Poor Ground Research Articles

KEY FACTORS IN THE FACE STABILITY ANALYSIS OF SHALLOW TUNNELS

Stability of the excavation face in shallow tunnels and in poor ground is at present a relevant problem in tunnelling. A new calculation procedure is illustrated in this study for the analysis of the effect on the face stability in shallow tunnels of the following key factors: pre-support structures, presence of groundwater, free length of the tunnel (length of the unsupported span close to the excavation face). The procedure is based on the Limit Equilibrium Method (LEM) applied to the ground core ahead of the face and it is able to offer also a detailed evaluation of the interaction between each reinforcement element at the face and the surrounding ground. The originality of this procedure is the fact that it is an unified one and permits to take into account all of the following terms: fiberglass longitudinal dowels, non supported tunnel length, pre-support structures and water level ahead of the excavation face. The main result of the calculation concerns the safety factor of the excavation face. Based on a real case (Biella tunnel), a parametric study has been developed to show the influence of the several elements that affect the tunnel face stability in shallow tunnels

English

The use of alkali ground water constitutes a major threat to irrigated agriculture in semiarid parts of India. The entire arid and semiarid region in India is characterized by low rainfall and has the problems either of water scarcity or poor quality ground water and it can be better utilized for irrigation through drip irrigation system. An experiment was conducted on tomato crop at Central Institute of Post Harvest Engineering and Technology (CIPHET) Abohar, Punjab to study the effect of blending fresh and saline irrigation water on yield and quality. The good quality canal water (EC of 0.38 dS/m) and ground water (EC 19.5 dS/m) were mixed in ratio of 100% Fresh (F), 75:25 (Fresh: saline; F:S) and 50:50 (F:S). The irrigation was done through drip system with three discharge rates (1.2, 2.4 and 4.2 lph) at three irrigation levels of 0.6, 0.8 and 1.0. The plant yield decreased significantly with increase in salinity levels of irrigation water (that is, increase in proportion of saline water). The maximum plant yield (3.55 kg/plant) was recorded with fresh water irrigation while 50% saline water blending in irrigation produced the lowest yield (2.64 kg/plant). The average yield decreased significantly when the discharge rate of emitters increased from 1.2 to 2.4 lph. The quality of tomato is observed inferior in saline water treatment compared to fresh water treatment. The TSS and acidity of tomato fruits increased with increase in the saline water ratios of irrigation water. As compared to 100% fresh water treatment, the mixing of 75% fresh and 25% saline water reduced tomato yield by 11% and gave a better quality tomato fruits at the discharge rate 2.4 lph and irrigation level 0.8. Hence, saline water can be utilized through drip system for sustainable yield and quality tomato production in water scarce area having poor quality ground water. Key words: Saline water, drip irrigation, tomato, quality.

Carbon and nitrogen pools and fluxes above and below ground in spruce, pine and birch stands in southern Sweden

We synthesised results on soil carbon (C) and nitrogen (N) fluxes and the accumulation of soil organic C and N under adjacent 50-year-old Norway spruce, Scots pine and silver birch stands growing on similar soils and evaluated the different processes involved. C and N budgets were calculated. Spruce stands had larger stocks of C and N in biomass and soil than birch stands, with pine intermediate. The differences in soil stocks were mainly found in the organic layer, whereas differences in the mineral soil were small. The study showed that there is no simple answer to what is causing the differences in soil C and N stocks, because several processes are interacting. Spruce and pine trees had higher biomass and litter production than birch trees, but total litter inputs showed no significant difference between stands, because the rich ground vegetation under pine and birch contributed with substantial litter inputs, in contrast to the poor ground vegetation under spruce. Decomposition rate (per g of C) was markedly higher under birch than under spruce and pine resulting in lower C and N stocks in the organic layer. This effect was amplified by higher abundance and biomass of earthworms, favoured by higher pH and palatable litter under birch. Earthworm bioturbation probably both increased decomposition rate and damaged the ectomycorrhizal network with negative consequences for the formation of mycorrhizal litter and C storage. In conclusion, the direct effects of spruce, pine and birch litter on C and N pools and fluxes were modified by indirect effects of understorey structure, pH and earthworm responses.

