Investigating the Nail Walls Performance in Jointed Rock Medium
Evaluation of the excavation-induced ground movements is an important design aspect of support systems in urban areas. Geological and geotechnical conditions of an excavation area have significant effects on excavation-induced ground movements and the related damage. This paper is aimed at studying the performance of excavation walls supported by nails in jointed rock medium. The performance of nailed walls is investigated based on evaluating the excavation-induced ground movements. For this purpose, a set of calibrated 2D finite element models are developed by taking into account the nail-rock-structure interactions, the anisotropic properties of jointed rock, and the staged construction process. The results of this paper highlight effects of different parameters such as joint inclinations, anisotropy of rocks and nail inclinations on deformation parameters of excavation wall supported by nails. Keywords—Finite element, jointed rock, nailing, performance.
Responses of Buildings with Different Structural Types to Excavation-Induced Ground Settlements
This paper compares the responses of buildings with different structural types on shallow foundations subjected to excavation-induced ground settlements and provides a better understanding of the complex soil-structure interaction in building response. Investigated structures include brick-bearing structures, open-frame structures, and brick-infilled frame structures. These structures are often encountered near a construction area, and the different structures may show very different behaviors to excavation-induced ground settlements. In this research, numerical studies were carried out to evaluate the responses of single brick-bearing walls and frame structures (both open and brick infilled) subjected to an identical progressive ground settlement and to provide key features of building responses in different soil conditions, structure conditions, and structural types. Each structure, which is four stories high, was modeled numerically with two different soil conditions, and the response was compared among other types of structures and between elastic and crackable conditions for the brick-bearing and brick-infilled frame structures. Comparison of building responses was investigated by using distortions and crack damages induced to the structures by excavation-induced ground settlements. The structures were modeled by using the two-dimensional (2D) universal distinct element code (UDEC 3.1) in which each brick unit was modeled as a separate unit, with the contacts between brick units having stiffness and strength characteristics of mortar. The numerical studies indicated that the structural response to excavation-induced ground settlements is highly dependent on structural type, cracking in a structure, and soil condition; therefore, their effects should be considered to better assess building response to excavation-induced ground settlements.
VLA stereoscopy of solar active regions. 2: Altitude, relative motion, and center-to-limb darkening of 20 centimeter emission
A newly developed method of stereoscopic correlation is applied to solar radio maps at a wavelength of 20 cm. On the basis of stereoscopic correlations between radio maps obtained on 6 different days we establish the presence of 66 radio source components associated with 22 active regions. We find the following statistical results for active region source structures at 20 cm: 1. The observed lifetime is consistent with an exponential distribution having an e-folding time scale of greater than 18 days. 2. The average altitude of 20 cm sources is 25 +/- 15 Mm; 90% of the sources are found in heights less than 40 Mm. 3. The average diameter of discrete source structures is 48 +/- 15 Mm, implying a vertical/horizontal aspect ratio of q(sub A) approx. = 0.5. 4. No significant source motion has been found with respect to the standard differential rotation rate of Omega = 13.45 deg - ((3 deg (sin(exp 2)B)). 5. We find a statistical limb darkening, which can be described by the relation (T(sub B)(alpha))/T(sub B)(0)) = 0.4 + ((0.6(cos(exp 2) alpha)) for sources with T(sub B) greater than 0.5 MK. 6. The degree of source polarization is 15% +/- 10% and is independent of source location. 7. Bright sources (greater than or approximately equal to 0.5 MK), or equivalently, long-lived sources (greater than or approximately equal to 5 days) show a systematic variation of their altitude as function of the center-limb distance.