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Ground improvement and stabilization techniques-Lowering of the groundwater table

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 Lowering the groundwater table will significantly improve the soil properties. Reducing of the groundwater table is a time-limited process and not always possible. Under running steams. Where the settlement could affect an important area adversely such as inside cities groundwater lowering should not be allowed. Also, it should not be permitted if the groundwater lowering could impact the flora and existing water supply aquifers. Groundwater lowering methods will required arrangement for storing the water. In some cases, it is necessary to treat the water before discharge it. 

In permeable strata where the permeability, k, exceeds about 10–3 cm/s, or where an aquifer can be dewatered below less permeable strata, the level of the water table over a wide area can be drawn down by pumping from boreholes and deep wells. These processes are widely used in open excavations and are also suited to cut-and-cover tunnels and shallow bored tunnel.

Figure 1




There are two common methods used for lowering groundwater table well points and deep filter wells. Well points method used widely to lower the groundwater table. Well points method cant be used to reduce the water table for depth more than 6 m approximately due to the capacity of the suction pump. However, staged well points can be used to lower water table from depths more than 6 m but this will result in the increase of the excavated area more than the required. The washing boring (use high-pressure water jet)will be used to drill well points. The well points will be installed at intervals of 1 to 3 m. The intervals between well points are decided by the permeability of the ground. Figure 2 showing a typical arrangement of well points method.

Deep filter well used for deep excavations. Figure number 3 showing a typical arrangement for this method. In this method, a well of 300 mm diameter or more drilled to the required depth. At the bottom of the well filter material is placed around the perforated pipe. a Submersible pump will be used to suck the water from the ground. It is essential to investigate the soil condition to establish a successful system that can lower the water table quickly without any delays. 
Lowering the groundwater table can result in consolidation settlement for the surrounding soil, and this could affect the nearby structures. Therefore the settlements and effects of lowering groundwater should be monitored closely.
Figure 2

Figure 3




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My name is Mohammad Hamdan, and I am a Civil/bridge Engineer with extensive professional background and experience in the field of construction. I have 10+ years of experience in the construction field. During my professional career, my emphasis has been placed on structural projects, mainly bridges, infrastructure and roads. Reading and practicing the design of structures is my passion.i was lucky to be a part of a big team that executed major highway interchanges. I believe in spreading the knowledge, thus, i compose these courses to share my experience and knowledge. My course focuses on the practical side of construction field. On other word, i am sharing some of what new engineers need to know about construction field. Beside working on construction field, i love writing some articles on my website ( curious civil engineer) Moreover, i wrote some engineering papers, you can check them  by searching my name on Google (Mohammad mamon Hamdan)