Study On The Behavior Of Travertine Deposition Under Hydrodynamic Force In Huanglong,Sichuan

Under the background of typical alpine karst accumulation geomorphology,Huanglong has extensive and thick travertine deposition and rich and colorful travertine landscape,which has high scientific research value and human value.In recent years,the phenomenon of some travertine landscape degradation and damage has attracted the attention of scholars.Taking the environmental geology of Huanglong Scenic area as the research background,the flow field distribution of typical travertine geological bodies under hydrodynamic action was studied by means of in-situ experiment,laboratory analysis and 3D numerical simulation of CFD software by selecting typical travertine pools,beach flows,waterfalls and microhills as research objects.The formation conditions of new travertine particles and their migration and deposition rules under different hydrodynamic conditions were investigated to clarify the deposition mechanism of travertine under hydrodynamic action.It provides scientific basis for sustainable development of tourism resources and conservation of travertine landscape in Huanglong.The results show that the water quality of Huanglong is HCO₃^--Ca²⁺type,and HCO₃^-and Ca²⁺play a leading role in travertine deposition.Ca²⁺concentration in Huanglong Multicai pool,Zhengyan color pool and Yingbin pool showed obvious stratification,and gradually increased from upper to lower layers.Under the influence of hydrochemistry,the particle size distribution of color pond also appeared obvious stratification phenomenon.The middle of each color pool and the outlet of the particle size distribution is similar,there is a trend from the upper to the lower particle size gradually increased,the maximum particle size also gradually increased.Due to hydrodynamic influence,the particle size distribution at the inlet is different from that at the middle and outlet,but the distribution law of each color pool is consistent.The numerical simulation results show that the distribution of caichi particles is obviously stratified under the influence of turbulence,diffusion and gravity,which is consistent with the above experimental results.The overall flow of color pool is smooth,and the flow rate appears obvious partition phenomenon.The flow velocity at the entrance of color pool is mainly affected by the flow velocity of incoming flow,and the turbulent kinetic energy is small.The upper water brings a large number of travertine particles,among which the large particles are deposited along the side wall,and the small particles diffuse backward with the mainstream.Under the inlet,due to the interaction between the main stream and the original water,there is a backflow area with violent turbulence,which easily leads to the disturbance of suspended solids and increases the probability of collision between particles,thus forming large particles.In the diffusion zone at the middle and rear of the color pool,the flow velocity and turbulent kinetic energy are stable due to the uniform mixing of the flow velocity,and the flow velocity appears stratification.At the same time,under the influence of the chemical stratification of the color pool,the particle distribution stratification is obvious.In the vicinity of the edge-rock dam,the water level becomes shallower,the flow rate increases,the pressure decreases,and CO₂is easy to escape due to the influence of the edge-rock dam.Therefore,the deposition rate of travertine at the edge-rock dam is higher,leading to the increasing and thickening of the edge-rock dam.The surface area of planar flow at beach flow is larger,and the contact surface between water and air increases,forming a large range of travertine deposition.The variation of the velocity of beach current is mainly affected by slope and microtopography.The flow velocity of the waterfall is turbulent.At the same time,high-speed aerated water flow is generated at the scour to create better conditions for CO₂escape from the water.The geomorphic formation of microhills is influenced by both hydrodynamics and hydrochemistry.The flow rate and aeration value of travertine microhillock differed greatly between the impact point and the jump point.Hydrochemical analysis showed that Ca CO₃was generated during the process from the impact point to the jump point.The velocity of flow determines the radius of curvature at the microhump.