Large excavations and their effect on displacement of land boundaries

A study to estimate land surface movement caused by large surface excavations in sedimentary strata is presented.In stratified or jointed strata the stress relief driven movement adjacent to large excavations can be significantly larger than expected.High lateral stresses measured in Australia and other places around the world indicate that the ratio of horizontal to vertical stress has been particularly high at shallow depths.The in situ strata is in compression and during excavation,stress is relieved towards the opening causing strata movement.Large excavations such as,open cut mines or highway cuttings,can initiate an extensive horizontal slide of surface layers towards the excavation.These ground movements can be damaging to surface structures such as water storage dams and large buildings.Based on stress measurements at shallow depths in Australian coal mines the study presented here calculates and models the extent of potential ground movement along the bedding surface adjacent to large excavations and provides a new prediction tool of land movement at the excavation boundary that can benefit the geotechnical practitioners in the mining industry.

Diagnosis of Large Papillary Excavations in Developing Countries: From Automated Visual Field to OCT of the Ganglion Complex. About a Case

Background: Large papillary excavations constitute a true differential diagnosis of glaucoma in our environments. Aim: To present a clinical case of large papillary excavation simulating glaucomatous optic neuropathy in a young subject. Case Presentation: The ophthalmologic examination made it possible to note a visual acuity of LogMar 0.00, ocular hypertonia and a large papillary excavation in both eyes. The visual field noted bilateral perimetric involvement suggesting optic neuropathy. Optical coherence tomography (OCT) of the ganglion complex revealed an absence of involvement of the ganglion complex and the ganglion ridge essential to evoke optic neuropathy. An ocular hypotonizing treatment made it possible to normalize the intraocular pressure. Conclusion: The particularity of this observation lies in the fact that the perimeter involvement that preceded any involvement can simulate a glaucomatous involvement. Functional damage to the visual field must be correlated with structural damage to suggest glaucomatous damage in our ophthalmic patients.

Reliability Allocation of Large Mining Excavator Electrical System Based on the Entropy Method with Failure and Maintenance Data

In the design of large mining excavator electrical system,a practical reliability allocation method was introduced to allocate system level reliability requirements into subsystem and component levels. During the reliability allocation process,factors from the fault and maintenance data were only considered in reliability allocation scheme. It could avoid the disturbance from expert experiences. The entropy method was also used to obtain weights of reliability allocation indexes of large mining excavators considering different factors. Then the failure rate allocation of subsystems and components could be completed.

Finite Element Analysis of Effects of Improvement of Soil Between Double-Row Piles

Double-row pile(DRP)retaining systems have been widely used in deep excavations in China.Soil between the front and back-row piles(FBP soil)is often improved to decrease the displacement of DRPs in soft soil areas,but the improvement efficiency has rarely been researched.A large and deep excavation supported by a DRP retaining system is introduced,and the effect of FBP soil improvement is discussed by comparing the finite element analysis and the monitoring results.Then,a parametric study of DRP using the finite element method considering the small strain of soil is conducted to investigate the effect of FBP soil improvement.It was shown that the pile deflection and bending moment decrease when the FBP soil is improved.Moreover,the most efficient way to minimize the pile deflection and bending moment is to improve the FBP soil around the excavation level.The FBP soil improvement 2-4 m below the pile head is not very useful for reducing the pile deflection and can be eliminated when the pile displacement limit is not very strict.