Search Documents

By M. Reda

Inorganic oxidizing agents of the type MeOx-z such as Chromate, Vanadate, Tungstate, and Molybdate... etc. are widely used as corrosion inhibitor. In non acidic solution these oxidizing agent are reduced on the surface of the meta, according to OX + m e + p H20 Red + n OH" In which y = (n-m)/m. The purpose of this publication is to show that for many metals the value of y for any oxidizing agent determines the possibility of that oxidizing agent being an inhibitor or activator for the corrosion process. The inhibition efficiency for other ions such as Pertecnetate and Tellurate which have not been extensively studied can be predicted. A mathematical, equation was derived to express the relationship among the concentration of oxidizing agent, degree of retardation of the corrosion process I cord cor ° (ratio of corrosion current in the solution containing inhibitor to the base solution) , ionic strength of the solution and the coefficient y. The validity of y and the mathematical, equation were verified by many experimental, works on various metals such as zinc, aluminum and steel. Al, the above research works are based on the published research works of Prof. Mikhailoviskii (from 1979 til, 1998) from the Russian Academy of Science.

Jan 1, 2010

By Francis B. Gularte

The Dalles Dam is located 192 miles upstream from the Columbia River?s mouth. As part of an effort to increase survival rates for young salmon migrating downstream to the Pacific Ocean, a river spillwall was constructed to guide the young salmon into the thalway and out of the reach of predators. The spillwall consisted of 43 large precast concrete cells constructed onsite. The 120-ton cells are positioned on the bedrock riverbed to form the 830-foot-long spillwall. Large capacity post-tensioned strand anchors extend through ducts in the precast units, anchoring the wall to the basalt. One hundred seventy-eight tie-down anchors consisting of 30, 32, or 40 strands were installed and post-tensioned to secure the cells. The logistic and technical challenges presented by positioning, installing, and stressing the precast cells in the tailrace of a large dam required a high level of cooperation and planning between the owner, general contractor, subcontractors, and suppliers in order to finish the project within the allotted in-water work windows to minimize impacts on seasonal salmon migration.

Jan 1, 2010

By Dan A. Brown

The foundations at the Huey P. Long Bridge in New Orleans presented special challenges for construction due to the requirements for very deep drilled shafts in the Mississippi River beneath the existing bridge structure. Drilled shafts were constructed to depths of approximately 200ft in alluvial soils using a rotator system with full-length segmental casing, and base grouted to improve axial resistance. This paper describes the design and construction of the work platform to provide access to the restricted-access site beneath the existing bridge, the approach used to construct the drilled shafts, and the results of a load test program to verify the axial resistance.

Jan 1, 2010

By Eric S. Lindquist

Two microtunnel access shafts were constructed using the Cutter Soil Mixing (CSM) method in the San Joaquin Delta region of California, east of San Francisco. Unlike conventional slurry walls and diaphragm walls that utilize concrete, soil mixing relies on blending the soils in situ with a cement slurry to create a soil-cement wall. Cutter Soil Mixing technology utilizes two sets of vertically mounted cutting wheels rotating about a horizontal axis to produce rectangular panels of treated soil. Overlapping of the soil mixed panels enabled the construction of two circular shafts. CSM panels were constructed to a depth of 29 m (95 ft) for the microtunnel jacking shaft and to a depth of 19 m (63 ft) for the microtunnel receiving shaft. The site presented several challenges, including the high depth of treatment, the variable nature of the alluvial soils, and the high water table. This paper describes the CSM technique and presents the design, construction, quality control measures and advantages of using this method for this project.

Jan 1, 2010

By William M. Camp

Construction-induced earthborn vibrations have long been recognized as a potential problem with respect to the constructed environment and various vibration criteria are in use to prevent damage. A special case of construction vibration control is the protection of early-age or ?green? concrete. Unlike limits for damage prevention to building stock, there is no rational, widely accepted limit for protection of early-age concrete. Numerous criteria have been proposed or reported in the literature and the most relevant and rational proposals are summarized herein. These findings are applied to a case history involving both bored and driven piles. Vibration measurements were made during pile driving activities and the vibration magnitude was evaluated with respect to the exposure of freshly-placed and curing concrete to the earthborn vibrations. The maximum vibration magnitude at the applicable distances from pile driving was on the order of 0.3 inches per second. Based on the most persuasive literature, threshold values of 0.8 inches per second or even 1 to 2 inches per second for the protection of green concrete appear to be well-supported. Consequently, it was concluded that the pile driving activities and bored pile construction could proceed simultaneously.

