Partial Excavation Research Articles

Screening and Optimization of Soil Remediation Strategies Assisted by Machine Learning

A numerical approach assisted by machine learning was developed for screening and optimizing soil remediation strategies. The approach includes a reactive transport model for simulating the remediation cost and effect of applicable remediation technologies and their combinations for a target site. The simulated results were used to establish a relationship between the cost and effect using a machine learning method. The relationship was then used by an optimization method to provide optimal remediation strategies under various constraints and requirements for the target site. The approach was evaluated for a site contaminated with both arsenic and polycyclic aromatic hydrocarbons at a former shipbuilding factory in Guangzhou City, China. An optimal strategy was obtained and successfully implemented at the site, which included the partial excavation of the contaminated soils and natural attenuation of the residual contaminated soils. The advantage of the approach is that it can fully consider the natural attenuation capacity in designing remediation strategies to reduce remediation costs and can provide cost-effective remediation strategies under variable constraints for policymakers. The approach is general and can be applied for screening and optimizing remediation strategies at other remediation sites.

Load Calculation Method for Deep-Buried Layered Soft Rock Tunnel Based on Back-Analysis of Structural Deformation

After the excavation and unloading of deep-buried soft rock tunnels, support structures often experience deformation-related disasters such as concrete cracking, steel frame bending and twisting, and primary support instability under different forms of load. Accurately calculating the load borne by the primary support structure is the key to ensuring design rationality and construction safety. Especially in layered soft surrounding rock formations, the magnitude and distribution of the loads are different from those of conventional rock and soil masses, resulting in limited applicability of existing load calculation methods to similar formations. Therefore, based on the measured deformation of the tunnel structure, while considering the different geometric forms of the primary support structure during partial excavation, this paper proposes a deformation-structure (D-S) load calculation method. By comparing the calculation results of this method and a large number of sample data for typical deep-buried layered soft rock tunnels, the reliability of the D-S load calculation method is verified. In addition, the variation law of the loads during the tunnel construction period is enunciated, and the magnitude and distribution of the loads acting on the primary support are clarified. The D-S load calculation method provides a theoretical basis for load calculation in deep-buried layered soft rock tunnels.

Long-term effects of buried vertebrate carcasses on soil biogeochemistry in the Northern Great Plains.

Decomposing vertebrates impact ecosystems by stimulating animal, insect, and microbial scavengers, perturbing biogeochemical cycles, and transferring elements back to the environment. Most studies exploring the impacts of vertebrate decomposition focus on surface decay scenarios over timescales of days to years. Accordingly, our knowledge of ecosystem impacts of vertebrate decomposition in burial contexts and over longer time scales is limited. In 2000, six animal carcasses were buried in a shallow grave (<1.0 m) and allowed to decompose naturally until partial excavation in 2021, enabling evaluation of long-term soil biogeochemical responses to decomposing vertebrates. Soils were sampled along three vertical transects from the surface to the bone-bearing layer (~40 cm depth) and below. Comparison of the physical and chemical properties of the grave and control soils from equivalent depths indicate significant perturbations even 21 years after burial. Notably, soil pH was significantly more acidic in grave soils (p = 0.0296), and conductivity was significantly elevated (p = 0.0009). Grave soils were significantly enriched with respect to nitrogen stable isotopes, exhibiting δ15N values of 10.48 ± 3.6‰, which is ~5‰ greater than controls. Carbon and nitrogen content was also disrupted in the burial, with five times more nitrogen in the bone-bearing layer and almost double the carbon. Water and acid-based extractions of soils revealed significant differences between grave and control soils, driven largely by calcium, phosphorus (P), magnesium, and iron concentrations. P concentrations in acid extracts were significantly enriched at the bone-bearing layer, suggesting release of P from the bones. This study demonstrates that decomposition may result in long-lived impacts to burial environments and soil biogeochemistry, even after soft tissues decay. While not typically considered in ecosystem models, buried remains contribute to soils for decades or longer, and soil biogeochemistry serves a critical role in facilitating or preventing the long-term preservation of bone.

