Loess has the characteristics of large porosity, loose structure, uniform composition and strong collapsibility. When encountering heavy rainfall and irrigation prone to saturation, resulting in loess landslides, roadbed subsidence and dam instability. In order to study the effect of dry density and shear rate on the shear strength of saturated remolded loess, the consolidated undrained (CU) test was carried out in Yan'an City by using SLB-6A stress-strain controlled triaxial shear permeability test instrument. The shear rate, confining pressure and dry density were controlled during the test. The dry densities of the samples were 1.5 g / cm3, 1.6 g / cm3 and 1.7 g / cm3, respectively. CU tests of saturated remolded loess were carried out at different shear rates under the confining pressures of 100 kPa, 150 kPa and 200 kPa, respectively. It is found that the stress-strain curve of saturated remolded loess gradually moves upward with the increase of dry density. With the increase of dry density, the cohesion and internal friction angle of remolded saturated loess samples increase. At the same shear rate, with the increase of dry density, the deviatoric stress of the specimen increases significantly. ✉ * E-mail: xujiangbo@yeah.net 14 7 2022 17 7 e0271266 e0271266 15 7 2022 © 2022 Lai et al This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Abstract Loess has the characteristics of large porosity, loose structure, uniform composition and strong collapsibility. When encountering heavy rainfall and irrigation prone to saturation, resulting in loess landslides, roadbed subsidence and dam instability. Water infiltration and fine-grained soil backfilling lead to cracks on the road shoulder [ 2 ]. For example, large-scale agricultural irrigation has led to the frequent occurrence of loess landslides [ 3 ]. The influence of rainfall intensity on landslide was analyzed to build a rainfall threshold model [ 4 ]. The improved frequency ratio method is used to evaluate the sensitivity of landslides [ 5 ]. Sensitivity analysis is conducted on the landslide stability of Xiaojiang watershed in Yunnan Province [ 6 ], and a new landslide analysis model is proposed based on GIS [ 7 ]. Zizhou County of Yulin City is a typical loess plateau. The combination of cohesive binding factors of clay and organic matter in soil subjected to varying wetting conditions exert a strong influence on the resistance of the soil to sustained shearing stresses [ 12 ]. The influencing factors of soil shear strength after rainfall was studied. (Watson et al. [ 13 ]explored the role of rainfall on soil shear strength). The relationship between the soil-water characteristic curve and the shear strength of unsaturated soil is described, which is related to matrix suction [ 14 ]. An empirical, analytical model was developed to predict the shear strength in terms of soil suction. Saturated loess with different dry density through different stress paths are researched, and found that under the same path, the stress-strain, the size of dry density does not affect the shape of its curve, but the strength and anti-destructive ability of the soil [ 29 ]. The modified TFB-1 unsaturated soil stress-strain control triaxial apparatus is used to carry out saturation test and CU test on the remolded soil samples of Malan loess in the Dangchuan area, and the study found that the shear strength of saturation remolded loess under the same confining pressure increases first and then decreases with the increase of shear rate. Its physical properties are shown in Table 1 . The granular gradation curve of the soil is shown in Fig 2 . The size of the remolded soil sample in this test was 39.1 mm × 80 mm , wherein the sample diameter was 39.1 mm , and the sample height was 80 mm . Table 1 Basic physical parameters of soil samples. Moisture content/% Dry density/( g / cm 3 ) Percentage of soil particles at different particle sizes/% < 0.075 0.075–0.25 0.25–0.5 0.5–2 14.97 1.557 88.73 12.27 0 0 Fig 2 Granular gradation curve of loess. 2.2 Experimental method The device used in this test is an SLB-6A stress-strain controlled triaxial shear permeability tester. (2) Β = 1 1 + n C v C s where n represents the porosity of soil, C v represent three to pore volume compressibility, C s on behalf of the three to the volume compression coefficient of soil skeleton. Reason for saturated soil, completely filled with water in the pores, due to the compressibility of water is much lower than the compressibility of soil skeleton, Cv Cs →0, and B = 1; For dry soil, Cv Cs →∞, therefore, B = 0; For unsaturated soil, 0<B<1, the less saturated the soil, the smaller the B value.) Three dry densities of soil samples were used in experimental works 1.5 g/cm3, 1.6 g/cm, and 1.7 g/cm3. The permeability coefficient of loess decreases relatively when the dry density is relatively large, and uneven pore pressure will occur at an excessively high