scholarly journals The Effect of Suffusion Phenomenon in the Increasing of Land Subsidence Rate

2016 ◽  
Vol 2 (7) ◽  
pp. 316-323 ◽  
Author(s):  
Elmira Khaksar Najafi ◽  
Hadi Faghihmaleki
Keyword(s):  
Land Subsidence ◽  
Alluvial Soil ◽  
Ground Surface ◽  
Seepage Flow ◽  
Internal Erosion ◽  
Alluvial Soils ◽  
Sedimentary Deposits ◽  
Subsidence Rate ◽  
Internal Instability ◽  
Ground Surface Settlement

Land subsidence is defined as gradually ground surface settlement in an aquifer due to the compaction of unconsolidated sedimentary deposits. Since in an aquifer, deposits consist of cohesive or non-cohesive alluvial soil layers. The consolidation theory cannot be explained as the only reason for land subsidence. According to the susceptibility of alluvial soils to suffusion, internal erosion is also considerable to enhance the rate of the local settlement. Suffusion is explained as a process of soil particle movement in the soil body due to the effect of seepage flow on it. The subsidence rate in southwest and south of Tehran in Iran is very considerable whereby some structures have suffered significant damages due to this phenomenon. In this research, the contribution of suffusion and land subsidence was investigated in damaged building located at Ghale Morghi Street in southwest of Tehran, as a case history. Because of the incapability of available methods, in this article, a probability pattern is also proposed using statistical analysis for determination the likelihood of internal instability in alluvial soils in regard to soil cohesiveness.

Spatial and temporal progression of internal erosion in cohesionless soil

2011 ◽  
Vol 48 (3) ◽  
pp. 399-412 ◽  
Author(s):  
Ricardo Moffat ◽  
R. Jonathan Fannin ◽  
Stephen J. Garner
Keyword(s):  
Seepage Flow ◽  
Hydraulic Gradient ◽  
Internal Erosion ◽  
Cohesionless Soil ◽  
Cohesionless Soils ◽  
Multi Stage ◽  
Internal Instability ◽  
Post Test ◽  
Erosion Test ◽  
Permeameter Tests

Permeameter tests were performed on four widely graded cohesionless soils, to study their susceptibility to internal erosion. Test specimens were reconstituted as a saturated slurry, consolidated, and then subjected to multi-stage seepage flow under increasing hydraulic gradient. The occurrence of internal instability is described qualitatively, from visual observations through the wall of the permeameter during a test and from post-test observations; it is also described quantitatively, from change of hydraulic gradient within the specimen and from axial displacement during a test. The results provide a novel insight into the spatial and temporal progression of seepage-induced internal instability. This insight yields an improved characterization of suffusion and suffosion in cohesionless soils, the progression of which appears governed by a critical combination of hydraulic gradient and effective stress.

Results of an Instrumented Static Loading Test and Its Application to Design Compilation of an International Survey

2021 ◽  
Vol 15 (1) ◽  
Author(s):  
Bengt Fellenius
Keyword(s):  
Prestressed Concrete ◽  
Static Loading ◽  
Ground Surface ◽  
Loading Test ◽  
Text Book ◽  
Ground Surface Settlement ◽  
Static Loading Test ◽  
Residual Force ◽  
Available Information ◽  
Piled Foundations

Results of a static loading test were used together with soil exploration records in a survey comprising analysis of the test records and estimating settlement of piled foundation to support a pipe rack. The test pile was a strain-gage instrumented, 400-mm diameter, precast, prestressed concrete pile driven into a clay and silt deposit to 25 m embedment. Two main issues were expected to be addressed by the survey participants: First, realization that the strain records were affected by presence of residual force in the pile and, second, calculation of the settlement of the piled foundation expected from the foundation load. A total of 52 submissions were received from 20 different countries. Only 12 of the submissions realized the presence of residual force. Most submissions reported a calculated settlement of the piled foundations ranging from 10 mm through 50 mm; however, 11 reported values between 60 and 200 mm. Surprisingly, only 20 submissions reported ground surface settlement close to the 200-mm value resulting from text-book analysis based on the available information. The subsequent construction of the piled foundations coincided with placing a fill across the site and lowering of the groundwater table, thus, causing a general subsidence.

