تاثير نسبت‌هاي مختلف na/k محلول خاك بر مقاومت كششي و تردي خاكدانه‌ها

The Effect of Different Na/K Ratios in Soil Solution on Aggregate Tensile Strength and Friability

اين پژوهش با هدف بررسي اثر نسبت هاي مختلف na/k محلول خاكبا استفاده از شاخص نسبت كاتيوني پايداري ساختماني خاك (cross) روي رس قابل پراكنش، مقاومت كششي خاكدانه و تردي خاك انجام شد. براي اعمال غلظت هاي مختلف پتاسيم به خاك، شش تيمار با شوري يكسان3 دسي زيمنس بر متر به ترتيب از تيمار 1 تا 6 شامل پتاسيم با غلظت ﺻﻔﺮ ﺗﺎ 27/2 ﻣﯿﻠﯽاﮐﯽواﻻن ﺑﺮ ﻟﯿﺘﺮ و ﺷﺶ ﺗﯿﻤﺎر دﯾﮕﺮ ﻧﯿﺰ ﺑﺎ ﺷﻮري ﯾﮑﺴﺎن6 دﺳﯽزﯾﻤﻨﺲ ﺑﺮ ﻣﺘﺮ ﺷﺎﻣﻞ ﭘﺘﺎﺳﯿﻢ ﺑﺎ ﻏﻠﻈﺖ ﺻﻔﺮ ﺗﺎ 54/4 ﻣﯿﻠﯽاﮐﯽواﻻن ﺑﺮ ﻟﯿﺘﺮ ﺗﻬﯿﻪ و ﺑﻪ ﺧﺎك اﺿﺎﻓﻪ ﺷﺪﻧﺪ. ﺗﺮدي ﺧﺎك ﺑﻪدو روش ﺿﺮﯾﺐ ﺗﻐﯿﯿﺮات )F1( و رﺗﺒﻪﺑﻨﺪي )F2( ﻣﺤﺎﺳﺒﻪ و ﻣﻘﺎﯾﺴﻪ ﮔﺮدﯾﺪ. ﻧﺘﺎﯾﺞ ﻧﺸﺎن داد ﮐﻪ ﺑﺎ اﻓﺰاﯾﺶ ﻏﻠﻈﺖ ﭘﺘﺎﺳﯿﻢ ﻧﺴﺒﺖ ﺑﻪ ﺳﺪﯾﻢ در ﺗﯿﻤﺎرﻫﺎ اﻓﺰاﯾﺶ در ﭘﺮاﮐﻨﺶ رسﻫﺎ رخ داد. ﻧﺘﺎﯾﺞ آزﻣﻮن ﻣﻘﺎوﻣﺖ ﮐﺸﺸﯽ ﺧﺎﮐﺪاﻧﻪﻫﺎ ﻧﺸﺎن داد ﮐﻪ در ﺗﯿﻤﺎرﻫﺎي ﺑﺎ ﺷﻮري 3، ﺑﺎ اﻓﺰاﯾﺶ ﻏﻠﻈﺖ ﭘﺘﺎﺳﯿﻢ، ﻣﻘﺎوﻣﺖ ﮐﺎﻫﺶ ﯾﺎﻓﺘﻪ اﻣﺎ ﺑﺎاﻓﺰاﯾﺶ SAR، ﻣﻘﺪار ﻣﻘﺎوﻣﺖ اﻓﺰاﯾﺶ ﯾﺎﻓﺖ. ﺑﯿﺸﺘﺮﯾﻦ ﻣﻘﺪار آن )142 ﮐﯿﻠﻮﭘﺎﺳﮑﺎل( ﻣﺮﺑﻮط ﺑﻪ ﺗﯿﻤﺎر 1 ﺑﺎ 25/7 =CROSS و 22/9 =SAR و ﮐﻤﺘﺮﯾﻦ ﻣﻘﺪار )87 ﮐﯿﻠﻮﭘﺎﺳﮑﺎل( در ﺗﯿﻤﺎر 5 ﺑﺎ 14/8 = CROSS و 0/99 =SAR ﺑﻮد. اﻣﺎ در ﺗﯿﻤﺎرﻫﺎي ﺑﺎ ﺷﻮري 6، ﭼﻨﯿﻦ روﻧﺪي ﻣﺸﺎﻫﺪه ﻧﺸﺪ و ﻣﻘﺎدﯾﺮ ﻣﻘﺎوﻣﺖ ﮐﺸﺸﯽ ﺗﻘﺮﯾﺒﺎً در ﻫﻤﻪ ﺗﯿﻤﺎرﻫﺎ ﻣﺸﺎﺑﻪ ﺑﻮدﻧﺪ. ﻧﺘﺎﯾﺞ ﻧﺸﺎن داد در ﺗﯿﻤﺎرﻫﺎي ﺑﺎ ﺷﻮري 3، ﺗﺮدي ﺧﺎك ﺑﺎ اﻓﺰاﯾﺶ رس ﻗﺎﺑﻞ ﭘﺮاﮐﻨﺶ، اﻓﺰاﯾﺶ ﯾﺎﻓﺖ )F1 و F2(. ﻣﻘﺎﯾﺴﻪ ﻧﺘﺎﯾﺞ ﻣﻘﺎدﯾﺮ ﻣﻘﺎوﻣﺖ ﮐﺸﺸﯽ و ﺗﺮدي ﺧﺎك ﻣﺸﺨﺺ ﻧﻤﻮد ﮐﻪ ، F1 ﭘﺎراﻣﺘﺮ ﻣﻨﺎﺳﺒﯽ ﺑﺮاي ﺑﯿﺎن ﺗﺮدي ﺧﺎك ﻧﺒﻮده و در ﻣﻘﺎﺑﻞ، F2 ﺗﻮاﻧﺴﺖ ﻫﻤﺎﻫﻨﮕﯽ ﺑﯿﻦ ﻧﺘﺎﯾﺞ ﻣﻘﺎوﻣﺖ و ﺗﺮدي )در ﺗﯿﻤﺎرﻫﺎي ﺑﺎ ﺷﻮري 3( را ﺑﻪﺧﻮﺑﯽ ﻧﺸﺎن دﻫﺪ. در ﺗﯿﻤﺎرﻫﺎي ﺑﺎ ﺷﻮري 6 اﺣﺘﻤﺎﻻً ﺑﻪ دﻟﯿﻞ ﻏﻠﯿﻆﺗﺮ ﺷﺪن ﻣﺤﻠﻮل ﺧﺎك، اﺛﺮ رس ﭘﺮاﮐﻨﺶ ﯾﺎﻓﺘﻪ ﺑﺮ ﻣﻘﺎدﯾﺮ ﻣﻘﺎوﻣﺖ ﮐﺸﺸﯽ و ﺗﺮدي ﺑﻪوﺿﻮح ﻧﻤﺎﯾﺎن ﻧﺸﺪ