Hunter Expressway, Australia: dealing with poor ground and subsidence

The A$1·7 billion (£1·13 billion) Hunter Expressway project near Newcastle, Australia, is an impressive 40 km motorway traversing a floodplain and rugged terrain by means of a series of bridges, viaducts and massive earthworks. Former underground coal mining activities and poor ground conditions presented exceptional engineering and construction challenges. Subsidence movements associated with the sudden collapse of standing pillars could leave some of project's structures unserviceable, while earthworks feature a proportionally large amount of poor quality materials derived from cutting construction. The designers incorporated expansive and carbonaceous materials, which would otherwise be spoiled because of their poor engineering properties. This paper chronicles the unique design and construction challenges associated with earthworks and mine subsidence for the eastern section of the project.

Investigating indoor air quality problems: best practice and case studies

Indoor air quality has an important impact on the health and well-being of people. Most people's lives are spent in indoor environments and therefore their exposure to air pollutants is determined by the indoor air quality. Prevention of poor indoor air quality requires an adequate ‘fresh’ air supply and sufficient control of internal sources of pollution to prevent the occurrence of levels of gases, vapours and particles that can cause adverse health and discomfort. The assessment of the performance of buildings with respect to indoor air quality and the investigation of occupant complaints require appropriate methods of measurement and a strategy optimised for the building or other internal environment and the nature of the problem. International standards are available that offer guidance on undertaking such indoor air quality investigations. This paper gives examples of their application to indoor air quality problems with a range of causes, including poor construction products, inadequate design, occupant behaviours, unforeseen incidents and ground contamination.

Evaluation of groundwater quality in five (selected) Grama Divisions (GN) of Maharagama urban area using Groundwater Quality Index (WQI)

The Maharagama urban area is located in Colombo district, Western province (79052‟E – 6050‟N and 79056‟E - 6053‟N) in Sri Lanka. It carries a high population density about more than 1600 km -2. Groundwater in this area is having a great vulnerability for pollution by anthropogenic activities such as excessive use of fertilizers and unregulated garbage dumping directly impact on ground water quality. The present study was carried out to study some important water quality parameters, to evaluate the quality of groundwater in the area using a Water Quality Index (WQI) and to compare the water quality between Grama Niladari (GN) divisions in the study area. Five GN divisions (Jambugasmulla, Gangodawila south B, Wijerama, Navinna and Wattegedara) in Maharagama urban area were selected and the study and fifty five wells were sampled once in three months for a period of nine month from November 2010 to July2011. Physico-chemical and microbiological parameters were measured and WQI was calculated for each well using twelve physico-chemical parameters including total alkalinity, hardness, conductivity, pH, chloride, nitrate, total phosphate and five heavy metals (Cd, Cu, Zn, Fe and Pb). First, a weight value was assigned for each of the twelve parameters depending on their relative importance. The maximum weight (5) has been assigned to parameters with major importance. The SLSI drinking water standards were used as a reference in calculations. Water quality classification based on WQI value of 50-100, 100-200, 200-300, >300 reference to excellent, good, poor, very poor and water unsuitable for drinking respectively. Microbiology parameters were considered separately. The resulted WQI values in groundwater ranged from 17.08 to 280.91. The results revealed that the water quality of the wells deviate from excellent to very poor quality. The nitrate concentration of some wells exceed more than >45mg/l and other physic-chemical parameters remained with the SLS water quality standards. Considering all the water quality parameters, the poorest water quality was recorded in Navinna GN division where located around Navinna garbage dumping site. Almost all tested dug wells were contaminated with fecal coliform and E. coli. In certain wells the fecal coliform counts were exceeded more than1100/100ml. It was observed that unregulated garbage dumping, uncontrolled application of organic and inorganic fertilizers, constructing toilet pits very close to wells and increasing human settlements in the study area positively effect on poor ground water quality of the area. Key words: ground water quality, nitrate, E.coli, anthropological activity

