高温养护下水泥改良风积沙抗压强度试验研究

研究目的:新疆和田至若羌铁路经过塔克拉玛干沙漠南缘,地表以风积沙为主,水泥改良风积沙是沙漠地区铁路路基基床填筑的关键技术。塔克拉玛干沙漠夏季地表温度最高可达70℃,水泥改良风积沙的力学性能和变形特性易受高温的影响,因此本文结合新疆塔克拉玛干沙漠的气候条件,开展水泥改良风积沙无侧限抗压强度试验,研究70℃高温养护条件下水泥掺量和压实系数对水泥改良风积沙的应力应变特征、无侧限抗压强度、峰值应变和刚度的影响。研究结论:(1)水泥改良风积沙的应力应变曲线近似正态分布,具有右偏态的特性;(2)高温养护条件下,压实系数为0.95时,水泥掺量为4%、5%、6%对应的水泥改良风积沙无侧限抗压强度分别为0.38 MPa、0.52 MPa和0.78 MPa,峰值应变分别为2.2%、2.4%和2.6%,刚度分别为10.4 MPa、16.2 MPa和22.8 MPa;(3)与标准养护条件相比,高温养护条件下水泥掺量为5%、压实系数为0.95的水泥改良风积沙的无侧限抗压强度和峰值应变分别降低了5.5%、22.7%,刚度增大了5.9%;(4)新疆和田至若羌铁路夏季施工时,考虑70℃高温养护条件,掺量5%的水泥改良风积沙能满足基床底层填料设计要求,避开高温施工环境条件,掺量4%的水泥改良风积沙能满足基床底层填料设计要求;(5)本研究成果可为风积沙铁路路基基床的设计、施工提供参考。

Experimental Research on the Unconfined Compressive Strength of Cement Improved Aeolian Sand under High Temperature Curing Condition

Research purposes: The Hetian-Ruoqiang Railway in Xinjiang passes through the southern edge of the Taklimakan Desert,and the surface is dominated by aeolian sand. The cement-improved aeolian sand is the key technology for filling the railway subgrade bed in the desert area. The land surface maximum temperature in the Taklimakan Desert can reach 70 ℃ in summer,and the mechanical properties and deformation characteristics of cement-improved aeolian sand are easily affected by high temperature. Therefore,in this paper,based on the climatic conditions of the Taklimakan Desert in Xinjiang,series of unconfined compressive strength tests of cement-improved aeolian sand were carried out to study the effects of cement content and compaction coefficient on the stress-strain characteristics,unconfined compressive strength,peak strain and stiffness under the 70 ℃ high temperature curing condition.Research conclusions:( 1) The stress-strain curve of cement-improved aeolian sand is approximately normal distribution,with right-skewed characteristics.( 2) Under the 70 ℃ high temperature curing condition,when the compaction coefficient is 0. 95,the unconfined compressive strength of cement-improved aeolian sand corresponding to the cement content of 4%,5% and 6% is 0. 38 MPa,0. 52 MPa and 0. 78 MPa,the peak strain is 2. 2%,2. 4% and2. 6%,and the stiffness is 10. 4 MPa,16. 2 MPa and 22. 8 MPa,respectively.( 3) Compared with the standard curing condition,the unconfined compressive strength and peak strain of the cement-improved aeolian sand with a cement content of 5% and a compaction coefficient of 0. 95 under the 70 ℃ high temperature curing condition are reduced by5. 5% and 22. 7%,respectively,while the stiffness is increased by 5. 9%.( 4) During the construction of the Hetian-Ruoqiang Railway in summer,considering the 70 ℃ high temperature curing condition,the cement-improved aeolian sand with 5% cement content can meet the design requirements of subgrade filling. Regardless of the high-temperature climatic condition,the cement-improved aeolian sand with cement content of 4% can meet the design requirements of the filling for the bottom of the railway subgrade bed.( 5) The research results are of conference value to construction and design of railway subgrade bed in aeolian sand area in the future.