Soil Mechanics

A database of 641 fall cone tests on 101 soil samples from twelve countries has been analysed to determine the best mathematical relationship linking undrained shear strength with liquidity index. From the database, it is shown that the use of a linear relationship linking liquidity index and the logarithm of undrained shear strength that uses the commonly assumed 100-fold factor increase in strength from liquid to plastic limit
over-predicts the measured data of soil strength. The use of a factor of about 35 for the ratio between the strength at liquid limit and that extrapolated to plastic limit is shown to be more realistic. Logarithmic liquidity index is examined and found to also correlate strongly with the logarithm of undrained shear strength, however it is shown that no great statistical improvement is present compared with the semilogarithmic
formulation. When considering data of individual soils a power law fitting is shown statistically to be the preferred mathematical function.

A new approach is developed to determine the shear wave velocity in saturated soft to firm clays using measurements of the liquid limit, plastic limit, and natural water content with depth. The shear wave velocity is assessed using the site-specific variation of the natural water content with the effective mean stress. Subsequently, an iterative process is envisaged to obtain the clay stiffness and strength parameters. The at-rest earth pressure coefficient, as well as bearing capacity factor and rigidity index related to the cone penetration test, is also acquired from the analyses. Comparisons are presented between the measured clay parameters and the results of corresponding analyses in five different case studies. It is demonstrated that the presented approach can provide acceptable estimates of saturated clay stiffness and strength parameters. One of the main privileges of the presented methodology is the site-specific procedure developed based on the relationships between clay strength and stiffness parameters, rather than direct correlations. Despite of iterative processes, the presented approach can be easily implemented using a simple spreadsheet, benefiting both geotechnical researchers and practitioners.

