Question

Cluil Enginuring Sie Invatgation Dynamie Con Penetro muter Erample bcP teat (byname Co Penetromaur) Ih resuts from Im on a secthon a 1 elown to a cle ptl af aloout he neo labo ratory budel ing parking for shown below: Penetrahon Alo 1Do oo 300 400500 600 00 00q001000 Blows 3 20 22 3 of IG Penetraton-i Cmm) a Plot 4he Cumu latwe number af. blows Penetraton Cuve b) betermin the numbur op layers anal thielene s3 of layer's +he var ous the various layers +e CBR of beter min sub sucpace conelrton su93eateal J bescribe the by e results Avel Memory Log (ceR)

pls provide detail explanations on how to plot the cumulative number of blows/penetration curve.
pls provide detail explanations on how to determine the CBR of the various layers.

Answer 1

No. of Blows	Cumulative No. of Blows (1)	Cumulative Penetration (mm) (2)	DCP Penetration/blow (mm)(3)	CBR (%) (4)	Average DCP Penetration/blow (mm) (5)	Average CBR Per Layer (%)(6)	Layer Thickness (mm) ( c)(7)	Soil Type (d) (8)
0	0	0	0		6.388888889	42.52706595	300mm (Layer 1)	Sand
16	16	100	6.25	43.52660775
16	32	200	6.25	43.52660775
15	47	300	6.666666667	40.65635696
3	50	400	33.33333333	7.418518196	41.66666667	5.859806599	Layer 2 (400mm)	Clay
2	52	500	50	4.832687417
3	55	600	33.33333333	7.418518196
2	57	700	50	4.832687417
20	77	800	5	55.104708	6.388888889	56.9264908	Layer 3 (300mm)	Gravelly Sand
20	97	900	5	55.104708
22	119	1000	4.545454545	60.94537781

Penetration Curve Blows 20 40 60 80 100 120 140 0,0 16, 100 Layer 1 200 32, 200 -47,300 400 50, 400 Layer 2 52,500 600 55, 600 57,700 800 71,800 Layer 3 97,900 1000 119, 1000 1200 DCP Penetration (mm)

Detailed Solutions

1. Since the number of blows per 100 mm penetration is given, cumulatively add the total number of blows for each successive 100 mm penetration, (Refer Column number (1)).

For calculating the DCP Penetration per blow ( Refer column No. (3)), divide the penetration required for 100mm by corresponding number of blows.

For eg. , DCP penetration per blow for 400mm penetration = (400-300)/ 3 = 33.33mm. Now plot the graph as shown in the above chart.

2. For finding the number of layers, identify the slope change of the penetration curve. Every change in slope represents a change in layer type.(Refer Chart)

Thickness of layer is the cumulative penetration (Refer Column (2)) at the bottom of the layer subtracted by the cumulative penetration at the top of the layer.

Calculate the average DCP penetration per blow for each layer (Refer column (5))

3. From the following given equation,

                log₁₀CBR = 2.48 – 1.057 log₁₀(DCP Penetration / blow)

            The CBR value of each layer can be computed as:

            Layer Average CBR = 10^{2.48 – 1.057 log}₁₀^{(Average DCP Penetration per blow (mm) for corresponding layer)}

4. The reference book: User Guide to the Dynamic Cone Penetrometer by Office of Minnesota Road Research has been used to correlate the CBR and DCP penetration values with soil type.
   Soil Type CBR Range DPI Range Clay (CL) Sand (S-W) Gravel (G-W) 53-100 5-2.7 2-17 127-15 17-45 15-6 Loose sands and gravel will have higher DPI values.