Ground penetrating radar investigations of buried remnants at ancient capital cities of Panchala and Vatsa kingdoms spread along Ganga-Yamuna doab of India from 600 BCE to 1100 CE

Ahichhatra and Kaushambi, ancient settlements located in Uttar Pradesh, comprise differential cultural deposits and architectural remnants from 2500 BCE to 1200 CE. These settlements flourished as the capital cities of once-prosperous urban kingdoms known as Panchala and Vatsa Mahajanapadas but remain abandoned in the present day. To provide ancillary data for the simplification of traditional archaeological explorational practices, a few portions located in and around the fortified areas of both settlements were considered for subsurface investigations using Ground Penetrating Radar (GPR). In Ahichhatra and Kaushambi, 2D and 3D GPR survey was carried out in the open areas devoid of vegetation for the understanding of the spatial alignment of the buried features within the fortified walls. The subsurface investigations at Ahichhatra have shown high amplitude reflections referring to buried wall structures, residential complexes, raised platforms, past-used surfaces and structural continuity. Also, the partial excavation carried out at Ahichhatra has revealed walls and compacted floors validating our findings. From Kaushambi, the findings include wall structures and interconnected chambered structures. The anomalies obtained in the data collected from considered survey sites located in Ahichhatra are 1–2 m wide and 2–4 m deep whereas in Kaushambi they are 0.5–1 m wide and 2–4 m deep. These findings helped us to determine the progressive urban relics of the ancient kingdoms which were known for their second phase of urbanism in Ganga Valley that prevailed until their abandonment. For a better understanding of the cultural history, detailed mapping of the contemporary sites can be carried out using integrated survey methods.

Qin Shi Huang Mausoleum Shouldn’T Be Completely Excavation

This paper mainly discusses whether the current level of archaeology can fully open Qin Shi Huang Mausoleum. It discusses from four aspects: existing technology, resource investment, social influence and relevant policies. Considering that it still lacks the ability for comprehensive archaeological excavation, the partial excavation is still a better choice.

Settlement Analysis of Ground Surface and Adjacent Building Caused by Driving and Expansion Excavation of Shield Tunnel Using Artificial Freezing Method

The artificial freezing method can effectively improve the stability of strata and provide favorable conditions for the construction safety of shield tunnel in water-rich strata. Based on the frozen shield tunneling project of a metro station, which is close to important buildings, a reasonable freezing method and parameters are proposed in this paper. The simulation model was established by using Plaxis 3D finite element software (Version 2017). The numerical model was verified based on a large amount of field data. The characteristics of segment deformation, ground surface settlement and vertical displacement of buildings were compared between frozen layer and nonfrozen layer during shield tunnel excavation. It was found that segment deformation in the nonfrozen layer is three times that in the frozen layer. The surface settlement above the frozen layer is less than 2 mm. Expansion excavation of shield tunnel was carried out to meet the space function of subway station using artificial freezing method. The deformation of frozen layer was compared between full section excavation and partial excavation. It was found that the deformation of the former is 4.5 times that of the latter, so the partial excavation was chosen as the main research object. Subsequently, the characteristics of vertical displacement and surface settlement of buildings under partial excavation were studied. It was found that the vertical settlement of buildings away from the frozen layer is greater than that of buildings near the frozen layer. All settlement values meet the requirements, thus ensuring the feasibility of partial excavation and ensuring the safety of construction.

