Model Test of Deformation Evolution and Multi Factor Prediction of Anchorage Slope Stability under Rainfall Condition

The primary factor influencing slope stability is the variation of internal mechanics within the soil-rock mixture caused by rainfall infiltration. Most existing research has focused on how rock content affects the failure of soil-rock mixture slopes. However, there has been insufficient investigation into the coupling effects of rainfall intensity and slope inclination on the stability of soil-rock mixture slopes. Therefore, the model test of soil-rock mixture slope was carried out. The coupling effects of rainfall intensity and slope inclination on water content, earth pressure, pore water pressure, and failure mode of soil-rock mixture slope were analyzed. The failure mode of soil-rock mixture slope induced by rainfall was revealed. The results indicated that an increase in rainfall intensity and slope inclination significantly contributed to the instability of soil-rock mixture slopes and the loss of fine particles. Additionally, the maximum values of water content, earth pressure, and pore water pressure increased progressively. Considering the two influencing factors of rainfall intensity and slope inclination, the calculation formulas related to the fine particle content, maximum water content, maximum earth pressure, and maximum pore water pressure of soil-rock mixture slope were established. The findings of this research provided theoretical support for the construction of soil-rock mixture slopes and the prevention and control of landslide disasters.

<p>Non-point source pollution has become the main pollution source of surface water , among which colloidal pollutants are a kind of important non-point source pollutants. Rainfall runoff is the main factor that causes non-point source pollutants to migrate to water. Vegetative filter strips is an effective measure to control non-point source pollution. Vegetative density is one of the important factors affecting pollutant removal efficiency. In order to clarify the removal efficiency of colloidal non-point source pollutants by vegetative filter strips with different densities under rainfall conditions, it is necessary to study the effects of vegetative density and rainfall intensity on the migration and removal mechanism of colloids in vegetative filter strips. Based on the numerical model established by coupling non-Darcy flow water balance equation and colloid transport equation, combined with laboratory experiments and numerical simulation, the removal mechanism of colloid at different migration distances was studied under the conditions of fixed inflow, different rainfall intensity and vegetative density.</p><p>The results show that: 1) Although there is no infiltration, the colloid diffuses from surface water into saturated sand, which increases the removal efficiency of colloid. 2) Increasing vegetative density will increase the removal efficiency of colloids in vegetative filter strips. With the increase of density, the velocity of flow decreases, which decreases the deposition capacity of colloids on vegetative and increases the diffusion of colloids from surface water to soil. 3) Under rainfall conditions, the presence of rainfall increases the removal efficiency of colloids by vegetative filter strips. Although rainfall weakens the ability of vegetative to deposit colloids, it enhances the ability of colloids to diffuse to soil. The deposition capacity of colloids on vegetative increased with the increase of rainfall intensity. 4) The interception ability of vegetative enhances the diffusion ability of colloids to soil, and enhances the removal efficiency of colloids by vegetative. 5) In the vegetative filter strips, the adsorption coefficient of colloids decreases with the migration distance, mainly due to the heterogeneity of colloids. In the process of colloid migration, the absolute value of surface potential and the colloid with smaller particle size along the course are easy to be removed by vegetative filter strips because of the smaller barrier between colloid and plant, the smaller second energy potential well and the strong adsorption capacity of colloid deposition.</p><p>The research results provide important theoretical basis and reference for designing vegetative filter strips to remove colloidal non-point source pollutants under rainfall conditions.</p>

