6585844955

150

USSR

be into the soli* However₉ to get the re-liable data on the relation between re— sults of sounding and properties of soils, the &xisymmatrioal problem of the theoiy of elasticity and the theory of plasticity should be solyed* This problem has not been solved as yet* But in oase it were₉ the great dif ficulties would be faced beoause of the changes of proper-ties of soils under yariable stress eon— dLitions#

That is why at present the relation-ahipa between sonie properties of soils and the results of sounding are found ex-peri men taiły by the comparisan of the results ot sounding with the re sults of the traditional methods that are taken as a standard*

A. SAND SOILS

I. DENSITY

For sand soils the density is one of the main properties defining their bea-ring capacity* It is well known that there is a certain relationship between the denadty of sand and the penetration resistance* It is also known thatthe penetration resistance of soils of equal density can be rather different depending on the coefficient of heterogeneity,the roughness of grains, the presence of smali quantity of silty particles and many other factors* Nevertheless, sounding is widely and rather reliably used for determining the density of natural sands*

In Table I the data on the penetration resistance of medium dense sands are summarised*

Table I

The characteristic of sand	Static sounding q kg/enr	Dynamie £ Pd kg/cm*	jounding ‘ ^N10
Coarse and medium 50-150		35-125	7-20
Fine	40-120	20-110	4-15
Silty	30-100	20-85
Si1ty9saturated	20-70		—

2* THE ANGLE OF INTERNAL FRIOTION

Many attempts to relate the results of the static sounding and the angle of intemal friction of sand were unsucces-sful because of ignoring the fact that at pressures less than about 1 kg/cm² (i*e* for the depth of penetration app-rozioately less than 6 m), the angle of intemal friction is not a oonstant and it inereases by 5 to 7° when the pressure decreases from 1 to 0.1-0#2 kg/cm²*

Taking into account this phenomanon, the theoretioal solution of Berezantzey and the experimental data Jarochenko (1964) gave the correlation between the point resistance and the angle of inter-nal friction of sands taking into ac-oount the depth ot penetration# The gra-ph drawn according to this data is gi-ven in Fig*4₉ it shows the dependence of the angle of internal friction on oyerburden*

Accounting to this₉ the data for the determination of the angle of intemal friction by the results of the static sounding are given in Table 2#

Table 2.

Characteristic of sand q kg/cm² 10    20    40    70    120 200 300

and oyerburden

Coarse ₉ medium and fine

Oyerburden 0*5 kg/cm!    28    30    32    3^    36    38    40

"    "    1 kg/cm^    26    20    30    32    J4    36    38

By the results of dynamie sounding the angle of internal friction is determined according to Table 3*

Table 3#

P4 kg/om^	Coarse and medium sand 6° E kg/cm^2	Fine	1 sand E kg/cm^2	Silty sand «S° E kg/cm^2
20	30 200-160	28	130	26	80
35	33 260-210	30	190	28	130
70	36 390-340	33	290	30	220
110	38 490-440	35	350	32	280
140	40 550-500	37	400	34	320
175	41 600-550	38	450	35	350