Detecting land deformation due to groundwater changes with InSAR observations - the case of the island of Gotland, Sweden

2021 ◽  
Author(s):  
Mehdi Darvishi ◽  
Fernando Jaramillo
Keyword(s):  
Land Subsidence ◽  
Groundwater Level ◽  
Ground Deformation ◽  
Soil Depth ◽  
Ground Surface ◽  
Groundwater Depletion ◽  
Groundwater Levels ◽  
Small Baseline Subset ◽  
Small Baseline ◽  
The Baltic

<p>In the recent years, southern Sweden has experienced drought conditions during the summer with potential risks of groundwater shortages. One of the main physical effects of groundwater depletion is land subsidence, a geohazard that potentially damages urban infrastructure, natural resources and can generate casualties. We here investigate land subsidence induced by groundwater depletion and/or seasonal variations in Gotland, an agricultural island in the Baltic Sea experiencing recent hydrological droughts in the summer. Taking advantage of the multiple monitoring groundwater wells active on the island, we explore the existence of a relationship between groundwater fluctuations and ground deformation, as obtained from Interferometric Synthetic Aperture Radar (InSAR). The aim in the long-term is to develop a high-accuracy map of land subsidence with an appropriate temporal and spatial resolution to understand groundwater changes in the area are recognize hydroclimatic and anthropogenic drivers of change.</p><p>We processed Sentinel-1 (S1) data, covering the time span of 2016-2019, by using the Small BAseline Subset (SBAS) to process 119 S1-A/B data (descending mode). The groundwater level of Nineteen wells distributed over the Gotland island were used to assess the relationship between groundwater depletion and the detected InSAR displacement. In addition to that, the roles of other geological key factors such as soil depth, ground capacity in bed rock, karstification, structure of bedrock and soil type in occurring land subsidence also investigated. The findings showed that the groundwater level in thirteen wells with soil depths of less than 5 meters correlated well with InSAR displacements. The closeness of bedrock to ground surface (small soil depth) was responsible for high coherence values near the wells, and enabled the detection land subsidence. The results demonstrated that InSAR could use as an effective monitoring system for groundwater management and can assist in predicting or estimating low groundwater levels during summer conditions.</p>

Analysis of Surface Subsidence Rule of the Shallow Subway Tunnel Construction

2013 ◽  
Vol 671-674 ◽  
pp. 1081-1086 ◽  
Author(s):  
Fei Fei Wang ◽  
Hui Ren Bai ◽  
Jing Jing Li
Keyword(s):  
Ground Surface ◽  
Calculation Model ◽  
Surface Subsidence ◽  
Surface Settlement ◽  
Tunnel Construction ◽  
Maximum Point ◽  
Subway Tunnel ◽  
Monitoring Frequency ◽  
Ground Surface Settlement ◽  
Value Range

In order to study the Dalian Metro section 202(Cujin Road station-Chunguang Street station, which is shallowly buried and covered with plain fill)’s ground surface settlement, the monitoring measuring station was built during the construction. After 3 months’ measuring by precision level,the data shows that the maximum point is in the center line of the tunnel of the upper part. The settlement is about 25.66-31.82mm. This paper put forward the concept of the distance span ratio β, β effective value range was - 4 <β< 4,Surface subsidence is closely related with β, Severe surface subsidence stage is -2 <β< 2, Occupy whole deformation is 67.5-77.6%,settlement rate about 0.84-0.93mm/d, so should strengthen the monitoring frequency, Suggest increases site tour. Field test results and the ground surface settlement calculation model winkle are identical with each other; the monitoring results have important guiding significance and reference for Dalian subway and the similar shallow depth excavation tunnel construction.

scholarly journals Deformation Characteristics of Raising, Widening of Old Roadway on Soft Soil Foundation

Symmetry ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 2117
Author(s):  
Keke Li ◽  
Wenyuan Xu ◽  
Liang Yang
Keyword(s):  
Lateral Displacement ◽  
Soft Soil ◽  
Ground Surface ◽  
Surface Settlement ◽  
Deformation Characteristics ◽  
Construction Methods ◽  
Ground Surface Settlement ◽  
Total Settlement ◽  
Soil Foundation ◽  
Soft Soil Foundation

