1. Figure 9.18 is representative of soil conditions at a construction site. If y
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Question
1. Figure 9.18 is representative of soil conditions at a construction site. If you are the con tractor, select a dewatering method you would consider appropriate for each of the projects described below. Consider the information given in this chapter, earlier chapters and any other information that may be appropriate. Describe in detail how your system would be built and operated. Justify clearly any assumptions you make. Discuss what difficulties you may encounter and how you should plan for them A circular reservoir 100 ft in diameter is to be built with a bottom slab 25 ft below pre- sent ground surface. The groundwater level must be held at least 2 ft below the slab a. until the reservoir is filled Standard penetration resistance, Depth, Soil description 0 50 100 Sandy gravel, some cobbles 3/22/72 20 30 Loose to medium dense fine silty sand ? 40 FEI 60 70Explanation / Answer
The strategies for dewatering utilized for the different activities are as per the following:
a) Wellpoint strategy for dewatering can be utilized for the case. This is on account of sewer line should be put at a profundity of 16ft subterranean level henceforth wellpoint technique would be adequate to make legitimate drawdown as this strategy is limited to make drawdown around 5 to 6 meters beneath the wellpoint pump level. Since the dirt layer experienced has low penetrability henceforth wellpoint strategy will be favored. Since the geologic conditions experienced likewise allow close separating of gadgets.
b) Deep well strategy for dewatering can be utilized as a part of this case. This is on account of the pump station is to be established on basalt shake which is 65ft profound and for the profound well technique the profundity of the wells could reach upto 30m.
c) Open sump directing technique for dewatering can be utilized as a part of this case. This is on account of the pipeline must be laid at 28ft subterranean surface in sandy soils.
The troubles that might be experienced and the means that could be taken to counter with the challenges are:
1) Creating profound well upto the level of basaltic shake might be troublesome.
The boring piece ought to be tipped with hard cutting material (Tungsten Carbide or mechanical precious stone) connected to the penetrate bar through a sledge system in the middle. Compacted air is utilized both for pivoting the bore bar and in addition creating a consistent pounding activity on the joined bore.
2) Installation of wellpoint framework could be minimal costly.
Supporting conditions should be enhanced to avert disappointment of the dewatering framework.
3) For profound well frameworks the measure of intensity required to work the pump couldn't be legitimately accessible in specific zones where access to powergrid isn't appropriate.
The alernative backup choice for power ought to be masterminded heretofore for the areas of profound well dewatering.
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