Archaeological explorations at ‘En Qobi in the Jerusalem Highlands and the identification of Qube/Qubi

The article presents the results of archaeological excavations and surveys undertaken at and near the spring of ‘En Qobi. ‘En Qobi is a spring in the upper reaches of Nahal Qobi, a tributary of Nahal Refai’m, West of Jerusalem. There is evidence of human activity near the spring from the Bronze Age to the present – a span of approximately 3,000 years. The article presents and discusses (a) the spring and its water system; (b) partial excavations and the preservation of the interior of the medieval church located near the spring; (c) H. Tasit and a nearby refuge cave, both located west of the spring; (d) H. Qobi, situated east of the spring. Our team cleaned the water system, which consists of a long spring tunnel, a large underground reservoir, an open pool and other elements typical of systems used to tap spring water in the Judean Hills. This system was apparently built in the Early Roman period, was renovated again and again and remained in use until recent times. The medieval church has a rectangular nave, oriented east-west with well-preserved ashlar walls. The inner walls were covered with polychrome frescoes. Elbow columns topped with capitals, characteristic of Frankish (Crusader) architecture in the Jerusalem area, were found in situ on the northern and eastern walls. Our funds permitted only a partial excavation of some portions of the inner walls. Inadequate funding prevented a full excavation of the church walls and floors, so the construction phases of the structure were not fully clarified. H. Tasit is a relatively small site, apparently an agricultural estate from the Roman and Byzantine periods. Unfortunately, the site was looted extensively in the past. On the nearby slope we detected and explored a small karstic cave that was apparently used for refuge purposes in the first – second centuries CE. H. Qobi is a small, ruined village located on a prominent hilltop above the spring. Without extensive excavation it is difficult to ascertain its function and past. An underground olive press and some looted tombs on the slopes were explored. Pottery and finds from the Late Hellenistic, Early Roman, Byzantine, Medieval, Ottoman and British Mandate periods were collected. ‘En Qobi has been identified as Qobi, a location near Bethar mentioned in a story in the Babylonian Talmud (Sanhedrin 95a) and in additional Roman-period, late antique and medieval sources. The article describes the sites and discusses their historical-geographical significance and identification.

Study on stress variation of advance fiberglass anchor bolts during tunnel excavation process

One of the main causes for excessive deformation within a tunnel is due to the instability of the soil or soft rock ahead of the excavation face. Fiberglass bolts have been shown to be a useful advance reinforcement method for the excavation face. In this paper, an improved ADECO-RS (Analysis of controlled deformation in rock and soils) method had been proposed for soft rock mountain tunnels, in terms of the partial (mainly the upper bench) excavation face reinforcement and also for the bench excavation method. Strain gauges were used to test the micro-strain in the fiberglass bolt to investigate how the axial force of the fiberglass bolt varied during the tunnel excavation. In addition, combined with the field tunnel deformation monitoring data, the relationship between the reinforcement parameters of the fiberglass bolts and the tunnel construction phase were discussed. The research results show that: (1) The stress state of the anchor rod is related to the reinforcement length of the anchor rod; (2) Excavation within the lap area of the fiberglass bolt leads to an increase in the axial force of the bolt, while excavation outside the lap area of the fiberglass bolt has no effect on the anchor; (3) Reducing the reinforcement area of rock mass will affect the stability of the excavation. To ensure the stability of the excavation face, the initial support construction loop should be completed as soon as possible; (4) In a future project with similar conditions, the recommended lap length of the fiberglass bolt could be 3 m utilizing the fiberglass bolt grouting face reinforcement method.

A Randomized Control Trial of Clinical Success and Acceptability of the Hall Technique and Resin-Modified Glass Ionomer Cement Restorations in Sealing Carious Primary Molars

