6585844987

Japan

197

3.2    Testing procedurę

For weak soils, weights are placed on the rod successively in the increasing order of 5,

15, 25, 50, 75 and 100 kg; and the rod penetra-tion in each loading stage is measured and re-corded as W_sv . After 100 kg loading on the rod, a handle is attached to the rod and the num-berof half turns reąuired for the rod to penetrate 25 cm is counted. Four times as great as this number gives the number of half turns needed for 1 m penetration, which is registered as N_Sfr ?)

When such count for a 5 cm penetration ex-ceeds 50, the test is terminated, supposing that the hard stratum has been reached.

3.3    Appraisal and use of test data

Swedish Sounding is applied for collecting generał data on the formation of soil layers in weak soil zones as well as the stiffness and com-pactness of soils. By virtue of its simplicity, this method is often used in preliminary subsur-face investigations.

As for the test data of W_sw and N_sv , the relations in Figures 12 and 13 have been estab-lished from studies on correiations between these data and the unconfined compression strength Q or the tf-value obtained by the Standard Penetration Test9)» 10)

1.4

1.2

1.0

as

as

0.4

a2

„ Relation batwean								A y
		a"* Qc af «li«f rSknlinn							7
			1					; *7 /
			\				y
					%	s
					y
		W
0 25 50 75 100 3 5						5 75 100 r.			>5 150 1

H'.. (kg)

KJ    tiirnd /ml

?.<kt/c«^,)=ao04SW',.(kg>+a007$/V.. (Ha W iurn./m)

Fig. - 12 Relation between W_sw, N_sv of

Swedish Sounding and Unconfined Compression Strength <]_u in Japan ( by M. Inada )

Fig. - 13 Relation between N_sw of Swedish

Sounding and tf-value of S.P.T. in Japan (by M. Inada, Y. Ueda,

G.Miki, T. Tatemoto)*^

On account of the drawback that no soil sample is collected and the skin friction of the rod gives an increasing influence on the test data as the depth increases Swedishing Sounding is seldom applied for design purposes. As men-tioned above, however, it is often used for preliminary studies.

4. STATIC DEEP SOUNDINGS 4.1 Penetrometers used in Japan

In Japan, static penetrometers for deep sounding as listed in Table 3 are in use. The proposed standard ( 1968) for the Dutch Double-tube Type Cone Penetration Test by the Japanese Society of Soil Mechanics and Foundation Engi-neering is based mainly on the device manufac-tured by Goudshe Machinefabriek in Delft?^

The proposed standard specifies two types with capacities of 10 t and 2 t each having a mantle-cone with a tip angle of 60° and a base area of 10 cm% but the use of a single rod type is allowed, as long as it can indicate the net penetration resistance of the cone. Therefore, all the items except the top in Table 3 have their own cone, rod, and measuring method.

The static penetration resistance ( 9_C ) which shouid be common to all the penetrometers is calculated by the following formula, in which the mantle-cone penetration resistance includes the wcight of the inner rod:

„ Mantle-cone penetration resistance _,__

--Śase area of the cone-^(kg/cm >

4.2 Testing procedurę

The proposed standard specifies an inter-mittent penetration method in which the value of q- is calculated from the penetration resistance of the cone penetrating 5cm from the measuring depth. The depth interval is 25 cm and the ratę of penetration 1 cm/sec?' In the case of a single rod type penetrometer the penetration is continu-ous.

The instrument to measure penetration resistance consists of pressure gauges proving rings, or load cells for the double-tube type; and freąuently of wire strain gauges for the single rod type. In the latter case, the cable is led to the ground surface for automatic recording of penetration resistance.

4.3 Appraisal and use of measured data

The reiationships between the values of q_e and the soil strength are indicated in Table 3. These relations largely depend on the shape of cones, notably on the presence of a mantle or sleeve, their lengths and the characteristics of soil. Commonly such relations indicate <ł_e =

10 - 20 c for clayey soils and q_c « 4 - 6 N for sandy soils.

According to the results of investigations carried out by the present committee in 1970 on the situation of sounding practice}D 34% of agencies (clients) and 35% of investigators