The Stability Analysis of the Lusi Mud Volcano Embankment Dams using FEM with a Special Reference to the Dam Point P10.D

Since the eruption of the Lusi Mud volcano in Sidoarjo, East Java, on May 2006, soil embankment dams have been built to keep hot mud within the ponds. Unfortunately, since the dams were sitting on poor weak ground, land subsidence intensively occurred around the dams. A finite element method (FEM) was, then, applied to evaluate the stability of the dams particularly of the dam point P10.D, being considered as the most unstable point over 29 other dam points. Results show that the dam displacements in vertical and horizontal directions were high. The total displacements of the final design were about 1.5 m in both static- and dynamic-state conditions. These modelled data show a similar trend with field measurement data. The dam had only a factor of safety of about 1.1, and the dam might fail through a deep slide mode.

Sediment Removal by Prairie Filter Strips in Row‐Cropped Ephemeral Watersheds

Twelve small watersheds in central Iowa were used to evaluate the effectiveness of prairie filter strips (PFS) in trapping sediment from agricultural runoff. Four treatments with PFS of different size and location (100% rowcrop, 10% PFS of total watershed area at footslope, 10% PFS at footslope and in contour strips, 20% PFS at footslope and in contour strips) arranged in a balanced incomplete block design were seeded in July 2007. All watersheds were in bromegrass ( L.) for at least 10 yr before treatment establishment. Cropped areas were managed under a no-till, 2-yr corn ( L.)-soybean [ (L.) Merr.] rotation beginning in 2007. About 38 to 85% of the total sediment export from cropland occurred during the early growth stage of rowcrop due to wet field conditions and poor ground cover. The greatest sediment load was observed in 2008 due to the initial soil disturbance and gradually decreased thereafter. The mean annual sediment yield through 2010 was 0.36 and 8.30 Mg ha for the watersheds with and without PFS, respectively, a 96% sediment trapping efficiency for the 4-yr study period. The amount and distribution of PFS had no significant impact on runoff and sediment yield, probably due to the relatively large width (37-78 m) of footslope PFS. The findings suggest that incorporation of PFS at the footslope position of annual rowcrop systems provides an effective approach to reducing sediment loss in runoff from agricultural watersheds under a no-till system.

Torino Metro Line 1 south extension – modelling and settlement monitoring / Süderweiterung der Turiner Metro Linie 1 – Modellierung und Monitoring der Setzungen

AbstractThe excavation of a 3.6 km long tunnel for the Torino Metro Line 1 South Extension was recently completed by a 7.8 m diameter EPB TBM. A critical section of the tunnel was near Corso Spezia, in the Lingotto area, where the main difficulties were the presence of the water table and the poor ground conditions encountered. Another concern was the effect of the excavation on two five‐storey masonry buildings adjacent to the tunnel alignment, which were constructed in 1930 and suffered severe damage during World War II. Continuous monitoring was undertaken during excavation as time dependent settlements occurred. 2D Finite Element modelling was used to simulate the excavation and its effects on the buildings. This paper describes the most significant performance monitoring data, which is compared with the results of modelling.Kürzlich wurde der Vortrieb eines 3,6 km langen Tunnels für die Süderweiterung der Turiner Metro Linie 1 mittels einer EPB‐Tunnelbohrmaschine mit einem Durchmesser von 7,8 m abgeschlossen. Ein kritischer Abschnitt des Tunnels lag nahe dem Corso Spezia, im Lingotto Bereich. Die Hauptschwierigkeiten dort waren die Lage des Grundwasserspiegels und die schlechten angetroffenen Bodenverhältnissen. Eine weitere Sorge galt den Auswirkungen des Tunnelvortriebs auf zwei nahe der Tunneltrasse gelegene, fünfstöckige Mauerwerksgebäude, die in den 1930er Jahren erbaut wurden und bereits im zweiten Weltkrieg erhebliche Schäden erlitten hatten. Während des Vortriebs wurde daher eine kontinuierliche Überwachung der auftretenden zeitabhängigen Setzungen durchgeführt. Eine 2D Finite‐Elemente Modellierung diente der Simulation des Vortriebsvorgangs und dessen Auswirkungen auf die Gebäude. Im vorliegenden Beitrag werden die wichtigsten Daten des Monitorings dargestellt und mit den Modellierungsergebnissen verglichen.