shear rate, which limits the selection range of shear rate, thus the thixotropy of loess can not be expressed. The effect of shear rate of loess is controlled by many factors, such as dry density and confining pressure. The strain -softening phenomenon is weaker in soils with relatively low thixotropy, and the shear strength increases with the increase of strain rate. When the dry density is large, the strength of saturated loess increases relatively with time in the shear process. The relationship between the cohesion, the internal friction angle of the remolded soil sample and the shear rate is plotted. As shown in Fig 10A–10C , the total and effective internal friction angles of saturated remolded loess under different dry densities, always increase first and then decreases with the increase of shear rate. When dry density is equal to 1.5 g/cm 3

This study aims to determine the extent to which rainfall affects soil subsidence on peatlands in PT. BGA. TBk., Pundu, Central Kalimantan. The research was conducted at Katari Estate, PT BGA, Tbk. Pundu Central Kalimantan in September - December 2019. The research method used is the survey method, which consists of two stages, namely the preliminary survey and the main survey. A preliminary survey was conducted to determine the research location while the main survey was carried out to obtain research data, namely monthly rainfall data and subdidence in 2014 – 2018. To see the relationship between rainfall and land subsidence, Linear and Polynomial Regressions were made at lag 1, lag 2, and lag 3. Regression with lag 1 is the relationship between rainfall last year with land subsidence this year and rainfall last month with land subsidence on peatlands this month in the same year, and so on for lag 2 and lag 3. The results show that the regression between The best rainfall with soil subsidence on peatlands is the annual Lag 1 Linear Regression. This means that last year's rainfall has an effect on this year's subsidence. with the equation, Y = - 0.004 X + 1.209, where R² = 0.582. This equation is obtained from the correlation between X (average rainfall) from 2015-2018 and Y is soil subsidence also from 2015-2018. While the regression between last month's rainfall and this month's land subsidence in each year (2015 – 2018), shows a low correlation. Rahayu et. all Juatika Vol. 5 No.1 2023 45 DOI :https://doi.org/10.36378/juatika.v5i1.2652 JUATIKA eissn 2656-1727 JURNAL AGRONOMI TANAMAN TROPIKA pissn 2684-785X VOL.5 NO. 1 January 2023 Hal : 45 – 56 Land Subsidence in Peatlands Due to Rainfall: Case Study in Pundu, Central Kalimantan Enny Rahayu*, Idum Satia Santi dan Chandra Riski Alfikri Harahap Agrotechnology Program Study, Agriculture Faculty of INSTIPER Yogyakarta, Jln Nangka II, Maguwoharjo, Depok, Sleman, Yogyakarta, *email : enny@instiperjogja.ac.id ABSTRACT Land subsidence can be caused by peatland soil compaction, drainage pract ices, an extended dry season, or both. But what frequently happens is drainage brought on by land conversion or by little rain during the dry season. The purpose of this study is to ascertain how much rainfall impacts peat land subsidence. From September t o December 2019, the study was carried o ut at Katari Estate, PT BGA, TB K. Pundu, Central Kalimantan. The survey method is the one that was employed for the study, and it consists of two stages: the preliminary survey and the major survey. While the primary survey was done to collect research data, such as monthly rainfall data and land subsidence during 2014 to 2018, preliminary surveys were carried out to choose study areas. On lag 1, lag 2, and lag 3, linear and polynomial regressions were performed to ex amine the link between rainfall and land subsidence. The findings demonstrated that the annual Linear Regression Lag 1 was the optimum regression between rainfall and land subsidence on peatlands. This indicates that this year's land sinking was influenced by the rainfall from last year. according to the formula Y = - 0.004 X + 1.209, where R2 = 0.582. This equation is derived from the association between Y, which is land subsidence from 2015 to 2018, and X, which is average rainfall from 2015 to 2018. The r egression between previous month's rainfall and this month's land subsidence each year (from 2015 to 2018) reveals a weak association. Keywords: Rainfall, Land Subsidence, Peatland, Regression, correlation Copyright © 2023. The authors. This is an open access article under the CC BY license (https://creativecommons.org/licenses/by/4.0/) Rahayu et. all Juatika Vol. 5 No.1 2023 51 2021). According to the study's findings, an equatorial rainfall pattern can be seen in the average rainfall from 2015 to 2018. However, a very noticeable change can be seen if you examine the annual rainfall pattern from 2015 to 2018. According to study (Jayanti, 2016), changes in rainfall patterns lead to shifts in the seasons.The pattern of