Sand, uniform, round grains:  27 - 34 (Friction Angle (degrees))

Sand, well graded, angular: 33 - 45

Sandy gravels: 35 - 50

Silty sand: 27 - 34

Inorganic silt: 27 - 35

each soil sample has different parameters of friction angle and cohesion parameters.

In addition to the items mentioned by Dr. Ahmad, this table may be useful to you.

Hi Behzad,

Thanks for question.

I have N-value, liquid-limid, plastic-kimid, type of soil, ρt and ρsat.

Please refer to Eurocode 7 regarding the applicability of SPT blow counts for estimation of strength parameters of fine and coarse grained soils.

Index properties that you have may serve you mainly for estimation purposes.

Bear in mind that c and phi are stress dependent. For this you can search the papers by Maksimovic, for both the strength of coarse and fine grained soils in terms of peak and residual strength.

Read Skempton "Consolidation of clays by Gravitational Compaction", Burland on Intrinsic Soil Properties. Schofield and Wroth text book on Critical State Soil Mechanics is now available FoC on line

Hi Ayaka Oya

Your question is a difficult one to answer. Except for loose sand, silts and normally consolidated cays under mean stress less than 500 KN/sq.m a soil does not have unique c' and φ'.  For the aforementioned soils  c' = 0 and and φ'= 28 to 30 degrees. The  c' and φ' for overconsolidated sands and clays  the c' and φ' are variable. For an OCC the  c' and φ' will depend on the preconsolidation stress  Generally the higher the  c' the lower the φ'.  When sand or rock is tested under large large stress range then the actual failure envelope is curved. When this curved envelope is fitted with a straight line a fictitious cohesion appears that  makes the soil stronger than it si at low stresses. Every granular soil has zero cohesion at zero normal stress. For fitting of the power-type nonlinear failure envelopes to triaxial test data you can refer to my paper     

Source

Nonlinear Power-Type Failure Laws for Geomaterials: Synthesis from Triaxial Data, Properties, and Applications

https://www.researchgate.net/publication/255962696_Nonlinear_Power-Type_Failure_Laws_for_Geomaterials_Synthesis_from_Triaxial_Data_Properties_and_Applications?_iepl%5BviewId%5D=A6w7xfWUpEC61Odsgb4SHFob&_iepl%5BprofilePublicationItemVariant%5D=default&_iepl%5Bcontexts%5D%5B0%5D=prfpi&_iepl%5BtargetEntityId%5D=PB%3A255962696&_iepl%5BinteractionType%5D=publicationTitle

Article

Article Nonlinear Power-Type Failure Laws for Geomaterials: Synthesi...

c' and φ' vary in terms of soil types. As both of this parameters denotes the effective condition but there is a simple method to estimate this.

The strength of soil can be determined by Mohr coulumb equation. The formula is Ԏ = C + σ tanФ. For clay, internal friction will be zero as because it depends on grain size. So in that case, the strength would be equal to the cohesion i.e. Ԏ = C. On the other side, for sand i.e. non-cohesive soil, Ԏ = σ tanФ because c only depends on electrostatic attraction that is present only in cohesive soils.

Direct shear test is the easiest procedure to build up the relation between stress and strength i.e. cohesion and friction values. Following references are attached that will be helpful for your work.

http://osp.mans.edu.eg/geotechnical/Ch1C.htm

Dear Ayaka Oya,

I recommend you check this interesting and very complete manual.

Best regards,

Cristian 

Dear Ayaka

In general, the soils at the site consist of sandy clay, sandy silt, and silty sand. Values of φ′ and c′ determined from these tests are as follows: .... Effective stress friction angles were calculated using these values of φo and ∆φ.

you can find useful information in this article:

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&cad=rja&uact=8&ved=0ahUKEwjVhtX9s7rVAhVPbFAKHZStB_UQFggyMAI&url=https%3A%2F%2Ftheses.lib.vt.edu%2Ftheses%2Favailable%2Fetd-093099-180817%2Funrestricted%2FChapter5.PDF&usg=AFQjCNGnKM1BGj1A0hhGx3ZkP3lHAufdkA

Good luck

Milad

The best practice is to use the results of laboratory tests. It might seem a banal answer, but it is only through lab testing that you get the most accurate and less uncertain answer. In case you use empirical correlations, you must be aware of the uncertainties they carry, of the uncertainties of your own input information in the empirical correlation (e.g. sand: which mineralogy? which grain size? which grain shape? which normal stress? temperature? shear rate? etc.) and, finally, you must be aware that you have to use an appropriately increased safety factor when you present your calculation outputs.

Dear Cristian Soriano,

Thank you for the useful link!

Best regards,

Boriana

Dear Neil Bar,

Thank you for the useful handbook!

Best regards,

Boriana

"

Dear Ayaka,

Geotechnics is not an exact science (definitely)