Background: A paradigm shift in the caries management propelled interest in techniques for sealing caries and restorations with selective caries removal. Preformed Metal Crowns (PMCs) and Resin-Modified Glass Ionomer Cement (RMGIC) have been preferred choices of restorations for carious primary molars. This is the first study from India on the Hall Technique used to seal carious primary molars.&#x0D; Objective: To compare the clinical success and acceptability of the Hall Technique and RMGIC restorations in sealing carious primary molars.&#x0D; Methods: Sixty 7–8-year-old children having caries with ICDAS scores 3-5, requiring two or more restorations; a total of 140 teeth were randomized into Group A: HT (n1 = 73 teeth) or Group B: RMGIC (n2 = 67 teeth). A single calibrated operator assessed the ‘Major’ failures (abscess, secondary caries, new caries) and ‘Minor’ failures (dislodgement) over a period of 15 months. Children, parents, and operator rated the acceptability. The average time taken for each procedure was recorded.&#x0D; Results: ‘Major’ failures were statistically significantly higher in the RMGIC group (p=0.008). At the 12-month follow-up, the HT outperformed RMGIC restorations. Additional failures were seen in Group B: RMGIC restorations at 15-month follow-up, whereas no failures were seen with HT. The result was statistically not significant. Children, parents, and the operator preferred the Hall Technique, which was statistically significant (p&lt; 0.001).&#x0D; Conclusion: HT is a successful and acceptable technique and superior to RMGIC restorations with partial excavation of caries in primary molars but with mild postoperative discomfort.

Grouting technology and construction schemes of a tunnel in aeolian stratum: a case study of Shenmu No. 1 tunnel

The naturally formed aeolian sand dunes in northern Shaanxi exhibit unique engineering characteristics. Several challenges, such as the poor self-stabilization ability of the surrounding rock, difficultly in injecting grout, and insufficient construction experience, restrict the construction of road tunnels under this stratum. Therefore, in this study, a case study of the Shenmu No. 1 tunnel was conducted to investigate the engineering characteristics of aeolian sand tunnels, compare the grouting effects of commonly used grouting materials, and discuss the reinforcement effects of different construction schemes in aeolian sand tunnels. Based on a field grouting test, it was determined that it is difficult to inject ordinary cement grout into an aeolian sand layer. Furthermore, it was determined that superfine cement grout and modified sodium silicate grout can be injected, but the former exhibits a poor reinforcement effect. Additionally, results of numerical analysis indicated that an approach based on a concept of “horizontal jet grouting pile + benching partial excavation method with a temporary invert” is suitable for the construction of tunnels in aeolian sand in China.

Analysis for bearing performance and construction mechanical behavior of supporting structure for the large cross-section tunnel by half bench CD method.

Based on the engineering practice of large cross-section highway tunnel, this paper reveals the space-time coordinated evolution law of the construction mechanical characteristics and deformation distribution of the support structure in the construction by half bench CD method through field test. At the same time, the mechanical response calculation model of the supporting structure in the partial excavation is constructed, and the mechanical characteristics of the support structure in the partial excavation process are analyzed by above mechanical calculation model. Then, the mechanical and deformation distribution of the feet-reinforcement bolt in the steel frame—foot-reinforcement bolt combined support system is analyzed under different levels of surrounding rock load and different structural parameters of the feet-reinforcement bolt. The research results show that: (1) The internal force of the supporting structure changes most obviously during the excavation of Part Ⅰ, Part Ⅱ and Part Ⅲ, and the internal force of the support structure gradually tends to be stable after a slight increase in the excavation of Part Ⅳ and Part Ⅴ; (2) The horizontal deformation and vertical deformation of the support structure mainly occur in the excavation process of Part Ⅰ, Part Ⅱ and Part Ⅲ, and the excavation of Part Ⅳ and Ⅴ has little effect on the deformation response of the structure. The vertical displacement of the supporting structure is larger than the horizontal displacement, and the dynamic response of the temporary diaphragm structure during tunnel excavation is shrinkage-expansion-shrinkage-expansion; (3) The bending strain of each measuring point decreases with the increase of the distance from the loading point, and the bending strain of section 1 and section 2 is much larger than that of the other three sections; (4) With the increase of the angle, the section position with strain close to 0 gradually moves to the deeper position of the bolt, and the axial strain of each section on the bolt gradually changes from positive strain to negative strain.