The deformation characteristics of a raised and widened old Chinese roadway on a soft soil foundation are investigated in this study via finite element numerical simulation. The rules of ground surface settlement, slope foot lateral displacement, and ground surface settlement evolution of the roadbed under three modes (one-time construction of an eight-lane expressway, widened four-lane expressway, and raised/widened four-lane expressway) are compared. The ground surface settlement process of the eight-lane road foundation, which is formed by first widening and then raising the road, is highly complex. The ground surface settlement curve under the old road foundation increases and then decreases. The lateral displacement of the slope foot also interacts with the widening and raising of the eight-lane roadbed foundation. The range of lateral displacement is 70.05, 42.58, 124.81, 104.54 mm. Fifteen years after construction, the total settlement of the raised and widened roadbed is much larger than that of the one built directly. The total settlement values at the center of the two roadbeds are 297.05 and 234.85 mm, respectively. This manuscript provides data support for the reconstruction and expansion of roads on soft soil foundations, for choosing appropriate construction methods to build roads, and for avoiding major road damage, which is of great significance to the construction of road infrastructure in the future.

scholarly journals Regulating Subsidence and its uncertainty in the Dutch Wadden Sea

2020 ◽  
Vol 382 ◽  
pp. 63-70
Author(s):  
Johannes A. de Waal ◽  
Mathijs W. Schouten
Keyword(s):  
Natural Gas ◽  
The Netherlands ◽  
Land Subsidence ◽  
Wadden Sea ◽  
Gas Production ◽  
Reservoir Rock ◽  
Proper Management ◽  
Subsidence Rate ◽  
Non Linear ◽  
Regulatory Approach

Abstract. At the start of gas production its effects on land subsidence are not certain. There are uncertainties in mechanisms, models and parameters. Examples are non-linear deformation of reservoir rock, fault transmissibility, behaviour of overlaying salt and aquifer activity. Looking back at historical cases in the Netherlands, a factor two or three difference between initial prediction and final outcome is quite common. As the Dutch regulator, SSM is tasked with assuring proper management by operators of the risks associated with land subsidence from natural gas production in The Netherlands. Large initial uncertainties can only be tolerated if operators can demonstrate that timely actions can still be taken when predefined subsidence limits are at risk of being exceeded now or in the future. The applied regulatory approach is illustrated by the case history of gas production induced subsidence in the Dutch Wadden Sea area. This environmentally highly sensitive UNESCO World Heritage Site is a natural gas province. Extensive legal, technical and organisational frameworks are in place to prevent damage to its natural values. Initial uncertainties in the predicted subsidence (rate) were later exacerbated by the detection of strong non-linear effects in the observed subsidence behaviour, leading to new concerns. It was realised that – depending on the underlying physical cause(s) – there will be a different impact on future subsidence. To assure proper management of the additional uncertainty by the operator, several improvements in the regulatory approach have been implemented. Possible underlying mechanisms had to be studied in depth and improved data analysis techniques were requested to narrow down uncertainties as time progresses. The approach involves intensified field monitoring, scenario's covering the full range of uncertainties and a particle filter approach to handle uncertainties in predictions and measurements. Spatial-temporal double differences, production data and the full covariance matrix are used to confront scenario predictions against measurements and to assess their relative probability. The regulator is actively involved in assuring this integrated control loop of predictions, monitoring, updating, mitigation measures and the closing of knowledge gaps. The regulator involvement is supported in the Mining law and by appropriate conditions in the production plan assent. With the approach it can be confidently assured that subsidence (rate) will remain within the allowed range.

scholarly journals The properties of river alluviums of the Upper-Dniester alluvial plain

2017 ◽  
pp. 293-303
Author(s):  
Khrystyna Perets ◽  
Oksana Vovk ◽  
Oleh Orlov ◽  
Olena Lutsyshyn
Keyword(s):  
Granulometric Composition ◽  
Alluvial Soil ◽  
Chemical Properties ◽  
Soil Formation ◽  
Hydrological Regime ◽  
Clay Content ◽  
Fine Sand ◽  
Alluvial Plain ◽  
Alluvial Soils ◽  
Floodplain Soil

