Question

standard Proctor compaction test conducted on a clay sample gave the following results Weight of wet soil in the mould (g) | 1765 1860 1924 1947 1928 1906 Moisture content (%) 13.1 14.9 16.8 18.9 21.1 23.2 If the volume of the sample mould is 944 cm3, Determine the maximum dry density and optimum moisture content of the clay Draw on the same graph 5% voids ratio line. Sketch the dry density-moisture content curve you expect from modified Proctor compaction test on the sample on the same graph A road subbase is to be formed using this clay at 95% standard Proctor compaction, As the site engineer how you instruct the contractor to carry out this operation, and what equipment to be used How do you monitor the compaction process?

Answer 1

From the given data we get following results.

From the given data we get following results. We have assumed G (specific gravity = 2.7). For calculation of 5 % void line we have used formula gamma d = (1 - n) * G * gamma w) ? (1 + w * G) G has been taken as 2.7 and n as 5 %. From the graph, we obtain maximum dry density = 2.0625 g/cc Also Optimum Moisture Content = 18.9 % As we have to go for 95% compaction, so we have to maintain density as 0.95*2.0625 = 1.96 g/cc We will calculate the soil required for a layer of particular thickness (say 15 cm) and add water content equal to optimum moisture content. Then it will be compacted by rammers or rollers. similarly, more layers will be made till be reach to the desired thickness of subbase according to design considerations. For monitoring of compaction process, we have various options.

We have assumed G (specific gravity = 2.7).

For calculation of 5 % void line we have used formula $\gamma d = (1-n)*G*\gamma w)/(1+w*G)$

G has been taken as 2.7 and n as 5 %.

From the graph, we obtain maximum dry density = 2.0625 g/cc

Also Optimum Moisture Content = 18.9 %

As we have to go for 95% compaction, so we have to maintain density as 0.95*2.0625 = 1.96 g/cc

We will calculate the soil required for a layer of particular thickness (say 15 cm) and add water content equal to optimum moisture content. Then it will be compacted by rammers or rollers. similarly, more layers will be made till be reach to the desired thickness of subbase according to design considerations.

For monitoring of compaction process, we have various options. We may take samples at specified locations after specific time and check its density and moisture content. There are also some highly sophisticated monitoring equipments available which work on real-time basis.