress. As a result, the calculations will lead to the criterion of allowable bearing capacity of reinforced soft clay with timber pile.