precipitation will shift in the fifth year, which will result in a change in the seasons, after returning to normal in the preceding four years. In this instance, it is anticipated that it will return to 2015 in 2019. This is what we need to be on the lookout for, and we can utilize it to get ready for ho w to prevent land sinking in peat. Table 2. Subsidence of peat soil in block G 55a, PT. BGA. Tbk. Pundu, Central Kalimantan A. Soil subsidence The dynamics of peat sinking in Afdeling Katari PT BGA, Tbk. Pundu Central Kalimantan from 2015 to 2018 are shown in Table 2. In Figure 6, a graph of soil subsidence in peat over four years, from 2015 to 2018, is displayed. A positive value implies that the soil subsidence brought on by accelerated decomposition due to aerobic (oxidative) soil atmosphere produced by insufficient rainfall (subsidence). High numbers of increasing or rising grou nd levels as a result of rain and flooding of peatlands are indicated by negative numbers (-). The rate of soil subsidence (subsidence of the soil surface) on land is highest in June, August, and September, as can be seen in Figure 6 above. Months PEAT SUBSIDENCE IN BLOCK G 55a Average 2015 2016 2017 2018 January 0 2,2 -0,6 -0,6 0,25 February -0,5 -0,2 -0,2 0,6 -0,07 March 0,2 -0,2 3,8 -2,4 0,35 April 0,7 0 -0,8 0,8 0,18 May 0,4 0,2 -0,2 0,4 0,2 June 0,5 1,6 0,6 1 0,93 July 1,2 -1 -0,2 1,5 0,38 August 0 2,1 0,3 0,5 0,73 September 2 1,1 0,3 -0,5 0,73 October 0,8 -0,4 -0,2 -0,5 -0,07 November -0,8 -1,4 1 0 -0,3 December -1,2 -1,2 0,8 -0,5 -0,53 Rahayu et. all Juatika Vol. 5 No.1 2023 55 2018 Lag-0 y = -0,015x + 0,450 0,078 y = 0,001x 2 - 0,106x + 1,458 0,283 Lag-1 y = -0,037x + 1,168 0,404 y = -8E-05x2 - 0,032x + 1,100 0,405 Lag-2 y = -0,003x + 0,174 0,002 y =

Land Subsidence | U.S. Geological Survey Skip to main content # Land Subsidence Active By Water Resources Mission Area ## Sea-Level Rise, Subsidence, and Wetland Loss ### Changes to the Mississippi River Delta Watch Video ## The Science of Sinkholes ### When the ground below your feet...isn't ## Sinking Earth ### Land subsidence from groundwater pumping Read More - Overview - Science - Multimedia - Publications - News - FAQ More than 80 percent of known land subsidence in the U.S. is a consequence of groundwater use, and is an often overlooked environmental consequence of our land and water-use practices. Increasing land development threatens to exacerbate existing land-subsidence problems and initiate new ones. Subsidence detection and mapping done by the USGS is needed to understand and manage our current and future land and water resources in areas where subsidence is a problem or may be in the future. Media Sources/Usage: Public Domain. View Media Details Approximate point of maximum subsidence in the San Joaquin Valley, California. The land surface subsided roughly 9 meters from 1925 to 1977 due to aquifer-system groundwater withdrawals. Signs on the telephone

icense information Roles Sid Perkins : Science Writer Issue date 2021 May 18. Published under the PNAS license . PMC Copyright notice PMCID: PMC8157975  PMID: 33980717 Earth’s surface is ever changing. Sinkholes swallow neighborhoods, river deltas slowly slide beneath the waves, and fertile fields lose elevation as farmers draw large amounts of water for irrigation from underlying aquifers. Whether gradual and subtle, or sudden and dramatic, these phenomena are known as subsidence—the lowering of the ground’s surface owing to the subterranean movement of material. Open in a new tab As farmers pump out water to irrigate crops, ground water levels drop and massive sinkholes can form, such as this one in Dover, FL, that formed after a freeze event in January of 2010. Image credit: USGS/Ann Tihansky. Many instances of subsidence stem from natural processes. For instance, the same flows of groundwater that dissolve limestone to form caves far below ground can also operate at shallower depths, sculpting caverns that grow until their roofs can no longer support overlying strata. When those roofs collapse, a sinkhole can form. But now, researchers are finding that subsidence more often results from human activity. According to the US Geological Survey, in the United States, more than 80 percent of the known subsidence—which together covers an area that’s nearly 17,000 square miles and spread across 45 states—stems from groundwater use. Worldwide, almost one-fifth of the planet’s population lives in areas where subsidence driven by groundwater withdrawals is a major threat, a new analysis finds. Humans cause subsidence in other ways, too. The sheer weight of large cities can depress Earth’s crust several centimeters—a substantial threat for coastal cities now that sea level is on the rise. Most types of anthropogenic subsidence are not reversible, meaning that prevention is the best remedy. Fortunately, satellites offer a convenient way to monitor wide swaths of landscape, a