Construction Of Vertical Shafts Research Articles

Numerical investigation of spatial aspects of soil structure interaction for secant pile wall circular shafts

Implementation of fast and cost-effective shoring systems has become very necessary to overcome the technical challenges such as variable soil and rock profiles, high groundwater tables and limitations imposed by the built environment. Secant pile wall shoring systems allow the construction of overlapped piles in almost all subsurface conditions. They are constructed in a circular plan layout to form a vertical shaft which provides unique advantages such as compression ring behavior. This paper presents a numerical study to investigate various aspects of the behavior of circular shafts constructed using secant pile walls. The studied aspects include the identification of earth pressure distributions exerted on circular shafts, the impact of excavation of single and multiple holes on the shaft stresses, and the stresses in the shaft in the case of sloping bedrock. A three-dimensional finite element model is developed to conduct the present analyses taking into consideration the actual behavior of soils surrounding the walls. The stress concentrations calculated for circular shafts were seen to vary from the results of the infinite plate with hole solution. The sloping bedrock was also seen to result in significant deviations from the compression ring behavior. A large increase in the maximum compressive stresses and emergence of some significant tensile stress zones were observed for bedrock inclinations larger than 20°. The results presented in this study address some practical design concerns and were considered to be of interest to those involved in design and construction of vertical shafts.

Application of Rocks Removal Technologies before Shield-Driving in the Line 9 Guangzhou Metro

Detailed geological profile and complementary prospecting histogram revealed a series of hard rocks in the Line 9 tunnel of the Guangzhou metro, greatly increasing the difficulty of shield construction. The geological and hydrological condition of the project was very complex and vertical shafts were used to remove the rocks in order to reduce the cost of the project. Reverse construction technology was applied to the construction of vertical shafts. The calculation of internal forces and relevant design of the vertical shaft wall are introduced herein. The vertical shafts and surrounding buildings were monitored and the monitored contents are also described in detail. At the same time, some emergency measures were applied to ensure the safety of the project. The rocks removal technologies before shield-driving in the line 9 of the Guangzhou metro are introduced herein and the results can be referenced to other similar projects.

Study on the Stratum Displacement Changes Caused by the Vertical Shaft Construction in Saturated Ultra Soft Soil

In view of Wenzhou saturated super soft soil, This article studied the influence of different soil parameters for the shaft excavation construction and the stratum displacement change law by using Plaxis finite element software, according to the data obtained in field tests. The considered factors included the lateral brace stiffness, the stiffness of the underground diaphragm wall, and the surrounding soil disturbance. The calculation results provided much important engineering information, such as the horizontal displacement nephogram, the vertical displacement nephogram and the total displacement incremental vector diagram of each construction steps, which can be referred for the construction of the similar underground projects in soft soil areas.

Noise control for 24-hour rock drilling in urban area

Dill and blast is often utilized for construction of vertical shaft in hard rock geology for various tunneling projects in Hong Kong. Such excavation work is usually restricted during 1900-0700 hours due to noise concern, especially in urban area. For MTR West Island Line Contract No. 703 SHW to SYP tunnels, extensive noise mitigation measures have been employed at the Tunnel Boring Machine (TBM) launching shaft where located less than 10m from the nearest noise sensitive receiver (NSR). A well deigned shaft cover is the most prominent feature of noise mitigation measures and the insertion loss of the shaft cover was found to be minimum 49dB(A) on site. Groundborne noise impact from rock drilling was predicted within the statutory criteria and verified on site. Construction noise permit for 24-hour rock drilling by 2-boom jumbo drill was obtained.

The Application of Pre-Grouting in the Construction of Vertical Shaft

The paper introduces the application of surface pre-grouting in the construction of the main coalmine and the auxiliary coalmine of Xuandong No.2 coalmine.The engineering has achieved remarkable results for the grouting into more than 700 meters deep. To the characteristics of shaft deep and aquifer centralized, the practical for sealing and grouting scheme has been introduced in this paper. According to the high water pressure in the special aquifer, the special measure of increasing grouting pressure and increasing grouting quantity has been taken and which ensured the grouting effect. The paper also introduces the engineering practice of using new material, new technology in vertical shaft for reducing water yield into the shaft. So the water plugging up rate of the main and the auxiliary shaft is more than 99%. The engineering has achieved the target of high quality.