| Redbed mudstone is a kind of typical soft rock.Its engineering geology and environmental geology problems caused by rapid and intense weathering are very prominent.It is an important problem that can not be avoided in many projects.Alternating ambient temperature and moisture are the main external causes of rapid weathering of soft rock in the red beds.Temperature fluctuations can cause thermal weathering of mudstones.In wet and dry water cycles,mudstone hydration and swelling can also lead to rapid weathering and spalling.At present,the weathering process and weathering characteristics of mudstone under a single temperature field,moisture field,and temperature-moisture physical field are lacking.This article takes the red mudstone in Chongqing area as the research object,and combain mudstone thermal expansion test results,thermal weathering test results,hydration expansion-weathering test results,temperature-moisture weathering test results,accumulative damage analysis with software simulation to spall characteristics of the thermal weathering and hydration expansion of mudstone-weathering and temperature-moisture weathering.The main research contents and conclusions of the paper are as follows:1)Using a TOP INDUSTRIE intelligent rock triaxial tester,a stepwise temperature-expansion thermal expansion test was conducted on a 50mm diameter and100mm high mudstone specimen.The results show that mudstone is a poor conductor of heat and that the internal temperature of the heating process is circularly distributed.An axial deformation of about 0.025 mm can be generated and the thermal stress can reach0.57 MPa.2)15 cycles of thermal weathering under temperature cycles of 16?35?,16?50?,and 16?65? are interviewed.The results show that the mudstone is damaged by weathering under the temperature cycling conditions of 16?35?.The accumulative damage is about 0.3?0.5.At 16?50?,the accumulative damage in the mudstone is about0.4?0.6,and about 0.6?0.8 under 16?65?.The fatigue accumulative damage analysis and simulation results show that under the condition of 16?35? and 16?50?,the thermal stress of mudstone does not reach its fatigue strength after 15 times of weathering,and the thermal stress within mudstone varies from 0.08MPa to 1.02MPa at16?65?.After 4 times weathering,mudstone surface angular thermal stress positions reached fatigue strength and there was a clear flaking phenomenon.3)Under the conditions of water supply for 1 min and water application rate of 2 g,4 g,and 8 g,6 cycles of hydration and expansion weathering tests were conducted.The results show that the average mass of weathered exfoliation of mudstone is approximately 1.54kg/m~2 when the water application rate is 2g.The thickness of peeling formed is 1 cm.The weathering accumulative damage depth reaches 2.33cm after 6cycles,and the average mass of exfoliated mudstone is approximately 2.61kg/m~2 when the water application rate is 4g.The thickness of peeling formed is 0.67cm.The depth of weathering injury after 6 cycles reached 2.67cm;at 8g,it was 4.05kg/m~2.The thickness of peeling formed is 1 cm.After 6 cycles,the depth of weathering accumulative damage was 4cm.4)The effect of temperature first changes the characteristics of the internal voids in the mudstone and provides conditions for the entry of water.Afterwards,the hydration expansion-weathering and thermal weathering processes jointly accelerate the weathering accumulative damage of the mudstone.Temperature-moisture weathering tests were conducted under conditions of temperature gradients of 35?,50?,65?,watering time of 1min,and water application rates of 2g,4g,and 8g.The results showed that at 2 g water application rates,under 35?,50?,65?,After 6 cycles the depth of injury reached 2.67cm,2.33cm,and 2.67cm in turn;at 4g of water application rates,the depths of injury of 3cm,2.67cm and 4cm at 35?,50?,and 65? followed by 6 cycles;Under the 8g water application volume,the depth of injury reached 3cm,4cm,and 7cm in turn at 35?,50? and 65? after 6 cycles. |
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