Comparison of Partial and Complete Caries Excavation in Permanent Teeth: An 18 Months Follow-up

Objective: To compare performance and survival of composite restorations in primary teeth using partial caries removal (PCR) versus complete caries removal (CCR). Methodology: In this trial, 70 permanent molars having deep caries lesions were selected and divided equally into CCR and PCR groups. The study duration was Jan-2018 to Jan-2020. In CCR group, complete dentin removal was done and confirmed by applying dentin detector dye for 10 seconds. In PCR group, visual &amp; tactile criteria were followed for dentin removal. After dentin removal all cavities were filled using RMGIC cement resin. Follow-up was done at 06, 12 and 18 months. Results: Mean age in CCR group was 23.4+5.5 years and 25.6+4.9 years in PCR group. Male patients were 19 and 17 in CCR and PCR groups respectively (p= 0.59). Regarding lesion type, 25 patients in CCR were having occlusal and 5 having Occluso-proximal lesion. In PCR group, 27 teeth were diagnosed with occlusal lesion and 3 with occluso-proximal lesion (p=0.44). At 18 months’ follow-up, success rate was 100% in CCR group and 93.3% in PCR group (p=0.49). Pulp exposure occurred in 23.3% procedures in CCR group and none in PCR group. Conclusion: Partial caries removal has nearly similar success rates as that of complete caries removal and is associated with significantly less pulp exposure rate as compared to CCR. Keywords: Deep carious lesions, Partial caries removal, Complete caries removal, Randomized clinical trial

Post-operative pain after 38% silver diamine fluoride application in primary molars with deep caries versus interim restorative therapy: A randomized pilot study

Aim: To compare the post-operative pain after application of Silver Diamine Fluoride (SDF) 38% in cavitated primary molars, in relation to Interim Restorative Therapy (IRT).Design: The study was performed on 20 carious primary molars in children aged 4-6 years attending the clinic in Pediatric Dentistry and Dental Public Health Department- Faculty of Dentistry -Cairo University. Partial excavation of caries on the walls of the cavity was performed then in group (A) SDF was applied in two visits with one-week interval, and finally Resin Modified Glass Ionomer Restoration (RMGI) was applied to the cavity. While, in group (B) Resin Modified Glass Ionomer restoration was applied immediately after partial caries excavation. Clinical and radiographic examinations were performed at three and six month’s follow-up periods for both groups.Results: In both groups, 100% of patients had no complications at three and six months follow up periods; except for 10% of patients experienced failure of restoration at three months in group B. The results showed insignificant differences between groups regarding clinical and radiographic outcomes at both three and six months. Conclusions: Silver Diamine Fluoride and Interim Restorative Therapy were clinically and radiographically successful when used in primary molars with cavitated dentin carious lesions.

Study of quality maintenance of fish habitats in small- and medium-sized mountain rivers with low flow rate

Many large-scale southwestern mountain rivers have intensive hydropower development in China, and it is difficult for the mainstream habitats to meet the needs of fish; thus, the replacement of tributary habitats has become an effective measure for river ecological protection. Appropriate ecological flow is an important tool used to repair fish habitats and plays an important role in the ecological protection of tributaries, but this practice has caused conflicts with the economic interests of hydropower owners, which has made the implementation of restoration work more difficult; therefore, it is imperative to ease the contradiction between the two. Based on field investigation and monitoring, this paper designs remedial measures for the horizontal and vertical sections of the river section, namely, dredging the river horizontally and constructing a water-retaining weir and underwater dam vertically. A two-dimensional hydrodynamic model was used to numerically simulate the hydrodynamic conditions before and after different ecological restoration measures, and the corresponding weighted usable area (WUA) was calculated to evaluate the different restoration effects on habitats. The results show that the suitable ecological flow rate of the study section is 16.80 m3/s (35% average annual flow), and the WUA increased by 317.37% compared with the initial state of 2.39 m3/s (5% average annual flow); when discharge flow is 4.80 m3/s (10% average annual flow), the improvement measures of habitat quality include the combination of river dredging and the construction of water-retaining weir, construction of water-retaining weir, construction of underwater dam, and river dredging. The initial state increased by 129.96%, 177.19%, 226.51% and 329.21%, respectively. The partial excavation and dredging have a complementary effect with the construction of the water trap, and the increase in the WUA caused by the combination of the two exceeds the increase caused by the appropriate ecological flow. In summary, targeted restoration measures can achieve the goal of maintaining a high level of habitat quality at lower flow levels.