본 연구는 강우재현장치를 제작하고, 화강암질 풍화토로 조성된 모형사면에 강우 및 사면조건에 따라 모형실험과 수치해석을 실시하였다. 모형실험에서 계측된 체적함수비와 간극수압의 변화특성을 분석하였으며 또한 수치해석 결과와 비교하였다. 체적함수비는 강우강도가 크고 사면경사가 급할수록 한계값에 도달하는데 짧은 시간이 소요되는 반면 강우강도가 작고 사면경사가 완만할수록 많은 시간이 소요되는 것으로 나타났다. 강우강도가 작고 강우지속시간이 짧을수록 더 큰 부의 간극수압을 나타내고 회복하는 시간도 짧은 것으로 나타났다. 이와 반면 강우강도가 크고 강우지속시간이 길수록 부의 간극수압을 회복하는데 오랜 시간이 소요되는 것으로 나타났다. 강우재현 모형실험과 수치해석을 수행한 결과 체적함수비와 간극수압의 분포경향이 유사하게 나타났다. 그러나 체적함수비는 최대 5% 정도, 간극수압은 최대 3kPa 정도의 차이를 보였다. This present study implemented a rainfall simulation system, and performed simulation and numerical analysis according to rainfall and slope conditions using a model slope built with weathered granite soil. Extensive analysis were conducted on the characteristics of changes in volumetric water content and pore water pressure measured in the simulation, and compared them with the results of numerical analysis. It took longer for the volumetric water content to reach the limit when rainfall intensity was high and the slope was steep and shorter when rainfall intensity was low and the slope was gentle. When rainfall intensity was low and the duration of rainfall was short, negative pore water pressure was higher and the time for restoration was shorter. On the contrary, when rainfall intensity was high and the duration of rainfall was long, it took a longer time to restore negative pore water pressure. In the results of rainfall simulation and numerical analysis, the distribution of volumetric water content and pore water pressure was similar between the two. However, the volumetric water content was different by up to 5%, and pore water pressure by up to 3kPa.

The rapid development of cities puts forward higher requirements for the resilience of the road network. As one of the unfavorable weathers, rainfall has a great impact on the operation of road traffic. Using weather and vehicle speed data of a city in China, this paper compares and analyzes changes in traffic operation indicators such as the standard speed and the percentage reduction of the standard speed under different rainfall intensities. Results indicate that under the same rainfall conditions and time period, the traffic operation of the elevated road is least affected by rainfall, and the traffic operation of underpass tunnels and flat roads is more affected by rainfall. With the increase of rainfall intensity, the reduction percentage of the standard speed of the underpass tunnel shows an increasing trend; however, it is less affected in light rain and moderate rain, and more affected in heavy rain and rainstorm. With the increase of rainfall intensity, the standard speed of the elevated road has no obvious change trend, and it is less affected by light rain and moderate rain, but more by rainstorm. In each time period, the standard speed reduction percentage of flat roads shows an obvious increasing trend with the increase of rainfall intensity.

The disaster-relevant authorities could make an uninformed decision due to the lack of a clear picture of the urban resilience to adverse natural events. Previous studies seldom examine the near-real-time human dynamics, which are critical to disaster emergency response and mitigation, in response to the development and evolution of a natural hazard. In this study, we used the aggregated Tencent location request data (TLR) to examine the variations in collective human activities in response to rains in 346 cities in China. Then we report a comprehensive study of the urban resilience to rains across the mainland China. Our results show that, on average, a 1-mm increase in rainfall intensity is associated with a 0.49 % increase of the human activity anomalies. In the cities of northwestern and southeastern China, human activity anomalies are affected more by rainfall intensity and rainfall duration, respectively. Our results highlight the unequal urban resilience to rains across China, showing current heavy rain warning standards underestimate the impacts of heavy rains on the residents in the northwest arid region and the central underdeveloped areas, and overestimate the impacts on the residents in the southeastern coastal area. An overhaul of current heavy rain alert standards therefore is needed to better serve the residents in our study area.

High urbanization adversely affects the hydrological behavior of watersheds. Therefore, different stormwater management strategies have been put forward to mitigate these negative effects. Grass swales are one of the environmentally friendly practices that are widely used today as an alternative to traditional infrastructure systems to reduce the peak flow rates, increase infiltration, and the time of concentration. The determination of the effective parameters on the hydrological characteristics of grass swales plays an important role in identification of proper design criteria. To this end, hydrological experiments were conducted by designing a grass swale module and integrating it into a large-scale rainfall-watershed-swale (RWS) experimental setup. The potential effective parameters (rainfall, soil, grass type, drainage area, and grass height) on the hydrological performance of the grass swales were tested with six different swale configurations by the controlled laboratory experiments. Experimental results show that swales decrease the peak flow significantly. In addition, hydrological performance of swales decreases with the increase in rainfall intensity or rainfall duration. Moreover, the soil and grass type have a significant effect on the peak flow reduction and drainage performance of the swales.