Tiller demography in tall fescue (Festuca arundinacea) swards as influenced by nitrogen fertilization, sowing method and grazing management

AbstractTall fescue is an important temperate grassland species globally, but in many regions the effects of drought, heat and poor grazing management, reduce its persistence in summer. Furthermore, poor ground cover and low tiller population density (TP) in winter result in low radiation capture and thus limited potential to increase the low growth rates at that time. Knowledge of the effect of fertilization, defoliation managements and establishment methods on demography of tall fescue would help to improve sward management for better persistence and winter growth. Accordingly, an experiment was carried out in Pergamino, Argentina, to study the effects of two N‐ fertilizer levels, two grazing frequencies and two seeding row arrangements upon tall fescue TP demography. Herbage mass, tiller appearance (TA) and death rates were measured over 3 years. Seasonal fluctuations in TA and death rates determined well‐defined periods of increase and decrease in TP density. Maximum values were found at the end of winter and minimum ones at the end of spring, after the reproductive period. Nitrogen shortage and high herbage mass limited TA. Tiller death rate followed TA rate and was affected by nitrogen supply and defoliation frequency in the same way that TA was. Sowing arrangement affected tiller demography at the beginning of the experiment.

Coupled Mechanical and Hydraulic Analysis of the Effect of a Front High Hydraulic Conductivity Zone on Shield Tunnelling

A localized high hydraulic conductivity zone with high water pressure is denoted as a hazardous zone. This study focuses on the 3D coupled mechanical and hydraulic analysis of the effect of a front hazardous zone on shield tunnelling. The tunnelling process is modelled by a step-by-step excavation. And a series of three-dimensional coupled mechanical and hydraulic analysis are performed to estimate the distribution of the TSR of the ground ahead of the tunnel face. The result show that the tunnelling directly influences on the distribution of the pore water pressure and the TSR. The maximum influence range of the hazardous zone on the face stability is within 4 times the R value. And the high water pressure can induce a failure of the ground at the tunnel face by itself in conjunction with a poor ground condition.

Wind Turbines Make Waves

People who live near wind turbines complain of symptoms that include some combination of the following: difficulty sleeping, fatigue, depression, irritability, aggressiveness, cognitive dysfunction, chest pain/pressure, headaches, joint pain, skin irritations, nausea, dizziness, tinnitus, and stress. These symptoms have been attributed to the pressure (sound) waves that wind turbines generate in the form of noise and infrasound. However, wind turbines also generate electromagnetic waves in the form of poor power quality (dirty electricity) and ground current, and these can adversely affect those who are electrically hypersensitive. Indeed, the symptoms mentioned above are consistent with electrohypersensitivity. Sensitivity to both sound and electromagnetic waves differs among individuals and may explain why not everyone in the same home experiences similar effects. Ways to mitigate the adverse health effects of wind turbines are presented.

