Geotechnical investigations and remediation design for failure of tunnel portal section： a case study in northern Turkey

Mass movements are very common problems in the eastern Black Sea region of Turkey due to its climate conditions, geological, and geomorphological characteristics. High slope angle, weathering, dense rainfalls, and anthropogenic impacts are generally reported as the most important triggering factors in the region. Following the portal slope excavations in the entrance section of Cankurtaran tunnel, located in the region, where the highly weathered andesitic tuff crops out, a circular toe failure occurred. The main target of the present study is to investigate the causes and occurrence mechanism of this failure and to determine the feasible remedial measures against it using finite element method(FEM) in four stages. These stages are slope stability analyses for pre-and postexcavation cases, and remediation design assessments for slope and tunnel. The results of the FEM-SSR analyses indicated that the insufficient initial support design and weathering of the andesitic tuffs are the main factors that caused the portal failure. After installing a rock retaining wall with jet grout columns and reinforced slope benching applications, the factor of safety increased from 0.83 to 2.80. In addition toslope stability evaluation, the Rock Mass Rating(RMR), Rock Mass Quality(Q) and New Austrian Tunneling Method(NATM) systems were also utilized as empirical methods to characterize the tunnel ground and to determine the tunnel support design. The performance of the suggested empirical support design, induced stress distributions and deformations were analyzed by means of numerical modelling. Finally, it was concluded that the recommended stabilization technique was essential for the dynamic long-term stability and prevents the effects of failure. Additionally, the FEM method gives useful and reasonably reliable results in evaluating the stability of cut slopes and tunnels excavated both in continuous and discontinuous rock masses.

A Study of Underpinning Methods Used in the Construction Industry in Nigeria

Foundation and retaining wall failures account for the highest case of structural failures.This is a report on a study of underpinning methods used in the construction industry in Nigeria.In view of underpinning,just like most engineering decisions,there is no unique solution,the research investigated technique of remedying foundation defects and whether there are innovations as regards to the underpinning methods used in Nigeria.To achieve the desired objective structured questionnaire,oral interviews and case study of an ongoing underpinning work were carried out.Result shows that differential settlement with a mean of 2.28 is the most frequent cause of foundation failure.While the continuous strip and reinforced mat with mean of 2.7 and 2.67 respectively,are most frequently used underpinning methods in Nigerian construction industry.Also 81.3%of the respondents agree that underpinning methods adopted are suitable and effective.Professionals in Nigeria have devised unique method of underpinning.It was recommended that proper and adequate site investigation should be carried out.Heavy penalties and sanctions should be meted on those construction firms that employ quack professionals.

Analysis on the Problems in Start-up and Debugging of Two 600 MW Generating Units in Yangzhou No.2 Thermal Power Plant

The problems including excessive flow of attemperating water for boiler, failure of butterfly valve at the outlet of circulating water pump, burnt-out of thyristor for excitation regulator, load variation rate of CCS not complying with the contract target, etc. occurred during start-up and debugging of two 600 MW generating units in Yangzhou No.2 Thermal Power Plant. Through analysis on these problems. the remedial measures were put forward, to which can be referred for similar units.

Assessments on slope instabilities triggered by engineering excavations near a small settlement(Turkey)

In this study,the mechanisms of slope instabilities triggered by engineering excavations at location of a planned tunnel portal in the northwest region of Turkey were assessed,and stability of the current slopes which has impacts on safety of a settlement(village)and agricultural fields was investigated.In the first stage of the study,in order to identify the geological units and structural properties of the sedimentary rocks in the area,to clarify the mechanisms of instabilities and to characterize discontinuity and rock mass properties field works were conducted.In this content,geotechnical boreholes,geophysical explorations between the boreholes,line surveys to explore discontinuity properties,preparation of slope profiles using topographical techniques and sampling of rock blocks and discontinuity planes were performed.In the second stage,laboratory tests were carried out on the samples to determine the geomechnical properties of the slope forming materials and discontinuities.Then,back analyses of the instabilities were made to assess the responsible shear strength parameters of the geological units during failures by considering laboratory shear test results too.Based on the backanalyses of the failures,the strength properties of the slope debris were estimated,and it has been clarified that the residual shear strength properties are the factors controlling slip mechanism along the beddings.Following the stability analyses,it is understood that a further instability along the mass or bedding planes in the failed and redesigned area are not expected,if the current slope geometry is not changed.However,safety factor calculated for the slope in the debris is 1.1 which is well below the recommended value in the literature.The minimum safety factor for currently stable slopes which were cut at the eastern part of the failed area is 1.22 which is also less than that suggested in literature.Some remedial measures such as mini-pile or slope flattening are suggested after analyses to increase the factor of safety for this part below the settlement.