To investigate the differences in spatially axisymmetric earth pressure of a foundation pit within unsaturated soils under various transient suction conditions, two representative transient suction methods were selected for comparative analysis. These methods were evaluated for their similarities, differences, and variations in suction behavior. The differential slip line equation and a transient iterative solution for the earth pressure surrounding a spatially axisymmetric circular foundation pit in unsaturated soils were formulated. The validity of the proposed solution was confirmed by comparing it with existing earth pressure solutions reported in the literature. Subsequently, parametric studies were conducted to examine the effects of these two transient suction methods on earth pressure in different soil types—sands, silts, and clays. The results indicate that the proposed transient iterative solution for spatially axisymmetric earth pressure is not limited to any specific transient suction method and can accommodate variations in rainfall intensity, duration, and soil unit weight, thereby offering better alignment with real-world engineering scenarios. During rainfall, both transient suction methods exhibit consistent performance regarding the magnitude and profile of matric suction as well as the earth pressure of foundation pits. As initial rainfall intensity increases, matric suction decreases while earth pressure increases. However, each method has its own scope of application; misapplication of a transient suction method may lead to an overestimation of earth pressure. For sands, the earth pressure of foundation pits is only slightly affected by rainfall intensity or duration. In contrast, for silts and clays, earth pressure significantly increases during rainfall with the rise in both rainfall intensity and duration. After rainfall ceases, earth pressure initially rises and then declines over time, which can be attributed to the gradual increase in matric suction caused by evaporation, exhibiting a certain time delay.

This paper uses the catastrophic landslide that occurred in Zhongxing Town, Dujiangyan City, as an example to study the formation mechanism of landslides induced by heavy rainfall in the post-Wenchuan earthquake area. The deformation characteristics of a slope under seismic loading were investigated via a shaking table test. The results show that a large number of cracks formed in the slope due to the tensile and shear forces of the vibrations, and most of the cracks had angles of approximately 45° with respect to the horizontal. A series of flume tests were performed to show how the duration and intensity of rainfall influence the responses of the shaken and non-shaken slopes. Wetting fronts were recorded under different rainfall intensities, and the depth of rainfall infiltration was greater in the shaken slope than in the non-shaken slope because the former experienced a greater extreme rainfall intensity under the same early rainfall and rainfall duration conditions. At the beginning of the rainfall infiltration experiment, the pore water pressure in the slope was negative, and settling occurred at the top of the slope. With increasing rainfall, the pore water pressure changed from negative to positive, and cracks were observed on the back surface of the slope and the shear outlet of the landslide on the front of the slope. The shaken slope was more susceptible to crack formation than the non-shaken slope under the same rainfall conditions. A comparison of the responses of the shaken and non-shaken slopes under heavy rainfall revealed that cracks formed by earthquakes provided channels for infiltration. Soil particles in the cracks of slopes were washed away, and the pore water pressure increased rapidly, especially the transient pore water pressure in the slope caused by short-term concentrated rainfall which decreased rock strength and slope stability.

The piezoresistive silicon pressure transducers based on the piezoresistive effect have demonstrated their potential in the accurate monitoring of pressure. However, their usage in the pore and earth pressure monitoring at the pile surface under hydraulic jacking has not yet been explored. In this study, two self-made model piles (one is a closed-ended pile and the other is an open-ended pile) were instrumented with piezoresistive silicon earth transducers and pore pressure transducers and then driven into the soil using a hydraulic jack. A comprehensive investigation was first carried out for the structure of the model piles, the installation procedure of the transducers, and the composition of the test system. The pore and earth pressure measurements of the transducers were used for the evaluation of the distribution of the pore pressure, excess pore pressure, radial earth pressure, and radial effective earth pressure. The model test results indicate that the piezoresistive silicon pressure transducers are suitable for monitoring the pore and earth pressure at the pile surface during jacking. In addition, the pore pressure, excess pore pressure, radial earth pressure, and effective radial earth pressure along the test piles were affected by the penetration depth and the pile end form.

Contribution of raindrop impact to the change of soil physical properties and water erosion under semi-arid rainfalls.

An experimental study on dynamic processes of ephemeral gully erosion in loess landscapes

Landslide disasters are one of the most severe geological hazards in China. Soil slopes are prone to triggering landslides under the influence of main factors such as rainfall, resulting in economic losses, casualties, and ecological damage. Taking a residual soil landslide in Xingguo County as an example, this study investigated the influencing factors and mechanical properties of soil slope stability under rainfall infiltration through physical model experiments. The main conclusions were as follows: with the increase in rainfall intensity, the amount of rainwater infiltration and the weight of the soil mass increased, which led to greater changes in soil pressure. The maximum amplitude of the experimental process was 5.51 kPa. The response time of pore water pressure under a rainfall intensity of 45 mm/h was 20–30 min earlier than that under a rainfall intensity of 21 mm/h, with a larger fluctuation range. The maximum amplitude of the experimental process was 6.66 kPa. Under the condition of rainfall intensity of 21 mm/h, the slope undergone local shallow sliding failure, while under the condition of rainfall intensity of 45 mm/h, the slope undergone overall shallow sliding failure. The physical model experimental results were consistent with the historical deformation of the landslide and the actual situation on site. The conclusions of the experiment can provide a reference for the research on the failure mechanism of similar landslides.

