2.6.3 The Convergence Method This approach is a plain strain method which simulates a 3D effect. Since ground displacement occur prior to tunnel excavation, and the support can be installed with a time delay behind the excavation face, this approach can take into account this features. It can be spitted into: stiffness reduction method and load reduction method [3]. a.) Stiffness reduction method This method implies the gradually reduction of material stiffness inside the periphery of the tunnel lining. In this manner the excavation process will be modeled accordingly. This procedure allows us to determine both the settlement ahead the face of the tunnel (prior to lining installation) and the settlements parallel to the tunnel. There is a certain amount of deformation before the lining is install therefore is important to determine the wall deformation prior to support installation [3]. Figure 12. Stiffness reduction [4] The material stiffness inside the periphery of the tunnel lining is going to be reduced by an α-factor resulting in a reduced Young modulus (1- αi)E. This is to say that for the material in the future opening, using a factor of α=0 represents the same stiffness as the one …show more content…
As in the gap method, ground deformation is limited by the outer diameter of the tunnel lining and similar to the stress reduction method a pressure boundary condition along the excavated tunnel boundary applies. But unlike the stress reduction method which is reducing the acting initial stresses along this boundary, it will be shown that the grout pressure method replaces the initial stresses by a given grout pressure distribution, which differs considerably from the distribution of initial stresses. In the following the grout pressure method will be proposed as an improved installation procedure for shield
Yan, F., Feng, X., Chen, R., Xia K., Jin, C., Dynamic Tensile Failure of the Rock Interface
Chapter four contains a series of linear and non-linear time-history analyses and includes a very thorough analytical study on the stress histories at the critical locations of the buildings. Furthermore, the contribution of each mode of vibration to total stress is investigated.
[4] Muni Budhu. Soil Mechanics and Foundations 3rd Edition and Foundations and Earth Retaining Structures (Combined book made for UBC). John Wiley & Sons, Inc. 2011.
However, before doing this we had to look more into depth on the materials we will use to construct our bridge. We also have to consider the possible environmental and geological factors that should be taken into consideration for our model. Pertaining to environmental and geological factors, there are many stipulations that structural engineers take into consideration before the construction of a truss bridge begins. The main objective of the geotechnical engineers are to protect the lives of others and avoid property damage from happening which can be caused by various geological conditions. Geological engineering uses principles of soil and rock mechanics to find surface conditions and materials.The Geotechnical engineers complete works such as: geological hazard assessments, material properties, landslide and slope stability, erosion, flooding, dewatering, and seismic investigations. These engineers closely examine all of these important factors before constructing a bridge in a certain location. According to Teach Engineering.com, constructing a safe and efficient bridge requires an ample amount of time and energy. Environmental and geological factors play a major role in construction, as
In the majority of mining projects, there is a large amount of overburden that must be removed in order to access the mineral deposits. The overburden, often times in enormous amounts, is stored on site as piles or as backfills in open pits [7].
A simplified and efficient soil structure interaction (SSI) method has been proposed for structures supported by pile foundation system using recently proposed lumped parameter model with gyro-element (GLMP) which shows efficient and accurate representation of frequency dependent impedance function (IFs) of the soil-foundation systems. The original GLPM has been transformed to make the gyro-element compatible with the conventional software framework. The transformed GLPM has been verified with the IFs of a pile group supporting a single degree of freedom system and implemented in multi-story building supported by a pile group. The effects of frequency dependent characteristics have been studied for the multi-story building by comparing the results with conventional Kelvin-Voigt model and rigid foundation system. OpenSees software framework has been used in the modelling of superstructure and foundation system with GLPM. The results show significant effects of the frequency dependent IFs on the response of the foundation.
The most economical method for ground improvement is aggregate piers. Before aggregate piers were used, engineers had to replace the weak soil with an engineering fill in order to use shallow foundations, but in some cases (load is very high) they had to use deep foundations, which is much more expensive. By using aggregate piers, we can now use shallow foundations in marginal soil without having to replace it. By using compacted aggregate to create stiff pier element, aggregate piers help to increase the bearing capacity, liquefaction resistance, shear strength, rate of consolidation and it reduces settlement.
The 1.78 mile western span of the bridge between San Francisco and Yerba Buena Island presented the first obstacle. The bay was up to 100 feet deep in some places and required a new foundation-laying technique. Engineers developed a type of foundation called a pneumatic caisson to support the western section. A series of concrete cylinders were grouped together and then capped-off, having the air pressure of each cylinder identical to balance the beginning of the structure. From there, the workers added sets of new cylinders until the caisson reached the bottom of the bay. Then, in order to reach the bedrock, they inserted long drills down the cylinders, digging until they reached bedrock. After the caisson was balanced at the bottom of the bay, workers filled it with 1 million cubic yards of concrete, more concrete than was used for the construction of the Empire State Building! This caisson connected the two suspension bridges that make up the western part of the bridge.
Borehole mining (BHM) is a process that incorporates a high pressure waterjet cutting system and a down-hole slurry pumping system through a single borehole drilled from the surface into the mineralized rock. The waterjet cuts the material resulting the slurry flows into an eductor pump near the base of the tool and pumped out to the surface. A cavity will be created as a consequence of this excavation process [2]. Understanding the relationship between the cavity stability and the operational parameters is critical in designing any borehole mining system.
Strasky, J. (2004). Recent development in design of stress ribbon bridges. Retrieved from http://docs.google.com/viewer?a=v&q=cache:HZ_0RHziXHQJ:www.cement.org/Bookstore/download.asp%3Fmediatypeid%3D1%26id%3D7121%26itemid%3DIS617+stress+ribbon&hl=en&gl=us&pid=bl&srcid=ADGEEShElFbAnAHmbhR0Xr7oSO5RWxWd7CKzAA-IJAUKW3xsI0niIoTDH_BowhTg6N-rYhBlJ39EpWH4oEH2h9y4KY3_ekYc EY0lXD8K-Xrva1vl4yqAM58jGNMkI03-vCCCVe8RvYR5&sig=AHIEtbR6ZvE Amub84QgS4uUL-H1s-o0lbQ
Bending is generally carried out on a machine known as a press brake. This is a machine which can be operated both manually or automatically. Therefore, keeping this in mind, the bending method is also known as press brake forming. Press brakes are accessible in a variety of sizes which are regularly ranged in between 20 tons to 200 tons. They are made so robust and massive to be suitable for the given task performance. A press brake
I have conducted my research through interview with someone familiar with construction and development as how geometry is used in these fields.
Tubing continuously wraps and unwraps over its spool and over the tubing directional arch (“gooseneck”) as it goes in and out of the well. This bending and straightening causes an extreme amount of wear and tear. This process is known as cyclic bending and along with the internal pressure may result in a life expectancy of less than 100 cycles. Another downfall is the tendency for the walls to thin, thus increasing the diameter of the tubing as cycles increase. Tests have shown up to 30% increase in the diameter. This plastic type growth is sometimes referred to as ballooning. This effect is worse on the tubing that does not rotate during deployment and the walls thin more on one side that the other. Elongation is another effect that results from the forces of fieldwork, with reports stating up to ten feet of permanent elongation per trip!
Milne, R. J. W. Structural Engineering: History and Development. London: E & FN Spon, 1997. Print.
Engineers set up all building codes based on accurate calculations that are based on theories and actual observations known as seismic assessment. . There are two different types of seismic performance assessments, experimental assessment and numerical assessment. Experimental assessments are very expensive since engineers need to build a scaled m...