Jan 1, 2010

By Satyajit A. Vaidya

This paper presents a case-study in the design and construction of deep foundation element supported mats for two residential towers on an18,000-square-foot site in Brooklyn, New York. Based on site sub-surface conditions, conventional mat foundations bearing on medium dense sand, having an allowable bearing capacity of 3 tsf, were originally anticipated for the 16 and 25-story towers. However, when the tower shear walls were relocated to the edges of the mat foundations due to architectural revisions, the significantly increased mat edge contact stresses applied to the soil subgrade resulted in calculated settlements of a magnitude that would adversely impact the proposed structures and the neighboring/bordering lot-line building and rail transit subway structures. To address this issue, deep foundation element supported mats were designed for the towers. The design was performed as an iterative process involving structural SAFE and geotechnical Plaxis finite element computer analysis to develop a coordinated geo-structural model of the foundation system. Initial presumptive design values of 45 pci and 445 kips/inch were used for the modulus of subgrade reaction and minimum deep foundation element stiffness, respectively. The designed foundation system consisted of 40 and 60-inch-thick mat foundations for the 16 and 25 story towers, respectively. Initially, the deep foundation elements were designed as 50-foot-long, 14-inch-diameter elements installed to sustain a maximum individual compressive load of 250 tons. The final deep foundation element design was subsequently refined to consist of a 48-foot-long, drilled and grouted IBO Titan 103/51 element designed to sustain a maximum load of 167 tons. Subsequent field load tests on the deep foundation elements confirmed element stiffness ranging from 1,040 to 1,530 kips/inch, with measured mobilized side shear of about 29 psi. The mat foundation reinforcement was adjusted for the pile stiffness values determined in the field load tests, and the deep foundation supported mats were constructed. The two towers were subsequently constructed, and have performed successfully.

Jan 1, 2010

By Josef K. Alter

Long-term performance and behavior of post-tensioned ground anchors subjected to axial cyclic loading constitutes an important aspect of the stability, reliability and overall performance of wind turbine deep foundations. Axial cyclic loading of post-tensioned (PT) ground anchors in soils has not been thoroughly investigated as evidenced by the research conducted for this topic. This paper evaluates research test data, available literature, and industry expert opinion on the current status and problems of deep foundation post-tensioned ground anchor (PTGA) technology, as applicable to the wind energy industry. It also introduces a proposed design solution that addresses the problems of construction cost and long-term performance of wind turbine deep foundations in soils subjected to dynamic cyclic axial loading. Deep foundations using ground anchors for wind turbines have only recently gained attention as a possible viable alternative to the mass spread footings currently in use. One of the primary problems with general acceptance of current PTGA designs is the need for long-term anchor maintenance. The research that was conducted for this study indicates that current literature only partially addresses the many factors influencing load capacity and pullout performance of ground anchors. The lack of information indicates the deep foundation industry has fallen behind in designing and implementing new technology to improve safety and performance, ensure sustainability, reduce costs, and address environmental responsibility. This paper describes the significance of this problem as it applies to the wind energy market, and proposes a new technology solution. The research, expert opinion, and analysis presented by the author is used to support the premise that ground anchor construction cost and long-term maintenance can be reduced with PTGA systems using the Con-Tech Systems (CTS) patent-pending Groutable Void Form (GVF) technology.

Jan 1, 2010

By Helen D. Robinson

Traditional practice to resist large lateral loads on foundations is the use of large diameter caissons, battered driven piles, or battered micropiles. Dense urban construction environments, however, limit the usefulness of these systems due to the close proximity of below- and above-grade obstructions. This paper presents two micropile construction projects in the United States where a complex scheme of battered micropiles and grade beams was developed to counteract large lateral loads at the foundation level. The paper also presents a procedure used to design vertical micropiles for large lateral loads, which can greatly simplify the design of foundations subject to significant lateral loads in urban environments. A design example shows a case where vertical micropiles were used to support allowable design lateral loads greater than 80 kip per micropile.

Jan 1, 2010

By Lorie M. Dilley

Alaska Village Electric Cooperative (AVEC), an electric utility cooperative providing power to 51 Alaska villages, has made a concerted effort to install wind turbines in the villages they serve in an effort to mitigate the growing costs of electrical power generation. The subsurface soils in several of these villages consist of sands and silts with ground temperatures of between 30°F and 32°F. The presence of warm, degrading permafrost in three of the villages has required innovative foundation designs, including the use of helical piers and piles to support steel and concrete wind turbine foundations. The design of the deep foundations had to account for the effects of degrading permafrost likely resulting from observed climate change patterns. Uplift forces imposed on the foundations were approximately 100 kips per pile. Uplift pile load testing was conducted on the installed piers and piles in order to determine the actual working load that each pier or pile could sustain. In addition, pile driving analyzer testing was conducted on several piles installed in the permafrost and compared to pile load tests. Results indicated that the installed piers and piles achieved the necessary capacity with sufficient factors of safety. Thermosyphons were installed near the foundations in order to limit the effects of climate change on the permafrost. The two to four wind turbines in each of the three villages are currently operational. Refinement of the design based on the pile testing from the first village to the third has decreased the cost of the tower foundations and improved our understanding of designing for warm, degrading permafrost.