This research was carried out to study the effect of different ratio of Na/K in soil solution on dispersible clay, aggregate tensile strength and soil friability using the cation ratio of soil structural stability (CROSS) index. In order to apply different potassium concentrations, 6 treatments with the same EC (3 dS m-1) including 0 to 27.2 meqL-1 K+ and another six treatments with EC=6 dS m-1 including 0 to 54.4 meqL-1 K+ were prepared and added to soil. Soil friability was calculated and compared through two methods i.e. the coefficient of variation (F1) and ranking order (F2). The results showed that increasing the K+ concentration in treatments relative to Na+ could increase the water dispersible clay. Also, the results of aggregates tensile strength test showed that in treatments with EC=3 dS m-1 by increasing the K+ value, the soil strength decreased but with increasing the SAR value, soil strength increased. Maximum amount of tensile strength (142 kPa) was observed in treatment 1 with CROSS = 25.7 and SAR=22.9 and the minimum amount (87 kPa) was in treatment 5 with CROSS=14.8 and SAR=0.99. This trend was not observed in treatments with EC=6 dS m-1 and the aggregate tensile strengths were almost similar in all treatments. The results demonstrated that soil friability (F1 & F2) increased with increasing the dispersible clay at EC=3. Comparison of the results of tensile strength and friability revealed that F1 was inappropriate parameter for expression of soil friability while F2 showed the good agreement with the strength and friability amounts (in treatments with EC=3). In treatments with EC=6, the effect of dispersible clay on tensile strength and friability was not observed, probably due to the higher concentration of the soil solution.