Перевод методики испытаний (на англ.яз)

Study of soils applying dynamic sounding by soil sampler (SPT)

The meaning of the method of “Standard penetration test” is in special construction split soil sampler driving below borehole bottom. The sampler used for soil samples collecting serves at the same time as tip and together with rods makes a driving sound.

Sampler is a hollow glass cut into two halves length-wise for more convenient sample extraction. By means of adapter (serving

for connecting sampler with rods) and cutting shoe divided parts are connected into the whole making a driven sampler with outer diameter 51mm.

The sampler is put into a borehole bottom on rods with diameter 42mm. Such sound is driven into soil by blows of free falling hammer from height of 80,0сm weighing 60,0kg.

Hence energy of one blow of hammer in this method of testing is 480,0 kgf/сm, which practically corresponds with the parameters of the rig UPB-15 m.

Prior to releasing samples with rods, borehole bottomis cleared from slam and checked for its location with regards to casing pipes lower part; borehole bottom should be located not higher than casing pipes.

After this the sampler is driven to the depth of 20 cm by light blows, considering that soil below could not be disturbed in the process of boreholes drilling. And further directly proceed with the testing by sounding which is driving of sampler into following 30 cm of depth and soil sampling.

When performing SPT geotechnicians of GEL Consultants defined value of failure being at 50 blows.

Soil samples with undisturbed structure preserving natural moisture were collected with the following waxing.

Data of testing by sampler (to the depth of 5,0m every meter and below 5,0m to the depth of   every 15,0m 1,5m) is fixed in drilling journal and its results are presented in the form of graph where geologic description of boreholes is registered with the results of testing.

The study results of soils by dynamic sounding bysampler (SPT) are given in Appendix 11/1-11/8).

Testing of soils by impeller for shear

Shear meter – impeller (further - impeller) is purposed for testing weak soils by method of rotary cut as per GOST 20276-99 (Soils. Methods of field defining of characteristics of strength and deformability). Impeller allows to define resistance to cut t max, MPa.

Testing by rotary cut is done by applying horizontal tangent load and displacement of soil on cylinder surface formed by rotation of impeller. Conditions for conducting rotary cut method – with pressing shear meter from drilling borehole bottom of specially drilled borehole with depth to 6m.   Depending on type and state of soil, impellers of type I are used for testing clayey

soils with 0,5

readings are fixed till reaching maximum reading N max, mm,  corresponding with the maximum value oftorque M max, kN*сm (see table  11).

 Then rotation is kept till conditional stabilization of torque values reached for 2-3 full turns of the rod, settled reading of N set is fixed, corresponding with the settled value of torque  Mс, кN*сm.  When testing soil in boreholes friction of rods of impeller on soil can be not taken into account and torque for overcoming this friction can be taken as equal to zero.

As per data of testing torques we calculated Mmax, Mc b Mo (kN*сm) as follows:Mmах  = (ni xNmax)/10, Mmах  = (ni xNуст)/10, Mmах  = (ni xNо)/10. where: ni – constant characteristic of measuring device kN, defined asper the results of calibration (see Report of Calibration. Appendix 1); Nmах, Nуст – maximum and settled readings of measuring device (indicator Ich-10), (mm); Nо – readings of measuring device characterizing friction of rods on soil with switched off impeller, del (mm). Resistance of soil to shear t max, MPa is defined by formula: t max = 10*(Mmах – Mо)/В,  (MPa) where: Mmах and Mо are defined by calibration graph of impeller – shear measureror by formula at the calibration graph (кN* сm); В – constant of impeller, сm3, is accepted depending on impeller type. В = (3,14хd2)/ 2 x (h+d/3);  where: d – diameter and h – impeller height, сm.

Dataof testing were fixed in drilling record and its results were shown in the form of passport of testing soils by method of rotary cut, where   geologic description of boreholes isregistered with the results of testing and changing of resistance to shear (see table 11).  Processing of field data was done applying special software.