空军汉口新机场试验路段石灰改性膨胀土试验研究

EXPERIMENTAL RESEARCH ON IMPROVED EXPANSIVE SOIL WITH LIME IN TEST SECTION OF THE NEW HANKOU AIRFIELD

空军汉口新机场试验路段石灰改性膨胀土(简称灰土)试验研究包括室内和现场试验研究。室内试验研究包括:天然膨胀土与击实膨胀土的基本物理特性和胀缩特性试验、灰土击实试验以及膨胀土掺石灰改性试验等。室内试验结果表明:击实膨胀土比天然膨胀土的膨胀潜势更大;在道面下一定范围内,填料不能采用膨胀土,而必须用灰土;石灰能有效地对场区内的膨胀土进行改性,最优石灰掺合比为6%～8%;不同灰土层的最大干密度与最佳含水量差异较大,现场施工填料不能混填。现场试验包括:碾压试验、压实灰土基本物理特性和胀缩特性试验、浸水载荷试验、测定路基回弹模量和回弹弯沉试验等。现场试验结果表明:在有效控制灰土的石灰掺量和含水量情况下,采用激振力为450 kN的碾压机对松铺厚度为50和30 cm的灰土进行碾压,分别需碾压8和6遍,路基压路度才能达到95%,表面沉降才趋于稳定;现场压实灰土的膨胀潜势很低,仍有明显失水收缩特性,在施工时应注意采取保水措施;压实灰土具有较高承载能力、强度特性和吸水稳定性。

Experimental researches are comprised of inside experiments and field tests on improved expansive soil with lime（IESL） in test section of the new Hankou airfield. Inside experiments consist of general physical properties, impaction and swelling characteristics of natural, impacted and improved expansive soils. Some results are drawn, such as the impacted expansive soils are more expansible than natural expansive soils, not expansive soils but IESLs are filled in superstratum of roadbed： it is effective that expansive soils are improved with lime, optimal lime contents are 6% to 8%, different filling cannot be mixed because there are much difference in maximal dry density and optimal water content of IESL. Field tests include roller compacting of IESL, general physical properties and swelling characteristics of compacting IESL, load test with pouring water, resilient module and deflection of roadbed. Some conclusions are drawn, for example, if compactness of IESL can arrive at 95 percent or settlement of IESL can arrive gradually at stabilization on condition that lime and water content are controlled effectively; roller compacting number must be over eight times to loose filling thickness of 50 cm, and six times to 30 cm, when exciting force of roller is 450 kN; though swelling capacity of in-site impacted IESLs is very low, impacted IESLs still have shrinkage characteristic because of water reducing： and measures which prevent water from falling would be taken： the impacted IESLs have larger bearing capacity, intensity and water stability.