# Sandy Loam Soil Shear Strength Parameters and Its Colour
## 3 Measuring the Shear Cohesion and the Internal Friction Angle of Sandy Loam Soil  
The measurements were carried out at the Hungarian University of Agricultural and Life Sciences using soil from the university area. The soil used is sandy loam soil (shown in Figure 1), composed of 90.50% sand (0.05-2 mm), 3.20% silt (0.002-0.05 mm), and 6.30% clay (<0.002 mm). The method used for measuring the shear strength results at different moisture contents is the direct shear test machine that is available in the laboratory (ELE 26-2112/01). The direct shear test machine is shown in Figure 2.  
The soil samples were prepared in boxes and were moistured by adding water and then stirred till they became uniform. The moisture of each of the samples was measured using the moisture analyser (HE53 230 V; shown in Figure 3) that works based on the drying principle. An amount of soil is placed in it (on a tray) and dried by the analyser's heating plates. For calculating the moisture percentage, the remaining mass is deducted from the initial wet mass and then divided by the initial wet mass (wet base moisture content calculation). The samples were placed and covered in plastic boxes to avoid the decrease in the moisture content. Starting with the first sample, the soil was placed in the direct shear box of the machine--approximately the soil amount was placed symmetrically in the two frames (upper and lower frame of the shearing box)--and then the upper frame was covered by the plate (cover plate). The screw pressing on the plate (used for applying the consolidation load by masses) was tightened but not with a high torque (smooth tight just for anchoring the plate and levelling the soil surface). A 30 kg consolidation load was applied on the plate to compact the soil, since the soil used in the test is disturbed (taken from field), while the soil in the field is undisturbed. The soil was compacted by the 30 kg mass for 5 min as a chosen compaction period (compacting the soil for a longer period influences the shear strength result). After compacting the soil for 5 min, the 30 kg mass was removed and a 10 kg mass was applied as measuring consolidation stress (applied when shearing the soil); then, the machine was operated. The shearing speed was set to be 9 mm/min (maximum speed in the machine). New soil amounts from the same sample (same moisture) were tested with the same compaction load applied for five minutes (except for the 15.03% moisture) but having 20, 30, 50, and 70 kg as measuring consolidation masses (normal stress if the load is divided by the area of the shear box). Figure 1: Sandy loam soil. The 15.03% moisture content soil sample was not compacted for 5 min to avoid water drainage, because the moisture is high. The tested soil saturation level (approximately liquid limit level) was around 27%, and that was obtained by adding water to dry soil (at ambient conditions) prepared in a box till it stopped the absorption of water and a small water layer appeared on the surface. The surface water (additional small amount)  
Figure 3: Moisture analyser HE53 230 V.  
Figure 2: Direct shear test machine (ELE 26-2112/01). was removed carefully and the moisture was measured by the analyser. For checking the saturation level in another way, the hygroscopic effect of the soil was checked by filling dry soil in a tube and then inverting on a box; water was added into the box (small amount) till the soil (in the tube) stopped absorbing water and the moisture was measured by the anaylser, showing a value close to 27%. Unsaturated soil is of a shape that is more complicated when compared to saturated soil. This complex structure has an impact on the strength, deformation, and the seepage of the soil [16; 17]. The obtained shear strength result at each of the applied loads was recorded (maximum stress value in the stress-displacement diagram). The same test was repeated on the same soil type with different moisture contents.