Jan 1, 2010

By Gordon Chen

As part of a value engineering envisioned by East Coast Slurry, Weidlinger Associates, Inc. designed a unique elliptical slurry wall cofferdam for construction of the 65 ft. deep MWRA North Dorchester Pump Station. A conventional rectangle cofferdam with multiple levels of bracing would have been time consuming and costly and imposed a significant obstruction to the pump station construction. A circular slurry wall, while eliminating the bracings, conflicted with adjacent structures and required excessive backfilling around the final pump station structure. The ellipse shaped cofferdam fit the needs of the project well; however, it created a significant design challenge without the use of bracings. Unlike a circular cofferdam which primarily only has hoop stresses, the ellipse still has to be designed for horizontal bending moments in each panel because of the non-axial symmetric conditions. The more eccentric the cofferdam shape; the higher the horizontal bending. The challenge was to develop a three dimensional finite element model that could analyze both the hoop stresses and horizontal bending stresses above and below the bottom of excavation induced by soil and water pressure and unbalanced construction surcharge loads. This paper discusses the techniques used to model the soils and structure interactions and results of stresses on this challenging unbraced configuration.

Jan 1, 2010

By Fei-chiu Huang

A 17-acre landslide occurred in February 2001, on a slope below Via Bellota in the City of San Clemente, California. Three homes were destroyed and many others placed in jeopardy. The landslide, involving portions of five separate developments, continued to move significantly in the years following. Litigation ensued among the affected parties, and investigations continued through 2007. A mediated repair resolution was ultimately reached among the parties. The agreed upon repair consists of a multi-million dollar stabilization program that included grading, drainage, and structural systems. Part of the construction cost was offset by creating 4 new ocean view custom lots and 20 new mobile home lots. The landslide repair and slope stabilization design involved removal and replacement of portions of the landslide debris and construction of buttress and stabilization fills as well as installation of 74 shear pins in two rows. The shear pins were designed as 4-foot diameter by 50 feet in length and incorporated continuous W30x211 wide flange steel. The shear pins were designed to be installed 25 feet above the slide plane and 25 feet below the slide plane at each location. Construction of the 74 shear pins was initiated in 2008 and completed in 2009. Four-foot diameter holes were drilled by utilizing a truck-mounted, flight-auger-style drilling rig with a 4-foot diameter solid-flight auger. Prior to the installation of the shear pins, an engineering geologist downhole logged strategically selected holes to further evaluate the actual slide plane elevations. The wide flange steel shear pins were then lowered to the desired elevations and encased within 4,500 psi, Type V, 0.45 maximum water/cement ratio concrete. Inclinometers installed within four pin shafts and behind the pin rows indicated performance in accordance with the design. Slight to non-perceivable shear displacement was measured which mobilized the intended capacity at the monitored shear pins. No excessive slope movement was detected at any of the inclinometer locations during or after the construction period. Actual shear displacement of the steel wide flange elements was less than the movement anticipated before shear pin installation.

Jan 1, 2010

By Ameir Altaee

Unconventional means and methods were utilized to install over 650 contractor-designed micro-piles for the replacement of the Bronx approach to the Bronx-Whitestone Bridge in New York City. The method utilized reverse circulation (RC) drill rods and down-hole-hammers (DHH) along with grouting through the DHH bit. The overall construction sequence of drill-down, grout-up, place reinforcing is similar to auger-grout piling. The extremely tough drilling conditions required the use of a percussive DHH. The piling subcontractor refers to this pile as a hammer-grout pile. Project background, constraints and subsurface conditions are given. The proposed means and methods as well as the collaboration between stakeholders are detailed. Results of load testing and production installation are summarized.

Jan 1, 2010

By Walter Valery, Sarma Kanchibotla

Due to the global financial crisis, the world economy has turned upside down and most major economies in the world are facing severe recession for the past one and half year. During this period most commodity prices have tumbled by more than half from their peaks and such a sudden and severe economic downturn is not seen since the great depression. This sudden drop in commodity prices and lack of credit made many mining operations unviable and even those mines that are marginally viable at this point are operating under severe cost pressures and capital expenditure restrictions.