So far, drying systems have not been classified systematically. However, drying methods can be broadly classified on the basis of either the mode of heat transfer to the wet solid or the handling characteristics and physical properties of the wet material. The first method of classification reveals differences in dryer design and operation, while the second method is most useful in the selection of a group of dryers for preliminary consideration in a given drying problem. According to the mode of heat transfer, drying methods can be divided into: (a) conduction drying, (b) convection drying, and (c) radiation drying. There are other methods of drying also, namely, dielectric drying, chemical or sorption drying, vacuum dryi ng, freeze drying, etc. Of them, convection drying is commonly used for drying of all types of grain and conduction drying can be employed for drying of parboiled grain. Conduction drying When the heat for drying is transferred to the wet solid mainly by conduction through a solid surface (usually metallic) the phenomenon is known as conduction or contact drying. In this method, conduction is the principal mode of heat transfer and the vaporised moisture is removed independently of the heating media. Conduction drying is characterised by: (a) Heat transfer to the wet solid takes place by conduction through a solid surface, usually metallic. The source of heat may be hot water, steam, flue gases, hot oil, etc.; (b) Surface temperatures may vary widely; (c) Contact dryers can be operated under low pressure and in inert atmosphere; (d) Dust and dusty materials can be removed very effectively; and (e) When agitation is done, more uniform dried product and increased drying rate are achieved by using conduction drying. Conduction drying can be carried out either continuously or batch-wise. Cylinder dryers, drum dryers, steam tube rotary dryers are some of the continuous conduction dryers. Vacuum tray dryers, freeze dryers, agitated pan dryers are the examples of batc h conduction dryers. Convection drying In convection drying, the drying agent (hot gases) in contact with the wet solid is used to supply heat and carry away the va porised moisture and the heat is transferred to the wet solid mainly by convection. The characteristics of convection drying are: (a) Drying is dependent upon the heat transfer from the drying agent to the wet material, the former being the carrier of vaporis ed moisture; (b) Steam heated air, direct flue gases of agricultural waste, etc., can be used as drying agents; (c) Drying temperature varies widely; (d) At gas temperatures below the boiling point, the vapour content of the gas affects the drying rate and the final moisture content of the solid; (e) If the atmospheric humidities are high, natural air drying needs dehumidification; and (f) Fuel consumption per kg of moisture evaporated is always higher than that of conduction drying. Convection drying is most popular in grain drying. It can be carried out either continuously or batch-wise. Continuous tray dryers, continuous sheeting dryers, pneumatic conveying dryers, rotary dryers, tunnel dryers come under the continuous system, wherea s tray and compartment dryers, batch through circulation dryers are the batch dryers. Convection drying can be further classified as follows: Pneumatic or fluidised bed drying: When the hot gas (drying agent) is supplied at a velocity higher than the terminal velocity of the wet solid, the drying of the wet solid occurs in a suspended or fluidised state. This phenomenon is known as fluidised bed drying. Drying may be carried out in a semi-suspended state or spouted bed condition also. Generally, the convection drying is conducted under ordinary state, i.e., drying agent is supplied at a velocity much lower than the terminal velocity of the wet m aterial. In natural air drying, the unheated air as supplied by the nature is utilized. In drying with supplemental heat just sufficient amount of heat (temperature rise within 5 to 10°C) only, is supplied to the drying air to reduce its relative humidity so that drying can ta ke place. In heated air drying, the drying air is heated to a considerable extent. The natural air drying and drying with supplemental heat methods which may require one to four weeks or even more to reduce the grain moisture content to safe levels, are generally used to dry grain for short-term storage in the farm. Heated air drying is most useful when large quantity of grain is to be dried within a short time and marketed at once. It is used for both short and long-term storage. Comparative advantages and disadvantages of the three convective drying methods are given as follows: NATURAL AIR DRYING: Advantages: (1) Lowest initial investment and maintenance cost. (2) No fuel cost. (3) No fire hazard. (4) Least supervision. (5) Least mould growth compared to supplemental heat. Disadvantages: (1) Very slow drying rate, drying period may be extended to several weeks. (2) Weather dependent. (3) More drying space necessary in comparison to heated air drying. (4) Useful particularly for short-term storage in the farm. (5) Not useful for humid tropics. SUPPLIMENTAL HEAT DRYING: Advantages: (1) Lower cost of equipment and maintenance. (2) Independent of weather. (3) Requires less supervision. (4) Most Convection drying Drying under Fluidised state Drying under Spouted bed condition Drying under ordinary state Natural / unheated air drying Heated air drying Air drying with supplemental heat

Abstract Dispersive soils are characterized by an unstable structure (disperse and crumb
ssistance in water of low salt concentration. These soils are highly erodible in nature and
tend to erode under low flow rate. Using dispersive soils in different structures like dams,
embankment and roadway may cause serious engineering problems which are worldwide,
and several structure failures have occurred and reported in many countries. Soil dispersion
is a physical chemical phenomenon that is caused due to presence of certain approach ...

This paper examines biocementation via the microbial-induced carbonate precipitation (MICP) process as an appropriate and promising new technology for stabilisation of loose sand and silty sand deposits as a method to mitigate wind erosion. The technique involves spray treating the sand surface layer with a mixture of cementation and bacterial-cell solutions, the ensuing reactions causing calcite precipitation to occur between the sand grains, thereby lightly cementing them together over time. The bench-scale experimental programme presented investigates the proposed technique's effectiveness for stabilisation of silica and carbonate sands with different gradations, determination of the optimal reagent concentrations, the time-dependent shear strength development for the crustal sand layer following single-and double-MICP spray treatments, as well as wind tunnel experiments. Of particular novelty were investigations of the effect of dew formation on crustal shear strength development with curing period and the efficiency of the MICP treatment for the outdoor environment compared to laboratory-controlled test conditions. The wind tunnel experiments demonstrated that 28-day cured singly MICP-spray-treated crustal sand layers were stable to simulated 20 m·s−1 winds measured at 20 cm above the layer surface.

