Permafrost and geotechnical investigations in Nalaikh Depression of Mongolia

Mongolia is a land-locked country in Central Asia, located between Russia and China. The country＇s high altitude results in cold, dry, and harsh climatic conditions with permafrost being widespread through the territory. Although the capital city Ulaanbaatar is situated in an area with discontinuous permafrost, the downtown section has recently seen a disappearance of permafrost due to an underground central heating system. During the last decade, expansion of the suburbs toward the Nalaikh Depression has resulted in construction of a new residential complex （Urgakh Naran）, construction materials trading center, cement factory and agricultural products market. In the next 10 years, projects such as a university campus, logistics center, residential complex, railway and highway extensions connecting Russia and China have been planned. Engineering-geological and geotechnical investigations have been conducted for these construction projects. This paper presents some of the results determining the engineering geocryological conditions of Nalaikh district and offers foundation design options.

The Use of Ground Penetrating Radar in Municipal Solid Waste Landfill Geotechnical Investigation

The use of GPR （ground penetrating radar） as an auxiliary tool in geotechnical and environmental site investigations has increased in Brazil during the past few years. GPR has been used to delineate contamination plumes, to aid in geological modelling, to detect buried structures and in archaeological surveys. This paper describes and discusses the results ofa GPR site investigation carried out at Gramacho Municipal Solid Waste Landfill in the State of Rio de Janeiro, Brazil. A field study was conducted to detect failure surfaces in its slopes and within the waste mass. The results have shown that： （l） Slip surfaces could be indicated by small continuous voids within the waste mass since there is a good contrast between the dielectric constant of air and municipal waste; （2） Greenhouse gases pools could also be indicated by large voids within the waste mass since there is a good contrast between the dielectric constant of carbon dioxide, methane and municipal waste; （3） Leachate pools present a high electric conductivity that could be easily detected by GPR.

Importance of Geotechnical Investigation for Design and Construction of Shafts over 1000 m Deep

In most cases, copper ore deposits occur at great depths, so the optimization of excavation costs is of utmost importance to identify the most cost effective and productive mining methods, such as block caving or similar methods specifically developed for these deposits. To be able to apply such methods, it is necessary to have a detailed knowledge of the rock mass in terms of its geomechanical, engineering geological and hydrogeological characteristics. This research aims to reduce geological and geotechnical unknowns, analyze in detail the geological environment, and predict geotechnical conditions for the construction of the shaft. This paper uses the example of Borska Reka Copper Deposit, located in Serbia to illustrate the importance of geotechnical investigation to enable best practice in design and construction of shafts that are over 1000 m deep.

The Effection Analysis of Geotechnical Investigation on Foundation Pit Supporting Construction

With the continuous development of the construction industry,the density of engineering construction and the difficulty of underground construction are also increasing.As an important construction protection measure,foundation pit support construction is widely used in underground construction.Starting from the characteristics of foundation pit support construction,this paper analyzes the influence of geotechnical investigation on foundation pit support construction,and analyzes the problems that need to be paid attention to in the survey process.

Incorporating geotechnical and geophysical investigations for underground obstruction detection:A case study

Determining the location and boundary of underground obstructions and/or anomalies is a common problem and often a great chal-lenge for tunneling and underground construction.In this study,geotechnical investigations(penetration tests and borehole drilling/sam-pling)and geophysical investigations(surface wave method and cross-hole seismic method)were conducted with the aim of identifying the location and boundary of rock obstructions in Changi East,Singapore.The surface wave method is frequently used in the sites with lateral homogeneity in previous studies,but its application in the sites with rock obstructions is rare.The experimental results of this study indicate that the surface wave method is also able to determine the upper surface of rock obstructions,but difficult to identify the lateral and bottom boundaries of rock obstructions.To improve the precision of detection,the full waveform inversion(FWI)method was used to process the data from the cross-hole seismic survey.The results indicate that the inversion precision of P-wave is higher than that of S-wave.The horizontal and vertical ranges of rock obstructions in the P-wave inversion results are 14–26 m and 7.5–11.0 m respectively,roughly consistent with the results of penetration tests(about 15–25 m)and borehole log(8.85–10.80 m).This result proves that the sequential application of first-arrival time analysis and FWI can effectively delineate the boundary of rock obstruc-tions.Finally,the results of various detection methods were analyzed and compared in this study.Considering the advantages of various methods,we propose a cost-effective and high-precision workflow containing both geotechnical and geophysical investigations.

Geotechnical forensic investigation of a slope failure on silty clay soil--A case study

Qila Bala Hisar is one of the noteworthy places of Peshawar,Khyber Pakhtunkhwa.The fort was constructed on a flled ground during the 18th century and it was renovated several times by the occupants ever since.Recently,due to an earthquake of magnitude 7.3,the upper part of the south-western wall of the fort collapsed.The collapse of the wall was attributed to the failure of the retained slope.This research was undertaken to characterize the slope material,study causal factors of failure and evaluate remedial strategy.The investigation involved conventional field and laboratory testing and geophysical investigation using electrical resistivity technique to evaluate the nature of stratum.Also,X-ray Diffraction and Scanning Electron Microscopy was used to study the slope material at a molecular level to evaluate the existence of swelling potential.The analysis has shown that excessive seepage of water caused by the poor maintenance of runoff and sewage drains is the causal factor triggered by the seismic event.A remedial strategy involving soil nails,micro piles and improvement of the surface drainage is recommended.