Understanding the Safety, Health and Environmental （SHE） Challenges of Xenobiotics and Their Remedial Approaches

With the use of over 100,000 industrially produced chemicals, there have been several concerns on human health and environment. Most of these chemicals are exposed into the natural environment during the life cycles of their production, transportation, storage, consumption, and as by-products and wastes. The rising rates of cancer, obesity, and infertility suggests that there are compounds recently introduced to the environment that have altered the chemistry of the human body, and it is only with the monitoring of xenobiotics such as Bisphenol A （BPA）, nonyphenols, estrogen （natural and synthetic） and other endocrine-disrupting compounds （EDCs） that patterns and links could be drawn. This paper investigates the safety, environmental and health （SHE） impacts caused by BPA, nonyphenols and estrogens. Derived from petroleum, bisphenol A is used in manufacturing plastic consumer products, including certain water bottles, in dental sealants for children＇s teeth, and in resins used to line tin cans. Nonyphenol is one of the by-products of alkylphenolpolyethoxilates which is widely used as nonionic surfactants. Synthetic estrogen used for birth control pills as well as natural estrogen excreted by women through urine enters the domestic wastewater streams. These compounds are considered to be EDCs and have severe SHE concerns. In this paper, the challenges of entry of these compounds （xenobiotics） into nature, health and environmental issues and their remediation have been reviewed in detail.

Slope Instability at Nablus-Al Bathan Road, Palestinian Territories (Causes, Analysis and Remedy Measurements)

Nablus-Al Bathan Road which connects Nablus City and Jordan Valley in the West Bank of Palestinian Territories, was widened, reconstructed and rehabilitated in 2009, however, between 2010 and 2012 road defects at several locations were observed. To fix these defects especially at station 2 + 100 of the road, soil replacement in the body of the road and big boulders to support the edge of the road were used. Unfortunately, large settlement occurred in the part of the road under maintenance and more sliding and slope instability occurred in the road at station 2+ 100 during the remedial measures. Studies were carried out to find the causes of this problem. These included surveying of the area, geotechnical studies (making trial pits, performing geophysical seismic exploration and digging out several boreholes), in addition to slope stability analysis. It was found that the main causes of landslides were types of soils at the site, high slopes, groundwater recharged from rainfall and changing of weights (cut and fill). Remedy measures were suggested to overcome sliding problem based on available resources and local technology.

Assessment of the Cause and Effect of Early Damage of Cobble Stone Road Construction and Its Remedial Measurements:A Case of Nekemte Town Cheleleki Sub City

Road constructing in Ethiopia is increasingly in demand to meet its medium and long term development programs.Most internal roads of Oromia city/town are cobblestone and gravel.Some portions along the alignment proposed and existing roads traversed low resistance of the subgrade that affect the stability of the upper layers of cobblestones.Structural failure is observed on cobblestone roads,and it would be constructed with good quality or low quality of materials.Nekemte Cobblestones Projects have been started in 2014 widely which were filled in most areas today as we observed that needs to be addressed and a corresponding remedial measures must be drawn.A possible counteractive actions had been ordered for every observed destroyed to achieve the standard road situation of the study zone.An evaluation was made use observation,interviews,laboratory test and field test to govern an appropriateness of cobblestones.The lie beneath soil used for bottom layers of road structure based on standard of Ethiopian Road Authority(ERA)low volume road standards.Therefore,result from the field test and laboratory test shown,causes of cobblestone road failures of Nekemte street segment were mostly because of the construction steps/sequence,quality of materials,road construction time,absence of appropriate design,quality supervisor,absences of drainage structures,lack of highly compaction,lack of accurately fill fine aggregate and suddenly high loads vehicle applied on cobblestone road.