— Surface or shallow compaction is one of the earliest, cheapest and commonly used techniques to improve the physical and mechanical properties of loose soil specially for imported structural fill. It is simply rearranging of soil particles to reduce air ratios using surface static or vibrating mechanical effort. Usually, shallow compaction procedure includes subjecting the loose soil to certain number of compacting equipment passes to archive the accepted compaction level; this number of passes is a function of many parameters such as type of soil, initial soil parameters, compacting equipment characteristics and thickness of soil lift. International codes, specifications and handbooks include just guidelines about the required number of passes; accordingly, it is usually determined based on personal experience and field trials. This research has two goals, the first is to estimate the properties improvement of certain natural surface loose soil under certain surface compaction procedure by calculating the enhancement in soil properties after each pass and updating the soil properties for next pass calculations. The second goal is to use the previous approach to develop set of equations to design surface compaction procedure for imported structural fill, this includes calculating minimum compaction equipment characteristics, maximum lift thickness and minimum number of passes to enhance certain imported fill from certain initial condition to certain final condition. The proposed approach for the first goal was verified using case studies and showed good matches, and the developed designing equations for surface compaction procedure were verified using case studies and showed good matches.

Digital geoinformation for the surface and subsurface is virtually never integrated in civil engineering projects. Reasons are that the surface information is gathered by different person’s and that the subsurface information is in different formats from the surface information. Likelihood and uncertainty of subsurface models is not quantifiable. To quantify the likelihood and correctness of the subsurface information the civil engineer would have to have full access to the original data, which is not available due to the none integration of the data. In the last 10 years considerable progress has been made in use of geographic information systems but the progress in the integration of data and the addressing of likelihood of subsurface data is limited.

Landslides at continental margins are natural hazards for submarine installations and coastal regions. The occurrence of gas hydrates at continental margins is thought to be one major cause for these slides. It is assumed that the decomposition of gas hydrates increases the water content of the host sediment and thus lowers the strength of the soil. In order to predict

The detection of buried land mines in soil is a well-studied problem; many existing technologies are designed and optimized for performance in different soil types. Research on mine detection in shallow water environments such as beaches, however, is much less developed. Electrical impedance tomography (EIT) shows promise for this application. EIT uses current-stimulating and voltage-recording electrode pairs to measure trans-impedances in the volume directly beneath the electrode array, which sits flat over the ground surface. The trans-impedances are used to construct a conductivity profile of the volume. Non-metallic and metallic explosives appear as perturbations in the conductivity profile, and their location and size can be estimated. Lab testing has yielded promising results using a submerged array positioned over a sand bed. The instrument has also successfully detected surrogate mines in a traditional soil environment during field trials. Resolution of the detector is roughly half the pitch of electrodes in the array. In underwater lab testing, non-conducting targets buried in the sand are detected at a depth of 1.5 times the electrode pitch with the array positioned up to one electrode pitch above the sand bed. Results will be presented for metallic and non-metallic targets of various shapes and sizes.

The effects of the working depth of mechanical aeration of a grassy sward were performed at a golf
green in Tunisia. The study focused on measurements of roots length, soil resistance to penetration
and its bulk density before and after passage of a hollow tines aerator working at a depth of 6 cm and
12 cm treatments. The perforation density of 250 holes/m
2
was applied for the two treatments. Results
showed that mechanical aeration was a means of loosening adequate for grassy soils which preserved
the existing culture. Indeed, six days after aeration, there was a reduction in soil resistance to
penetration compared to the initial state for both treatments. This was also observed at 21 and 40 days
after aeration. However, 53 days after aeration, the soil returned to its original state before aeration.
Bulk density also showed the same pattern. In parallel, the roots were marked by an increasing
development for the first three measurement dates to stabilize at 53 days after aeration. However, it
should be noted that aerating at 12 cm of depth, provided the best results of the measured parameters.