Lightning electromagnetic radiation over a stratified conducting ground: 2. Validity of simplified approaches

In the first part of this paper, the rigorous theory describing the electromagnetic field radiated by a lightning return stroke over a two-layered conducting ground was presented and the exact expressions for the lightning electromagnetic fields were developed and discussed. In this part of the paper, the theory along with its time domain numerical evaluation algorithm is used for the assessment of the validity of simplified approaches proposed in the literature for the vertical electric and horizontal magnetic field components. The simplified approaches are based on the concept of ground surface impedance and its corresponding attenuation function. It is shown that the results obtained using the simplified approaches are in excellent agreement with exact results in both near (50 m) and intermediate (1000 m) distance range. However, since the vertical electric and azimuthal magnetic field components are not appreciably affected by the ground finite conductivity, they can also be evaluated assuming the ground as a perfectly conducting ground. On the other hand, the horizontal electric field above a horizontally stratified ground is very much affected by the ground electrical parameters. Its waveform is characterized by an early negative excursion due to the currents flowing into the ground followed by a late time positive excursion which is due to the elevation of the observation point from the ground level. The magnitude of the negative peak is sharper for subsequent return strokes than first return strokes and is higher for lower conducting grounds. A new formula is proposed for the evaluation of the horizontal electric field at a given height above the air-ground interface. The formula can be viewed as the generalization of the Cooray-Rubinstein formula for the case of a two-layer ground. We show that the new formula is able to reproduce in a satisfactory manner the horizontal electric field above a two-layer ground. The proposed formulation is, however, less accurate at distances as close to 10 m from the channel base and for very poor ground conductivity (0.0001 S/m).

Energy from Waste Facility at Lakeside, London, UK—An Economic and Sustainable Solution to Waste Management

The Lakeside Energy from Waste (EfW) plant is a state-of-the-art facility to convert household, commercial and industrial waste into electrical energy by utilising the heat energy generated from an incineration process to power a super-heated steam turbine. The plant is situated to the west of London, UK, and is incorporated into the existing waste handling strategies in the area. EfW facilities are subjected to very stringent planning processes and have always demanded a high level of architectural presence to satisfy these requirements. Therefore the process equipment is placed inside a large open-spaced steelwork framed shell. This requirement generated a number of structural design and construction challenges for the steelwork frame, including the provision of hybrid columns and large-span curved cellular roof beams. The EfW process requires a continual supply of waste material. In order to facilitate the required volume of material, it is necessary to form a bunker structure within the ground and to extend the walls to the elevated tipping hall floor. Construction of this deep bunker in poor ground conditions necessitated the use of secant piles and innovative slip-form techniques.

Effects of Ground Constituent Parameters on Array Mutual Coupling for DOA Estimation

Effects of ground constituent parameters on the mutual coupling (MC) of monopole antenna array are investigated. This work augments an existing MC compensation technique for ground-based antennas and proposes reduction in mutual coupling for antennas over finite ground as compared to the perfect ground. The work is investigated by finite element method analysis, and numerical results are presented. A factor of 4 decrease in both the real and imaginary parts of the mutual coupling is observed when considering a poor ground versus a perfectly conducting one, for quarter-wave monopoles in receiving mode. A simulated result to show the errors in direction-of-arrival (DOA) estimation with actual realization of the environment is also presented.

Case study analysis of construction excavator H&S overturn incidents

PurposeConstruction plant and equipment harbour significant health and safety hazards. One particular item, the mini‐excavator, presents a hazard from its inherent instability and tendency to overturn during use. The purpose of this paper is to investigate turnover incidents to observe prominent factors and contribute to development of best practice guidance for improving health and safety relating to mini‐excavator use.Design/methodology/approachComprehensive documentary data from eight case study incidents, along with anecdotal data from a further three, were qualitatively analysed in terms of: machine weight, machine activity, ground type/topography, operator competence, type of overturn, damage to property, and injury to person(s). Results were presented to experts in the field for comment and conclusions/recommendations accordingly developed.FindingsObserved prominent casual factors include: inadequate assessment of risk and non‐adherence to safe working practice, working on poor ground, and working on inclined surfaces. The use of sealed operator cabs and proprietary seat restraint mechanisms seem to mitigate risk of personal injury to operators during overturn incidents. A need for cyclic training to reiterate good operator and banksman practice is emphasised, while construction managers should also be aware of the risks, and help implement risk controls.Research limitations/implicationsFindings will inform construction plant management research generally, and the subject of mechanised workplace transport stability specifically.Practical implicationsBest practice protocol will inform health and safety management of mini‐excavators at the workplace.Originality/valueAcademic research into mini‐excavator stability is embryonic; this paper furthers evolving knowledge in the field.