Alluvial soil formation is a dynamic process, the main prerequisite of which is the regular, periodic flooding of the river floodplain with flood waters, which are enriched with multidispersed organic and mineral particles. During the last century, about 80 % of territory of the Upper-Dniester alluvial plain was transformed by means of hydrotechnical construction: waterproof dams and drainage channels have broken the wide river floodplains into isolated fragments, making impossible the free flow of flood waters, enriched with silt. The results of the study of stratification patterns of the river silt in the riverbed floodplain, depending on the flow velocity, granulometric composition, physical and chemical properties, given its role in the floodplain soil formation are given. The granulometric composition of the Dniester River silt changes downstream from the sandy to the heavy-loamy; In the floodplains of the Stryj and Svicha rivers medium- and heavy-loamy deposits are postponed, respectively. In the upper part of the Upper- Dniester alluvial plain (Chaikovichi 1, 2) accumulates a silt with predominance of the medium and fine sand fraction, which forms a good filtration ability of soils, whereas downstream the physical clay content increases (up to 47.2 %), which makes the river silt an important source of mineral nutrition of plants. The domination (over 40 %)in silt granulometric composition the rough dust fraction (Ustia 1, Zalisky 1) contributes to the improvement of the water-physical properties of alluvial soils and provides optimal conditions for the biota functioning. For the investigated river alluviums an alkaline reaction of the extract (pH (H2O) = 7,44–8,03) and low content of humus (0,54–3,80 %) are characteristic. The amount of nitrogen in the silt varies within 1,47–18,20 mg/100 g of soil. The river alluviums of the Upper-Dniester alluvial plain are an active factor in floodplain soil formation, since it optimizes the water-physical and physical-chemical properties of alluvial soils. But the influence area of silt on the soilsis sharply reduced and is limited only to the space in front of the dams. In the soils outside the dam, to which no fresh alluvial material comes, the hydrological regime is rebuilt and properties change substantially, up to the loss of their typological alluvial features. Key words: river alluviums, silt, floodplain, the Upper-Dniester alluvial plain, alluvial soils, hydrotechnical fragmentation.

scholarly journals An Equal-Strain Analytical Solution for the Radial Consolidation of Unsaturated Soils by Vertical Drains considering Drain Resistance

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Feng Zhou ◽  
Zheng Chen ◽  
Xudong Wang
Keyword(s):  
Analytical Solution ◽  
Unsaturated Soils ◽  
Ground Surface ◽  
Matrix Analysis ◽  
Governing Equations ◽  
Vertical Drains ◽  
Ground Surface Settlement ◽  
Parametric Studies ◽  
Strain Model ◽  
Good Agreement

Developing an analytical solution for the consolidation of unsaturated soils remains a challenging task due to the complexity of coupled governing equations for air and water phases. This paper presents an equal-strain model for the radial consolidation of unsaturated soils by vertical drains, and the effect of drain resistance is also considered. Simplified governing equations are established, and an analytical solution to calculate the excess pore-air and pore-water pressures is derived by using the methods of matrix analysis and eigenfunction expansion. The average degrees of consolidation for air and water phases and the ground surface settlement are also given. The solutions of the equal-strain model are verified by comparing the proposed free-strain model with the equal-strain model, and reasonably good agreement is obtained. Moreover, parametric studies regarding the drain resistance effect are graphically presented.

INFLUENCE OF PLANT DENSITY, COMPOST AND BIOFERTILIZER ON TRUE SHALLOT SEED GROWTH IN ALLUVIAL SOIL

2020 ◽  
Vol 21 (2) ◽  
pp. 70
Author(s):  
Gina Aliya Sopha
Keyword(s):  
Allium Cepa ◽  
Plant Density ◽  
Alluvial Soil ◽  
Fertilizer Application ◽  
Alluvial Soils ◽  
Seed Growth ◽  
Plant Densities ◽  
Main Plot ◽  
Bulb Yield ◽  
Plot Design

<p>True shallot seed (<em>Allium cepa var Aggregatum group</em>) is an alternative way of growing shallot. Different environments and cultivars need a specific study. The aim of this research was to find out the best technology to grow Trisula true shallot seed by managing plant densities and applying compost and biofertilizer in alluvial soils. The study was performed from May to October 2015, using a split-plot design with four replications. The main plot was plant density: 100 plants m-2 and 70 plants m-2. Subplots were five fertilizer application combinations, they were 100% recommended dose of NPK (R-NPK), 100% R-NPK + compost, 100% R-NPK + compost + biofertilizer, 50% R-NPK + compost and 50% R-NPK + compost + biofertilizer. Results showed that biomass and bulb yield were significantly affected by plant density and fertilizer application. The reduced 50% R-NPK by substituting with compost and biofertilizer was unable to maintain shallot bulb yield equal to 100% R-NPK, suggesting insufficient nutrients derived from compost to satisfy the shallot requirement. The best technology to grow true shallot seed of Trisula variety was 100 plants m-2 plant density and 100% NPK (consisting of 180 kg N ha-1, 52 kg P ha-1 and 50 kg K ha-1) with 2.5 t ha-1 compost that achieved the highest bulb yield of 9.83 t ha-1 and increased the revenue.</p>

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