Regarding the issue of changes in the aerodynamic force of the bridge main beam under the action of wind-driven rain, this article explores the changes in air density caused by rainfall, the calculation theory of raindrop impact force and its simplified mass-weighted equivalent method (MWEM), and the calculation method of water accumulation thickness on the surface of the main beam. The calculation shows that the changes in air density caused by rainfall can be ignored, and the error of the MWEM increases with the increase in rainfall intensity; however, even at a rainfall intensity of 709 mm/h, the deviations in the MWEM value of the horizontal and vertical raindrop impact force is only about +5% and −4%, respectively. Then, based on the above analysis, a calculation model for the aerodynamic three-component forces of the main beam caused by rainfall under the action of wind-driven rain is provided. Finally, taking two typical main beam sections as an example, static three-component force tests are carried out on the main beam model under different rainfall intensities. The experimental results show that the drag coefficient variations obtained through the MWEM are in good agreement with experimental data, which proves the correctness of the theoretical model of the raindrop impact force. But for the lift and torque coefficient, the differences between theoretical and experimental values are much more significant than the drag coefficient, and it increases with the increase in rain intensity. It can be seen that the surface ponding model and influence of rainfall intensity need to be further explored. In summary, the theoretical calculation method for the additional aerodynamic force of wind-driven rain on the main beam proposed in this article is convenient and practical, and it can provide a certain reference for the rapid safety assessment of bridges under extreme meteorological conditions.

This paper focuses on investigating the effects of different rainfall intensities on traffic operations of urban road networks. Macroscopic Fundamental Diagram (MFD) and Spearman correlation coefficient are used to quantitatively describe the network's operation and measure the rainfall impact on it. Mastering the rainfall impact on urban road traffic operation is not only important for the traffic state evaluation in rainy days, but also for the development of effective management strategies under rainy conditions. An empirical analysis is carried out on a major arterial network located on Haizhu district of Guangzhou, China. The results indicate that the rainfall events increased the uncertainty in network performance, and the reduction is in an increasing tendency with the increase in rainfall intensity. Furthermore, the different rainfall intensities have divergent impacts on macroscopic traffic variables. The heavy rain and rainstorm have remarkable negative effect on macroscopic traffic parameters, which produced Critical Accumulation and Maximum Production reduction of 10.5%, 16.7% and 21.0%, 18.7%, respectively. While the light rain and moderate rain have relative small impact on network's operation. What's more, the precipitation resulted in a significant decrease effect on the parameters of weighted free-flow speed and weighted jam density of the study network, the average reduction is 9.7% and 12.3%, regardless of the intensity. The production and weighted speed are also reduced by rainy condition, but the parameter of accumulation is not rainy-sensitive.

Quantification of runoff and soil loss variabilitities are important aspects of hydrological processes. The present study was designed to evaluate the effect of six consecutive storms on variability of descriptive characteristics of runoff and soil loss under different rainfall intensities. To achieve the objectives, a set of laboratory experiments were conducted using rainfall simulator and a 6 × 1-m erosion plot with a depth of 0.5 m and a slope of 5%. The rainfall intensities of 30 and 90 mm/h were applied to a silt loam soil sampled from Kojour rangeland watershed, northern Iran. The results showed a decreasing trend in Coefficient of Variation (CV) of runoff volume with increase in rainfall intensity from almost 50 to 28%. A decreasing trend was also observed for CV of soil loss in consecutive storms from almost 65 to 50% under rainfall intensity 30 to 90 mm/h. The results further indicated a 1.8- and 1.3-times increase respectively for CV of runoff volume and CV of soil loss under low intensity compared to those of 90 mm/h in different consecutive storms. The comparative analysis of the results using One-Way ANOVA also verified significant difference (p > 0.05) among runoff amounts in both rainfall intensities except in 2nd and 6th consecutive storms. In addition, amounts of soil loss were not significantly (p > 0.05) different in 3rd, 4th and 6th consecutive storms under rainfall intensities of 30 and 90 mm/h.