Active and Passive Seismic as an Indicator of Large Equipment Interactions with the Oil Sand

The strain softening of oil sand in the underfoot of ultra class mobile mining equipment, due to the loading action of large mobile mining equipment such as trucks and shovels, yields a highly unstable condition for the operation of this ultra-class equipment. Soft ground conditions in oil sand, due to the low stiffness of the material a condition especially present in the summer, can cause high rack, pitch, and roll in trucks, leading to fatigue failure in structural compo- nents. For shovels, poor ground stability can cause twists in car bodies and undercarriages, resulting in major damages. Track and shovel frame failures due to this instability result in high maintenance costs. The authors carried out a geophysical study of the oil sand in order to evaluate the ground conditions under large mobile mining equipment. A geophysical investigation per- formed in summer 2001 encountered 6-8 m of thick soft material, commensurate with very low velocities, caused by the loosening of the surface material by heavy mining machinery and excavation; and a transi- tion zone of up to 25-26 m depth approaching the in situ oil sand below. The depth of the oil sand zones can be calculated by using the refraction analysis technique. Spectral Analysis of Surface Waves was used to estimate the ground stiffness. A new technique is proposed to evaluate the changing ground stiffness during the use of ultra-class mobile mining equipment.

Stability of Earthfill Dam on a Poor Ground

Stability of Earthfill Dam on a Poor Ground

Removal of excess fluoride ions from Saharan brackish water by adsorption on natural materials

Water supply for people in the Sahara region is mainly assured by poor quality ground water which has excessive minerals, hardness and high concentration of fluoride. This leads to many teeth and bones diseases such as fluorosis. The purpose of this study is to eliminate the excess of fluorides from the El Oued Souf City water supply located in the South East of the Algerian Sahara by retention process onto montmorillonite clay using potentiometric method. Two types of natural clays were tested. The first one contains a higher percentage of calcium (AC) and the second one without calcium (ANC). These adsorbents were activated chemically and thermally with temperatures ranging between 200 and 500°C. Experimental results showed that chemical activation proved effective adsorption reaching up to 88% whereas the thermal activation is ineffective and reached only around 5%. Moreover, the acidity of the medium and the alkalinity affect the adsorption considerably. The retention predicted from the adsorption isotherms is in agreement with Langmuir's model. The kinetic analysis of the reactions indicates that reaction is slow with diffusional control. The low values obtained for the heat of adsorption mean that the adsorption is exothermic with no specific type. An ionic mechanism exchange for fluoride removal is proposed in this study.

Face stabilisation of shallow tunnels using fibreglass dowels

Stability of the excavation face in shallow tunnels and in poor ground is at present a relevant problem in tunnelling. Even though face reinforcement with fibreglass dowels has proved to be efficient, there is still no reliable routine design method available. A new calculation procedure is illustrated in this paper for the analysis of face reinforcement with fibreglass dowels in shallow tunnels. The procedure is based on the limit equilibrium method (LEM) applied to the ground core ahead of the face, and it is able to offer a detailed evaluation of the interaction between each reinforcement element and the surrounding ground. The main result of the calculation concerns the safety factor of the excavation face with dowel reinforcement. Based on this safety factor, it is possible to identify the appropriate length and number of dowels. The procedure has been applied to two real cases, and satisfactory results have been obtained.