With the aim of determining the mechanisms of deformation on fill slopes at the time of an earthquake, 1G shaking table tests were carried out on a saturated model slope focusing on the frequency properties. From the results, it was found that the stability of fill slopes in an earthquake is determined not only by the magnitude of the input acceleration but also strongly depends on the relationship between the natural frequency of the constructed embankment slope and the input frequency. Specifically, the following were concluded. When the input frequency is substantially equal to the initial natural frequency of the slope surface, resonance is produced from the initial stage, and the acceleration is amplified (increase in inertial force). Simultaneous to accumulation of plastic deformation, the mean effective stress is reduced and stiffness decreases. Eventually, the stiffness is lost locally in a shallow part where the confining pressure is small, and slip occurs locally. As the excitation stage increases, the slip extends and expands, and slip occurs in deeper parts. RÉSUMÉ : Dans le but de déterminer les mécanismes de déformation des pentes de talus artificiels lors d'un tremblement de terre, des tests sur table à secousses 1G ont été effectués sur une maquette de pente saturée, en se concentrant sur les propriétés des fréquences. D'après les résultats, on constate que la stabilité des pentes de talus artificiels lors d'un séisme n'est pas seulement déterminée par la magnitude de l'accélération en entrée, et qu'elle dépend également fortement de la relation entre la fréquence naturelle du talus artificiel et la fréquence en entrée. En particulier, nous avons conclu ce qui suit. Quand la fréquence d'entrée est sensiblement égale à la fréquence naturelle initiale de la surface de la pente, la résonance se produit dès l'étape initiale, et l'accélération est amplifiée (augmentation de la force d'inertie). Simultanément à l'accumulation de la déformation plastique, la contrainte effective moyenne est réduite et la rigidité diminue. Tôt ou tard, la rigidité est perdue localement sur une zone peu profonde où la pression de confinement est faible, et un glissement localisé se produit. À mesure que la phase d'excitation augmente, le glissement s'étend et s'accroît, et le glissement se produit sur des parties plus profondes.

Moisture content is a critical factor that affects the engineering behavior of soils, especially cohesive soils. Therefore, the monitoring and determination of the water content is an essential task in an experimental study in the field of geotechnical engineering. There are different techniques and standards to measure soil water content. ASTM D2216 is a laboratory standard test method for the determination of water content of the soil widely used in the United States as well as many other places around the world. The complete drying process of a soil sample in a conventional laboratory oven for twenty-four hours is the core of this standard. However, the process is rather time-consuming. On the other hand, halogen moisture analyzers reduce the time required to determine the soil water content significantly. This study focuses on assessing the applicability and precision of the halogen moisture analyzers versus the conventional laboratory ovens to obtain the soil moisture content. For this purpose, different soil types, cohesive and granular, at different moisture contents were tested using both methods. The conventional measurement method of soil moisture content according to ASTM D2216 as the reference. The results obtained by the halogen moisture analyzer were compared with the results obtained by the conventional method. The results were in good agreement, and the comparison showed that the halogen moisture analyzer is a fast, simple, and relatively inexpensive alternative method to determine the soil moisture content. Consequently, a halogen moisture analyzer as an energy-efficient device can measure soil moisture content with a reliable and relatively automated process minimizing user errors.

The design of bored piles in Malaysia is usually based on the results of the standard
penetration test. It is important to predict the geotechnical capacity of a designed bored pile
through the multilayer soil strata. The back-analysis of a test pile is a reliable means of
obtaining the range for the ultimate skin factor (K su) and the ultimate end-bearing factor (K
bu). In this research, two case histories of maintained load tests on single bored piles (PTP-1
and 2) under full-scale static load (up to twice designed load) are examined. ..

The Intergovernmental Panel on Climate Change (IPCC) provides convincing evidence of global warming as a result of increased greenhouse gas production. There has been a greater occurrence of extreme climate events in recent decades. We need to ensure that our buildings and infrastructure can cope with such events and possibly more extreme events in the future. A good grounding in unsaturated soil mechanics will be necessary to understand future changes involving the drying and desiccation of soils that will occur in dry seasons and the wetting and infiltration processes that prevail during wet seasons. To predict the impacts of climate change will require the use of robust numerical modelling of climate/soil interactions that can be used to model the effects of future climate regimes. To achieve this we need high quality field observations involving climate/soil interaction that can be used to validate the models. This paper reports on a study in the UK to acquire such data.