The Saint-Jean hornwork in Soissons: archaeological remains and historical context [abridged version

The partial excavation of an outwork of the Soissons (Aisne) urban fortification, built and dismantled during the 19th century, has provided an opportunity to compare the abundant archival documentation relating to this feature and field observations. Archaeology makes it possible to verify the reliability of written sources and to shed light on those parts of the history of the fortification not covered by the texts. Therefore, this research study allows to follow the evolution of a structure from the preliminary project up to its dismantling, via its construction and its functioning hazards. At the end of this study, it is possible to measure the relevance of excavating a recent structure, despite the great number of preserved archival records.

CONSERVATIVE APPROACH TO DEEP CARIES LESIONS MANAGEMENT IN CHILDREN

The aim of the study was to systematize effective deep caries management methods in children in order to determine the indications for their use. The author used Google search engine to find articles and scientific publications published between 2006 and 2019.&#x0D; Reversible pulpitis is an indication for applying the methods preserving pulp vitality performed under aseptic and antiseptic conditions, provided the absence of decompensated form of caries and chronic somatic pathology. To prevent the accidental pulp exposure, it is better to use a partial excavation of the affected dentin followed by an indirect pulp capping. During direct pulp capping and pulpotomy the bleeding should be arrested within 3-5 min in primary teeth and within 5 min – in permanent ones. Direct pulp capping with MTA is indicated at the spot pulp exposure in permanent teeth, the use of this method in the primary teeth requires further research. Direct pulp capping with 5.25% sodium hypochlorite used as a hemostatic agent and MTA-type cement application under endodontic microscope or pulpotomy with MTA or Biodentine can be applied when treating reversible pulpitis in permanent teeth. In asymptomatic temporary teeth affected by reversible pulpitis full pulpotomy is adviced which is more effective with MTA.&#x0D; A promising direction in deep caries management research is direct and indirect pulp capping of primary teeth with Biodentine.

WITHDRAWN: Operative caries management in adults and children.

WITHDRAWN: Operative caries management in adults and children.