Jan 1, 2010

By Stephen Mansfield, Johannes Schoeman

In August 2006 a technical alliance was formed between Orica Mining Services and Century Mine to provide blasting solutions. The alliance is in the form of a Rock to Specification (R2S™) service, one of Orica’s Blast Based Services (BBS™). The ultimate goal was to facilitate the rapid expansion of material movement from 26 to 41M m3 (34 to 53M yd3) per annum while maintaining a reliable ore supply to the mill.

Jan 1, 2010

By Gungor Tuncer, Ali Kahriman, Abdulkadir Karadogan, Umit Ozer

The environmental problems such as vibration, and air blast are often faced, and discussed on mining, quarrying, civil constructions, shaft-tunnel, pipeline, and dam operations where blasting is inevitable. It is necessary to establish national standards towards to minimize the environmental problems induced by blasting and judicial matters in our country as it is in USA, EU countries and the other developed countries. This necessity and the obligatory of accepting the European Union criteria for Turkey that has started the procedure of joining to EU emphasize the importance of this study. In other words, the establishment of a particular national standard related with this subject is inevitable for Turkey. This will be possible only by studying, applying scientific methods and techniques by the experts.

Jan 1, 2010

By John Cory, David Lily, Bill Hissem

The Lafarge granite quarry in Cumming, Georgia is using Principal Component Analysis (PCA) and Biplot charting to identify important variables and control air blast and vibration. Every blasting situation is unique and PCA and Biplot charting help to clarify the major variables determining air blast and vibration.

Jan 1, 2010

By Robert Pumpelly

During my nearly 30 years with ATF, (Bureau of Alcohol, Tobacco, Firearms & Explosives), I conducted hundreds of inspections. In many cases hours of time were wasted because the licensee or permittee, who had basically done everything right, was not prepared for the audit. In these cases, required documents were scattered, personnel were unprepared and no plan was in place. This paper will provide some simple steps to avoid these embarrassing delays. A list of common violations is also provided.

Jan 1, 2010

By Martti Hagfors, Jussi Saavalainen

The underwater explosions has been used as a test method for the determination energy content of explosives. The test method is suitable for all kind of explosives; homogeneous, heterogeneous, wa-ter-resistant, no-water resistant, cap sensitive, booster sensitive, explosives with hard confinement, explosives without confinement etc. It is also the only test method by which shock, gas heave and to-tal energy values of the explosives can be measured separately. This feature makes it possible to use the test method to develop the explosives for different purposes; the military high explosives need more shock energy where as the gas heave energy is very important feature for the blasting and sea mine explosives.

Jan 1, 2010

By V. Tang

In this paper, Chinese economic situation are estimated and prospective developments predicted to assist those US firms who have been trying to do business in China, or are considering to pursue the China market.

Jan 1, 2010

By Ismet Canbulat

"In order to ensure the stability of roadways, Anglo American Metallurgical Coal (AAMC) has developed a roof support design methodology that integrates analytical, numerical and empirical modelling. This methodology currently is based on a deterministic approach (a single factor of safety against failure is calculated). However, an improved methodology, based on stochastic modelling technique, has also been developed and currently being evaluated. The main advantage of this methodology is that the design is based on the probability distributions of input parameters; thus the outcome is based on a distribution of factors of safety rather than a single factor of safety. An evaluation of factors of safety may also be used to determine the likelihood of failure, which in turn may be utilized to quantitatively determine and evaluate the associated risks in decision making process. This methodology has been evaluated at Grasstree and Moranbah North Coal Mines in the designs of roof support in various critical areas and has been proven to be successful and a better way of determining the roof support requirements.This paper demonstrates the application of this methodology in a design of an install road roof support at Moranbah North Mine, where the 1,750 tonne capacity ''world's highest rated longwall"" has recently been installed.INTRODUCTIONAnglo American Metallurgical Coal Australia (AAMC) operates three longwall (LW) mines located in Central Queensland. There is an increasing emphasis on the reliability at these operations, as the longwalls are getting deeper and facing more geologically challenging conditions. In addition, the Anglo American Vision is to achieve ""Zero Harm"" through the effective management of safety at all businesses and operations. In order to accomplish this vision, AAMC has developed a proactive ground control management system for a safe and efficient production of underground reserves.Proactive ground control management involves understanding the impacts of the geotechnical environment on likely ground behavior, and it consists of approximately 15 major elements. One of the most essential fundamentals of proactive ground control management is to utilize a roof support design methodology that considers different failure mechanisms and also takes into account all important elements. The design methodology becomes even more important when the area in question is a critical area, which is defined as a high risk roadway where any failure may cause increased levels of safety and financial risks to underground workforce and operations."

Jan 1, 2010