In this paper numerical analysis is carried out to identify borehole log at a particular location of a site thus producing a number of parameters which are empirically related to SPT values. The Standard Penetration Test (SPT) remains the most common site investigation tool used throughout the world. Physical properties of soil is found by correlations with values of recommended standard N60, determined in SPT tests. Janjira Ap-proach road of ongoing Padma Multipurpose Bridge Project was considered for this study to collect 15 bore-hole log along 20 km stretch. Disturbed soil sample were collected up to 19.5m depth in every 1.5m interval to perform Sieve-analysis test. Spreadsheet was used to input of over 600 data including SPT-N values, Percent Sand & Percent Fines at depths, Reduce Level & Ground Water Table at different Chainage locations. By us-ing all these data- a mathematical model was developed in MATLAB, a high-level language and interactive environment for numerical compu...

An earth anchor is a device designed to support structures, most commonly used in geotechnical applications. Also known as a ground anchor, earth anchor or mechanical anchor, it may be impact driven into the ground or run in spirally, depending on its design and force-resistance characteristics. They are used in both temporary and permanent applications. Ground anchors are effectively restraining devices used in many different types of structures including retaining walls, dams, wharves, bridge abutments and foundations for buildings. Ground anchors are stressed to prevent structural movement and they typically transfer their load over a fixed length. These are commonly referred to as tension anchors and are suited for strong rock conditions. For anchors founded in soil or weak rock, load distributive compressive and tension anchors are used as they have small successive bond lengths rather than one unique longer bond length. Ground anchors consist of a specific anchoring assembly designed to transfer home anchoring loads to the ground are are used extensively in manufactured home instal¬lations. Ground anchor movements of several inches can have significant negative impacts on long-term performance. In cohesive soils, such anchor movements in a vertical direction can approach or exceed the soil’s shear strength. In such cases, the ground anchor is supported by the soil’s residual shear strength, resulting in a decrease in anchor capacity.

This paper represents a new advance in the study of engineering properties and material applications of phyllite clays. Considering their potential use as construction materials for structures subjected to low stress levels, this laboratory research investigated the stabilization and improvement in engineering properties of a Spanish phyllite clay achieved by the addition of 3, 5 and 7 wt.% lime. Geotechnical properties investigated include the consistency limits, compaction, California Bearing Ratio, swelling potential and water-permeability. The phyllite clay–lime mixtures had good compaction properties and very to extremely low permeability-coefficient values, with a semi-logarithmic correlation between increasing permeability and increasing proportion of lime additive. The addition of 3 wt.% lime was sufficient to reach the index of capacity amble specified in the Sheet of Technical General Prescriptions for Works of Roads and Bridges PG–3 (Spanish Highways Agency, 2008), significantly reducing the plasticity index value, with the compacted mixture undergoing no swelling under soakage. The required pavement thicknesses for the raw phyllite–clay material and the phyllite clay–lime mixtures are compared and discussed. Potential applications for phyllite clay–lime mixtures include for pavements/road sub-grade, earth construction, building materials and for impermeabilization purposes.