An overview of the Muara Laboh geothermal system, Sumatra

The Muara Laboh geothermal system is a liquid-dominated, fracture-controlled reservoir showing some characteristics of both intrusion-related and fault circulation systems. The developed reservoir has moderate to high-temperature (230–310 °C) with a long NNW outflow (160–230 °C) extending to the Sapan Malulong boiling chloride springs. Reservoir fluids generally have low salinity (∼400-1600 ppm Cl) with benign chemistry and low non-condensable gas (NCG) content (∼0.5 to 2 wt% in steam). The proven reservoir is divided into distinct SW and NE sectors. The principal deep upflow zone (270 to 310 °C) is located in the SW and is associated with Patah Sembilan volcano and satellite vents (Anak Patah Sembilan). The SW upflow is characterized by relatively low salinity (∼400-600 ppm Cl), whereas fluids in the NE emerge from a second upflow along faults and fractures at 240–250 °C (1200–1600 ppm Cl) and ascend to an initial-state steam cap near the Idung Mancung fumarole. The shallow NE part of the geothermal system is hosted mainly by Quaternary to Miocene Age andesitic to rhyolitic rocks, whereas the deeper SW part of the system occurs in a Mesozoic to Cenozoic Age plutonic complex and its host rocks that are cut by younger dikes. Rock porosity and permeability trends can be related to reservoir age, volcanic deposit type, and alteration history. Fracture permeability is high, whereas matrix porosity (<1-7%) and permeability are moderate to low and decrease with depth. The volcanic sequence is capped by tuffs dated at ∼34,000 to 41,000 years BP, incapsulated in debris flows. This sequence may have formed during and shortly after likely sector collapse episodes of the Patah Sembilan volcano. The shallow clay cap of the system wraps around the crater, suggesting that it was excavated during crater formation.Permeable fracture patterns and their origins differ somewhat between the deep SW and the shallow NE reservoir. In the deep SW reservoir, fluids ascend along fractured margins of stock and dike intrusions. Steeply dipping intrusions and open fractures strike from WNW to NNW, subparallel to the main Great Sumatra Fault trend, with a secondary set of N to NE fractures and intrusions parallel with the inferred maximum horizontal stress direction (SHMax). In the shallower NE steam cap and outflow, N to NE steeply dipping fractures dominate, with bounding N to NNW faults. Bulk rock alteration includes shallow argillic and transitional clay zones overlying phyllic and propylitic zones. High-T propylitic alteration (secondary amphibole) and rare potassic alteration (secondary biotite) are associated with intrusion. Vein paragenesis in the SW reservoir indicates that portions of the initially permeable propylitic zone have been sealed by calcite and quartz ± prehnite. Late calcite veins suggest ingress of steam-heated bicarbonate waters contributed to resealing of the system. These relationships suggest that the SW system underwent extensive boiling, fluid loss, and inflow of dilute bicarbonate waters, possibly related to sector collapse and partial excavation of the topseal of the system (now Patah Sembilan crater).

The mixed‐bed glacial landform imprint of the North Sea Lobe in the western North Sea

AbstractDuring the last glacial cycle an intriguing feature of the British‐Irish Ice Sheet was the North Sea Lobe (NSL); fed from the Firth of Forth and which flowed south and parallel to the English east coast. The controls on the formation and behaviour of the NSL have long been debated, but in the southern North Sea recent work suggests the NSL formed a dynamic, oscillating terrestrial margin operating over a deforming bed. Further north, however, little is known of the behaviour of the NSL or under what conditions it operated. This paper analyses new acoustic, sedimentary and geomorphic data in order to evaluate the glacial landsystem imprint and deglacial history of the NSL offshore from NE England.Subglacial tills (AF2/3) form a discontinuous mosaic interspersed with bedrock outcrops across the seafloor, with the partial excavation and advection of subglacial sediment during both advance and retreat producing mega‐scale glacial lineations and grounding zone wedges. The resultant ‘mixed‐bed’ glacial landsystem is the product of a dynamic switch from a terrestrial piedmont‐lobe margin with a net surplus of sediment to a partially erosive, quasi‐stable, marine‐terminating, ice stream lobe as the NSL withdrew northwards.Glaciomarine sediments (AF4) drape the underlying subglacial mixed‐bed imprint and point to a switch to tidewater conditions between 19.9 and 16.5 ka cal BP as the North Sea became inundated. The dominant controls on NSL recession during this period were changing ice flux through the Firth of Forth ice stream onset zone and water depths at the grounding line; the development of the mixed‐bed landsystem being a response to grounding line instability. © 2018 John Wiley &amp; Sons, Ltd.

Stability Analysis of Shallow and Bias Loess Tunnel Based on Finite Difference Method

Based on the Mohr-Coulomb elastic-plastic model and the practical engineering background of Mopanshan tunnel, this paper applies the finite-difference software FLAC3D to simulate and analyse the whole process of loess tunnel construction. Then, it analyses the stability of the surrounding rock and sup-port structure after partial excavation of the loess tunnel under the shallow burying and unsymmetrical load-ing condition. The study showed that in the absence of support, the shear failure occurred to the top/upper pilot tunnel of the tunnel face, the failure zone under tensile stress happened to the shallow soil of the earth surface, and the soil of tunnel face appeared to be damaged. Finally, according to the analysis results, a rea-sonable construction method suitable for the shallow and bias loess tunnel is determined.