Natural organic biomass burning creates black carbon which forms a considerable proportion of the soil’s organic carbon. Due to black carbon’s aromatic structure it is recalcitrant and has the potential for long-term carbon sequestration in soil. Soils within the Amazon-basin contain numerous sites where the ‘dark earth of the Indians’ (Terra preta de Indio, or Amazonian Dark Earths (ADE)) exist and are composed of variable quantities of highly stable organic black carbon waste (‘biochar’). The apparent high agronomic fertility of these sites, relative to tropical soils in general, has attracted interest. Biochars can be produced by ‘baking’ organic matter under low oxygen (‘pyrolysis’). The quantities of key mineral elements within these biochars can be directly related to the levels of these components in the feedstock prior to burning. Their incorporation in soils influences soil structure, texture, porosity, particle size distribution and density. The molecular structure of biochars shows a high degree of chemical and microbial stability. A key physical feature of most biochars is their highly porous structure and large surface area. This structure can provide refugia for beneficial soil micro-organisms such as mycorrhizae and bacteria, and influences the binding of important nutritive cations and anions. This binding can enhance the availability of macro-nutrients such as N and P. Other biochar soil changes include alkalisation of soil pH and increases in electrical conductivity (EC) and cation exchange capacity (CEC). Ammonium leaching has been shown to be reduced, along with N2O soil emissions. There may also be reductions in soil mechanical impedance. Terra preta soils contain a higher number of ‘operational taxonomic units’ and have highly distinctive microbial communities relative to neighbouring soils. The potential importance of biochar soil incorporation on mycorrhizal fungi has also been noted with biochar providing a physical niche devoid of fungal grazers. Improvements in soil field capacity have been recorded upon biochar additions. Evidence shows that bioavailability and plant uptake of key nutrients increases in response to biochar application, particularly when in the presence of added nutrients. Depending on the quantity of biochar added to soil significant improvements in plant productivity have been achieved, but these reports derive predominantly from studies in the tropics. As yet there is limited critical analysis of possible agricultural impacts of biochar application in temperate regions, nor on the likelihood of utilising such soils as long-term sites for carbon sequestration. This review aims to determine the extent to which inferences of experience mostly from tropical regions could be extrapolated to temperate soils and to suggest areas requiring study.

This briefing highlights the difficulties of standard triaxial compression testing of fibrous peat and representing its
behaviour in a Mohr–Coulomb framework. Experimental values of effective angle of shearing resistance, phi', and apparent cohesion, c', reported in the literature for fibrous peat are scrutinised, from which the authors conclude that high phi' values determined from triaxial compression testing can be grossly unconservative. Furthermore, given that shearing in a peat which is not completely humified involves tearing of entangled fibres and cellular connections in addition to shearing at frictional contacts, the authors postulate that the apparent cohesion value of fibrous peat is most likely greater than zero. Hence fundamental research on peat strength and how it is derived needs to be performed; also there needs to be further development of existing and new specific material models to simulate more accurately the soft and viscous nature of peat, and the general cross-anisotropic fabric and reinforcement
provided by fibres in peats with low humification.

In India as the population of the country gallops towards alarming proportions, the generation of waste has increased. Much attention is not imparted towards the development of methods to dispose or make use of the waste generated in a useful manner. India has large tracks resting on expansive soil covering an area of 0.8 million square meters which is about 20% of total area of India. These expansive soils undergo volumetric changes with change in moisture content, swelling and shrinkage of these soil causes severe damage to the foundations, buildings, roads, retaining structures etc. In recent days it has been investigated that addition of fibres will improve the ductility behavior of soil. Thereby reducing the cracks during the shrinkage. Use of artificial fibres poses the environmental problems, hence natural fibres like coir, jute and wood pulp can be used as a reinforcing material to soil. In this project an attempt is made to study the influence of coir fibre reinforcement on compaction and strength properties of expansive soil. Coir fibre is made up of the coarse fibres extracted from the fibrous outer shell of coconuts. The individual fibre cells are narrow and hollow, with thick walls made of cellulose. They are pale when immature but later become hardened and yellowed as a layer lining is deposited on the walls. The main objective of our study is to evaluate the effect of fibre inclusions on strength parameters and CBR value of clay soil. In order to achieve the objectives detailed laboratory tests were conducted on virgin sample and fibre reinforced clay. Tests are performed by varying the fibre content in different proportions so as to achieve optimum fibre content ensuring maximum increase in bearing capacity of the soil.